Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session S01: Poster Session & Refreshment Break (3:47 - 4:45 p.m.) |
Hide Abstracts |
Room: Hall 1 |
|
S01.00001: DFD POSTERS
|
|
S01.00002: Deriving early warning signals of turbulent thermoacoustic system using principal component analysis Yue Weng, Yihong Zhu, Vishnu R Unni, R. I. Sujith, Abhishek Saha In modern combustors, predicting thermoacoustic instability is critical for preventing potentially catastrophic system failures. Recent research on turbulent thermoacoustic systems has revealed an underlying universality in the self-organization behavior observed during transitions, where ordered patterns emerge from initially disordered states. Inspired by these studies, our work identifies the principles governing the topology change of phase trajectories in high-dimensional space as turbulent thermoacoustic systems transition from combustion noise to periodic oscillation. The phase space is reconstructed using the Hankel matrix. We decompose the dynamics in phase-space topology into orthogonal modes by employing principal component analysis (PCA). Our investigation reveals that as the system transitions from low-amplitude aperiodic oscillation to thermoacoustic instability, significant changes in phase space modes occur before the root mean square of the pressure fluctuation reaches its maximum value, providing early warning signals of impending instability. Subsequently, the relative changes in the principal components will be analyzed by providing scaling relations. We will show that the topology change of the phase space trajectories, quantified by the aspect ratio, follows a power law across multiple systems. |
|
S01.00003: Ground Effect Modelling Using Vortex Particle Method and Ground Panels Krishma R Mehta, Muhammed K Yurt, Nagabhushana R Vadlamani Modelling ground effects over fixed and moving wings is crucial for estimating aerodynamic characteristics, which change significantly near the ground. Computationally efficient methods like the Vortex Particle Method or Free Vortex Wake Method have been used to capture wakes and other flow characteristics. Ground effect has been modeled using methods like the Method of Images and panel methods. Unlike the Method of Images, which can model only plane grounds, the panel method can model arbitrary ground shapes like shipsdeck. However, there's limited literature on the accuracy of ground panels when coupled with vortex particles. In this study, we use source panels, coupled with the vortex particle method and the blade element method, to study ground effects and the accuracy of source panels in different scenarios, such as fixed-wing wake and the pitching and heaving motion of a single-wing. We validate the source panel by comparing its results with the Method of Images. The vortex particle code, accelerated using the fast multipole method, is validated with flow diagnostics such as vorticity and linear momentum, while the blade element solver is validated with analytical results for elliptic wings. We also explore using source panels to model ground effects near other arbitrary surfaces like buildings. |
|
S01.00004: Characterizing Vortex-Induced Vibrations of a 3D Printed Circular Cylinder in a Wind Tunnel Jacob C Sherman, Vansh Garg, Emad Masroor When a cylinder is placed in a fluid of sufficiently high Reynolds number for vortices to form in the wake, vortex-induced oscillations will occur when the vortex shedding frequency approaches the natural frequency. Research on vortex-induced oscillations is motivated largely by either vibration suppression of structures such as underwater pipelines or vibration enhancement for small-scale energy harvesting. In this work, we analyze the vortex-induced oscillations of a 3D printed circular cylinder of high structure-to-fluid mass ratio (m*) in an open circuit wind tunnel. The cylinder is mounted horizontally with four springs that can be replaced to change the spring constant (k). We consider a mass ratio of 108 and a moderate Re range of 103-104 to determine the lock-in range for different values of k. We also look for the presence of hysteresis, which has been found in previous studies on vortex-induced vibrations. Additionally, we explore the relationship between vortex shedding frequency, natural frequency, and frequency of oscillation. Using MATLAB’s image processing toolbox, our results indicate a peak non-dimensional response (A*) of 0.8 at a reduced velocity (Vr = U/(fnD)) of 6.7. |
|
S01.00005: The wake behind paired Savonious turbines: a characterization for an optimal spatial distribution in urban milieus. Etien Martinez Roman, Riccardo A Merli, Robert J Hearst, Tania K Bracchi The use of vertical axis wind turbines (VAWTs) for “green” and on-site energy production in urban environments is a promising strategy receiving noticeable interest in academic and industrial contexts. Despite this, the main shortcoming of VAWTs is their low efficiency which can be improved by placing arrays of two or more turbines nearby, in turn resulting in challenges related to the aerodynamic interactions between them. Therefore, more experimental characterization is required to elucidate the interrelations between the turbine’s wakes and thus get an optimal spatial distribution. Addressing these issues, we measure the velocity in the wakes of two Savonius turbines positioned at various lateral distances in a wind tunnel. Power measurements are also conducted to assess the turbines’ performance, comparing with the isolated case, in the different configurations tested corresponding to different tip-speed ratios, shaft-to-shaft lateral spacing (H), and directions of rotation. We found that small variations in H (from 1.4 to 1.8 times the turbine’s diameter) produce a significant reduction in the turbulence level in the wakes and a momentum enhancement around the turbines. The co-rotating configuration exhibits the most significant variations in terms of power when H changes, and the inwards counter-rotating case displays the smallest turbulent wake. Thus, these results provide a guide for an optimal spatial distribution of the turbines in small spaces like those typically found in urban milieus. |
|
S01.00006: New theories for universe expansion and galactic rotations William Kenneth George, Gunnar T Johansson We review our recent papers for the universe expansion and galactic rotations where we presented new solutions for both. Unlike previous theories, our solutions to the Einstein Field and galactic equations are in excellent agreement with the JWST and other recent space telescope results. There is no need for dark energy or dark matter. We used standard turbulence two-time similarity ideas in which both time and space independent variables are scaled with a single time-dependent length scale that grows linearly with gravitational time, but exponentially with atomic clock (and proper) time. The energy density is shown to have evolved by a factor of -120 orders of magnitude to the currently measured values from the quantum field BIG BANG estimate (the so-called `Worst Prediction in the History of Physics’). The Hubble parameter is H/Ho = to / t = 1+z where to is the age of the universe and z is the redshift. Ho =63.4 provides an excellent fit to ALL the data, and corresponds to an age of the universe of 15.4 billion years. Excellent agreement is also shown with the supernovae data, previously believed to imply the universe is accelerating. We also identify why previous theories were in error. |
|
S01.00007: Type II Migration due to Multiple-Embedded Planets in Protoplanetary Disks Sudat Khan, Wenrui Xu Investigating the formation and evolution of protoplanetary disks allows us to understand the process of planet formation and migration. Specifically, planet-disk interactions shape planetary orbits through migration and produce substructures within disks such as spirals, vortices, and gaps. For planetary masses equal to or greater than ~1 𝑀J the Lindblad torque comprises of a positive torque applied to the planet by its inner wake and a negative torque generated by its outer wake. The planet gives angular momentum to the outer disk (the region beyond the planet's orbital radius) while absorbing some from the inner disk. There is also the corotational torque, which is the torque due to disk material that on average corotates with the planet. When the torque exerted by the planet on the disk exceeds the viscous torque, it results in the formation of an annular gap around the planet's orbit. This non-linear regime is called Type II migration. |
|
S01.00008: Characterizing attraction flows at sea lamprey traps entrances Aline J Cotel, Mariana I. Fernández Correa, Kaylin Jones, Julien Malherbe The sea lamprey (Petromyzon marinus), an invasive species significantly impacting the Laurentian Great Lakes ecosystem, has traditionally been managed using lampricides since the 1950s. However, emerging research highlights adverse effects of these chemicals on native lampreys and other fish species, necessitating alternative removal methods. Trapping is one such method, although current traps are relatively inefficient and predominantly used for monitoring. The flow patterns induced by these traps, presumed crucial for trapping success, remain unquantified. |
|
S01.00009: Female Reproductive Biofluids: A Uterine Contraction Flow Model for Embryo Transport Jeremiah Ameer Lucas, Yasser Aboelkassem Reproductive biofluid mechanics, an emerging field, addresses challenging and complex flow physics problems, including fluid-tissue interactions at various scales. Most current research in this area focuses on the initial stages of reproduction and the transport phenomena during the fertilization process. Specifically, researchers study how sperm travels from the vaginal canal, through the cervix, into the uterus, and to the fallopian tube, where it meets the released ovum. For a successful pregnancy, the pre-embryo (fertilized ovum) must travel back into the uterus and implant in the uterine wall. Unlike sperm, which propels itself, the ovum or embryo is passively transported by the movement of tidal fluid induced by contractions of the female reproductive tract wall. In this study, we propose a mathematical model to describe the induced flow motion within a finite-length tube. This model is then used to simulate intrauterine flow patterns and ovum transport phenomena resulting from various observed rhythmic wall contractions in the uterus. |
|
S01.00010: Rheological responses of Coral Surface Mucus Under Healthy and Bleaching Conditions Mauricio A Rios Maciel, Amy Q Shen This study examines the rheological characteristics of the surface mucus layer of Acropora corals in healthy conditions and in response to environmental stress-induced bleaching. We discovered that the mucus exhibits gel-like properties with a detectable yield stress. Comparative analyses demonstrate a substantial decrease in both extensional and shear rheology following coral bleaching, indicating a degradation in the structural integrity and functional capabilities of the mucus layer. This research is pioneering in its focus on the rheological behavior of coral mucus in healthy and bleaching conditions, providing new insights into coral resilience. Such knowledge is crucial for developing effective conservation strategies and enhancing predictive models for coral reefs amid climate change and other human impacts. |
|
S01.00011: A Reaction-Diffusion-Chemotaxis Model to Understand the Collective Behavior of Microbial Life Ethan J Coleman, Siamak Mirfendereski, Ankur Gupta Micro-organisms play a pivotal role in the existence and function of life. Despite the simplicity of their anatomy, these creatures display complex phenomena, including autopoiesis, biofilm formation, bioluminescence, and, of course, virulence. Existing literature establishes that these phenomena arise due to microbial communication, such as quorum sensing and chemotaxis. While these communication pathways have been extensively studied in isolation, mathematical models that predict how microorganisms respond collectively when multiple communication pathways are present remain underexplored. To this end, we developed a large-scale Eulerian-Lagrangian numerical framework to investigate the emergent collective dynamics and structures under multiple communication pathways. In this framework, we treat microbes as colloidal particles that can produce, consume, and respond to dissolved species in the suspended media. By tracking the spatiotemporal variation of the dissolved species, we evaluate the dynamical trajectories and states of microbial entities. The framework is able to qualitatively recover some features observed in experiments and provides a scalable method to predict the collective response of microbial life. |
|
S01.00012: On Generating Realistic Flows for Controlled Insect Orientation Studies Jayden Stout, Jared Vazquez, Justin Maxwell, Neil Vickers, Agastya Balantrapu Mosquito orientation behavior is well-researched due to their disease transmission capability. However, predictors of mosquito activity remain poorly understood due to lack of extensive datasets that document their field activity and a lack of realistic controlled studies. Typically, mosquito activity has been analyzed for correlations with measured atmospheric properties such as temperature, relative humidity, ambient light, and windspeed (Rudolfs, 1923). More recently, bioassay methodologies, including tracking of individual mosquitoes in fabricated flow conditions with various odor attractants, has been pursued, but correlations between mosquito activity and atmospheric flow conditions has not been investigated. We aim to address this through investigating mosquito activity and its correlation with atmospheric properties documented from 2018-2024 in various habitats in Salt Lake City. Mosquito activity was documented using a Biogents Sentinel trap and flow properties were documented with a sonic anemometer and lagrangian particle tracking system. We report the data along with the results that reveal the flow conditions (such as turbulence kinetic energy, shear stress etc.) that permit high mosquito activity. These results reveal the flow conditions, which are difficult to replicate, but are essential for a realistic controlled wind tunnel study. |
|
S01.00013: 3D underwater swimming kinematics in aquatic insects Jean-Paul C Edwards, Snigdha Shiuly S Tikader, Margaret L Byron Multimodality (i.e., efficient travel across aerial, terrestrial, and/or aquatic domains) is a common quality among animals but is difficult to build into engineered devices. Many insect species are especially adept at multimodal movement and could potentially serve as a model for new bioinspired vehicles or other technology; however, our understanding of the physical mechanisms underpinning their abilities is limited. Here we investigate the swimming behavior of three distinct insect families that regularly locomote across and between air, water, and land: water boatmen (Corixidae), backswimmers (Notonectidae), and diving beetles (Dytiscidae). In each of these insects, swimming is primarily driven by a pair of elongated, bristled hind legs that row like paddles, with a distinct power-recovery cycle; during the power stroke, the bristles are extended, and during the recovery stroke they collapse (increasing and decreasing, respectively, the effective area of the paddle). We qualitatively compare the paddle kinematics and overall swimming trajectory/speed between these three insects to identify similarities and differences in swimming patterns. Our results carry implications for both fundamental biology and the potential for bioinspired design; they will serve as a baseline for future work exploring the forces generated by bristled appendages in the context of underwater locomotion. |
|
S01.00014: Experimental study of the distribution of drag coefficients in water generated by streamlined bodies Sejin Jung, Su-bin Oh, Ganghee Lee, Heungchan Kim, Chang Hyeon Seo, In Sung Jang, Jihoon Kim Fish have a mechanism for gaining momentum through various motions to move underwater. Tail movements with more than 3 Hz are necessary for rapid propulsion. However, other methods of reducing drag are also required. In this study, we investigated the drag coefficient of a fish's body. The study used a reduced scale model with dimensionless coefficients at a maximum flow velocity of 1.0 m/s or less using a circulating water channel. The distribution of the drag coefficient was determined as a function of the scale model's yaw angle and periodic rotational motion. In the future, we plan to utilize these results to design self-powered unmanned underwater robots. |
|
S01.00015: An experimental study of the morphological influence of fishtails through reciprocating motion Ganghee Lee, Su-bin Oh, Sejin Jung, Heungchan Kim, Chang Hyeon Seo, In Sung Jang, Jihoon Kim Fishtails can generate hydrodynamic propulsion, control, and more underwater through various structures and geometries. In particular, preliminary studies have shown that the shape of the tail can increase propulsion by up to 20%. This study performed various morphological analyses from a hydrodynamic perspective by mimicking a fishtail. Even with the same area, the width and size of the vortices generated underwater varied at flow velocities below 1.0 m/s. The asymmetry required for directional control was also confirmed through parametric experiments. In the future, this research will be utilized to implement underwater robot control. |
|
S01.00016: Computational Chemo-Fluidic Modeling of Thrombotic Occlusion in Aneurysms due to Flow Diverting Stents Zhitong Lin, Jun-Hee Seo, Justin Caplan, Rajat Mittal Intracranial Aneurysms (IA) pose a significant risk of rupture, leading to subarachnoid hemorrhage with high fatality rates. Traditional treatments involve surgical clipping, endovascular coiling, and cerebral bypass surgery. In the last decade, Flow Diverting Stents (FDS) have emerged as a promising alternative. These stents are placed within the artery to reduce blood flow into the aneurysm, inducing flow stagnation and triggering thrombosis. The resulting thrombus restricts flow, preventing subsequent growth and rupture. Additionally, the stent acts as a scaffold for endothelium reconstruction. Despite these advancements, some IA cases still experience post-treatment rupture due to insufficient occlusion. To address this, we propose a more precise analysis using Computational Fluid Dynamics (CFD) modeling and simulation. Our approach models the stent as a porous membrane, allowing efficient computation. We use an inhomogeneous force model to account for tangential and normal component of the stent resistance force separately. By placing the membrane as an immersed boundary, we avoid complex meshing procedures. Our results demonstrate improved flow reduction inside the aneurysm and accurately capture the stent’s deflecting effect. For thrombosis modeling, we adopt a simplified approach based on platelet binding controlled by fibrin concentration, residence time, and shear stress. Our chemo-fluidic coupled simulations provide valuable insights for optimizing IA treatment. |
|
S01.00017: Quantifying cerebral vessel pulsatility in awake and anesthetized mice. Tuguldur Taylor Bayarerdene, Kimberly A Boster, Hashmat Ghanizada, Shakleen Ishfar, Maiken Nedergaard, Douglas H Kelley Cerebrospinal fluid flows through perivascular spaces surrounding blood vessels, transporting nutrients, drugs, and metabolic waste in and out of the brain. Failure of this flow is linked to a variety of conditions, such as Alzheimer's disease. Pulsations of cerebral arteries help drive this flow, so quantifying pulsatility is crucial to understanding solute transport in the brain. Here we show how pulsatility differs for data collected from mice that are awake and anesthetized through measurement of cerebral artery diameters in microscope images. Analysis of these arterial diameter measurements and corresponding electrocardiogram data shows much higher magnitude and variance in cardiac pulsatility in awake mice over anesthetized mice. We also quantify slow vasomotion, or low frequency changes in vessel diameter. |
|
S01.00018: Comparison of Cerebral Vessel Pulsatility Using Vessel Diameter Algorithms Devin T Wong, Aditya Ranjan, Kimberly A Boster, Douglas H Kelley Neurodegenerative diseases such as Alzheimer's and neurological diseases such as stroke are linked to abnormal cerebrospinal fluid (CSF) flow. Normal CSF flow plays a role in clearing metabolic waste and is driven, in part, by the expansion and contraction of arteries adjacent to CSF-filled spaces. This study aims to measure and quantify arterial wall motion to better understand CSF dynamics and associated metabolic waste removal. We simulated microscopic data to measure vessel pulsations by creating movies of pulsing vessels with varied artifacts including translation and adjusting the noise-to-signal ratio. The average diameter, root mean square diameter, and pulsatility (quantified as the diameter interquartile range) error were calculated with three MATLAB algorithms and then compared against the ground truth. Among the algorithms, typically, the image intensity-based diameter measurement algorithm resulted in the highest pulsatility error, followed by the Radon transform-based algorithm, and finally the edge-detection-based algorithm. The comparison of these vessel diameter measurement algorithms highlights their respective limitations, offering insight into the most suitable algorithm for different datasets. |
|
S01.00019: High temporal resolution, in vivo imaging for improved measurements of cerebrospinal fluid flow in mice Dorothea Tse, Cooper Gray, Daehyun Kim, Lily Watkins, Turki Alturki, Thomas Ruhl, Silas Simpson, Anika Volker, Jeffrey Tithof The glymphatic system, a recently discovered pathway for flow of cerebrospinal fluid (CSF) in the brain, has been shown to play a key role in the clearance of toxic cellular waste from the brain's extracellular space. In vivo visualization of this system however is challenging due to lack of optical access through the opaque skull, the fragile nature of the brain environment, and the difficulty of experiments due to invasive surgeries. Several imaging techniques have been used to image this system in vivo such as transcranial fluorescence macroscopy, functional magnetic resonance imaging, and confocal microscopy; however, the coarse spatial and temporal resolutions that can be achieved with these techniques also limit our ability to draw conclusions about driving mechanisms of CSF flow. To overcome these limitations, prior studies (e.g., Mestre et al 2018) employed two-photon microscopy, where they were able to measure CSF velocities with imaging resolutions on the order of 1 µm at 30 Hz. Their work showed that arterial pulsations stemming from the cardiac cycle are a key driver of CSF flow, but the chosen imaging rate was still rather coarse for the mouse heart rate (~6 Hz). To build on their work, we imaged CSF flow at rates as high as 440 Hz. This drastic increase in temporal resolution enables rigorous quantification of how CSF pulses in synchrony with arterial pulsations and improved estimates of the wall shear stresses experienced by pial vessels and astrocytes due to glymphatic flow. |
|
S01.00020: A comparative analysis of compartmental and computational fluid dynamics modeling of cerebrospinal fluid clearance Mei Ling Wood, Saba Mansour, Mahdi Esmaily The global prevalence of Alzheimer's Disease (AD), a neurodegenerative disease linked to aging, is rising. With limited current treatments, early diagnosis and intervention are crucial to reducing mortality rates. Recent studies indicated that slow clearance of toxic brain waste may cause neurodegeneration, sparking interest in cerebrospinal fluid (CSF) dynamics as it removes brain waste. Due to limited noninvasive methods for humans, most data come from animal models. A promising in-vivo approach uses dynamic PET imaging to track radioactive contrast material, requiring complex image processing based on traditional compartmental modeling. An alternative modeling approach is to use computational fluid dynamics (CFD) to analyze the spatiotemporal transport of the PET contrast agent. Both methods estimate the CSF clearance rate as turnover time. Our study compares these models by solving an inverse problem to match model predictions with clinical data. The CFD model uniquely accounts for variations based on simulated brain compartment volume. In a sample of 10 patients, the compartmental model better fits clinical measurements, with a mean absolute percent error of 6.9% compared to 12% for the CFD model. The higher error produced by CFD might stem from simplified assumptions and a limited sample size. Nevertheless, CFD can provide valuable insight and has the potential to aid in the early diagnosis of AD. |
|
S01.00021: A Study of Ocean Surface Roughness Using Field Observations Jere Combs, David Ortiz-Suslow, Walter C Smith Ocean surface roughness is a key boundary condition to simulating and predicting the ocean-atmosphere coupled system on a global scale. Deriving an accurate model for ocean roughness is complicated by the nonlinear interaction of wind and surface waves. Large-scale models have parameterized roughness solely in terms of the tangential wind stress, however this is a well-known oversimplification of the physics. Using a high quality marine atmospheric boundary layer data set collected from a unique ocean platform, the ocean surface roughness, z0, will be directly calculated and compared to state-of-the-art empirical roughness models. Surface roughness was directly calculated using the eddy covariance, profile, and bulk methods from the observations collection aboard FLIP, the Floating Instrumentation Platform, during a 2017 Southern California ocean expedition. Preliminary analysis of the direct measurements revealed both u*-1and u*2 dependence of z0 as the wind forcing approached 0; conventional models predict only the u*-1 form in the low wind regime. Values of z0 at higher wind stresses follow the expected dependence on u*, but are significantly lower than predicted from empirical relations. This presentation will showcase a comparison of observed and predicted roughness using both wind- and sea state dependent models. The physical meaning behind the low u* divergence in the observed z0 will be discussed. |
|
S01.00022: Turbulent flow past a low-aspect-ratio finite wall-mounted circular cylinder at various degrees of upstream sheltering Benjamin Mlavsky, Timothy Belin, Ali Hamed Planar particle image velocimetry (PIV) was used to investigate the flow past a finite wall-mounted circular cylinder (FWMCC) immersed in a turbulent boundary layer and subjected to various degrees of upstream sheltering. The effects of upstream sheltering were investigated using one to four upstream FWMCCs positioned in tandem at various streamwise spacings and height ratios (defined as the ratio of the upstream cylinders height to the downstream cylinder height). The upstream FWMCCs were positioned at streamwise spacings of 2d and 6d, where d is the diameter of the cylinders. The upstream cylinders had a height ratio of h1/h2 = 0.5 and 1, where h1 refers to the height of the upstream cylinders and h2 denotes the height of the downstream cylinder. In all cases, the downstream cylinder was positioned in the same location and occupied approximately 20% of the incoming boundary layer thickness. The flow measurements were made at a Reynolds number of 60,000, based on the boundary layer thickness and freestream velocity. The results highlight the effects of upstream sheltering by multiple cylinders on the mean flow and turbulence past the downstream cylinder. Attention is focused on the changes to the downstream cylinder wake as a function of the incremental addition of upstream cylinders from one to four upstream cylinders. |
|
S01.00023: Response of a Turbulent Boundary Layer to Temporal Acceleration and Deceleration Aaron Maschhoff, Tomek M Jaroslawski, Haowei Wu, Beverley J McKeon
|
|
S01.00024: Characterization of Near-surface Wind Profiles Based on Atmospheric Thermal Stability and Turbulence Characteristics Elliott J Walker, Hudson S Hart, Chloe M Amoroso, Wei Zhang, Corey D Markfort Characterizing the atmospheric boundary layer (ABL) wind is vital for wind turbine power generation, air pollution control and wind loading design on civil structures. However, the behavior of winds in the ABL is heavily influenced by turbulence, something which has not been adequately considered for the prediction of mean wind flow speeds. Vertical wind speed profiles predicted by the power-law (PL) model are commonly used for wind speed extrapolation in wind power forecasting. We investigated how the power-law shear exponent varies based on different quantifications of thermal stability and turbulence using ABL weather data collected by both cup anemometers and high-resolution ultrasonic sensors from a 106m meteorological tower at Cedar Rapids, Iowa. Bulk and flux Richardson numbers were compared as indicators of stability. Autocorrelation analysis was performed to determine integral time and length scales of surface-layer turbulence. With such tools in hand, we employ a basic machine learning (ML) approach and compare the results of traditional PL models and ML methodology to better understand alpha value distributions across various stability and turbulence stratum. |
|
S01.00025: Bubble Velocity in Hele Shaw cell Yichen Guo We studied how size of the bubble affects bubble velocity in the Hele Shaw cell |
|
S01.00026: Analyzing Simulations of Flameholder Cavity Designs to Prevent Unstart in Scramjet Engines Mckenna DuFrene, Jung-Han Kimn, Jeffrey Doom Flameholder cavities are an essential part of scramjet engines. They provide extra time for air and fuel to mix, which creates a more reliable air-breathing engine. However, with the volatile nature of internal supersonic airflow, the design of the flameholder cavity is important for managing the back pressure at the engine's outlet to avoid unstart: a phenomenon at the inlet of the engine that restricts the delivery of oxygen to the combustion section. Excessive amounts of back pressure or strong shockwave interactions with the boundary layer can cause unstart. The shape of the flameholder cavity affects these components, so five cases were simulated in StarCCM+ using Reynolds Averaged Navier Stokes (RANS) model, specifically the SST turbulence model. The first case was the accepted shape for scramjet engines – a rectangular cavity with a ramp leading out of it toward the outlet. The next four cases were compared to the original: a rectangular-shaped cavity with no ramp, a circular-shaped cavity, and two triangular-shaped cavities with different depths. In each of the cases including the original, the residuals spiked multiple times, and back pressure was evident in the scalar scenes. The circular-shaped cavity had the most stable results along with the rectangular cavity with no ramp. Knowing which cavity geometries will positively affect airflow in scramjet engines will lead to less risk of unstart. |
|
S01.00027: Stability and control of a model double ramp hypersonic intake Michael Stoddard, Gaurav Kumar, Aditya G Nair The flow dynamics of an inlet-isolator model scramjet with a steep double ramp intake is investigated at hypersonic flow conditions. With a deflection angle of 30-deg for the leading ramp, a variety of aft ramp parameters (deflection angle and ramp length) are analyzed at various free stream flow parameters. Then passive and active flow control strategies are tested for enhancing the range of operational mach numbers. |
|
S01.00028: Locomotion trade-offs for rigid bodies: CFD of scaphitid ammonites Kathleen Ritterbush, Garrett Butler, Nicholas Hebdon We examine hydrodynamics constraints of swimming strategy among ammonites, extinct squid-like animals from the time of dinosaurs that produced iconic spiral seashells. We consider shape variance among juvenile specimens of Hoploscaphites collected from the Upper Cretaceous Pierre Shale of Montana and synthesize four digital 3D specimens, varying both compression and ornamentation. We use computational fluid dynamic simulations (CFD) in ANSYS Fluent to simulate drag forces within velocities from 1-20 cm/s on specimens 4-5 cm in diameter. Simple ribbing on these shells causes a relative reduction in drag on inflated conch forms. We interpret this as a consequence of premature shear experienced at the ribbing interface along the conch flank, and at the umbilical shoulder. For juvenile scaphites, inflation and ornamentation cause opposing trade-offs in drag force with increasing turbulence. Between two individuals, the inflated form should favor maneuverability and acceleration, while the compressed form should travel greater distance for the same effort. Ribbed ornament appears to help the inflated conch behave more like a compressed conch. Collectively, juvenile scaphites appear to occupy every position within a highly constrained maneuverability-efficiency-speed landscape. |
|
S01.00029: Jets from Shocked Metal Surfaces with Ridges Arianna Carter, Bryan E Kaiser, Jesse Canfield This paper explores the dynamics of ejecta resulting from shock-induced perturbations in defected metal surfaces. An analysis of the outflow mass and its maximum velocity aims to establish a relationship between the geometry of the defect and the behavior of the ejecta. By varying the aspect ratio (height to width ratio) and volume in distinct experiments, the study aims to assess how the height of the defect and its total volume influence the jetting characteristics. The paper will explore the influence of ridge geometry on ejecta mass and velocity, comparing triangular and sinusoidal ridges to clarify how changes in ridge parameters affect the jetting phenomena. |
|
S01.00030: Investigating fluid dynamics via gas diffusion using Bout++ fluid simulation GAURAV KUMAR, Hitendra K Malik Investigating gas diffusion is crucial to the understanding of fluid dynamics via particle diffusion. The diffusion is realized whenever there exists a gradient in Gibbs free energy or chemical potential of the fluid. In order to study such a dynamics, we simulate gas diffusion utilizing fluid simulation via BOUT++ by developing a mesh generator, and compiling a series of challenging test problems for diffusion codes in addition to a basic neutral fluid model. The gas diffusion fluid equations in one-dimension as well as in two-dimensions are solved with and without convective terms. This shows a significant impact of the convective term in the process of diffusion for different kinds of gases having different diffusion coefficients. The further insight is drawn through different fluid properties by changing the initial density profile of the gases. Starting from the very basic density profile as the Gaussian profile, we develop results by introducing the density gradient in the profile via changing the rising and fall times, and broadening of the peak region. A quick diffusion is obtained for the case of fluid having larger density gradient. The results could be important for the transport and turbulence in various kinds of fluids. |
|
S01.00031: Two-way Electro-Hydro-Dynamic coupling modeling of ionic wind within an external flow José M Marques, David Fabre, Franck Plouraboue This contribution is interested in the modeling of ionic wind generated by a stationary corona discharge within a steady imposed external flow as in [1]. Since, the electro-drift velocity of charges in air is generally of few hundred meter per second, whereas ionic wind flow velocity is of the order of few meter per second, the influence of fluid advection is generally neglected resulting in a one-way coupling of the charges onto the flow [2]. Nevertheless when considering an adverse fluid velocity larger than ten m/s, this approximation fails and two-way coupling arises between charges drift and fluid flow. This is the focus of our investigation. Developing over the asymptotic multi-scaled two-domain approach of [3], we hereby propose an asymptotic two-way coupling method based upon a non-dimensional number Mc being the ratio between the external velocity flow to the drift charges one. This approach predicts a linear dependence of the current with velocity which is successfully compared with recent experimental measurements. [1] Seville Chapman. Corona point current in wind. J. of Geophysical Research, 75(12):2165– 2169, 1970.
[2] F. Picella, D. Fabre, and F. Plouraboué. Numerical Simulations of Ionic Wind Induced by Positive DC-Corona Discharges. AIAA J. , 1–12, 2024.
[3] N. Monrolin and F. Plouraboué. Multi-scale two-domain numerical modeling of stationary positive DC corona discharge/drift-region coupling. J. Comp. Phys. 443:110517, 2021.
|
|
S01.00032: A regularized discrete unified gas-kinetic scheme for incompressible viscous flows Yiming Qi, Jie Shen, Zhaoli Guo, Shiyi Chen, Lian-Ping Wang In computational fluid dynamics, the Gauss-Hermite-quadrature-based mesoscopic methods, including the lattice Boltzmann method (LBM), the discrete unified gas kinetic scheme (DUGKS), have attracted much attention in the past decades. Similar to the LBM, DUGKS, as a second-order finite volume method, has the flexibility of using non-uniform and non-structured grids and maintains the asymptotic persevering property when simulating continuum flows. However, these approaches may encounter numerical instability when the flow Reynolds number and Mach number exceed certain limits. To enhance the numerical stability, regularization has been introduced to remove spurious moments, by projecting the distribution function onto the Hilbert space with a specific Gauss-Hermite quadrature accuracy. In this poster, we apply such regularization to the DUGKS approach, to examine its effects on the numerical stability and physical accuracy. Preliminary numerical results for three-dimensional decaying homogeneous isotropic turbulence illustrate that the regularization significantly enhances the numerical stability for athermal flows without affecting the accuracy of physical results. |
|
S01.00033: Implementing conservation of mass to wind flow field solvers to bridge the analytical wake model physics gap Zane R Frey, Marc Calaf, Nicholas Hamilton Currently, full computational fluid dynamic (CFD) simulations are required to simulate fluid flow through wind farms. These CFD simulations are computationally expensive and therefore limit wind farm optimization analysis. Conversely, analytical wake models that model turbine wake deficits have been developed and implemented into industrial-grade software over the past several years, such as FLORIS from NREL. These models allow for extremely fast flow and power estimation for different wind turbine configurations, making them ideal for optimization and agile decision-making processes. Unfortunately, the resulting fields of these models do not necessarily conserve mass, nor momentum. This study investigates the impact of imposing mass conservation as a first-order improvement to analytical wake models on flow fields and power estimates. To do so, a rapid mass-conserving workflow is used, where results are compared to those obtained both through a full scale Large-Eddy Simulation (LES) approach, and through the superposition of analytical wake flow models. Results show that the newly tested mass-conserving approaches generate flow fields and power estimates more similar to those obtained with LES while simultaneously maintaining simulation times on the order of seconds. The comparatively low computational cost of the workflow highlights the potential of incorporating additional physics into analytical wake models while maintaining their computational efficiency. |
|
S01.00034: Computational Assessment of Electrical Stimulation Effects on Cell Temperature Ashley M Jorgensen Electrical stimulation (ES) therapy has been shown to promote the healing of chronic epidermal wounds and suppress degeneration of articular cartilage. However, there are still unanswered questions regarding the optimization and limitations of this treatment. One of the main challenges of ES therapy is the potential for ohmic heat generation, which can lead to cell degradation and even cell death. This study presents a simulation-based analysis of the ohmic heating effects created by electrical stimulation in the body to identify essential parameters for treatment. A representative model of human tissue and articular cartilage was input into a Computational Fluid Dynamics model to assess a variety of voltages while monitoring temperature and time. This study aims to ascertain the point at which cells sustain irreversible damage due to temperature exposure. Computational models were developed to compare the impact of blood flow in the intermediate layers of the skin and to examine the thermal dissipation characteristics in joints, enabling the application of higher electric fields without reaching hazardous temperatures. Research and clinical studies have demonstrated that ES can significantly increase the rate at which a wound heals. Understanding the thresholds for when thermal damage occurs will enable clinicians to optimize this process. |
|
S01.00035: Kinetic spectral simulations with implicit-explicit time integration Oleksandr Chapurin, Oleksandr Koshkarov, Gian Luca Delzanno, Cale Harnish, Alexander A Hrabski, Salomon Janhunen, Ryan T Wollaeger, Zach Jibben, Peter T Brady, Daniel Livescu Kinetic models for plasma or rarefied gas problems include physics with drastic time scale separation, which we address with the implicit-explicit (IMEX) temporal integration approach. |
|
S01.00036: Numerical Modelling of the Transport of Cancer Cells Meraj Ahmed, Thien-Tam Thien Nguyen, Ankur Deep Bordoloi, Margherita Tavasso, Trung Bao Le Cancer metastasis leads to the transport and widespread of malignant cells from the primary tumor to other parts of the body by exploiting body fluids (lymphatic fluid, bloodstream, and interstitial fluid). While the transport of a single cancer cell in fluid flow has been studied in the past, it is unclear how an aggregate of cancer cells (called a tumoroid) deforms and migrates under the impact of hydrodynamic force in vasculature. In this work, we address this knowledge gap by investigating the migration process in a tumoroid in a constricted micro-channel using both experimental and computational methods. Our numerical model is based on a hybrid continuum-particle approach. The cancer cell model includes the cell membrane, nucleus, cytoplasm and the cytoskeleton. The Dissipative Particle Dynamics method was employed to simulate the mechanical components. The blood plasma is modeled as a Newtonian incompressible fluid. A Fluid-Structure Interaction coupling, leveraging the Immersed Boundary Method is developed to simulate the cell's response to flow dynamics. Our computational model allows an accurate estimation of fluid shear stresses on the cell's surface and resolves the local cellular dynamics while providing large-scale flow patterns in the vasculature. Our numerical findings are compared with the accompanied experimental data. Our results suggest that the mechanical response of the tumoroid differs from one of a single cell. We hypothesize that the intracellular and extracellular dynamics response of the multicellular systems is intrinsically linked to their cellular constituents which certain configuration displayed strong resistance to the fluid-induced forces and the ability to migrate in various directions. Our computational framework provides new capabilities for designing bioengineering devices for cell manipulation. |
|
S01.00037: Dispersion of Respiratory Aerosols in Indoor Turbulence Nolan Zigler, Aditya Parik, Leonardo Chamorro, Som Dutta Respiratory particles or aerosols are released in the indoor environment during expiratory events such as talking and breathing. Similar particles are also central to indoor pollution. Understanding how these particles move through the indoor environment is essential for quantifying the ability of the pathogen-laden particles to spread respiratory diseases and indoor pollution mitigation. Previous studies have observed the motion of particle clouds due to natural convection and flow induced by symmetric airflow induced by air-conditioning systems. Though, detailed characterization of the turbulence within this environment is relatively unexplored. Especially, for cases where the air inflow through the HVAC system is at a relative higher or lower temperature than the ambient, which is often the case in winter or summer. Thus, the current study focuses on characterizing the indoor turbulence produced due to buoyancy-effect induced by the incoming HVAC air. Additionally, the particulate transport the flow induces for small particle clouds released at different spatial location is simulated. High-resolution large eddy simulations (LES) are used to model the indoor flow and turbulence, and one-way coupled Lagrangian particle tracking for simulating the dispersion of particles. The equations defining the flow are solved using high-order spectral element methods (SEM). Stokes drag, lift, gravity and thermophoretic forces are accounted for in the particle-tracking model. First and second-order turbulence statistics are used to characterize the flow. The general flow structure of the room shows substantial difference due to buoyancy, inducing major difference in dispersion of the particle cloud. |
|
S01.00038: A One-Dimensional Turbulence model with particles replicates cloud microphysical properties from a convection chamber Corey Bois, Manikandan Rajagopal, Kamal Kant Chandrakar, Steven K Krueger Clouds produced in a laboratory convection chamber consist of droplets of water, each experiencing a lifecycle consisting of activation, growth/decay, and sometimes fall out. These lifecycles are influenced by each droplet's unique trajectory through moist turbulent air and are coupled to the local temperature and water vapor fields via supersaturation. We efficiently model populations of these individual droplet lifecycles using One-Dimensional Turbulence (ODT) with the addition of cloud-droplet microphysics. ODT can simulate the Pi Chamber at Michigan Technological University, a moist Rayleigh-Benard Convection (RBC) chamber with configurable aerosol species and aerosol injection rates. Despite consisting of only one spatial dimension, ODT accurately replicates many aspects of direct numerical simulations of the Pi chamber microphysics due to its Kolmogorov-scale resolution and eddy implementation that resolves the wall boundary layers. Additionally, ODT demonstrates agreement with the Pi Chamber's basic microphysical characteristics such as mean droplet radius and in some cases droplet size distributions. Since ODT evolves individual droplets and is computationally efficient, it can simulate large parameter spaces to test theories of cloud microphysics. |
|
S01.00039: Non-Dimensional Analysis of Droplet Size Distributions in a Convection Cloud Chamber Grant Daniels, Steven K Krueger In a laboratory convection cloud chamber, supersaturation is produced by turbulent mixing of air from the saturated warm bottom and cool top surfaces. A model simplification of supersaturation is using a stochastic differential equation (SDE). Under a constant rate of injection of CCN, a steady-state droplet size distribution (DSD) can be achieved. A better understanding of the equilibrium DSD is critical for understanding chamber and cloud physics. A general solution for the equilibrium DSD for cloud chamber conditions (such as those in the Pi Chamber at Michigan Tech University) has evaded the scientific community. Previous research suggested solutions for the case of an equilibrium DSD without aerosol effects (i.e., without curvature and solute effects in the droplet growth equation), without supersaturation fluctuations, or with supersaturation fluctuations on the DSD modeled (in the equation for the PDF of droplet radius squared) as a diffusivity that is linearly proportional to the supersaturation variance and the Lagrangian autocorrelation time scale of the supersaturation fluctuations. Non-dimensional analysis is a powerful tool to simplify the domain of initial conditions. Using this, we can investigate the solution of the non-aerosol case, with application to the aerosol case. Contrary to the diffusion domain, my results suggest using a term proportional to the supersaturation standard deviation times the squared Lagrangian autocorrelation time scale instead of diffusivity. |
|
S01.00040: Direct Numerical Simulations of Supergravitational Thermal Convection: From Gravitational to Centrifugal Buoyancy Dominance Olga Shishkina, Mohammad S Emran, Andrei Teimurazov, Zhongzhi Yao We report our DNS results on supergravitational thermal convection in an annular container heated at the outer sidewall and cooled at the inner wall, all subjected to a constant rotation around a vertical axis (as in the ACRBC facility in Chao Sun's Lab at Tsinghua University). For a fixed Rayleigh number Ra (thermal driving) and increasing Froude number Fr from 0 (no-rotation) to 100 (strong centrifugal buoyancy), we observe an evolution of the global flow structure and heat transport scaling properties from those typical for vertical convection, where the imposed temperature gradient is orthogonal to the driving force (gravitational buoyancy), to those typical for Rayleigh-Benard convection, where the temperature gradient is parallel to the force (centrifugal buoyancy). With the centrifugal buoyancy dominating, the flow undergoes a transition from a 3D global flow structure to a quasi-2D one with a suppressed mixing in the vertical direction, where larger Ra-values require larger Fr-values for the transition. |
|
S01.00041: ABSTRACT WITHDRAWN
|
|
S01.00042: Pinch-off dynamics of nanobubble-dispersed suspensions Jonah Salvatore, Jiawen Song, Arindom Sen, Hossein Hejazi Nanobubble dispersions have unique properties, such as increased stability, enhanced mass transfer and slow-rising velocity. Droplets saturated with nanobubbles find applications in pulmonary drug delivery, water treatment, and agricultural technology. Although the droplet pinch-off for monodisperse, bidisperse and polydisperse particulate suspensions is well documented, the effect of incorporating micro- and nanoscale bubbles on liquid thread breakup, and thus droplet formation, is still unknown. Herein, we investigate the pinch-off dynamics of a water-glycerol-surfactant solution in a surrounding oil medium, before and after the addition of micro- and nanobubbles. We report a noticeable difference in the thread length at pinch-off, and how bubbles affect the filament breakup process. Unlike the accelerating effects of particles on neck thinning dynamics, our preliminary data indicates that micro- and nanobubbles slow down the thinning process. |
|
S01.00043: An Experimental Study on the Dynamic and Thermal Behaviors of Colloidal Droplet in a Freezing-Based Inkjet 3D Printing Method Xiaoxiao Zhang, Haipeng Zhang, Yang Liu Inkjet-based 3D printing is extensively utilized; however, this technology encounters several critical challenges, including coarse resolution, inadequate adhesion, and inconsistent manufacturing. A key factor contributing to these challenges is that the colloidal suspension droplets remain in a liquid state during the printing process. To overcome these limitations, we propose an innovative freezing-based sublimation 3D printing technology. Experiments will be conducted with both sessile and jetting droplets on a subfreezing substrate. The droplet dynamics and freezing process will be recorded using a high-speed imaging system, while temperature variations across the droplet diameter will be captured by an infrared thermal imaging system. Following freezing, the sample will be transferred to a freeze dryer for sublimation. Two thermodynamic processes have been designed to achieve sublimation: Process A involves a vacuum at a constant sub-freezing temperature, and Process B involves heating at a constant low pressure. In both processes, it is anticipated that the droplet will undergo sublimation successfully and continuously. The designed experiments and their results will analyze the mass and heat transfer during the freezing and sublimation processes, correlating the freezing rate and sublimation rate with various deposition morphologies. Through this comprehensive process, we aim to significantly enhance the stability and resolution quality of the printing. |
|
S01.00044: A Fundamental study of the dynamic and thermal behaviors of droplet interacting with plasma discharge MD Sohaib Bin Sarwar, Jorge Ahumada Lazo, Petr Lelikov, Yang Liu The study of the interaction between dielectric barrier discharge (DBD) and water droplet emphasizes the influence of plasma conditions on droplet behavior, providing insights for enhancing plasma-based technologies. This study investigates the interaction of surface and in-flight DBD plasma on water droplets, specifically examining changes in voltage-current (V-I) properties, flow characterization, and droplet shape. For the surface plasma, two PMMA plates, for in-flight plasma two glass plates were used as a powered electrode and ground electrode, and a droplet of water was released to impact the plasma surface. The analysis of the V-I behavior as well as the plasma emissions around the droplet, was considered for both plasma configurations. For surface DBD plasma, this analysis also involved the use of Schlieren visualization, infrared thermal imaging, and high-speed imaging to look at induced airflow, droplet evaporation, and thermal effects. On the other hand, in the case of in-flight plasma, High-speed images showed that droplets moving through plasma undergo considerable changes in shape and spreading dynamics. The droplets were dispersed above a DBD plasma reactor at varying altitudes to assess the effects of their impact on a hydrophobic surface, followed by a specific focus on droplet size, generation frequency, and trajectories. |
|
S01.00045: Thermocapillary flow of droplets on axisymmetric heated surfaces: A stability analysis Juan Manuel Gomba, Ramiro A Mansilla, Carlos A Perazzo This research examines the stability of a droplet situated at the center of a horizontal disk, which is subject to an axisymmetric thermal gradient that induces a stress at the liquid-air interface. We numerically the unsteady base flow and perturbations together as they evolve over time. The base state axisymetrically spreads, but its thickness transitions from a droplet to a ring, the front position and the maximum thickness following power law trends with time. We find that the perturbations travel at the same speed as the advancing front and develop their maxima near the contact line. Interestingly, the dominant wavenumber increases with time after a brief transient where all of the perturbations are stable, aligning with recent experimental observations on contact line motion in axial thermocapillary outward flow (Journal of Fluid Mechanics, 892, A8, 2020). |
|
S01.00046: Prediction of pinch-off height from dip-coated hydrophobic surface MD Erfanul Alam When an irregular solid shape is removed from a liquid, it causes a layer of fluid to adhere to the surface of the solid. After a droplet is generated, the ligament connecting the drop to the solid thins down and eventually pinches off. In this paper, we experimentally investigate the thinning and pinch-off of drops from dip-coated surfaces with different sizes of solids and liquids. The selection of system variables such as the velocity and surface area of the solid, viscosity and surface tension of the liquid modulates the appearance of a different pinch-off height. We predict pinch-off height due to the upward velocity of the solid using an ensemble learning algorithm comprised of four base algorithms. We train and test our algorithm with original experimental data. Our approach permits the determination of the relative importance of the input features in producing variation of pinch-off heights. |
|
S01.00047: Vaporization supression of aerodynamic drop breakup Sid BECKER, Yue Ling, Bradley Boyd Direct numerical simulation is used to investigate the vaporization of a freely moving liquid droplet in a uniform high-temperature gas stream. The geometric Volume-of-Fluid (VOF) method is used to track the sharp liquid-gas interface and The incompressible Navier-Stokes equations are solved in conjunction with a two-fluid model for the thermal energy advection and conduction, with an immersed Dirichlet boundary condition at the interface to implicitly account for the latent heat absorption. The open-source solver, Basilisk, is used to evaluate the model using adaptive quadtree/octree mesh for spatial discretization and that allows for adaptive mesh refinement of the region near the interface. A simulation is conducted of an acetone droplet at a moderate Weber number in which the drop deforms into a bag shape and experiences breakup. The rate of vaporization of the drop is then increased to study the influence of vaporization on the drop breakup behaviour. It is observed that by increasing the rate of vaporization, the breakup of the droplet is suppressed, making an otherwise unstable droplet stable. |
|
S01.00048: Spinning Twisted Ribbons Formed in the Corona Splash of Drop Impact on Liquid Film Yuan Liu, Jack Lo, Tariq Alghamdi, Muhammad Faheem Afzaal, Sigurdur T Thoroddsen When a liquid drop impacts a thin liquid film at high speed, it generates a thin corona sheet, followed by a splash. The thin corona sheet spontaneously ruptures, forming multiple holes as its thicknesses rapidly decreases. These ruptures result in many secondary droplets. In this study, we reveal an interesting underlying mechanism. We find that the ruptured sheet evolves into structures that resemble spinning twisted ribbons before the formation of ejecta. We develop a simple model to explain this phenomenon and validate it with experimental data. Our findings provide new insights into the mechanisms of splashing. |
|
S01.00049: Enhancing Hot Droplet Repellency of Superhydrophobic Surfaces by Adding Macrotextures Yang Yang, Naumi Noshin Chowdhury, Samira Shiri Superhydrophobic surfaces are known for their ability to repel water, minimizing contact time and reducing heat transfer from hot drops. However, drops that bounce on a superhydrophobic surface when warm can stick if they approach evaporation temperatures or the melting point of microtexture material. This phenomenon is likely due to evaporated vapor from the drop condensing on the solid surface, causing the drop to transition into a Wenzel state or surface to lose its roughness due to melting. This presents a challenge to identify materials or surface coatings that can overcome this limitation. In this research, we examine superhydrophobic surfaces modified with macro-textures that effectively split water drops into smaller droplets. By analyzing impact dynamics and heat transfer modifications, we aim to determine the surface topology that most effectively enhances the ability of superhydrophobic surfaces to repel hot drops. Understanding this can aid in developing materials that better prevent burns from scalding water. |
|
S01.00050: CFD Research on a Nozzle Inlet for a Hydrokinetic Power Generator Gedeon K Kabamba, Munyinda Mushala, Simeon Smith, Alan Chan, Zane Cox, Sabino Gonzalez Leon Hydrokinetic power generation is directly correlated with water flow velocity. Existing turbine designs primarily focus on deployment in high-velocity water currents. To enhance turbine performance, this research investigates the use of a nozzle or concentrator to increase inlet flow velocity. The nozzle design aims to maximize flow acceleration while minimizing downstream flow recirculation, which can negatively impact turbine wake development. |
|
S01.00051: Study and Investigation of behavior of Janus particles in different concentration KCl electrolytes mixed with glycerol Sandeep Ramteke, Jordan E Dehmel, Alicia Boymelgreen, Jarrod Edward Schiffbauer Previously, it has been demonstrated that in the presence of an electric field metallodielectric Janus particles exhibit distinct forward (dielectric hemisphere forward) and backward (metallic hemisphere facing forward) motion when subjected to low and high frequencies respectively. This behavior is significantly influenced by the concentration of potassium chloride (KCl) in the suspending solution, which affects the velocity magnitude and crossover frequency (where particles switch from forward to backward motion).
The addition of glycerol to the KCl electrolyte addresses the persistent issue of bubble formation within microfluidic chips. Due to the small scale of these devices, bubble formation can easily cause blockages that are difficult to remove. One effective strategy to minimize or eliminate bubble formation is the selection of fluids with very low gas solubility. Glycerol, known for its high viscosity and compact molecular structure, reduces the solubility and movement of gas molecules, thereby preventing bubble formation. Moreover, glycerol helps in preventing particles from sticking to the walls of the microfluidic channels.
In our study, we prepared a mixture consisting of 0.55 weight fraction of glycerol with KCl electrolytes of varying concentration and measure the mobility of the Janus particles under an AC electric field. It is shown that in accordance with previous work, the KCl electrolyte affects both the velocity magnitude and frequency dispersion of the Janus particles. At the same time, adhesion to the substrate and bubble formation are minimized.
|
|
S01.00052: Continuous Dielectrophoretic Molecular Separations Nicholas Burch, Nicholas A Mirra, Craig Snoeyink For over two decades dielectrophoretic forces have been used to trap proteins in a batch process. Here, we present a novel approach that permits continuous molecular separations using dielectrophoretic forces. A solution is flown through a microfluidic channel across which an electric field gradient is applied perpendicular to the flow. In aqueous solutions the solute is transported to the low-field side of the channel. Immediately following the electric field, the channel is split and the enriched solution (from the low field side) and the depleted fluid (high field side) are separated. In addition to detailing how the chip is fabricated we will present results showing the separations efficiency as a function of field strength. |
|
S01.00053: Model Turbine Design for Small-Scale Waste Heat Recovery Griffin L Heider, Bryan Lewis, Marcus E Anglin Waste heat recovery operations typically require at least 500 kW of waste heat. However, there is an large untapped potential for waist heat recovery at lower power levels. This study explored the design of a small gas/vapor turbine for waste heat recovery operation on the order of 5 kW. Steam and gas turbines are typically not designed for such low power applications. The volumetric flow rate, temperature, and pressure of an air compressor were measured to characterize a fluid flow, finding that air at 22 °C and 86 psi was available at a flow rate of 0.067 Lps. Similarity was implemented to determine a power output of a small model turbine that would produce 5 kW for a full prototype turbine. The model turbine was designed in SolidWorks and 3D printed. The inlet diameter used was 20 mm for the rotor casing and 10 mm for the rotor hub. An ideal Rankine cycle was used to determine the potential heat input needed for a 5 kW turbine to function properly. The costs and benefits were roughly estimated to determine if this small-scale heat loss recovery is viable and profitable. |
|
S01.00054: A Comprehensive Study of Heat Transfer Characteristics of Shallow Closed-Loop Geothermal Energy Systems Krishna Chaitanya V Nallacheruvu, Indrajit Chakraborthy, Vivek V Ranade, Matthias Vandichel Decarbonisation of heat is essential to reduce CO₂ emissions and can be achieved by utilizing clean and stable geothermal energy systems for building and space heating. This paper presents a comparative study on the heat transfer characteristics of two different shallow closed-loop ground heat exchangers (GHEs): a single vertical U-tube and a gravity-assisted thermosyphon heat pipe (THP). The study harnesses shallow geothermal energy resources. A heat transfer model using existing correlations of heat transfer coefficients investigates the thermal performance of these GHEs. For the U-tube GHE, an energy conservation model with sensible heat transfer evaluates the heat extraction rate using a single-phase fluid, water. For the THP, a phase change heat transfer model considers pool boiling, evaporation, and condensation using different working fluids (ammonia, propane, methanol, R134a). The model is validated with experimental data. The results, analyzed as the THP to U-tube heat extraction rate ratio, indicate that THPs with ammonia have a higher heat transfer rate due to phase change, compared to the U-tube system. This study aids in optimizing geothermal heat pipes, advancing sustainable energy technologies. |
|
S01.00055: Bio-inspired Floating Offshore Wind Turbine Foundations and Experimental Technquies to test the Foundations Harshit Agarwal, Owen Mecklem, Xiong (Bill) Yu With global climate change, our energy production has come under scrutiny. Deep water wind energy remains largely untapped despite availability of higher wind speeds, and therefore higher energy generation potential. Moving towards deeper waters requires the wind turbines to stand atop floating foundations. However, challenges remain to leapforward existing floating foundations to improve their stability, manufacturability, and fatigue durability. Therefore, this study explored bio-inspired designs of floating foundations to address these challenges. These included tree fractals, flower fractals, and honeycomb lattice structures. The stability and performance of these designs were tested in a tub of water with a box fan to simulate ocean and wind currents. The testing process aimed at evaluate the performance of bioinspired floating foundations (a) for stability: data from a multi-axis accelerometer, (b) for fatigue resilience: static load testing and (c) for ease of manufacturing: subjective analysis of the unit cells to assemble the overall floating foundation structure. From the experimental data, parameters in the areas of stability, redundancy, stiffness, isotropy, and load capacity for fatigue resilience were obtained to evaluate the multi-matrice performance. The optimal design can be selected based on a balanced consideration of multiple mechanical and wind energy production performance indicators. |
|
S01.00056: Event-Based Imaging Velocimetry for Dimensionality Reduction in Turbulent Flows Luca Franceschelli, Marco Raiola, Christian Willert, Stefano Discetti This study examines the use of neuromorphic event-based vision (EBV) cameras for low-order modeling to assess their potential for real-time flow control. We compare their performance to conventional Particle Image Velocimetry (PIV). A synchronized experiment using Event-Based Image Velocimetry (EBIV) and PIV was conducted on a submerged water jet flow at Re=2600. The findings show that EBIV provides comparable flow statistics and spectral content to PIV, despite higher noise levels in high-frequency regions (St>1.5). Proper Orthogonal Decomposition (POD) analysis revealed that EBIV effectively identifies dominant flow structures and spectral energy distribution, demonstrating its potential for applications in real-time flow control. Furthermore, a Low Order Reconstruction (LOR) study confirmed that EBIV provides comparable spatial and temporal bases to those of conventional PIV, with discrepancies below a few percentage points. The study underscores EBIV's promise for real-time, imaging-based flow control, advocating for dedicated data-processing frameworks to enhance measurement quality. Future work will focus on optimizing algorithms and exploring broader fluid dynamics applications, integrating EBV cameras into closed-loop control systems. |
|
S01.00057: Are marine glaciers melting quicker under ocean turbulence? Insights from homogeneous isotropic turbulence laboratory experiments. Muhammad Ahmad Mustafa, Alexander Zimmer, Chris Lai We present a set of simultaneous flow and temperature field measurements next to a melting vertical ice face. These experiments were done inside a 2.4m-by-1m-by-0.3m (L x H x W) water tank in which an ice block (1m tall, 0.3m wide and 0.075m thick) was placed at one end of the tank . A combined system of two-color LIF and planar PIV were used to measure the temperature and flow fields, respectively, at different heights of the ice block. Different background (ocean) turbulence levels were created inside the tank using the random-jet-array approach; 48 water bilge pumps arranged on a vertical grid were fired randomly in space and time. Our goal is to study the dependence of the background melt rate on the four parameters: (1) ambient temperature Ta, (2) ice temperature Tice, (3) turbulent intensity urms, and (4) integral length scale L. Further, we compare our measured data with the theoretical model suggested by Wells and Worster (2008, JFM). |
|
S01.00058: Real-Time Model-Based Reinforcement Learning for Active Flow Control on the NASA Hump Model Mason Lee, Jennna Eppink, Louis Edelman, Yao Chung-Sheng Active flow control (AFC) offers promising approaches for enhancing aerodynamic performance by manipulating flow structures. The NASA wall-mounted hump model, a benchmark for separated flow control, provides an ideal testbed for investigating AFC strategies. However, optimizing control parameters in complex flow regimes remains challenging due to the high-dimensional, nonlinear nature of fluid dynamics. |
|
S01.00059: ABSTRACT WITHDRAWN
|
|
S01.00060: Interfacial Instability in Couette-Poiseuille Flow of Two-Layer Viscoelastic Fluids Supriya Gupta, Paresh Chokshi Linear stability analysis of shear flow in two-layer viscoelastic fluids, modeled using the upper convected Maxwell (UCM) framework, is performed. The present study investigates plane Couette flow under low Reynolds number conditions, with and without an applied pressure gradient, to understand how differences in elastic properties affect interfacial stability. The numerical analysis spans a broad range of disturbance wavenumbers to construct a stability map based on fluid Weissenberg numbers, highlighting regions of interface stability. The study also considers the influence of pressure gradients on the stability of coating processes for optical fibers. Results show that adverse pressure gradients increase interface stability when the more elastic fluid is in the region of lower shear rates, while favorable pressure gradients enhance stability when the less viscous fluid has higher elasticity. Further analysis reveals that viscosity stratification, combined with elasticity differences, impacts stability, with adverse pressure gradients stabilizing interfaces when the more viscous fluid is more elastic, and favorable pressure gradients stabilizing interfaces when the less viscous fluid is more elastic. |
|
S01.00061: Hydrodynamic interactions between viscoelastic fluid and biomimetic cilia-like structures Arisa Yokokoji, Amy Q Shen In this research, we explore the mechanisms underlying the emergence of waves and elastic turbulence in a viscoelastic flow around a micropillar array that mimics ciliary structure. Recent investigations in our research group have uncovered intriguing wave patterns within the regime of canopy elastic turbulence. These wave patterns manifest within the viscoelastic fluids as they flow through microchannels containing micropillar arrays, closely mimicking ciliary structures. However, the origin of the wave patterns is still not well understood. Here we employed micro-particle imaging velocimetry (µ-PIV) and flow-induced birefringence to examine how the rheological properties of the fluid and geometric features of the ciliary structures, such as the number and density, affect the flow dynamics and the characteristics of wave patterns. This work could enhance knowledge of natural ciliary systems and microscale fluid-structure interactions. |
|
S01.00062: Blast wave induced flow and coaxial liquid jet interaction at the open end of a shock tube Saini Jatin Rao, Akhil Aravind, Saptarshi Basu Liquid interfaces interacting with high-speed gas (air) flows are prevalent in both natural and practical settings, resulting in unstable interfacial waves and atomization. This study investigates the flow field created by blast waves or unsteady shock waves at the shock tube exit and its interaction with a liquid jet, demonstrating primary atomization, which is important for efficient injection in combustors, engines, and high-throughput atomizers. A miniature shock tube using the wire-explosion method is used to generate blast waves, enabling a wide range of shock Mach numbers (1.1-1.8). The blast exiting the shock tube diffracts at the inner tube lip, causing the induced flow to roll up to form a compressible vortex ring with a trailing jet. A coaxial metal tube through this rectangular shock tube cavity with its opening just outside the tube exit is employed to maintain a liquid jet that interacts with this decaying flow field, depicting rich interfacial dynamics. The unstable waves of short wavelength are created on the fluid interface which then soon depicts a complex wave structure with wave breaking leading to a cascade of sheets, ligaments, and droplets. This is due to the significant shear generated by the early high-speed airflow, which subsequently decays, and waves with longer wavelengths grow and become more evident in the later stages, leading to a fishbone morphology. |
|
S01.00063: Exploring Hydrodynamic Flow-regulated Deformable Microfluidics for Nanoparticles Trapping and Release Xinye Chen, Ruo-Qian Wang, Ke Du Studying the regulation of hydrodynamic flow within a micro-/nanofluidic channel, in recent years, has been an attractive field and it could be beneficial for biomedical applications, such as cell or particle manipulation, nanotechnology, and optical sensing. The deformable microfluidic devices could be an excellent candidate for targeting a well-tunable micro-/nanoparticles trapping and release. Initially, we proposed a one-dimensional nano-sieve device 1, consisting of deformable polydimethylsiloxane (PDMS) layer and a narrow channel (~200 nm in thickness) on a glass substrate, to achieve the microparticles trapping and release by simply tunning the applied flow rate. A theoretical model was built to explore the fluid-structure interaction between the hydrodynamic flow and target particles, which reveals the mechanisms behind the experimental data, further predicting the capture efficiency within such a nano-sieve device. Leveraging the capacity of this nano-sieve system, we introduced a three-dimensional (3-D) beads-stacked microstructure to enhance the efficiency of capture and enable the concentration of target particles from bio-samples 2. The profile of stacked beads induced by hydrodynamic flow within the nano-sieve channel was investigated using computational fluid dynamics (CFD) model 2 and the theoretical model 3. This study could play a crucial role in optimizing next-generation deformable microfluidic devices, enhancing their efficiency in manipulating micro-/nanostructure. |
|
S01.00064: Multidimensional geometry of Riemann in theory of integration of the Navier-Stokes equations Valerii S Dryuma To integrate a system of Navier-Stokes equations, we consider an associated 14-dimensional space equipped with a Riemann metric, in which the Ricci tensor vanishes on the solutions of the system of equations. The metric belongs to the class of partially projective Riemannian spaces with scalar invariants equal to zero and is found in the theory of gravitational waves. E. Cartan invariants or classical Beltrami-Laplace invariants can be used to study metrics of this type. The geodesic lines of the introduced metric are solutions to a system of four second-order nonlinear ODES in coordinates (x,y,z,t) and four second-order linear ODES for dual coordinates (u,v,w,p) with coefficients depending on the components of the curvature tensor of the Riemann space. The six additive coordinates are flat and they form a configuration of six straight lines as geodesics. An important role in the theory of integration of the Navier—Stokes equations belongs to the conditions of their compatibility. They allow a geometric description based on the study of the properties of a six-dimensional space equipped with a Riemannian metric with special conditions for its components. The coordinates (x,y,z,t) and (u,v,w,p) are dual to each other, and their properties are determined by the geometry of spaces of normal projective connectivity by E. Cartan for the corresponding pair of coordinates. They form the basis of a geometric approach to integrating the Navier-Stokes equations into Euler or Lagrange variables by studying сorresponding metrics of four-dimensional or eight-dimensional Riemannian spaces. |
|
S01.00065: Characterization of Hurricane Boundary Layer Turbulence Kishore R Sathia Numerical simulations of hurricanes using models such as WRF rely on simple parameterizations of the boundary layer that do not resolve turbulence. Since observational studies of the hurricane boundary layer (HBL) are limited, high-fidelity numerical approaches such as large-eddy simulations (LES) provide a fruitful pathway to study HBL turbulence. However, the stringent resolution requirements of an LES make it computationally challenging to simulate an entire hurricane. Recent studies have suggested LES frameworks to simulate HBL turbulence outside the eyewall in smaller domains that take large-scale hurricane dynamics into account. In this work, we use the approach described in Momen et al. (2021) to generate a large database of HBL flows, programmatically varying input parameters such as radial distance, baroclinicity strength, surface roughness, etc., and analyze the sensitivity of flow statistics to these variations. The focus is on quantities that are of interest from a wind engineering perspective, analyzed using time-series and flux budgets. These include mean wind, second-order statistics, wind gust factors, and spectral flow characteristics. This work aims to develop improved mean wind and turbulence parameterizations for the evaluation of wind loads on structures. |
|
S01.00066: Modeling the Effect of Ocean Spray on the Vertical Enthalpy and Momentum Transport in Hurricanes with a Multi-Fluid Approach Yevgenii Rastigejev, Sergey A Suslov In-depth understanding and accurate modeling of air-sea heat, moisture, and momentum exchange is essential for reliable forecasting of hurricanes and severe tropical storms. These complex processes are influenced by factors such as wind speed, waves, and ocean spray. To describe the effect of ocean spray on the vertical fluxes, we have developed an Eulerian multifluid model of a hurricane's spray-laden marine atmospheric boundary layer (MABL). Unlike the mixture models traditionally used in this field, the multifluid model treats dry air, water vapor, and droplets of various sizes as separate interacting and interpenetrating turbulent continua. Each continuum is characterized by its velocity, temperature, and turbulent energy, and obeys mass, energy, and momentum conservation laws. Our findings reveal that the spray strongly affects important mechanical and thermodynamic characteristics of the hurricane’s MABL such as turbulence suppression rate, air-sea drag coefficient, wind speed, and magnitudes of heat fluxes. Furthermore, these spray effects depend sensitively on the droplet size and, consequently, on the droplet size distribution. We have demonstrated that predictions based on the multifluid model differ noticeably from those made using traditional mixture models. |
|
S01.00067: Anderson localization of oceanic waves in ice-covered seas Daniel Hallman, Norman Murphy, Kenneth Golden, Elena Cherkaev In recent years, there has been an increasing need to incorporate the interaction of oceanic waves with floating sea ice covers in order to significantly improve current Earth/climate models and predictions of seasonal sea ice evolution. In most climate models, simple power and exponential laws are assumed to describe the frequency-dependent wave attenuation that occurs as oceanic waves propagate further into the ice pack. However, it is becoming clear that these simplistic assumptions lack the fidelity to properly capture the vast complexity that actually occurs in Earth’s polar regions. The work presented here combines the mathematics of quantum mechanics with homogenization theory in order to establish broad and applicable relationships between the geometry of sea ice floes and the subsequent attenuation of oceanic waves. This is accomplished by analyzing the spectral statistics of real symmetric, random matrices which govern mechanical wave transport through viscoelastic composite materials. For certain geometric configurations of ice floes, we observe the hallmarks of Anderson localization - the spectral properties produce band gaps, mobility edges, and transitions toward universal statistics of the Gaussian orthogonal ensemble. |
|
S01.00068: Non-isothermal ice melting and hydrodynamics in waterbodies of varying salinity Zhukun Wang, Daisuke Noto, Douglas J Jerolmack, Hugo N Ulloa Understanding the exact mechanisms driving ice melting and the related convection in high-latitude marine and lake environments remains critical for assessing climate change impacts yet is challenging to examine. Previous laboratory research has focused mostly on investigating isothermal ice melting in both initially quiescent waters and background flows. Yet, the integration of the inside-ice temperature distribution has been so far ignored in experiments. Here, we report laboratory experiments designed to quantify the co-evolution of the non-isothermal ice melting and ambient hydrodynamics as a function of a salinity concentration, which is incremented from 0% to 4%. The ice-water interface evolution is tracked by imaged analysis, whereas the resulting buoyancy-driven flow is examined via particle image velocimetry. In particular, our results will illustrate the sensibility of the solid-liquid water dynamics to salt concentration and progress towards understanding ice-melting in sheltered shallow aquatic environments like nearshore marine regions and proglacial lakes. |
|
S01.00069: Internal Tide-Driven Mixing Above a Rough and Sloping Seafloor Chih-Lun Liu, Henri F Drake Turbulent mixing is a fundamental process in ocean dynamics, significantly affecting both stratification and circulation. A key component of this mixing is internal tide-driven mixing occurring over rough topography. To investigate the abyssal slope currents generated by tides without the influence of mesoscale eddies, we employ large eddy simulations (LES) with realistic topography from a rough canyon in the Brazil Basin. Our findings reveal a notable difference from previous theories and field campaigns, where upwelling was observed near the bottom boundary and downwelling above it. Instead, we simulated tidal-driven mixing that induces Eulerian mean downwelling within the bottom boundary layer and upwelling in the upper part of the boundary layer and the adjacent interior. The sloping seafloor facilitates restratification, which counterbalances fluid homogenization due to tidal-driven mixing. This interaction allows for the development of a non-transient flow and the potential onset of marginal instability. Internal waves break down into patches of turbulence, driven by mechanisms such as shear instability or convective instability. Our analysis indicates that the bulk mixing coefficient varies with depth and should not be treated as a constant. This depth-dependent variation is crucial for accurately modeling and understanding ocean mixing processes. |
|
S01.00070: GRAINS DISCHARGE EXPERIMENTS DUE TO A SUDDEN DEFLECTION OF AN ALASTIC GATE. DIEGO B GARCIA, Abraham Medina Ovando, Abel López Villa, Ronier Diez Barroso Abstract. |
|
S01.00071: Characterization of Lunar Regolith-Metal Powder Mixtures for Manufacturing in Space Ian Jones, Nadia Kouraytem With renewed interest in Lunar exploration, scientists are investigating the colonization of the moon. Building lunar habitats requires high strength materials and fast processing. The process of additive manufacturing (AM), colloquially known as 3D printing, is ideal for this approach. Utilizing in-situ materials represents an abundant resource for building with AM in space. One such material is lunar regolith, the loose powder material that covers the moon’s surface. |
|
S01.00072: Decelerative motion of a sphere rolling up a granular slope Takeshi Fukumoto, Ken Yamamoto, Makoto Katsura, Hiroaki Katsuragi Vehicles are sometimes getting stuck by the wheels spinning out on loose sand surfaces. To understand the fundamental aspect of spinning out occurrence, we carry out a set of simplified experiments. Previous studies investigated the dynamics of the sphere rolling down/on a granular surface. However, the decelerative dynamics of the sphere rolling up a granular slope have not been examined. Here, we experimentally investigate the dynamics of the sphere rolling up a granular slope to characterize its decelerative motion both in rolling and translational directions [Fukumoto et al., Phys. Rev. E 109, 014903 (2024)]. In this experiment, the radius of the spheres is 6.35 mm. The typical glass bead size is 0.8 mm. We vary the slope α (0°<α<20°), the density of the sphere ρs ( ρs=930, 1400, 2600, 3900, and 7900 kg/m3 ), and the initial velocity v0 (0.2 m/s < v0< 0.7 m/s) with which the sphere enters the granular slope. In some cases, when the translational motion halts, rolling remains. Namely, we can observe the stuck occurrence in this experiment. According to the experimental results, the dynamics of the translational and rolling motions show constant deceleration. Based on this observation, we estimate the friction coefficients in rolling and translational motions. As a result, the rolling friction coefficient can be regarded as a constant value. The translational friction coefficient is proportional to the sinking depth of the sphere, and this relation can be applied to the case of vehicles rolling on a terrain. |
|
S01.00073: Experimental Modeling of Pressure Dynamics through Compressed Air Network for Estimating Air Consumption and Predicting End-use Pressure Yohei Kono, Yoshinori Mochizuki This note addresses the modeling of a compressed air network system, which supplies compressed air from air compressors through a pipe network to end-use points. Compressors' discharge pressure is set according to the maximum air demand, implying that discharge pressure is unnecessarily high when end-use devices consume low volume of air. It is energy-efficient to reduce discharge pressure while keeping air pressure at end-use points at the minimum level necessary to drive the devices. |
|
S01.00074: Optimizing Metachronal Paddling with Reinforcement Learning Alana A Bailey, Robert D Guy Metachronal paddling is the rowing-like motion many aquatic creatures perform with their limbs to propel themselves forward in a fluid. Studies have shown that metachronal paddling is a consistently optimal swim stroke across a range of Reynold's numbers, yet the design mechanics of the paddling organisms differ; for example, the number of limbs, spacing of the limbs, and flexibility of limb joints may vary by species. Examining these trait variations is imperative to designing the optimal paddler for different ranges of Reynold's numbers, however, paddling simulations become computationally expensive with increasing degrees of freedom. To mitigate this challenge, we leverage a reinforcement learning (RL) approach to test different paddler designs in fast simulations in which the paddler self-learns the optimal swim stroke. To this end, we frame the paddling problem as a Markov decision process with state and action spaces representing a discretized version of a full paddle stroke. The reward for each state-action pair is defined as the net displacement of the paddler to incentivize forward motion. The reward values are computed using hydrodynamics simulations and the optimal strokes found through RL are then compared to traditional metachronal paddling strokes. |
|
S01.00075: Meta-Learning for Dynamic Stability Analysis of Atmospheric Entry Vehicles Shafi Al Salman Romeo, Furkan Oz, Ashraf Kassem, Omer San, Kursat Kara Entry, Descent, and Landing (EDL) is a critical stage of space missions, where atmospheric entry vehicles experience oscillations due to aerodynamic forces. Uncontrolled oscillations can lead to catastrophic outcomes, such as failed parachute deployment or tumbling. Hence, it is essential to understand the vehicle's dynamic stability characteristics during the design phase. However, identifying these stability coefficients with associated uncertainties in predictions is challenging due to the complex physics involved. This study proposes a meta-learning approach to estimate dynamic stability coefficients, integrating numerical and experimental datasets to enhance prediction accuracy. Our method involves: (i) reconstructing trajectories from sparse Ballistic Range (BR) data, (ii) fusing Free-Flight Computational Fluid Dynamics (FF-CFD) and BR data using meta-learning, (iii) estimating stability coefficients with the Markov Chain Monte Carlo (MCMC) method, and (iv) introducing a data source bias to ensure robustness. This approach reduces uncertainties and improves model generalization across different flow conditions, addressing limitations in both experimental and computational techniques. The results promise a more accurate, cost-effective method for dynamic stability analysis, contributing to a comprehensive aerodynamic database for atmospheric entry vehicles. |
|
S01.00076: Experimental Validation of Magnetohydrodynamic Force Affected Turbulent Seawater Boundary Layer Computational Fluid Dynamics Modelling Victor Baran, Thomas Chyczewski, Daniel Leonard Computational Fluid Dynamics (CFD) simulations of turbulent seawater boundary layers affected by a streamwise magnetohydrodynamic (MHD) body force are performed and validated using previously published experimental results. MHD devices pose as an effective solution for various seawater applications, primarily due to their lack of moving parts. However, the complexity and cost of the electromagnetic technologies within them makes developing and implementing MHD systems challenging. Additionally, the complex electromagnetic and hydrodynamic interactions make using simulation aids effectively more difficult. While MHD experimental and simulation literature exists, little has been done to validate CFD models for seawater flows with experimental data. CFD results are presented for steady-state turbulent seawater flow over a flat plate containing an array of MHD magnets and electrodes. Through the favorable comparison of boundary layer profiles, turbulence intensities, wall shear stresses, and electromagnetic fields between experimental and simulated results, the numerical MHD CFD models are validated. Due to the improved confidence in the simulation models, they can function as a more effective tool in the development and implementation of future MHD seawater systems. |
|
S01.00077: Machine Learning-Assisted Optimization of Magnetic Field Effects on Hydrogen Production in Water Electrolysis YEN-JU CHEN, Yan-Hom Li, Ching-Yao Chen Hydrogen production through water electrolysis has been a research topic of concern in recent years. However, hydrogen bubbles generated during the electrolysis process tend to adhere to the electrode plates for prolonged periods, resulting in ineffective electrolysis space and reduced efficiency. This study uses magnetohydrodynamics theory(MHD) and places magnets parallel to the external sides of the electrode plates to generate Lorentz forces on the electrode plates, thereby inducing flow in the electrolyzer to accelerate bubble detachment from the electrode surface, enhancing electrolysis efficiency. It has been proven that adding a magnetic field during water electrolysis can create vortices that effectively increase hydrogen production and improve electrolysis efficiency. Nevertheless, the optimal size ratio between the added magnetic field and the electrode plates for maximum electrolysis efficiency remains to be explored. |
|
S01.00078: Transport of Magnetic Particles Around a Magnetized Wire via a Combination of Experiments and Simulations Mohd B Khan, Jamel Ali, Theo Siegrist, Munir Humayun, Hadi Mohammadigoushki We study the interaction of magnetic particles with a non-uniform magnetic field around a single stainless-steel wire. The present study uses numerical simulations and experiments to investigate the transport of particles over a broad range of conditions: concentration of 0.01 ⩽ c ⩽ 0.1 g/lit, magnetic field of 0.25 - 1 T; and wire diameter 0.8 - 3.17 mm. Two types of nano-particles are studied including a paramagnetic manganese oxide and a diamagnetic Bismuth oxide. The experimental setup consists of a standard cuvette and a wire placed between the two poles of an electromagnet. Experiments show that the paramagnetic particles form vortices close to the wire under the magnetic field, where the magnetic field gradient is high, leading to particle enrichment near the wire. Additionally, as particle concentration increases, the magnetophoresis phenomenon is strengthened due to magnetic convection around the wire. Conversely, the diamagnetic particles are repelled from regions of high magnetic field gradients, resulting in their movement away from the wire. Due to gravitational forces, the diamagnetic particles move downward and settle at the bottom of the cuvette. Furthermore, we find that larger wire diameters enhance the separation process, leading to greater particle enrichment around the wire. This phenomenon occurs as a result of the magnetic gradient produced by the increased surface area of the wire. |
|
S01.00079: Parametric Instability of Arc-Polarized Alfvén Waves and Wave Packets in 1D Periodicand Open Systems Maile Marriott, Anna Tenerani Although Alfvén waves are an exact solution to the nonlinear magnetohydrodynamic (MHD) equations, they are subject to the parametric decay instability (PDI) at large amplitudes. Though PDI has been widely studied, few investigations have examined wave packets of finite size and the effect of different boundary conditions on the growth rate. From a linear analysis of circular and arc-polarized wave packets in periodic and open boundary systems, we find that both types of wave are 4-5 times more stable in open boundary conditions compared to periodic. Additionally, once the wave packet width $\ell$ becomes smaller than the system size L, the growth rate decreases with a power law $\ell$/L. We demonstrate that the growth rate of daughter waves depends on the conditions upstream and downstream the pump wave and on the fraction of volume it fills. Implications of our results for the interpretation of simulations, experiment, and solar wind observations are discussed. |
|
S01.00080: Thermoelectric response of liquid electrolyte in graphene nanochannel membranes Chih-Chang Chang, Wei-Hao Huang, Jing-En Huang, Ruey-Jen Yang Recent theoretical studies have suggested that the liquid electrolytes confined in nanofluidic channels exhibit a much higher ionic Seebeck coefficient than those in bulk. However, little experimental investigation has been conducted on this phenomenon, especially for electrolytes in sub-nanometer nanochannels reconstructed by the two-dimensional (2D) layered materials. In this study, we experimentally investigated the thermoelectric response of simple binary electrolytes, specifically KCl solution, in graphene oxide (GO) nanochannel membranes. The results showed that the ionic Seebeck coefficient with increasing the KCl concentration, and the largest negative ionic Seebeck coefficient of -0.4 mV/K was obtained at a KCl concentration of 0.1 mM. It was suggested that ionic thermoelectric response is dominated by the classical Soret-type thermodiffusion in the high KCl concentration regime, resulting in a small value of positive ionic Seebeck coefficient. However, in the low KCl concentration regime, as the electrical double layer (EDL) becomes thicker, ion diffusion driven by the temperature-dependent ion electrophoretic mobility (TDEIM) becomes a dominant, resulting in a large negative ionic Seebeck coefficient. The experimental results were shown to be qualitatively in agreement with numerical results based on the continuum model. In other words, the trend in the variation of ionic Seebeck coefficient with the electrolyte concentration ar consistent with the thermoelectricity theory of nanoconfined electrolytes proposed in recent literature. These findings may have implications for the development of nanofluidic-based thermoelectric generators using 2D materials in the future. |
|
S01.00081: Diffusiophoresis-Induced Rayleigh-Taylor Instability Lucas Bayer, Filipe H Henrique, Siamak Mirfendereski, Ankur Gupta Diffusiophoresis plays an important role in the transport of colloids in ionic solutions. Prior literature has demonstrated the utility of diffusiophoresis in membraneless water filtration, zeta-potential measurements, Turing patterns on vertebrate skin, and exclusion zone formation near ion exchange membranes. While preliminary results indicate that diffusiophoresis can induce Rayleigh-Taylor instabilities, a comprehensive analysis of such phenomena remains unexplored in the literature. Here, we conduct an integrated experimental and theoretical investigation to identify and isolate the mechanisms behind the formation of this instability. To this end, we build a vertical capillary device consisting of dissolved salt and a polystyrene suspension with an ion-exchange membrane. Due to concentration gradients, particles move diffusiophoretically, creating an exclusion zone and subsequently induce a Rayleigh-Taylor instability. We analyze images captured with a high-resolution camera and extract details of the exclusion zone as well as the instability. We also perform simulations using a classic Rayleigh-Taylor model where density variations arise due to banding induced by diffusiophoresis. Our work provides new insights into diffusiophoresis-induced instabilities, which might have been overlooked in systems with concentration gradients. |
|
S01.00082: Numerical investigation of the flow dynamics in a low-aspect ratio spiral microchannel Arash Ghasempour Farsani, George W Hitt, Roi Gurka Spiral microchannels have unique flow characteristics that make them applicable for chemical analysis, biomedical applications, and lab-on-a-chip technologies. The key feature of these channels is the complex interaction between centrifugal, inertial, and viscous forces. Dean instabilities arise from imbalances in shear-induced forces when an external force shifts the maximum velocity from the center to the concave wall, resulting in a sharp velocity gradient and increased pressure. Dean flow dynamics in these channels assume two counter-rotating vortices, a condition validated at low Reynolds numbers (Re<20). In this study, we numerically studied the incompressible steady laminar flow in a hybrid elements computational domain representing a low-aspect ratio spiral microchannel to examine the flow structure at a Reynolds number greater than 100. The simulation confirms the sinusoidal behavior of vorticity and the presence of two counter-rotating vortices. Additionally, by analyzing the change in the Dean number, we examined the adjusted pressure and velocity vector distributions due to the interaction of forces. Our study concludes that a high Reynolds number alone does not alter Dean vortices; it is necessary to examine its overall effect through the Dean number. |
|
S01.00083: Evaluation of heat flux around water vapor-rich microbubbles using quantitative phase imaging Seiji Fukuhara, Naoki Yasuda, Kyoko Namura, Motofumi Suzuki Water vapor-rich micro bubbles generated by local heating of degassed water induce strong convection [1], and the maximum flow speed around the bubble can reach 1 m/s. In this study, we measure flow velocity and temperature distributions around the bubble and evaluate the amount of heat transferred by the convection. By focusing a laser onto a FeSi2 thin films, we generated the bubble in degassed water. The flow velocity distributions around the bubble were obtained by observing the movement of polystyrene spheres suspended in the degassed water with a bright-field microscopy. Furthermore, the phase distribution of light transmitted through the water was measured using quantitative phase microscopy and converted into a temperature distribution, considering temperature-dependent changes in the refractive index of water. Comparison of flow velocity and temperature distributions revealed that hot water was jetting in a direction perpendicular to the substrate surface. Therefore, from those two distributions, we estimated the amount of the heat transferred by the convection. The results showed that about 3 mW was carried away by the convection, when the heat generation at the laser spot is 16.9 mW. Detailed evaluation such as a cooling efficiency per unit area will be explained in the presentation. |
|
S01.00084: Effect of water/ethanol mixture concentration on flow speed around microbubbles Mizuki Kato, Kyoko Namura, Motofumi Suzuki This study investigates how the ethanol concentration in water/ethanol mixtures affects the formation of vapor-rich bubbles and the surrounding flow speed. Bubbles were generated by local heating of FeSi2 thin films immersed in the water/ethanol mixture using a continuous wave laser. The results showed that vapor-rich microbubbles were generated stably in an ethanol concentration of 1.5–50 wt%, even though the mixture was not degassed. We found that air-rich bubbles with a diameter of approximately 1 µm were exhaled from the generated vapor-rich bubbles and the solutal-Marangoni force acting on these air-rich bubbles contributed to keep them away from the vapor-rich bubbles. Therefore, vapor-rich bubbles could exist stably without absorbing large amounts of air molecules. Furthermore, observations on the flow speed induced by vapor-rich bubbles revealed that the flow speed was higher at the ethanol concentration of 0–20 wt% than in degassed water. The maximum flow speed was achieved for an ethanol concentration of 5 wt%, which was 6–11 times higher than that when degassed water was utilized. This flow is expected to be applied to driving and agitating fluids in micro heat exchangers. |
|
S01.00085: Microfluidic Monodispersed Microbubble Generation for Cavitation Modeling Renjie NIng, yuan Gao Microbubbles, acting as cavitation nuclei, undergo cycles of expansion, contraction, and collapse. This collapse generates shockwaves, alters local shear forces, and increases local temperature. Cavitation causes severe changes in pressure and temperature, resulting in surface erosion. Shockwaves strip material from surfaces, forming pits and cracks. Prolonged cavitation reduces the mechanical strength and fatigue life of materials, potentially leading to failure. Controlling bubble size and generating monodispersed bubbles is crucial for accurately modeling cavitation phenomena. |
|
S01.00086: Adaptive Microchannel Heat Sink for Enhanced Thermal Management Using ThermoMechanoSensing Amin Isazadeh, Davide Ziviani, David E Claridge This study introduces an adaptive microchannel heat sink designed to dynamically alter channel geometry, reducing thermal and flow resistances while ensuring uniform surface temperature. Our evolutionary smart adaptive amorphous microchannel heat sink employs ThermoMechanoSensing, a novel technique that leverages material deformation under thermal and mechanical stress for real-time optimization. Channels are equipped with temperature sensors along their length, allowing for dynamic adjustments that improve temperature uniformity and hotspot control. This deformation acts as a flow modulator and creates dynamic microstructures, such as micro-fins and micro-cavities, enhancing heat dissipation. Additionally, a memristor-based sensor system records thermal stress and pressure oscillations, generating precise thermal maps for optimization algorithms. Our research includes extensive literature reviews, numerical simulations, and a comparative analysis with state-of-the-art designs, aiming to optimize flow distribution and surface structure. This innovative approach promises significant advancements in thermal management for various applications. |
|
S01.00087: Study on the Spray Characteristics of an Internal-mixing twin fluid Nozzle under Crossflow Conditions DONGGYUN NAM, DONG KIM This study investigates the spray characteristics of an internal-mixing twin-fluid nozzle in crossflow conditions, focusing on the effects of Air-to-Liquid mass ratio (ALR) using flow visualization techniques. The spray characteristics depend on the ALR and Reynolds number of crossflow. As the ALR decreased, the droplets did not receive sufficient energy for breakup, resulting in reduced atomization. Consequently, the penetration distance increased due to the momentum of larger droplets, and relatively higher velocity was observed in the spray core region compared to the crossflow velocity. To analyze the droplet size, droplet diameter with areas equivalent to the spray droplet regions and distribution were obtained in the shadowgraph images. Droplet sizes were measured according to the ALR, spray distance, and spray height. A higher ALR typically results in smaller droplets due to more efficient atomization. This study is significant because it provides detailed insights into the atomization processes of a jet in crossflow using a twin-fluid nozzle. By analyzing the effects of the ALR on spray characteristics, this study helps in understanding how different parameters influence droplet formation and behavior. This knowledge is crucial for optimizing industrial applications that utilize twin-fluid nozzles. |
|
S01.00088: Numerical and Experimental Study of Electrohydrodynamic Interactions in Two-Phase Flow under Constant and Transient Electric Fields Om Jagtap, Tanjina Akter, Katharina Stapelmann, Igor A Bolotnov The dynamic interactions between plasma and liquid media are pivotal for environmental and agricultural engineering advancements. The behavior of plasma within gas bubbles in a liquid environment is particularly promising for wastewater treatment and agriculture due to its ability to transfer reactive species to the liquid phase. This study bridges the gap between experimental observations and computational predictions of electrohydrodynamics. We have enhanced PHASTA (Parallel Hierarchical Adaptive Stabilized Transient Analysis), a FEM-based DNS solver, to simulate electric field interactions in two-phase flow scenarios. |
|
S01.00089: 4D Flow field measurements of air-entrained turbulent impinging water jets onto a quiescent water surface Sang Hwan Park, DONG KIM, Michael Chukwuemeka Ekwonu This paper presents a time-resolved three-dimensional flow field measurement of the continuous phase of a turbulent impinging jet using Lagrangian particle tracking velocimetry utilizing the Shake-The-Box algorithm. Time-series images of fluid tracer particles were acquired using systems equipped with four high-speed cameras. The Vortex-in-cell sharp method was used to reconstruct the Eulerian flow fields of the particle tracks. The impinging jet was characterized as plume-like along the vertical direction with two distinct layers: developing shear (recirculation zone) and fully developed shear. The buoyant bubbles influenced the streamwise vortex structures of the continuous phase. The results revealed high amplitude oscillations of acceleration and deceleration near the jet source, forming ring-like vortices that break down as the jet moves downstream with its momentum dissipated. The flow of the continuous phase of the impinging jet was self-similar at the developed shear layer and fully developed diffusion layer beneath the water pool and was characterized as homogeneous shear flow with anisotropy turbulence. |
|
S01.00090: Cavitation on Superhydrophobic Propellers John T Danby Cavitation characteristics are an important aspect of marine propeller performance. Cavitation caused by propellers is usually not desirable, and can cause pitting and erosion as well as unwanted noise. Altering the surface roughness on the propeller alters the cavitation dynamics. Experiments were done to characterize relative cavitation characteristics between one inch diameter superhydrophobic (SH) and smooth aluminum propellers. All propellers were polished, and SH surfaces were created by means of etching with sodium hypochlorite followed by treatment with hexadecyltrimethoxysilane. Propellers were placed in a water tunnel with low flow and rotated between 6000 and 20000 RPM. The propeller speed resulting in cavitation inception was found for each propeller. Cavitation inception is compared for both SH and non-SH propellers. Additionally, the location of cavitation inception at varied speeds was studied to determine the effect of SH surface treatment on propeller cavitation. Changes in torque coefficient between SH and non-SH propellers are also investigated as well as noise production. |
|
S01.00091: Axisymmetric Explosions in a Liquid Microjet Induced by Co-axial Nanosecond Laser Yanchu Liu, Qisheng Chen, Weiwei Deng We report an experimental investigation on the explosion of a liquid microjet induced by nanosecond laser. The jet is periodically perturbed by a piezoelectric actuator to generate highly controllable jet pinch-off. The laser is introduced co-axially and propagates through the liquid jet by total internal reflections. The pinch-off region serves as a light funnel to confine and concentrate the laser beam, and the optical power flux may exceed the threshold to induce plasmas and explosions. The explosive phenomenon evolves over four different time scales spanning from 10 ns to 100 μs. The growth of the explosion gap is logarithmic while the growth of the mist plume diameter is linear with respect to time, both of which can be described by a model relating plasma volume to absorbed energy. |
|
S01.00092: A Variant of 3D Lorenz Model under Gay-Lussac Approximation and its Dynamical Properties Caleb C Monoran, Sean R Breckling, Clifford E Watkins In this work, a variant of the well-known 3D Lorenz system is considered. The Lorenz system can be recovered from the Oberbeck-Boussinesq assumption applied to the 2D |
|
S01.00093: 3D computational simulations and mathematical modeling of non-Newtonian plug flow in straight and bifurcating capillary tubes Cory Hoi, Mehdi Raessi Liquid plug flow in capillary tubes is a classical problem in fluid mechanics with far reaching applications, especially in the medical field. Particularly, in surfactant replacement therapy (SRT), liquid plugs are instilled into the airway to treat preterm infants with respiratory distress syndrome. There is a growing body of literature dedicated to understanding the physics of targeted surfactant delivery, e.g., plug film deposition and plug splitting at bifurcations. However, most mathematical models and fluid simulation have only looked at the propagation of Newtonian plugs, when in practice, the surfactant used in SRT is of non-Newtonian behavior. To address this gap, we have developed a novel numerical method capable of capturing the complex interaction between a non-Newtonian fluid, Newtonian liquid, and gas. Using an in-house 3D flow solver and the Volume-of-Fluid framework, we simulate plug propagation and splitting at airway bifurcations. In addition, we quantify the asymmetry of plug splitting and compare the simulation results to a new mathematical model for non-Newtonian plugs. |
|
S01.00094: Dynamic Flow Behavior of Viscoelastic Fluids in Microfluidic Devices Mehdi Esmaeilpour In the natural world, intricate fluids are not only present but are also purposefully crafted for specific applications. This craftsmanship involves introducing macromolecules into a solvent, among other techniques, imparting viscoelasticity to the fluid. Viscoelasticity, a distinctive property of such fluids, leads to a myriad of flow instabilities and substantial alterations in fluid dynamics. These fluids belong to a category that exhibits both viscous and elastic characteristics. The modeling of viscoelastic fluids necessitates the formulation of constitutive equations for stress. Selecting the most fitting constitutive relationship can be a challenging task due to the nuanced nature of these fluids. Therefore, The focus of this study is the unsteady flow of Oldroyd-B and FENE-P viscoelastic fluid within a wavy microfluidic channel. A numerical analysis has been performed to study the combined effects of fluid elasticity and channel geometry parameters on flow characteristics, particularly at a low Reynolds number. The computations were carried out using the finite-volume-based open-source solver OpenFOAM®. The findings contribute to our understanding of the interplay between fluid properties and channel design in microfluidic systems. |
|
S01.00095: Numerical Study of Darcy Flow Through Porous Media Formed by Cylinders of Various Cross-Section Shapes Nathanael Hom, Benjamin Sam Savino, Wen Wu It is believed that the unique shape of shark dermal scales, known as denticles, is what gives a shark a hydrodynamic advantage against their underwater prey. A feature of the shark denticle that has been previously deemed irrelevant to hydrodynamics is the neck – a slender stem located beneath the crown. A recent DNS of a separating turbulent flow over shark denticles (Savino and Wu, arXiv:2403.14095), investigates the impact of the complete denticle, including the neck, on flow separation and drag reduction. The results show that denticles create microchannels between their necks, and a reverse pore flow (RPF) is formed in such porous cavity regions when the flow above is subjected to an adverse pressure gradient yet remains attached. This upstream-traveling RPF generates thrust, presenting a novel drag-reduction strategy. Among other features that enable the RPF and thrust, the non-circular cross-section of the denticle neck appears to favor the thrust generation. It possesses wide side bulges that enhance the pore flow shear and impaction; and a blunt front that potentially mitigate separation. The current research employs a 2D Darcy flow solver to predict the force generation capability of the pore flow. Various neck cross-section shapes, porosity, and Reynolds numbers are tested to explore the possible hydrodynamic advantages of the denticle neck. |
|
S01.00096: Predicting the pressure drop of gas-liquid flows through porous media Pranay P Nagrani, Amy M Marconnet, Ivan C. Christov Understanding gas-liquid flows through porous media such as packed-bed reactors (PBRs) under microgravity conditions is important for long-duration space journeys, specifically in designing life-support systems such as for water and air reclamation. These two-phase flows traverse the tortuous interstitial voids between the tightly packed solids comprising the PBR. Usually the liquid phase completely wets the solid packing, and hence, an Ergun-type correlation can be used for liquid-solid drag force, fls. The physics governing the gas-liquid interphase drag force, fgl, is complex, and coming up with a reduced-order description is more challenging. To this end, we start from a two-fluid model (TFM), assuming steady flow and uniform velocities. These assumptions allow us to rewrite the TFM with fgl as the unknown. Next, we leverage the pressure-drop data from NASA's microgravity packed-bed reactor experiment (PBRE) to fit the proposed 1D TFM formulation and obtain a correlation of fgl as a function of the gas and liquid Reynolds numbers, Regs and Rels, via composite fits. The developed correlation can then be used to predict the pressure drop of two-phase flow under microgravity conditions. We demonstrate its use by incorporating the proposed fgl(Regs,Rels) correlation into a 2D transient simulation of a two-phase flow through a PBR via an Euler-Euler formulation in ANSYS Fluent. The predicted pressure drop shows good agreement with the PBRE data. |
|
S01.00097: Elucidating Seismic Attenuation through Simulative Analysis of elastic wave in saturated rock Arka P Chattopadhyay, Mehdi Esmaeilpour, David Warner Seismic wave attenuation in rocks is predominantly influenced by fluid flow and mesoscopic losses generated by seismic activity. P-waves induce variations in fluid pressure at mesoscopic-scale inhomogeneities, larger than pore sizes but smaller than wavelengths, causing fluid movement and slow diffusion. In general, there are two detailed microscopic models of viscous dissipation: one for a highly elongate, partially fluid-filled crack, which achieves peak attenuation at seismic frequencies, and another for a moderately elongate, fully saturated pore, offering a more practical analysis approach and the focus of this work. Understanding elastic wave propagation in water-saturated porous media is crucial for various scientific and engineering applications. By integrating Darcy's law with Biot's theory of poroelasticity, we delve into the dynamic interactions between the solid matrix and pore fluid. Darcy's law introduces viscous damping due to fluid flow resistance, leading to energy dissipation and wave attenuation. Factors such as fluid properties, permeability, and wave frequency play a critical role in influencing wave velocity and modes, including compressional waves (P-waves) and shear waves (S-waves). This comprehensive analysis enhances the predictive capabilities regarding wave behavior in saturated porous media, driving advancements in fields such as geophysics, seismology, and civil engineering. |
|
S01.00098: Particle-resolved and Euler-Lagrange simulations of shock interaction with particle clusters using MFC Sam Briney, Thierry Daoud, Spencer H. Bryngelson, Thomas L Jackson, S Balachandar Shock propagation through a random distribution of particles is a problem of substantial importance in many engineering and environmental applications. In this work we compare the results of particle-resolved simulations performed with the exascale code MFC with companion Euler-Lagrange (EL) point-particle simulations. While the EL simulations are substantially cheaper their accuracy depends on the force coupling and Reynolds stress closure models being used. Here we use the state-of-the-art force model developed recently that includes quasi-steady, added-mass, and history force contributions to test its ability to reproduce the complex shock particle interactions observed in the particle-resolved simulations. The importance of simultaneous modeling of subgrid Reynolds stress closure is also investigated. |
|
S01.00099: Flame-driven subharmonic bifurcation in a multi-flame Rijke tube Yue Weng, Yihong Zhu, Abhishek Saha Studies on combustion instability have shown that thermoacoustic systems can exhibit a wide range of dynamics beyond periodic limit cycle oscillations. This is primarily due to the nonlinear interaction between the acoustic field and the unsteady heat release rate from reactive flows. Owing to its simplicity in design, the Rijke tube has been a popular setup for exploring dynamic states in thermoacoustic systems. Previous studies have demonstrated that simple Rijke tubes with laminar flames can exhibit quasi-periodic oscillations and chaos, though the underlying physics of these complex dynamics remains unresolved. Many of these studies have used multi-hole burners, which create several closely placed flames. In this study, we present an experimental investigation to assess the role of individual flame dynamics on the overall combustion dynamics observed when a multi-hole burner is placed inside a Rijke tube. Using a pressure sensor and high-speed Mie scattering imaging, we quantified and evaluated the individual flame shapes in a seven-hole burner and their relationships with the ensuing pressure time series. By utilizing hydrogen and methane premixed flames and varying the hydrogen percentages from low to high, we observed that the system transitions from periodic oscillations to quasi-periodic oscillations and finally to half-integer harmonics at higher hydrogen percentages, where the system exhibited both fundamental frequencies and half-integer frequencies. We will explain this behavior by analyzing the dynamics of closely packed flames in multi-hole burners. |
|
S01.00100: The Effect of Free-Stream Forcing on a Turbulent Boundary Layer Robert H Bryan, Vaishak Thiruvenkitam, Zheng Zhang, Ebenezer P Gnanamanickam This work investigated the interactions within a zero-pressure gradient turbulent boundary layer in the presence of free-stream external forcing. Controlled generation of energetic large-scale coherent structures was achieved by oscillating a NACA-0010 airfoil section of 8-inch chord length positioned at the entrance to a wind tunnel at mid-section height. This resulted in carefully controlled large-scale structures being introduced by free-stream perturbations. The amplitude and frequency of oscillation were independently varied, and the interactions within the resultant boundary layer were measured by means of a traversing hot-wire probe positioned about 3.0 m downstream of the trailing edge. Measurements were carried out at two friction Reynold’s numbers (Reτ) of approximately 1770 and 2500, respectively. The free-stream forcing was observed to have penetrated deep into the boundary layer as the flow developed downstream. The resultant energy spectra showed that this introduced scale reached the near-wall region. Hence, this method for generating controlled large-scale structures was found to be an effective technique to generate controllable, large-scale wall shear stress fluctuations. |
|
S01.00101: Measurement and Modeling of Optical Turbulence Through the Near-maritime Atmospheric Boundary Layer Toby J Davis, Cody J. Brownell, John Burkhardt, Charles Nelson
|
|
S01.00102: Application and Evaluation of Cognitive Search Algorithms for Pollutant Source Localization in Atmospheric Boundary Layer Flows: A Large Eddy Simulation-based Study Mahdi Farsi, Di Yang In the event of an accidental release of invisible harmful substances into the atmosphere, efficient tracing of the substance plume and quick identification of the source location are crucial for emergency response and hazard mitigation. Cognitive search algorithms are a category of search strategies that utilize information-theoretic rewards to optimally navigate a mobile sensor to the source location using sparse sensing cues along the way and sequential decision making under uncertainty. In this study, we demonstrate the applications of these cognitive search algorithms for pollutant source localization in atmospheric boundary layer turbulence using numerical simulations. In particular, a large-eddy simulation (LES) model is used to simulate the instantaneous flow velocity and pollutant concentration fields, using which the real-time progress of the source localization process of a mobile sensor (e.g., mounted on a drone) controlled by the cognitive search algorithms is simulated. This LES-based modeling framework allows for a comprehensive evaluation of various cognitive search algorithms under realistic environmental conditions. |
|
S01.00103: Investigating links between turbulence anisotropy and TKE budget by means of Large Eddy Simulations. Benjamin M Udina, Marc Calaf, Ivana Stiperski Monin-Obukhov Similarity Theory (MOST) is the workhorse for parametrizing first and second-order statistics in the atmospheric surface layer (ASL). First developed for homogeneous, stationary flows without subsidence. Later, it has been used for a wider range of flow conditions. However, it has been shown to break down in flows over complex topography and dense canopies. Recent developments have shown that turbulence anisotropy can be used to generalize MOST formulations for flows over all types of complex surface conditions. Additionally, MOST has been shown to work well in instances where a balance exists between turbulence production and dissipation. Thus, this work investigates the relation between production-dissipation imbalance and turbulence anisotropy in the ASL. For this, we use a suite of Large Eddy Simulations over different terrain configurations. Initial results indicate a relation between the anisotropy invariant yB and the imbalance in the TKE budget. A threshold value of yB ≈ 0.37 seems to separate between those instances in which the TKE imbalance is significant and positive from those in which it is close to zero. A considerable negative correlation is found between the decreasing percentage in the TKE residual and increasing anisotropy invariant yB. Finally, we investigate the meaning of the yB threshold value in relation to the return to isotropy and its meaning as a global scaling variable for first and second-order statistics of different turbulent flows. |
|
S01.00104: Scale interactions driving the nonlinear forcing and response in turbulent channel flow Yuting Huang, Beverley J McKeon In turbulence, non-linearity is essential for the transfer of energy between different scales, yet it remains a challenging part of our understanding and modeling efforts. This quadratic non-linearity is treated as forcing to the linear resolvent operator (McKeon and Sharma, JFM, 2010), and is studied in the Fourier domain, in which it becomes a convolution sum over all triadically compatible wavenumber-frequency triplets. These triadic interactions are dissected in this work to reveal the spatio-temporal nature of the interactions, by applying the linear resolvent operators to each pair of interacting triplets and quantifying the resulting contributions to the forcing and velocity fields. |
|
S01.00105: Characterization and Scaling of Pulsatile Helical Flow: An Experimental Investigation Sifat K Chowdhury, Yan Zhang Pulsatile helical flow is a prominent physiological characteristic in circulatory systems, including the heart, aorta, vessel bifurcations, umbilical cord, and respiratory systems. Helical patterns indicate healthy blood flow, offering benefits such as improved perfusion, reduced oscillating wall shear stress, and decreased energy loss. However, systematic characterization of these patterns is limited due to the lack of benchmark models. This study developed an experimental setup to observe laminar helical flow and its transition to turbulence across a range of Womersley numbers (Wo), Reynolds numbers (Re), and Pulsatility Indices (PI). Helical pipe models with physiological curvatures and torsions were incorporated into a closed flow loop with steady flow pumps and a programmable pulsating pump to maintain constant and oscillating velocity components. High-frequency pressure transducers and ultrasonic flow sensors recorded pressure and flow rates. Particle Image Velocimetry and Laser Doppler Velocimetry explored vortex flow characteristics along the helical tube, measuring helicity as a function of Wo, Re, and PI. Results suggest a reliable scaling law for global helicity, potentially allowing for quick, accurate estimation in clinical settings. Helical flow alters turbulence onset thresholds in pulsatile pipe flows. Understanding pulsatile helical flows provides insights and potentially leads to advancements in diagnosing and treating cardiovascular and respiratory diseases. |
|
S01.00106: Abstract Withdrawn
|
|
S01.00107: Free-Surface Proximity Effects on Flow-Induced Vibrations of a Flexible Circular Cylinder Alexis M Medeiros, Hadi Samsam-Khayani, Mostafa Khazaee Kuhpar, Banafsheh Seyed-Aghazadeh This research investigated the effect of free surface proximity on the flow-induced vibration (FIV) response of a flexible cylinder. Using water tunnel experiments, the study analyzed fluid-structure-surface interactions by varying the cylinder's submerged height. Digital image correlation (DIC) was employed to capture the dynamic response, focusing on the spanwise amplitude and frequency of oscillations. The system's response was examined across a wide range of flow velocities. Results indicated that for a fully submerged cylinder, increasing flow velocity led to transitions from low to high oscillation modes and the occurrence of lock-in regions for each excited mode. However, near the free surface, the system's response—regarding the onset of oscillations, excited modes, amplitudes, and frequencies—varied significantly, especially at higher reduced velocities where mode transitions occurred. Reduced submerged heights shifted the onset of instabilities to higher flow velocities, decreased oscillation amplitudes, and reduced the number of observed mode shapes across the tested flow velocity range. |
|
S01.00108: An experimental study of flow surrounding the migration of two forced-point-vortices. Yeojin Park, Khamis Ghaleb Al-Ghalayini, Giuseppe Di Labbio, Lyes Kadem, Hoi Dick Ng, Hamid Abderrahmane Vortex interaction and merging appear in several natural phenomena. This study explores the collision and merging of two point-like vortices generated by magnetic stirrers. These stirrers are independently operated by four motors and are located at the base of a shallow layer of water with a free surface. The objective is to identify the hydrodynamic conditions that result in the collision and merging of the two vortices, which have varying speeds and angular velocities. The study utilizes the Particle Image Velocimetry method to analyze the resulting flow patterns and comprehend the process of merging of the two vortices and the consequent flow dynamics. |
|
S01.00109: Abstract Withdrawn
|
|
S01.00110: Biomimetic Fluid Sensor for Detecting Frequency-Variable Hydrodynamic Footprints Bardia Salehi-Rad, Mostafa Khazaee Kuhpar, Hamed Samandari, Banafsheh Seyed-Aghazadeh Marine aquatic bodies move with varying speeds and directions, producing complex, frequency-rich hydrodynamic “footprints”. We introduce a novel class of biomimetic fluid sensors designed to detect and differentiate these complex flow features. The sensor system includes a harbor seal whisker-inspired module mounted on a multi-tuned mass-spring base, allowing it to undergo flow-induced vibrations, serving as the primary sensing mechanism. By positioning an object upstream from the whisker, we replicate the hydrodynamic footprints produced by aquatic bodies. Unlike traditional methods that use stationary cylinders to create simple vortex patterns as a footprint, our setup employs an upstream cylinder on a high-precision linear motor stage to generate dynamic, frequency-variable footprints that better mimic a range of aquatic footprints. Our water tunnel experiments show that this biomimetic sensor effectively captures and distinguishes between various dynamic flow features. Additionally, incorporating an extra degree of freedom through the multi-tuned mass-spring base design extends the sensor's flow velocity range, while structural nonlinearity further enhances sensitivity. |
|
S01.00111: Dye Visualization of a High-Angle-of-Attack Translating Wing Experiencing Ground Effect Ghali Ghassan G Anber, Matthew J Ringuette Ground effect (GE) happens when an aircraft flies near a lower boundary, increasing lift and lowering induced drag. At high angle of attack, the aircraft experiences unsteady flow due to vortices forming and shedding, substantially influencing lift. A small, maneuvering drone can experience flow separation and GE when above obstacles, and in real applications the ground length will be finite. This study uses a water towing tank with a translating, fixed-angle-of-attack wing and dye visualization to show the leading- and trailing-edge vortices and their interactions with finite ground obstacles. The tip-to-bottom-wall gap of the vertically-towed wing is small to help supress tip effects and simplify the interactions, and the grounds are rectangular. A gravity-feed system and small tubes on the wing deliver dye to the vortices, and dye is used to clearly show the ground interactions, via multiple colors. This project builds on the group's prior work which includes lift measurements and limited particle image velocimetry, for comparison and to form a more complete understanding of the interactions. The dye system is designed with minimum complexity to make it compatible with almost any setup in future studies. |
|
S01.00112: Toward Identification and Reconstruction of Vortical Structures Using Near-Wall Pressure Distribution Lamisa Musharrat, Saikishan Suryanarayanan It is well known that vortex cores are regions of low pressure; however, the influence of near-wall vortical structures on wall pressure is yet to be understood in adequate detail. Previous experimental observations suggest that there is a correlation between the wall pressure distribution and steady streamwise vortices near the wall, such as those produced by a vortex generator. Gaining a better understanding of this relationship is crucial for creating novel flow control solutions. We aim to extend the existing understanding to unsteady flow involving different kinds of vortical structures and explore the possibility of reconstructing a time-dependent vorticity field using only wall pressure measurements. Such a reconstruction would allow for precise targeting of specific vortical structures or mechanisms in technologically relevant scenarios, such as transition mitigation or stall alleviation. Direct numerical simulations are performed for a set of prototypical cases, including steady and unsteady streamwise vortices, a bluff body placed outside a laminar boundary layer, and roughness-induced transition. The effect of size, nature, and location of the vortical structure, unsteadiness, and the effect of wall shear on the pressure-vorticity relationship are analyzed. |
|
S01.00113: Ensemble Machine Learning and Synthetic Data Augmentation for Reliable Collision Prediction in Chaotic Advection Barath Sundaravadivelan, Alberto Scotti The ubiquitous random movement of particles within a deterministic flow field is known as chaotic advection. Due to its non-linear nature, predicting and validating chaotic advection models has been computationally expensive. |
|
S01.00114: Hamiltonian contour dynamics and applications Philip J Morrison, Glenn R Flierl It is known that contour dynamics (CD) can be viewed as a Hamiltonian system defined on a phase space of parameterization invariant functionals of closed curves [1-3]. This structure can be shown to follow from a general theory that reduces to both the noncanonical Hamiltonian structure of the two-dimensional Euler equations and CD. Generalizations to 2D and 3D quasigeostrophic systems also fit this general theory. This opens the way to use tools from Hamiltonian dynamics to interpret CD results. We will explore generalizations of the Kirchhoff vortex dynamics as integrable and non-integrable Hamiltonian systems, and Hamiltonian bifurcations. In addition, perturbation theory in terms of amplitude expansions for single and multi-contours will be discussed in several contexts including two contour barotropic instability and interactions between baroclinic and barotropic waves on a barotropic vortex. |
|
S01.00115: Developing Mesoscale Computational Models to Explore Hydrogel Friction Melodie Walla, Mehdi Karimi, Angela A Pitenis, Alexander Alexeev We develop a mesoscale computational model to investigate friction of polymeric hydrogels. Our model is based on dissipative particle dynamics (DPD). The gel is modeled as a network of randomly connected elastic filaments using the bead-spring approach. The gel is submerged in an explicit DPD solvent. We examine two configurations. In the first case, hydrogel slides over a flat plate, in which case no slip condition is imposed using bounce back procedure to the DPD bead crossing the solid boundary. In the second scenario, two gels move in opposing directions and slide along each other. To probe friction forces we vary the separation between the gel and the wall or between the gels and their relative velocity. We validate the model and apply it to examine friction of gels with different internal structure. |
|
S01.00116: Special Hydraulic Fractures: Cusps in a Hele-Shaw Cell and Dipoles during Extraction Zhong Zheng We first study the dynamics of hydraulic fracturing of an elastic solid in a Hele-Shaw cell. Compared with standard hydraulic fractures in an infinite elastic bulk (e.g., Spence & Sharp, 1985), the viscous resistance mainly comes from the drag by the two parallel plates that forms the Hele-Shaw cell rather than by the fluid-solid interface. Such a feature leads to a different nonlinear differential-integral system that describes the coupled evolution of the fracture shape and pressure field. Our theory leads to hydraulic fractures of cusp shapes in the neighbourhood of the fracture tip, which is consistent with recent experimental observations. Accordingly, there exists no pressure singularity at the location of the fracture tip, which is also fundamentally different from our previous understandings of hydraulic fracturing of elastic solids. |
|
S01.00117: Open-Source Thermodynamic Cycle Simulator: Interactive Analysis and Optimization Josue Melgar Gastelum, Bryan Lewis Presentation of a cycle simulator with an intuitive user interface. Designed with simplicity in mind, this tool allows users to easily simulate and analyze both individual machinery components and complete thermodynamic cycles. The simulator provides detailed insights into thermodynamic properties and efficiency metrics, making it an exceptional educational resource for students. Its straightforward interface and flexible configuration support comprehensive learning and experimentation, whether examining components in isolation or as part of an integrated system. This tool is particularly offers a simple yet powerful way to explore and optimize thermodynamic processes. |
|
S01.00118: Hydrodynamics of fossil ammonites: results of a Research Experience for Undergraduates Kathleen Ritterbush, Jaydon Anderson, Windy Martin, Quinn Purcell, Braxton Powell, Ethan Chase, Thomas James Ferril We present the framework of, and reflections on, a pilot Research Experience for Undergraduates focused on biomechanics in extinct ammonites (squid-like molluscs). We welcomed 5 students from Salt Lake Community College to the University of Utah for a 6-week course of immersive training in fossils, 3D modeling, and fundamental hydrostatics and hydrodynamics experimentation and simulation. Each student designed simple experiments to explore the locomotion trade-offs of ammonoid conch shapes. These seashell fossils record extensive shape variance through 400 Ma of global ocean system change. Students designed and 3D-printed ammonoid conch models that could achieve adjustable neutral buoyancy. By comparing the different models’ behavior in a swimming pool, each student tested an expected interaction between form and function, focusing chiefly on differences between conch geometry and ornamentation. Students also compared their observations to Computational Fluid Dynamics simulations in ANSYS fluent. Here, participants share their project results and broader lessons from the program. Funded by the National Science Foundation, this event shows the merits of inquiry-based experiential learning and is a baseline for an expanded annual REU Site. |
|
S01.00119: STUDENT POSTER COMPETITION: THEORETICAL/COMPUTATIONAL
|
|
S01.00120: Stability and visualization mechanism for spherical Couette flow 2-fold spiral state Isshin Arai, Kazuki Yoshikawa, Tomoaki Itano, Masako Sugihara-Seki Numerous studies have explored the flow of fluid within a sphere. Notably, spherical Couette flow (SCF), generated by the rotation of the inner sphere at a constant angular velocity and the outer sphere at rest within a fluid-filled concentric double spherical gap, has been linked to phenomena observed in celestial bodies and atmospheric dynamics. The primary parameters influencing SCF transitions include the radius ratio of the inner and outer spheres and the Reynolds number, which are known to determine transition route to various flow states, such as laminar basic flow, Taylor vortex flow, and turbulent flow. Among these transitional flows is the m-fold spiral state, characterized by an m-arm-like structure extending from the poles to the equatorial plane. Despite extensive research on these parameters, accurately mapping and reproducing the flow states has been remained a challenging issue due to the dependency of the transition on the hysteresis. |
|
S01.00121: Comparison of low and high-order data prolongation methods for two-dimensional flow Andras Bencze, Orkun Mert Ustun, Denis Aslangil Turbulent flows prescribed by Navier-Stokes equations are complex and highly nonlinear to solve numerically, and hence, large computing resources are required for accurate turbulent simulations. There are several strategies to reduce the computational costs of high-fidelity simulations of turbulent flows, and one of the widely used methods is Adaptive Mesh Refinement (AMR). AMR reduces the computational cost by dynamically refining the mesh resolution in the physics-rich regions to capture chaotic/turbulent structures, such as vortices and eddies while keeping the mesh in the rest of the domain at a relatively coarse level. However, during post-processing, it is beneficial to have solutions on a uniform grid, for example, to perform the Fourier Transform of different fluid fields. Thus, a data prolongation procedure of solutions obtained with an AMR grid onto a uniform grid is required. In this study, we explore the use of low- and high-order Lagrangian interpolation methods for projecting 2D Direct Numerical Simulation (DNS) solutions of compressible interfacial Rayleigh-Taylor Instability onto uniform grids. |
|
S01.00122: Turbulence-resolving simulations of frost buildup in a fin-and-tube heat exchanger Mahsan farzaneh, Nadim Zgheib, S A Sherif, S. Balachandar We present results from frost buildup on shell-and-tube heat exchangers under turbulent flow. This study investigates frost deposition and growth on staggered coil finned tubes within a heat exchanger for bulk Reynolds numbers of 60, 120, and 240. Our turbulence-resolving simulations are dynamically coupled, whereby we employ the immersed boundary method with direct forcing to account for the temporally evolving and spatially varying frost thickness and surface temperature on all surfaces. This is achieved by solving the mass and energy conservation for the frost phase. On the other hand, we solve the continuity, Navier-Stokes, energy, and mass conservation equations for the incompressible air phase. Our results indicate strong spatial variation in frost dynamics. More specifically, we observe the frost deposition to be largest on the fins than on the tubes. The frost is observed to grow at a rate that is two to times faster on the latter compared to the former. Similarly, we observe the frost surface temperature as well as the Nusselt and Sherwood numbers to follow the same trend with larger values on the fins than on the tubes. Finally, to make these simulations computationally feasible, we employ a slow-time acceleration technique to the slow frost phase whereby we accelerate its growth by a factor of 1000. |
|
S01.00123: Concept Design of a Large Water Tunnel Joseph U Improta |
|
S01.00124: Collective dynamics of coupled oscillator networks subjected to external forcing ZIZHUO LIN, Bo Yin, Larry K.B. Li Many natural and engineered flows behave as complex systems, characterized by collective phenomena emerging from interactions among their constituent parts. Such collective behavior, while difficult to predict through reductionist analysis, can offer practical benefits. We investigate oscillation quenching and synchronization in networks of Stuart-Landau oscillators interacting via time-delay coupling. By systematically varying the network topology and coupling parameters, we identify multiple collective states, including amplitude death, chimeras, and in-phase/anti-phase synchronization. Specifically, we find that amplitude death occurs most readily in ring networks with an odd number of non-identical oscillators. We further explore the combined effects of mutual coupling and external forcing by introducing time-periodic excitation of varying amplitudes and frequencies. Our results reveal that external forcing is more effective at weakening the self-excited oscillations in chain and star networks compared to ring networks. This research provides insights into the synergistic use of mutual coupling and external forcing to achieve specific collective states in networks of coupled limit-cycle oscillators, with potential applications in flow control and network dynamics. |
|
S01.00125: Modeling the Flow of Migrants through the US Southern Border Using a 2D Diffusion Equation Alexander Lipatov Migration remains a critical issue in contemporary society, with significant socio-economic and political implications. This study addresses the migration flow through the southern border of the United States by employing a two-dimensional (2D) diffusion equation model. The parameters of the model were calibrated using the most recent statistical data to reflect current migration trends. By solving the 2D diffusion equation, we were able to simulate the projections over the next 40 years, providing some insights into future migration dynamics. The findings from this study potentially offer a quantitative framework for policymakers to better understand and manage migration flows, thereby contributing to informed decision-making and strategic planning. |
|
S01.00126: Compressible flow over a heated sphere at Reynolds numbers 100 and 300 James Lu, Ahmet F Kula, Man Long Wong, Denis Aslangil We study flow over a heated sphere to investigate the effects of the temperature ratio (TR) between the free-stream flow and the surface of the heated sphere rigid body. We solve fully compressible Navier-Stokes equations, where the solid sphere geometry in the flow domain is represented by a second-order ghost cell immersed boundary method. In addition, we use a variable temperature-dependent (power-law with a power of 0.75) fluid transport coefficient model for the shear viscosity and a constant Prandtl number model for the thermal conductivity with the temperature-varying viscosity. Numerical simulations are carried out at Mach number 0.4 and Reynolds numbers 100 and 300, with TR values of 1.2 (low TR) and 3.0 (high TR). For validation purposes, fully adiabatic cases at these Reynolds numbers are also simulated and are shown to have good agreement with available experimental and numerical data. At Re 100, the flow is steady and axisymmetric for all investigated cases. However, at Re 300, the adiabatic case shows an unsteady flow, whereas for the high TR case, the flow stays steady and axisymmetric. This stabilization effect with an increase in TR is attributed to the larger viscosity coefficients in the vicinity of the sphere due to the increased temperature. Moreover, low and high TR cases lead to higher values for both the mean pressure and viscous drag coefficients compared to their adiabatic counterparts, with the changes becoming more prominent for the high TR cases. It is also observed that the TR effect on the mean wake recirculation length depends on the Re number. For example, at Re 100, compared to the adiabatic case, the recirculation length decreases with an increased TR, whereas at Re 300, it increases with TR. |
|
S01.00127: Studying transient granular flow in wedge-shaped hoppers. Afroz F Momin, Devang V Khakhar Granular materials consist of particulate particles found in industries that, behave macroscopically like liquids. A fundamental industrial unit operation is a hopper with a converging channel in which material flows downward under gravity and exits the storage bin through the bottom outlet. The simplest form of the flow is a wedge-shaped, quasi-two-dimensional geometry and radially directed gravitational force toward the apex of the wedge. To test existing theories and calculate stress and velocity fields for the system, we used discrete element method simulation. A parametric analysis is carried out to analyze the rheology by varying the hopper geometry and particle properties. The velocity increases as the flow rate increases but decreases as the wedge angle and friction coefficient increase. The studies were performed to examine the transient effects showing significant deviations from mean behaviour having large quasi-periodic oscillations making such deviations observable. The results show the utility of the transient effects to improve hopper flow as a model for the computational evaluation of rheological models. |
|
S01.00128: Separation of Intertwined Vortical Structures in Turbulent Channel Flow Using Contour Tree-Based Segmentation Zahra Poorshayegh, Adeel Zafar, Guoning Chen, Di Yang Vortices are fundamental to turbulent flow dynamics, often forming complex and intertwined configurations, especially at high Reynolds numbers. Traditional region-based vortex extraction methods (e.g., λ2, Q, λci, Rortex) are threshold-sensitive and struggle to differentiate individual vortices within intertwined vortical regions. Building on our previous work, where we developed a toolset for identifying and extracting individual vortices by exploring their spatial hierarchical representation and characterizing them based on their physical attributes (e.g., vorticity, enstrophy, velocity) and geometric information, we now employ a Contour Tree-based segmentation (CT) approach with an additional ‘layering’ step, aiming to improve the accuracy of separating vortices in complex regions. Traditional CTs utilize scalar field critical points for segmentation, which may overly separate vortices. To address this, we incorporate vorticity lines, to help determine whether two adjacent regions belong to one vortex or not. We demonstrate the effectiveness of our method by applying it to the Channel Flow DNS datasets from the Johns Hopkins Turbulence Database (JHTDB). |
|
S01.00129: Establishing Symbiosis in the Bobtail Squid Kyra Ruiz, stephen williams, Shilpa Khatri, Erica Rutter, Elizabeth Heath-Heckman Beneficial symbiosis, the partnering between organisms, is often vital for the survival of organisms. These relationships are often necessary for nutritional needs, environmental regulations, defensive mechanisms and much more. There is a growing interest in these relationships, with how they are established and the effects of changing climates. One example is the relationship between the bobtail squid, Euprymna scolopes (ES), and the bioluminescent bacteria, Vibrio fischeri (VF). The establishment of VF colonies within the squid allows the squid to have bioluminescent properties, making the squid able to camouflage itself in the dark. Many aspects of this colonization process have yet to be well understood. We are studying the fluid dynamics of the colonization of the bacteria within the squid. We use the Method of Regularized Stokeslets to develop a mathematical model and computational simulations to explore the fluid dynamics and the resulting colonization of VF within the squid. In addition, by varying different parameters, based on experimental data, we begin to understand the impact of external forces. With this, we have begun to evaluate how varying temperatures affect the symbiotic relationship of ES and VF. |
|
S01.00130: Bio-Inspired Turbine Blades for improved performance of Wind Turbines Smruthi Shashidhar, Pedram Tazraei, Shengbai Xie, Achyuth Rajendran, Yogiraj Deshpande, Daniel Lee, Kiran Bhaganagar Horizontal Axis Wind Turbines (HAWTs) have been used for decades as a source of renewable energy, but they come with their fair share of issues, such as their size, cost, and sensitivity to external conditions. In recent years, Vertical Axis Wind Turbines (VAWTs) have been created as an alternative to alleviate some of these issues, but they have some problems of their own. While they can operate over a wider range of conditions than HAWTs, they suffer from lower aerodynamic efficiency. To combat this issue, a blade model that mimics the shape of an albatross wing was considered, since their wings can deliver aerodynamic efficiency and maximize the lift to drag ratios. By using CAD modeling and fluid simulation modeling, it was possible to create and test the bioinspired blade against a normal straight VAWT blade and compare the differences in power production and efficiency. The TSR (tip speed ratio) will be plotted against the calculated power coefficient for the different types of blades, and by comparing the results it can be seen how modeling the blade shape after an albatross wing affects the data. |
|
S01.00131: The role of the diagnostic ultrasound intensity on pulmonary alveolus deformation Emma Slaght, Nazarii Koval, Avery Trevino, Mauro Rodriguez Focused diagnostic ultrasound, used for medical visualization of soft biological tissue, has been observed to generate harmful bioeffects such as hemorrhaging of the lung tissue. Prior 2D gas-liquid numerical simulations [Patterson and Johnsen, PRF (2018)] using a trapezoidal incident wave showed that hemorrhage may be induced due to vorticity-generated large perturbation growth at the interface. The hypothesis of this work is that the interface morphology-vorticity interaction can be dynamically modulated to safely use ultrasound waveforms and amplitudes outside recommended ranges and increase contrast. We perform 3D numerical simulations of the deformation of the lung tissue-alveolar interface due to the diagnostic ultrasound waveform and a model of the lung interface. We use the open-source Multicomponent Flow Code (MFC) [Radhakrishnan & Le Berre et al. Comp. Phys. Comm. (2024)] to examine the interface morphology for different wave frequencies and pressure amplitudes and their relationship with elasticity. Using a Fourier analysis, we present simulations using waveforms with different frequencies and pressure amplitudes that may inhibit interfacial instabilities that lead to rupture. |
|
S01.00132: Carotid Artery Blood Flow Patterns in Embolic Stroke of Undetermined Source Nathan Sudbury, Alexis Throop, Jeffery Weiss, Hediyeh Baradaran, Amirhossein Arzani Strokes without obvious cause are known as embolic strokes of undetermined source (ESUS). ESUS is currently defined as having both intracranial and extracranial arteries with less than 50% stenosis and lacking other identifiable causes. The uncertainty behind ESUS mechanisms challenges treatment and secondary stroke prevention. This study aims to use patient-specific computational fluid dynamics (CFD) to identify ESUS biomarkers. 3D computer models of the left and right carotid arteries for a cohort of ESUS patients and healthy subjects are constructed from CT scan data. CFD analysis is performed on each geometry to model pulsatile blood flow and study the hemodynamics. Quantitative and qualitative analysis is performed on the patients to identify hemodynamic biomarkers associated with stroke in a cross-sectional study. Standard wall shear stress (WSS) metrics and WSS topology are considered in the analysis. By integrating hemodynamic analysis with imaging data, our understanding of ESUS mechanisms can be improved enabling better clinical diagnostics. |
|
S01.00133: Turbulent Suspension Flows in Porous-Walled Duct Using Immersed Boundary Method Elmira Taheri, Abbas Moradi Bilondi, Marco Edoardo Rosti, Parisa Mirbod In this study, we employ Direct Numerical Simulations (DNS) combined with an immersed boundary method (IBM) to investigate the turbulent suspension flow of non-Brownian, non-colloidal, neutrally buoyant, rigid spherical particles in a duct with porous walls on all sides. We consider particle volume fractions (Φb) ranging from 0 to 20%, and the particles interact with but do not enter the porous layers. The porosity is constant at 0.6 while the permeability is varying. Our primary objective is to analyze how varying the permeability of the porous layers affects the dynamics of the suspension particles within a turbulent duct flow. The duct geometry leads to the formation of vorticities along the sides of the duct, which significantly influence the flow dynamics. On the other hand, increasing the particle volume fractions greatly enhances the turbulence activities throughout the duct. In addition, as wall permeability increases, the streamwise velocity intensity near the interface also rises, indicating that the slip velocity increases. This research provides insights into optimizing the design and operation of systems relevant to various engineering applications, such as filtration systems and biomedical flows. |
|
S01.00134: ABSTRACT WITHDRAWN
|
|
S01.00135: STUDENT POSTER COMPETITION: EXPERIMENTAL
|
|
S01.00136: Self-assembling and patterning of carbon nanotubes using solvent evaporation Yusaku Abe, Yu Matsuda Carbon nanotubes (CNTs) have been paid much attention because of their unique mechanical and electrical properties. Especially, field-effect transistors (FETs) of CNTs are expected to become semiconductor devices with high carrier mobility. However, difficulty of patterning billions of CNTs in desired position and fabricating of circuit patterns is still hindering the realization of EFTs of CNTs. In this study, we developed new patterning methods of CNTs by using self-assembly during solvent evaporation. CNTs have lyotropic liquid crystallinity in a certain condition. We realized fabrication of highly ordered structures of CNTs by utilizing liquid crystalline-derived spontaneous self-assembly. Additionally, we changed pattern structure of CNTs by optimizing initial concentration of CNTs solution and evaporation rate of solvent. Developed method can easily created the ordered structures by optimizing liquid crystallinity and evaporation behavior of CNTs solution; this method can contribute to the application of CNTs as innovative materials. |
|
S01.00137: Compound cavity formation and splash crown suppression by water entry through proximally adjacent polystyrene beads Sebastian Anzola, Freddy A Zeas, Korrie B Smith, Anthony A Cruz, Daren Antonio Watson We move forward the important topic of water entry by documenting splash dynamics arising from the impact of hydrophilic spheres with buoyant millimetric microplastics, mimicked in our study by polystyrene beads. Collision with small, buoyant beads is yet another means to manipulate splash dynamics. In this experimental study, we investigate the fluid-structure interactions between beads and hydrophilic spheres for Froude numbers in the range of 20-100. Generally, hydrophilic spheres entering a liquid bath below the critical velocity of 8 m/s produce minimal fluid displacement and no cavity formation. The presence of proximally adjacent beads atop the fluid with respect to impacting spheres promote flow separation and compound cavities for sufficiently large Froude numbers, while suppressing the growth of splash crowns. Compound cavities consist of a shallow, quasi-static first cavity that seals near the water line, and a second, deeper cavity produced in the wake of descending spheres. A vertically-protruding Worthington jet follows cavity collapse. The resulting splash metrics differ from those of cavity-producing spheres with respect to the properties of the impacted beads. We find impactors traversing a deep liquid pool layered with beads experience drag reduction when compared to entry into a clean pool due to the drag-reducing benefits of flow separation while not offering a high inertial penalty. Our study unravels the physics behind the widely encountered interaction of solid projectiles impacting passively floating particles and our results translate to the entry dynamics of water-diving creatures and projectiles into water bodies polluted by floating millimetric microplastics. |
|
S01.00138: Particle-Laden Flows: Erosion Experiments and Machine Learning Analysis Isaias Bahena Sahagun, Lane Ellisor, Jacob Riley Kathman, Claudia Falcon Understanding erosion is crucial for applications ranging from the effects on water streams and marine life to the damaging impacts on land and agriculture. Our research aims to understand erosion by studying particle laden flows and the effects it has on these particles over an incline. The experiments we ran included pouring oil mixed with particles over a particle bed of fixed mass on a ramp. The particle volume fraction in the oil was changed to study erosion effect under flows with varying particle concentration. Tracking these particles and fluid systems can be difficult, leading us to implement computer vision and machine learning tracking techniques to perform data analysis. The measurements include analyzing the front position of the eroded particles, the erosion amount, and the concentration of the eroded particles. Our results highlight the need of implementing time series analysis and performing particle image velocimetry analysis. |
|
S01.00139: The development of a low-cost system for measuring pressure fluctuations and transport over complex terrain. Ushanth S Balasuriya, Kelly Y Huang The presence of topography generates pressure perturbations, which in turn induces corresponding flow and scalar transport modulations. However, current models typically assume flat, homogeneous terrain which fails to capture the complexity of the flow caused by topography. This complexity also challenges the interpretation of tower measurements using eddy-covariance systems, which does not take into account the advective terms generated. Thus, to better understand and model flow over complex terrain, there is a need to accurately measure static pressure perturbations and pressure transport terms in the field. Here, we present a scalable, low-profile, low-cost system for quantifying pressure fluctuations using off-the-shelf components and a sonic anemometer. As a proof of concept, the system is deployed on the University of Houston campus to study variations in the turbulent kinetic energy budget with atmospheric stability. The presented system can be easily integrated into existing meteorological instruments, which will serve to enhance our understanding of atmospheric processes over complex terrain. |
|
S01.00140: Particle attraction to walls by diffusion induced stratified flows: experimentation Tyler J Britt, Roberto Camassa, Richard M McLaughlin, Saiful I Tamim We present experiments for a new phenomena in which particulate suspended in stable stratification are attracted to vertical walls. The mechanism originates from a broken symmetry in the diffusion induced stratified flow exterior to a sphere near a vertical wall which creates an effective force of attraction arising through the viscous stress tensor. This boundary layer behavior drives particles initially within one radius of the wall to collapse in finite time. Details of the experimental observations will be discussed and further contrasted with prior self-assembly phenomena which documented two spheres collapsing in finite time in a stratified water column (https://www.nature.com/articles/s41467-019-13643-y). |
|
S01.00141: An experimental and numerical study of the effect of venous valve morphology on flow conditions Jessica Burton, Branson Carter, Kylee Schramm, Matthew S Ballard Venous valves are critical components of the circulatory system. They work in tandem with skeletal muscles to help pump blood from the lower extremities back to the heart against the pull of gravity. However, venous valves are notedly the typical location where venous thromboembolism (VTE) originates. VTE, which includes both deep vein thrombosis (DVT) and pulmonary embolism (PE), is a leading cause of death in the United States. Here, we utilize experiments using silicone venous valve models and numerical simulations using a three-dimensional fluid-solid interaction (FSI) model to investigate the effect of valve morphology on disease-conducive flow conditions in the vicinity of the venous valve sinus. This study moves us toward an understanding of how patient-specific valve morphology affects their risk of disease. |
|
S01.00142: Formation and Characteristics of Liquid Bells Over Conical Angled Impactors. Daniel Carlson, Chase T Gabbard, Joshua B Bostwick A falling liquid jet striking a conical impactor forms a radially expanding sheet, resulting in a bell-like structure known as a Savart bell (Savart, F. 1833). Here, we experimentally investigate the shape and stability of liquid bells, as it depends upon the flow rate Q, impactor angle φ, and flow history. High-speed imaging was used to capture the bell shape over a range of impactor angles (0° to 25°) and jet flow rates (0 to 4.5 L/min). The Weber number (We) defines the flow with higher We producing large bells that can be sustained at significantly lower flow rates during a decreasing Q sweep leading to a wide range of shapes not observed during an increasing Q sweep. For example, the bell width exhibits a non-monotonic relationship with Q leading to multiple stable bells with the same height. |
|
S01.00143: Shark Inspired MAKO Surface for Steady Laminar Separation Control Jessie Laine Chiella, Amy W Lang, Katelyn Heglas, Andrew James Bonacci, Alexander G Alberson Shortfin mako sharks have incredible agility and speed and it has been discovered that their flexible scales play an important role in this ability, despite being only about 200 𝜇m in size. In the presence of reversing flow, their scales can passively bristle up to angles of 50 degrees and this bristling capability has been shown to help control separation in water tunnel testing of real shark skin samples. This study investigated whether a mako shark inspired 3D printed flexible scale model (designated MAKO model) could act as a passive flow control device to control laminar separation. A previous experiment done with real shark skin in laminar flow showed separation control and this study attempted to reproduce those results with the MAKO model. Laminar boundary layer separation and subsequent reversing flow was induced with an adverse pressure gradient (APG) that was generated by a rotating cylinder above a flat plate in a boundary layer for four different Re up to 4x105. DPIV was used to measure the flow for a baseline case over the smooth plate. The same method was also used over two different plates where the MAKO models, which had crown lengths of 2.4 mm and 3.6 mm, were embedded so the degree of flow separation could be compared between the cases. |
|
S01.00144: Spatiotemporal Transitions of Deposition Nucleation Sites in Fully Developed Turbulent Flow Kyle A Dalrymple, Matt T Gorman, Rui Ni In familiar applications, including engine fouling problems and in dust filtration technologies, electrostatic charges naturally accumulate on particles due to tribocharging. In multiphase flow, charged particles stick to a non-conducting surface during fully developed turbulent flow. This study investigates changes in the growth rate of nucleation sites as charged particles are preferentially deposited on a surface over time. Experiments were conducted in a vertical turbulence channel to observe charged particle deposition dynamics. It was observed that electrostatic and turbophoresis effects work synergistically and antagonistically to induce particle adhesion to the wall. Individual deposits were not stochastic, but rather formed characteristically distinct patterns at preferred nucleation sites. Preliminary results show that not only do deposit locations vary in their geometric profiles, i.e. their morphologies, but they also vary in spatiotemporal complexity. In the several growth phases that characterized the nucleation sites, it was observed that the leading edge grows and typically outpaces the erosion of the trailing edge, both taking place vertically against the direction of the flow. It is this overall growth rate that is the subject of this investigation. |
|
S01.00145: Co-Analysis Experimentation of Synchronous Fluid-Structure Modes Nick DiPatri Fluid-Structure Interactions (FSI) describe the interplay between movable or compliant solids and surrounding fluid environments. Experimental FSI problems have historically been addressed through individual analyses of the fluid and structural responses in isolation, creating challenges in correlating fluid flows with associated structural dynamics. |
|
S01.00146: Creation and demonstration of a biomimetic distributed microfluidic pumping system Fernando Duran, Matthew S Ballard Microfluidic systems are ubiquitous in biosensing applications. However, distributed pumping within microfluidic systems remains a difficult task. Fortunately, distributed pumping of fluids through small channels at low Reynolds number is a problem whose solution is present in biological systems such as lymphatic valves and venous valves. In this study, we create and demonstrate a scaled prototype of a microfluidic pumping system that uses flexible bileaflet valves to harness pressure gradients in the microchannel to provide for continuous passive flow of a viscous fluid. We discuss design improvements that enhance the ability of this system to function on wearable biosensors, and demonstrate the effect of these improvements on device functionality. This research moves us toward implementation of an inexpensive method of providing passive distributed pumping in microfluidic devices such as wearable biosensors. Further, this system can be used as a readily-controllable platform for the study of thrombosis in physiological venous valves. |
|
S01.00147: Bayesian Machine Learning for Experimental Optimization of Fish Schooling Kinematics Quinn Early, Elizabeth A Westfall, Yuanhang Zhu, Daniel B Quinn A Bayesian machine learning algorithm is used to find the position and kinematics that maximize the propulsive efficiency of the follower in a tandem heaving hydrofoil system. The propulsive efficiency of the trailing hydrofoil is affected by wake interactions that depend on foil spacing, phase offset, and heave frequency/amplitude. As the number of experimental variables increases, grid search methods become impractical due to the exponentially growing test permutations. Therefore, we integrate a Bayesian optimization routine with the hydrofoil actuation system to find the global efficiency maximum with fewer trials. For each iteration, the algorithm builds a Gaussian Process surrogate model from observed data and evaluates the conditions with the highest likelihood of improving the current estimate. Preliminary results indicate that the Bayesian method's estimates deviate only 1.5% from the maximum efficiency found with a direct grid search while sampling nearly 80% fewer conditions. Our work demonstrates the potential benefits of machine learning for revealing the optimal kinematics for fish schooling. |
|
S01.00148: Development of New Polymer Refractive Index Matched to Water Olivia J Falciani, Roberto Capanna, Jack E Brown, Nicole Conte, Stephen Boyes, Philippe M Bardet We discuss several options of materials that are refractive index-matched to water near room temperature. They are fluorine-based polymers, some are commercially available, while we are |
|
S01.00149: The Development and Testing of an Experimental Apparatus Used to Explore the Evolution of Soap Films Formed and Detached from Novel Silicon Wafer Frames Having Patterned Boundaries. Ethan Gray, Tuyetthuc Nguyen, Hans C. Mayer Motivation for the apparatus described in this poster stems from fundamental questions regarding along-the-edge instabilities of retracting liquid sheets: Instead of using a wire frame on which to form and detach soap films, is it possible to use a microfabricated silicon wafer allowing for the micropatterning of the frame edge to induce disturbances of known spatial wavelength onto the liquid film edge? Using this novel approach, can the growth and evolution of these modulated disturbances on the detached film edge be measured? Here we document the development and testing of an apparatus to answer these questions. The work was completed by three undergraduate student research teams. Our results show that 200 um thick silicon wafers can be fabricated via traditional semiconductor processing techniques to form frames with electrically conductive patterned edges. Secured using 3D printed holders, the wafers can be repeatably withdrawn from a bath to form soap films whose thickness can be measured locally and globally. Detachment of the films is caused by Joule heating of the frame edge, with synchronized cameras capturing the evolution of the detached film. Future work using this apparatus will address fundamental scientific questions. |
|
S01.00150: Experimental Study of the Underwater Shock Wave and Impact upon Non-Spherical Collapse of a Cavitation Bubble near the Combined Boundaries. Seiya Haranaga, Akihito Kiyama, Kotaro Sato, Donghyuk Kang Cavitation of liquid can occur when the liquid pressure becomes sufficiently small. It is well known that the cavitation bubbles can cause damage to the fluid machinery. Therefore, the bubble dynamics have been an important research topic for a long time. In particular, numerous studies have focused on understanding the behavior of bubbles near a single boundary (for example, a rigid wall, a free surface, an elastic boundary, etc.). In recent years, further research on the bubble dynamics near multiple boundaries have also been conducted. To provide a deeper understanding of how the cavitation bubble dynamics can be affected by the surrounding boundaries, we focus on the non-spherical collapse of a bubble under the influence of them. |
|
S01.00151: In vivo observations of salivary filament breakup inside human vocal cords Amirhossein Heidarzadeh, Samantha J Yan, Daniel J Cates, Harishankar Manikantan, William D Ristenpart We describe high-speed and stroboscopic videos using a laryngoscope (i.e., a camera inserted through the mouth or through the nose) to directly visualize human vocal folds during phonation. Our preliminary observations suggest that salivary filaments or ‘strings’ form and break during each oscillation of the vocal folds, with the approximate location of each new filament conserved between cycles. We designed custom image analysis software to quantify the dynamics of filament formation and breakup across several individuals. Based on these preliminary observations, we provide statistics of individual variation in filament formation and its dependence on vocalization loudness and frequency. We anticipate the insights gained from this research will reveal mechanisms of salivary droplet generation during phonation and enhance our understanding of airborne disease transmission. |
|
S01.00152: Flow Characteristics of Variant Models of Leading-Edge Serrations of Barn Owl Feathers James Kofi Arthur, Ben Hong Understanding flow around the leading-edge serrations of barn owls is crucial for developing low-noise fluid machinery. The aim of the study is to analyze the unique flow characteristics of model serrations mimicking geometries of leading-edge serrations positioned at various points along the length of a barn owl’s feather. Thus, the physical system is tested in an experimental facility consisting of a channel flume with models of 3D serrations of second-order approximations, installed in the channel. The serration profiles were taken from defined geometries of serrations noted at 40% (near the base), 60%, and 80% (near the tip) of the vane length. Each model was connected to a base plate. Particle image velocimetry was used to obtain velocity measurements of the open-channel turbulent flow around each model. The results show flow outcomes proportional to geometry-induced blockages. Consequently, the tendency for flow resolution to the free stream conditions is in the order of 80%, 60%, and 40% model inserts. Each model also registers similar maximum turbulence intensities at the root of the serration. However, by far, the 80% model limits the wall-normal penetration distance of any self-generated turbulent effect to just about 30% of its length. |
|
S01.00153: Measurement of density field in fluids using self-optimizable background oriented schlieren (BOS) technique with flexible dynamic range Ayumu Ishibashi, Sayaka Ichihara, Yoshiyuki Tagawa We developed self-pattern determinable background oriented schlieren (BOS) technique using projected pattern using a projector, which technique has a potential for adjusting the dynamic range for measuring various density fields, such as a turbulent flow and acoustic field. BOS can measure the density field only requiring a background pattern and a camera. With comparing two background images, i.e. one with targets and another without, displacement field related to the measurement target is calculated using displacement detection technique. Existing BOS measurement utilizes a fixed background pattern. Our new method optimizes the suitable background pattern generated by a projector, based on one distorted image in Fourier domain (k-space) in each experimental condition. Our proposed method was compared with previous BOS method and theoretical values. This novel technique could quantify the density field with flexible dynamic range which is optimized for the density field. |
|
S01.00154: Impact of Leaflet Geometry on the Acoustic Spectrum in Mimicking Aortic Stenosis Sofia Iturbide, Isolde Edson, Hayden Kozola, Clayton Byers The non-invasive detection of an obstruction in fluid flow systems has applications ranging widely, including determining the severity of heart diseases. A quantitative study of the effect of leaflet thickness of model aortic valves is performed through assessing characteristic acoustic frequencies and their interactions. In the model setup, the flow of blood through the aortic valve is simulated with a system using water and a pulsatile pump. Flexible leaflets modeled after the tricuspid aortic valve are 3D-printed to represent different restrictions. Dynamic similarity between the model and actual human heart flow conditions is established by matching Reynolds and Womersley numbers. The sounds produced by the flow through the leaflets are measured with a contact microphone, mimicking the function of an electronic stethoscope. The sound signals are then decomposed into energy spectra showing the energy content across frequencies. From the associated Fourier transform, the bicoherence is calculated to evaluate interactions between frequencies. These results are then compared with those of real heart sounds spanning healthy to severe cases of aortic stenosis. In both this study and the real data, enhanced high frequency content and lower coherence levels are shown to correlate with more severe restrictions. |
|
S01.00155: Effect of stiffness of the base on impact-induced liquid jet velocity Ishin Kikuchi, Yuto Yokoyama, Hiroaki Kusuno, Hiroya Watanabe, Kohei Yamagata, Yoshiyuki Tagawa Dropping a liquid-filled test tube onto various bases generates a focused liquid jet. This study aims to clarify the relationship between the stiffness of the base and the jet velocity. Previous research focused on finding that jet velocity is proportional to the gas-liquid interface velocity just before ejection and developing a model for jet velocity on a metal base. We measured the jet velocity for various bases with elastic modulus from 0.186 MPa to 206 GPa. For elastic modulus between 7.50 MPa and 206 GPa, the jet velocities agree with the values obtained from the model equation. However, when the elastic modulus was below 1.15 MPa, the jet velocities were up to 66% lower than the values obtained from the model equation, which does not account for the effects of the stiffness of the base. Assuming that the gas-liquid interface velocity depends on the impact velocity of the test tube, the elastic modulus of the base, and the density of the liquid-filled test tube, dimensional analysis revealed an intriguing finding: the jet velocity is determined by the ratio of the inertial force of the test tube filled with liquid to the elastic force of the bases. Furthermore, we could describe the jet velocity using a model equation that considers the effect of the base's elasticity by applying the Cauchy number, which represents the ratio of the inertial force to the elastic force. |
|
S01.00156: Axisymmetric stress field around a laser-induced bubble Shuta Kurihara, Sayaka Ichihara, Yoshiyuki Tagawa We measure the spatiotemporal stress field around a laser-induced bubble by using a photoelastic method. Stress measurements using Particle Image Velocimetry are difficult to calculate the stress due to the inability to track particles near the bubble. The photoelastic method estimates the applied stress from the anisotropic change in the refractive index (birefringence) in the material and allows us to measure the stress field. In the experiment, a laser-induced bubble was generated in a fluid with water and nano-rod crystals, and photographed with a high-speed polarization camera. By applying a reconstruction method that assumes an axisymmetric field (Yokoyama et al., Opt. Lasers Eng., 2024, Ichihara et al., Exp. Fluids, 2022) and a stress-optic law, a three-dimensional stress field was obtained from the photographed images. The results were compared with the theoretical stress distribution around the bubble. The proposed method can be used to measure the shear stress generated when a bubble collapses near a wall or interface. |
|
S01.00157: The effect of anisotropic permeability on the flow past structured porous square cylinders Byeongju Lee, Taehoon Kim When flow passes twodimensional porous cylinders, the downstream flow structure is altered by the mutual interplay between longitudinal and lateral bleedings. Based on previous studies with isotropic porous cylinders, the bleeding jets and the resulting downstream flow are dominated by cylinder permeability. To further understand the permeability effect on the flow characteristics of twodimensional porous cylinders, this study investigates the downstream flow pattern of anisotropic porous square cylinders with a periodic and scalable structure based on a simple cubic lattice. The cylinders were designed to exhibit different permeability in longitudinal and lateral directions by manipulating the number of struts on each side of the unit cell. A high resolution stereolithographic 3D printer was used to fabricate the porous cylinders. The downstream flow pattern behind the cylinder was visualized in the $x$-$y$ plane by performing particle-image velocimetry (PIV) measurements, utilizing two high-resolution PIV cameras in tandem to maximize the streamwise field of view (FOV). The Reynolds number, based on the cylinder diameter, was set to O(10^4). Experimental results were systematically analyzed along with the data from isotropic cases in the previous study. |
|
S01.00158: Measuring the free-swimming speed of a model bacterium Jonathan McCoy, Kathleen Margaret Brown, Frank Healy, Hoa Nguyen, Orrin Shindell, Bruce E Rodenborn The Trinity-Centre collaboration experimentally calibrates numerical models for use as a non-invasive probe to extract forces and torques on bacteria moving near a boundary. Low Reynolds number macroscopic models provide precision data for these calibrations as opposed to biological observations with large uncertainties. Our previous experiments measured forces and torques as a function of boundary distance for helices, cylinders, and spheres, so that we could accurately model bacilli and cocci bacteria such as Escherichia coli, Pseudomonas aeruginosa, and Rhodobacter sphaeroides. However, our experiments have considered each model body part separately. We have now created a simplified model of a rod-shaped bacterium with a counterrotating a cylindrical body and helical flagellum. We measure the axial force and torque while tuning the rotation rates and translation speed to ensure forces and torques on the model are approximately zero. We can thereby create a force-free/torque-free swimmer with the goal of measuring the free-swimming speed as a function of boundary distance. |
|
S01.00159: Measuring ocean waves with Saildrone uncrewed surface vehicles Keller R Morrison, Dongxiao Zhang, Chidong Zhang, Edward Cokelet Ocean surface waves generated by hurricanes can pose a major threat to coastal life, property, marine ecosystems, and the shipping industry. Since the 2021 hurricane season, NOAA/AOML and PMEL have partnered with Saildrone Inc. to deploy 5-12 Saildrone Uncrewed Surface Vehicles (USV) every year to measure the air-sea interaction processes under hurricanes to improve hurricane forecasts. To evaluate the capability of the USV saildrones in measuring waves, this project compares wave directional spectra observed by saildrones within 10 km of moored NOAA National Data Buoy Center (NDBC) and Coastal Data Information Program (CDIP) weather/wave buoys during the 2021–2023 Atlantic hurricane seasons. Raw 20-Hz GPS and inertial measurements from saildrones were used to calculate wave information such as dominant energy spectra, wave direction, wave height, and wave period using spectral analysis techniques first developed by Longuet-Higgins et al. The introduction of updated filters and physical checks to previous methods were created to account for saildrone's non-spherical geometry. Statistical comparisons between measurements from buoys and saildrones were then used to determine the reliability of saildrone wave measurements. It was demonstrated that Saildrone Explorer USVs are capable of measuring surface ocean waves with accuracy comparable to the moored surface buoys that are specifically designed for wave measurements. Unlike moored buoys, the remotely piloted USVs can provide in situ wave measurements at global scale and target extreme conditions in remote areas. This research contributes to wind-wave and air-sea interaction research through the development of the capability of Saildrone USVs to measure ocean surface waves. |
|
S01.00160: Simultaneous Measurements of Flow and Termperature Fields Near Melting Ice-Water Interface Muhammad Ahmad Mustafa, Alexander Zimmer, Chris Lai We present a laboratory setup and associate measurements on the melting of a vertical ice face under the influence of a subglacial 2D (line) buoyant jet discharge. This experimental configuration is relevant to sea-terminating glaciers in Greenland whose mass loss has been recognized as a major contributor to sea-level rise and climate change. Heat flux measurements near the melting ice-water interface are needed to link the melt rate and the properties of the 2D jet together. The technical challenge lies in obtaining resolved spatial-temporal flow and temperature data near the ice face. We have tackled this challenge by combining the techniques of two-color LIF and planar PIV inside a 1m-by-1m-by-0.3m water tank with an overflow weir for steady flow control. We report heat flux and melt rate data at three different heights of a 0.8m-tall ice block. Previous applications of the two-color LIF technique were limited to small experimental setups e.g. microchannels or cross-sections of size less than 10cm. This is mostly because of laser power atteunation through dyed water and the subsequent reduction in signal-to-noise (SNR) ratio. We demonstrate here that the technique can be sucessfully applied in experimental setups up to 1m by judiciously choosing the laser power, optics, individual dye concentrations, and the concentration ratio of the two dyes. We also show that the chosen fluorescent dyes survive freezing-melting cycles and both remain potent, enabling us to measure the temperature fields of melt water. |
|
S01.00161: A Simple Boundary Condition Regularization Strategy for Image-Velocimetry Based Pressure Field Reconstruction Connor Pryce, Lanyu Li, Jared P Whitehead, Zhao Pan We propose a very simple and low computational cost boundary condition regularization strategy to suppress error propagation in pressure field reconstruction from corrupted image velocimetry data (e.g., Particle Image Velocimetry or Lagrangian Particle Tracking). The key idea is to replace the canonical Neumann boundary conditions with derived Dirichlet ones obtained by integrating the tangential part of the pressure gradient along the boundaries. Rigorous analysis and numerical experiments justify the effectiveness of this technique and provide an estimate for when practicing this regularization is beneficial. Despite only showcasing a straightforward, yet long-overlooked, idea in the current work, this technique inspires a new family of boundary regularization strategies. The high flexibility of these strategies can be easily extended and adopted as an "add-on" to many other data assimilation, regularization, and machine-learning techniques for flow reconstruction. |
|
S01.00162: UAS Embeded Icing Sensor Hector Ramirez Zeigler, John Pippin, Alyssa S Avery As unmanned aircraft begin integration into the National Air Space (NAS), icing hazards for unmanned aircraft systems (UAS) and advanced air mobility (AAM) systems need to be explored. Icing accretion sensors currently in use on manned aircraft are prohibitive due to size, weight, power and cost requirements for SUAS. Additionally, the low velocity and low altitude regime change present different needs from an icing sensor. |
|
S01.00163: Experimental Design of ExB Probe Analysis of Radio-Frequency Ion Thruster Teagan Lynn Riedel, Hoban Carney, Tanner Tripoli, Richard Branam Electric propulsion technology expands current deep space travel capabilities in addition to providing station keeping and attitude adjustments. The production of multiply charged ions within the thruster plasma plume contributes to decreased thruster efficiency and accelerated grid erosion due to the elevated energy state of the ions. This study consisted of an experimental design for plasma plume characterization of Busek's BIT-3 RF Ion Thruster through the determination of the fractional composition of the ion species with an ExB probe. This research aims to validate the probe setup and gather plasma data for potential future investigations. Future research can utilize the experimental setup established in this study to determine the locations at which different ion species form within the plume, the mass constituents present, and appropriate correction factors for thruster efficiency calculations. |
|
S01.00164: Imbibition in gel-coated capillary tubes Matthew Santos, Trinh N Huynh, Emilie Dressaire The surface tension of a droplet can deform a soft solid, resulting in the formation of a wetting ridge around the contact line. As a result, the motion of a partially wetting drop on a soft visco-elastic gel can cause dissipation in the solid. To study the influence of a soft substrate on the imbibition of a partially wetting fluid, we produce capillary tubes coated with silicone gel. Depending on the thickness of the gel layer, the gel precursor is deposited on the inner wall by spin coating or high-speed rotation around the axis of the tube. We characterize the imbibition rate for different tube diameters, gel thicknesses, and fluid properties. Our results indicate two imbibition regimes: at low gel-thickness, the dissipation is negligible; at high gel-thickness, the gel deformation influences the motion of the contact line and the imbibition rate. |
|
S01.00165: Experimental and numerical analysis of the growth, detachment and coalescence of oxygen bubbles on the electrode surfaces in alkaline water electrolysis Yusuke Suzuki, Kohei Nakano, Kohei Sato, Ikuya Kinefuchi Alkaline water electrolysis has been attracting attention as a method of hydrogen production due to its cost-effectiveness and stability. One of the disadvantages of alkaline water electrolysis is low current density caused by oxygen bubbles evolving on the electrode surfaces. To improve the efficiency of alkaline water electrolysis, a better understanding of bubble behavior on the electrode surfaces, including bubble growth and detachment, is required. While several numerical simulations of bubble behavior have been reported, further investigation is needed to obtain appropriate boundary conditions on the electrode surfaces. In this study, bubble behavior on a nickel electrode in KOH aqueous solution was observed to gain insight into the boundary conditions on the electrode surfaces. We fabricated electrodes with widths of a sub-millimeter scale to observe the growth, detachment and coalescence of bubbles. The time evolution of the diameter, contact angle, and contact area of bubbles on the electrode surface were measured using a high-speed camera. Moreover, numerical simulations of bubble detachment on the electrode surfaces were performed and compared with the experimental results. |
|
S01.00166: Estimating the local effective eddy viscosity in non-Newtonian Taylor-Couette flow Akihide Takano, Yuji Tasaka, Yuichi Murai Recently, we have developed a novel method to quantify the momentum transport by eddies in turbulent flows for drag reduction studies using non-Newtonian fluid such as a bubble suspension and a polymer solution. The present method, termed eddy viscosity profiler, captures the effective eddy viscosity as a profile from the mean velocity profile. In the present method, we firstly measure the mean velocity profile obtained in the Taylor-Couette flow, then the obtained mean velocity profile is substituted to the equation of motion of mean flow, namely Raynolds averaged Navier-Stokes (RANS) equation. |
|
S01.00167: Stall prevention of an S1223 airfoil using passive bleed Cody Taysom, Matthew S Ballard The Selig 1223 airfoil (S1223) is a high-lift airfoil used to obtain short take-off and high load capacity of fixed-wing unmanned aerial vehicles (UAVs) operating at relatively low Reynolds number. However, this airfoil's susceptibility to boundary layer separation at lower Reynolds numbers limits its usefulness in smaller UAVs. Here, we investigate the use of a flow control technique known as passive bleed to prevent boundary layer separation at lower Reynolds numbers. We characterize the modified airfoil's lift coefficient at various angles of attack and values of Reynolds number, and compare this to the performance of an unmodified S1223 airfoil. Prevention of boundary layer separation can allow for the effective use of S1223 airfoils to give a high lift coefficient to wings of small UAVs. |
|
S01.00168: Visualization of motion of individual polymer inside porous media Naoki Tomioka, Yusaku Abe, Taiki Okamura, Yu Matsuda Porous media have microscopic pores and play important roles in industry, such as catalysts, adsorbents, and filters. In particular, understanding the movement of polymers inside porous media is important to design efficient membrane filters and drug delivery systems. In order to develop porous media with the desired property, it is important to directly measure individual polymer diffusion inside these media. Aggregation and dispersion of polymers inside porous media is a key role to design functional macromolecules. In this study, we investigated the motion of polymers inside porous media by developing a single polymer tracking method. In this method, we visualized individual polymers by using fluorescent labeled polymers and tracking these polymers by fluorescence microscopy. We focused on the relationship between the aggregation state of polymers and their diffusion properties. As a result, we visualized the motion of polymers inside porous media. By analyzing the movement of individual polymers, we found that the diffusion speed and type differ depending on the aggregation state. |
|
S01.00169: Enclosed Pressure Analysis for Diesel-Fuel Combustion Kade S Townsend, Reilly A Nash, Joshua Bittle Diesel engines rely on precise mixing of fuel and air in an already hot cylinder which leads to autoignition and the combustion process. A near perfect combustion efficiency is critical for enabling the engine to get the most force possible out of the available fuel energy. However, diesel fuels are so complex that inefficiencies often arise during the reactions that lead to incomplete combustion and pollution. This study investigates the ignition behavior of diesel-like fuels in order to better understand their behavior and support effects to minimize inefficiencies. Studying the ignition process separate from the injection and engine piston motion requires specialized combustion vessel equipment. In this work, a system that was previously custom designed as an improvement over an existing commercial system was fully commissioned and used to complete preliminary experiments. The system supplies fuel via an air-multiplying pump and single-hole fuel injector that sprays into a pressurized inconel-based combustion chamber, where an induction heater surrounding the chamber heats the metal and thereby the air mixture to combustion-level temperatures. As fuel is injected precisely to achieve a desired global equivalence ratio, the auto ignition process is captured with an oscilloscope that reads the injector current and chamber pressure change against relative time. This allows for the fuels to be characterized at different pressures, temperatures, and equivalence ratios for the ignition delay behavior. Three fuels were considered: n-heptane, iso-octane, and a 80% n-heptane/20% butyl-acetate blend. A temperature sweep from 625 K to 850 K was performed for each fuel at an equivalence ratio of 1.0 and a chamber pressure of 5 bar. With these parameters, iso-octane was found to be the least reactive fuel by a wide margin. Additionally, the same temperature sweep was conducted for n-heptane itself and the blend at a chamber pressure of 10 bar. This experiment found that increasing the chamber pressure shortened the delay. With the n-heptane/butyl acetate blend, the ignition delay was slightly increased but not enough to deter butyl acetate from being used as additive. Moreover, butyl acetate could be considered as a useful renewable fuel for diesel engines. |
|
S01.00170: Fire ants survive raindrop collision forces and dispersed by outspreading drops David A Vidana-Fuentes, Zamar C Joseph, Freddy A Zeas, Sebastian Anzola, Daren Antonio Watson Fire ants typically build colonies in large mounds found in open areas exposed to rain. Despite extensive studies showing the fire ants' ability to navigate flooded environments, researchers are yet to systematically investigate the survival of fire ants when impacted by raindrops. In this experimental study, we use high-speed videography to film drop impacts on fire ants and dynamically scaled spherical mimics. Drops impart compression forces, coat insects, and disperse upon direct contact. We show the fire ant's low mass and characteristic size rendering it impervious to raindrop collisions. Our study demonstrates that small land-based insects are robust to adverse weather conditions like rain. |
|
S01.00171: Elucidation of injection behavior into skin-simulating soft materials using an impact-induced liquid jet Kohei Yamagata, Hiroya Watanabe, Yuto Yokoyama, Shoto Sekiguchi, Yoshiyuki Tagawa The needle-free injection has attracted attention as an alternative technique to the needle injection. Laser-induced jets are expected to have a thin jet tip and cause less pain and have attracted attention as a minimally invasive needle-free injection technique. However, there are still some concerns including the large size of the laser equipment. To overcome the disadvantage of laser-induced liquid jets for needle-free injectors, we developed a high-speed focused liquid jet mechanism driven by an impact, which is called the impact-induced liquid jet mechanism. This mechanism is smaller than a laser-induced focused liquid jet. Injection experiments into soft materials simulating human tissues succeeded using the impact-induced liquid jet mechanism and it was confirmed that the injection depth was found to be explained by the Reynolds number and Elastic Froude number (the ratio between elasticity and inertia) by varying liquid viscosity, liquid jet diameter, jet velocity, and soft material hardness. Based on these results, The injection phenomena of a focused liquid jet by an impact-induced liquid jet mechanism can be evaluated using drugs with different viscosities and skin of different hardness for needle-free injection. |
|
S01.00172: Using a Powerful Subwoofer as an Ex Vivo Model for Droplet Formation in the Human Larynx Samantha J Yan, Amirhossein Heidarzadeh, Daniel J Cates, Harishankar Manikantan, William D Ristenpart Micron-scale aerosol droplets formed in the larynx and emitted while speaking are a primary vector for transmission of lower respiratory infections, but very little is known about the fluid mechanics underlying the formation of these droplets. A key challenge is the difficulty in directly visualizing the droplet formation within the larynx, so it is desirable to construct an artificial model that mimics how the vocal folds open and close rapidly (at 100 to 200 Hz) with large (millimeter-scale) amplitudes. Here we describe an experimental apparatus featuring a powerful subwoofer, of the type commonly used in ‘monster trucks,’ that provides the requisite operating conditions. High speed video reveals that saliva forms salivary filaments or ‘strings,’ that stretch and pinch off. We quantified their dynamics as a function of frequency and amplitude, and we identified regimes where so called ‘beads-on-a-string’ structures yielded droplet formation. The results provide insight into physiological differences that causes a subset of the human population to emit significantly more aerosols during speech. |
|
S01.00173: Managing Gas Bubble Dynamics in Proton Exchange Membrane Water Electrolyzers for Enhanced Hydrogen Production Sanaz Marefati, Mehdi Mortazavi The urgent need to address climate change and reduce carbon emissions has intensified interest in hydrogen production as a sustainable energy source. Proton Exchange Membrane Water Electrolysis (PEMWE) offers a clean method for generating high-purity hydrogen by electrochemically splitting water into hydrogen and oxygen, utilizing renewable energy sources. However, the accumulation of oxygen as a by-product obstructs reactant and product flow within the porous transport layer, leading to increased reaction overvoltages and electrolyte resistance. This phenomenon results in mass transport losses and diminished catalyst utilization, ultimately compromising cell performance. To advance PEMWE technology and broaden its applicability, developing effective bubble management strategies is crucial. This poster presents a review of gas bubble behavior in PEMWEs, including bubble formation, two-phase flow, and their effects on performance across various operating conditions. Recent advancements in both passive and active bubble management strategies aimed at mitigating performance losses are summarized. Finally, key scientific questions and future research directions in this area are identified. By improving our understanding of bubble dynamics and multiphase flow in PEMWEs, this work supports ongoing research efforts and provides a pathway for advancing PEMWEs as a commercially viable solution for green hydrogen production. |
|
S01.00174: Simulation of Fluid-Particle suspension using the Immersed Boundary Method AZIM BABU V MEMON, Devang V Khakhar, Krishnaswamy Nandakumar, Partha S Goswami The Immersed Boundary Method (IBM) is a numerical technique for simulating fluid-structure interactions. It handles complex solid-fluid interactions by embedding boundaries in a fluid domain and using interpolation for fluid forces. IBM finds applications in bioengineering, aerospace, and biomechanics, enabling the study of physiological processes, aerodynamics, and biomechanical interactions. With the aim to model such flows, this work proposed to extend the Signed Distance Function Immersed Boundary Method (sdfibm) developed by Chenguang [1], which is bases on OpenFOAM v6. The suggested pyramid decomposition approach and signed distance field representation of the solid shape enable precise calculation of the volume fraction field generated by solids overlapping with a random unstructured fluid mesh. The present work emphasizes on analyses of two-dimensional study of flow past a circular cylinder and three-dimensional simulation of flow past a sphere. The study is done at different Particle Reynolds number between 0.1 and 100. The work is also extended for suspension of particles to analyse the flow between the interstices between particles in the suspension. The Immersed Boundary Method algorithm developed by Shirgaokar [2], implemented in CFDEM opensource simulator is also explored to solve flow around single particle and suspension of particles. |
|
S01.00175: Excitation-Induced Droplet Removal in Shearing Gas Flow Amir Abdollahpour, Sung Yong Jung, Mehdi Mortazavi The dynamics of sessile droplets under shear gas flow are of significant interest across various applications. In this study, the behavior of droplet detachment under shear gas flow is investigated, with a focus on the oscillatory motions observed before detachment. The forces involved include drag from the shear gas flow, adhesion due to surface tension and contact line pinning, and inertial forces resulting from the droplet’s oscillation. To enhance the detachment process, the application of acoustic pressure waves was explored. Varying acoustic frequencies were applied in conjunction with shear gas flow, and an optimal frequency that minimizes the droplet’s area at detachment was identified. For example, at a shear gas velocity of 2.3 m/s, the |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2025 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700