Bulletin of the American Physical Society
66th Annual Meeting of the APS Division of Fluid Dynamics
Volume 58, Number 18
Sunday–Tuesday, November 24–26, 2013; Pittsburgh, Pennsylvania
Session 1A: Student Poster Session (6:15PM-7:00PM) |
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Room: South Terrace Foyer, 3rd Floor |
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1A.00001: ENERGY AND APPLICATIONS . [Preview Abstract] |
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1A.00002: The Study of a Liquid Droplet Falling Through Two Immiscible Layers of Liquids Bianca Mesa In an exploratory experiment, we noticed the unusual behaviors of liquid droplets falling through layers of oil and water. A rectangular container was filled with an aqueous solution and a layer of oil. A dropper was used to control the size of the droplet. Water was mixed with Bromothymol Blue dye, a chemical indicator, to visualize the flow processes. Surface tension and the buoyancy of the oil layer between the liquid droplet and the water below caused the liquid droplet to be stopped at the interface. Over time, the support weakened and the droplet would fall quickly through the water. The first of two cases was a salt water solution with NaOH, and the second consisted of balsamic vinegar and NaOH. Once the salt water droplet touched the aqueous solution, it collapsed, sank and spread rapidly at the interface. The sinking motion dragged the spreading fluid back to its center and then down. For the second case, a trace amount of the droplet spread rapidly at the interface while the main portion of the droplet sank and then spontaneously exploded. The difference in behavior is mainly due to the surface tension of the droplet in water. The underlying mechanisms of the droplet's flow instability are from the effects of diffusion weakening the surface tension. [Preview Abstract] |
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1A.00003: The Effect of Magnetic Fields on the Capture of Magnetic Nanoparticles Chelsea Fujinaka, Chris Brazel, Rhythm Shah It is hypothesized that magnetic nanoparticles may be used in active targeting cancer treatment by localizing the particles in the area of the tumor. To test this hypothesis static and electromagnetic fields were applied to a flow system, and UV-VIS spectroscopy was used to calculate the percentage of particles captured. Uncoated Maghemite nanopowder and FluidMAG-PAD (Chemicell) nanoparticles coated with polyacrylamide were used. Dynamic light scattering was used to look at particles size with and without proteins. Proteins caused the uncoated particles to aggregate. The static field captured approximately 15{\%} of the maghemite nanoparticles in water in a flowing at 0.1 mL/s when using two neodymium magnets laid lengthwise along 2 mm inner diameter tubing. The electromagnetic field pulled the uncoated particles out of the dispersion, but did not capture any in one place. The FluidMAG-PAD particles could not be pulled out of solution by the static field or the electromagnetic field. In order to effectively treat cancer, nanoparticles with a coating would have to be used to avoid opsonization and aggregation within the blood stream; however they cannot be so well dispersed as to not be affected by the magnetic field. The uncoated particles exhibited the capture desired, but do not interact well with proteins. A stronger magnetic field may allow the same capture of the coated particles, but it may also be important to look for a dispersion of nanoparticles not quite as well dispersed as the FluidMAG-PAD. [Preview Abstract] |
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1A.00004: Using Thermo-Responsive, Fiber-filled Gels to Control Droplet Motion Gerald McFarlin IV, Xin Yong, Olga Kuksenok, Anna Balazs Using a polymeric gel and elastic fibers, we design a thermo-responsive composite film that can be harnessed to manipulate the droplet motion in microfluidic devices. At low temperatures, the fibers are hidden and unable to interact with external fluid. At higher temperatures, the gel shrinks and exposes the fibers to the external solution; hence the exposed fibers can be utilized to hinder the motion of fluid-driven droplets on the film surface. We use dissipative particle dynamics (DPD) to model our system. We construct the gel in a coarse-grained manner by crosslinking polymer chains. We examine the volume phase transition and swelling kinetics of the gel in explicit solvents and validate our model through comparisons with Flory-Huggins theory. During simulations, a hydrophobic droplet is introduced to the outer solvent and driven over the film surface by an external flow. We focus on the effects of the imposed flow, temperature variations, and droplet-fiber interactions on the droplet's motion. We show that by varying the temperature of the system, we can program the film to interact with the droplet in a well-controlled manner. Our findings reveal how nanofibers can be used to enhance the properties of thermo-responsive gel coatings. [Preview Abstract] |
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1A.00005: Effective Collecting Method of Volatile Organic Compounds in Water by Bubbling Hitoshi Kida, Hayato Hori, Yuzo Nonoguchi, Masaharu Kameda, Ryoichi Sato A technique is proposed to improve the collection efficiency of a small amount of volatile organic compounds in the gas by impinger, which is generally used as gas collection device for analysis. Eugenol was used as a simulated substance of explosives. The sample gas containing specific amount of eugenol was collected in pure water by the impinger. The concentration of eugenol in water was measured by gas chromatography. The experimental results shows that the collection efficiency of eugenol by the impinger increased as the water level (volume) increased. The bubble motion in the impinger observed by high-speed photography indicates that the averaged values of equivalent diameter and rising velocity of bubbles were reduced as the water level increased. This reduction yields the increase of the resident time of bubble per unit volume of water, which enhances the dissolution of eugenol. On the basis of these characteristics, small glass beads were stuffed into the impimger to increase the resident time per unit volume. The collection efficiency was improved by stuffing the glass beads. Now we test the odorant binding protein as additive for further improvement of collection efficiency. [Preview Abstract] |
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1A.00006: Electrospray of Solution Processed Nanomaterials Nicholas Brown, Paul Chiarot Electrospray is a technique that uses large electric fields to generate a spray of highly-charged, monodispersed droplets from a liquid solvent. Colloidal inks, consisting of nanoparticles dispersed in a volatile solvent, can be atomized using electrospray. In this study, we investigate the deposit structure of nanoparticle inks printed onto three different substrates: bare glass, silanized-patterned glass, and glass coated with a liquid film. The deposition morphology of colloidal inks printed onto these surfaces is predicted using mathematical modeling and statistical analysis. The goal of intervening at the substrate with surface patterns and liquid films is to exert control over the microstructure of the printed deposit. The advantage of electrospray is that it is an additive process which drastically reduces material waste that is inherent in other thin-film material processes. [Preview Abstract] |
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1A.00007: International Senior Design Service Learning Project: Creating a Water System for Kuna Nega in Panama City, Panama Dan Budny International service-learning projects are an effective educational tool for universities striving to meet the ABET engineering criterion, while also providing transformational experiences to their students and a service to needy populations in the world. This student poster discusses the benefits of an international service-learning project in Panama City, Panama. The presentation will discuss the design and installation of a water distribution system including a two pressure system, two ground storage tanks, a pump station and the various control systems to fill the tanks. To meet the water demand with the limited supply additional individual rain water collection systems were also installed at individual houses to provide a gray water system for bathing. The year-long process of development design and construction will be described and how it fits within the Swanson School of Engineering Department of Civil Engineering senior design course. This project was a collaboration between the senior design course, and a local chapter of Engineers Without Borders. [Preview Abstract] |
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1A.00008: Aerodynamics Simulations for the D8 ``Double Bubble'' Aircraft Using the LAVA Unstructured Solver Sean Ballinger The D8 ``double bubble'' is a proposed design for quieter and more efficient domestic passenger aircraft of the Boeing 737 class. It features boundary layer-ingesting engines located under a non-load-bearing $\pi$-tail and a lightweight low-sweep wing for flight around Mach 0.7. The D8's wide lifting body is expected to supply 15\% of its total lift, while a Boeing 737's fuselage contributes only 8\%. The tapering rear of the fuselage is also predicted to experience a negative moment resulting in positive pitch, produce a thicker boundary layer for ingestion by distortion-tolerant engines, and act as a noise shield. To investigate these predictions, unstructured grids generated over a fine surface triangulation using Star-CCM+ are used to model the unpowered D8 with flow conditions mimicking those in the MIT Wright brothers wind tunnel at angles of attack from $-2$ to 14 degrees. LAVA, the recently developed Launch Ascent and Vehicle Aerodynamics solver, is used to carry out simulations on an unstructured grid. The results are compared to wind tunnel data, and to data from structured grid simulations using the LAVA, Overflow, and Cart3D solvers. [Preview Abstract] |
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1A.00009: Improving wind turbine array efficiency through active flow control John-Michael Velarde, Guannan Wang, Patrick Shea, Mark Glauser, Luciano Castillo We attempted to demonstrate the capability of instrumenting three wind turbine blades with an air delivery system that provided active flow control in an effort to improve turbine performance in the presence of the wake turbulence that is inherent in a turbine array. Presently, turbines are being designed for set conditions, such as steady incoming wind and a set velocity profile, however conditions can be drastically different in the field -- thus causing poor performance from the turbines. The blades were instrumented with pressure transducers which measured the suction surface pressure; the sensor setup was such that three unique blade configurations existed: spanwise sensors, chord-wise sensors, and a reference sensor. The compressed air was delivered through a rotary union connected to the turbine hub with tubing attached to the suction side of the blades. The primary purpose of this test was to demonstrate the ability to deliver air to a rotating frame for active flow control. We collected data under three test conditions using an open-section wind tunnel, courtesy of Texas Tech University: static with no flow control, rotation with no flow control, and rotation with active flow control. [Preview Abstract] |
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1A.00010: Optimal Hydrofoil Kinematics for Tidal Energy Extraction Sarah Frank, Shreyas Mandre, Jennifer Franck The pitch and heave kinematics of an oscillating hydrofoil are explored for tidal energy extraction using 2D Direct Numerical Simulation in a non-inertial reference frame. The hydrofoil is modeled by an ellipse of aspect ratio 10 at a Reynolds number of 1000 in uniform freestream. Starting with sinusoidal motion in pitch and heave, the heaving magnitude, pitch angle, frequency, and phase angle between pitch and heave were varied. The optimal case had a maximum heave of .5 chord lengths, a maximum pitch angle of 75 degrees, a non-dimensional frequency of 0.15, and a phase of 90 degrees, which are consistent with similar computational studies, and parallel theory and experimentation. In order to further optimize the hydrofoil's stroke for fluid energy extraction, higher harmonics are systemically added to the kinematics, finding that small perturbations to the heave signal can increase the efficiency by up to 6.0\%. [Preview Abstract] |
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1A.00011: Development of a Burner System and Rayleigh Scattering Method to Measure Soot Concentration for Diesel-Relevant Fuels Sara Fletcher, Brian Fisher Soot, a harmful component of particulate matter, is found in high concentrations in diesel exhaust. This work aims to develop a better understanding of the relationship between chemical structure and soot evolution, which is expected to inform methods to reduce or eliminate soot in diesel combustion. Successful aspects of previous experiments have been combined into a new method to characterize soot formation, growth, and oxidation. Soot is quantified via combined Rayleigh scattering and extinction, using a pulsed 532-nm Nd:YAG laser and sensitive photodetectors. A methane/oxygen diffusion flame serves as a baseline, then species of interest are doped into the fuel stream in low concentration and the change in soot is quantified relative to the base flame. This perturbation method enables study of soot for different species in a flame that has nominally constant global properties. This study focused on fuel components n-heptane and toluene, which have straight-chain and aromatic molecular structures, respectively. Soot was quantified throughout the flame, and it was found that the soot scattering signal was significantly higher for toluene than for n-heptane. Analysis of the signals to quantify actual soot concentrations remains a topic of future work. [Preview Abstract] |
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1A.00012: Parameters of a Steady State Model for In-Cylinder Flow of an Internal Combustion Engine Elizabeth Fortner, Paul Puzinauskas, Nicholas Bolus Flow structures in an internal combustion engine are critical to engine performance and fuel consumption. Experiments are often conducted to explore how intake port geometry can be modified to induce desired tumble and swirl flow structures within the cylinder. To make these experiments cost-effective, they are often first conducted using a model cylinder on a steady flow bench prior to, or in lieu of, performing full unsteady engine tests. This research examines how model characteristics and experimental configuration choices affect results on these steady-flow tests. The experimental set-up uses DPIV to visualize the flow and a horizontally extracting swirl meter to measure the strength of the tumble structure. The configurations and characteristics examined included model geometry, seeding particle type and location of flow induction. The symmetric geometry experiment investigates how extraction affects the flow structures inside the cylinder. Three different seeding particles were used to see how particle properties affect DPIV results. Reversing the direction of flow through the system causes set-up challenges with removing leaks and introducing seeding particles, but is safer as it directs particles away from the flow bench. Deviation of results from the different test set-ups may indicate that cylinder model experiments need to be carefully designed to ensure high quality results accurate enough for use in designing full scale engine tests. [Preview Abstract] |
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1A.00013: JETS, ACOUSTICS AND SHOCKWAVES . [Preview Abstract] |
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1A.00014: Characterization of Noise and Instability in a Commercial Burner Stewart Carpenter, Ajay Agrawal A range of combustion applications produce noise as a significant and undesirable output. Concurrently, efforts to reduce emissions through lean premixed combustion have shown this process to be prone to developing instabilities. In this study a commercial-style combustor was investigated to characterize combustion noise and instabilities. Knowledge in this area is intended for future research involving the application of porous inert media (PIM) in industrial burners. Porous media has been used to passively suppress both combustion noise and instabilities in a laboratory setting, but has yet to be implemented in a commercial burner. Combustion experiments were conducted in an industrial-scale lean premixed burner using natural gas while varying equivalence ratio and reactant flow rate. Acoustic data was acquired using a microphone probe placed in the plane of the combustor exit. Measurements were analyzed in the frequency spectrum to quantify noise spectra and detect the development of instabilities. Results have indicated the occurrence of strong combustion instability at certain conditions. Additionally, research has supported the general relationship of increased noise production with increasing equivalence ratio and heat release rate. Adverse effects of combustion instability were accompanied with flashback and downstream acoustic excitation. [Preview Abstract] |
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1A.00015: Identifying Potential Noise Sources within Acoustic Signals Victoria Holcomb, Jacques Lewalle We test a new algorithm for its ability to detect sources of noise within random background. The goal of these tests is to better understand how to identify sources within acoustic signals while simultaneously determining the strengths and weaknesses of the algorithm in question. Unlike previously published algorithms, the antenna method does not pinpoint events by looking for the most energetic portions of a signal. The algorithm searches for the ideal lag combinations between three signals by taking excerpts of possible events. The excerpt with the lowest calculated minimum distance between possible events is how the algorithm identifies sources. At the minimum distance, the events are close in time and frequency. This method can be compared to the cross correlation and denoising methods to better understand its effectiveness. This work is supported in part by Spectral Energies LLC, under an SBIR grant from AFRL, as well as the Syracuse University MAE department. [Preview Abstract] |
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1A.00016: Comparison of Methods for Identifying Noise Sources in Far-Field Acoustic Signals Andrew Tenney, Jacques Lewalle Three different methods of extracting intermittent wave packets from unstructured background within complex time series signals were analyzed and compared. The algorithms are denoted ``cross correlation,'' ``denoising,'' and ``TFLE (Time-Frequency-Lag event)'' methods respectively. All three methods utilize Mexican Hat or Morlet wavelets for the transformation of time domain signals into time-frequency domain signals. Within the denoising and cross correlation algorithms, events are identified through comparison of high energy excerpts of each signal captured by individual far-field microphones, while the TFLE algorithm simply defines events by their contributions to positive correlation values. The goal of this analysis is to quantify the advantages and disadvantages of each of these methods. The results lend themselves to determining the validity of these methods as noise source identification algorithms to be used in jet noise characterization. This work is supported in part by Spectral Energies LLC, under an SBIR grant from AFRL; and by the Department of Mechanical and Aerospace Engineering REU Program at SU. [Preview Abstract] |
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1A.00017: Characteristics of Fluid Structure Interaction in a Turbulent Wake G. Dowell |
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1A.00018: Shock wave reflections in a liquid filled thin tube Shota Yamamoto, Yoshiyuki Tagawa, Masaharu Kameda We investigate a behavior of an underwater shock wave in a thin glass tube using an ultra high-speed camera up to 10$^{\mathrm{7}}$ frames per second. We here focus on the pressure of the reflected shock wave at interfaces (water-glass wall / water-air). A shock wave is visualized using the Background Oriented Schlieren (BOS) technique. We measure the time evolution of the shock front position and estimate the shock velocity, pressure, and internal energy as a function of the distance from the shock center. At the water-wall interface the reflected shock pressure is lower than the incident shock pressure, which agrees well with the theoretical estimation for an acoustic pressure wave. The reflected pressure at the air-water interface is much lower than the incident shock, indicating that the shape of the air-water interface may affect this reduction of the reflected pressure. [Preview Abstract] |
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1A.00019: A focused liquid jet using a pressure impulse Akihito Kiyama, Yuto Noguchi, Yoshiyuki Tagawa We examine a behavior of a focused liquid jet using a pressure impulse inside a test tube filled with a wetting liquid. It is found that the jet velocity depends on the initial height of the test tube while it is independent of the diameter of the tube. We rationalize these results by employing a pressure impulse approach and considering a flow focusing due to the concave shape of the meniscus. In addition, we generate the focused liquid jet consisting of two different liquids. The jet velocity varies non-monotonically with the ratio of the two liquids. [Preview Abstract] |
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1A.00020: A new classification for liquid jets dynamics Bowen Ling, Ilenia Battiato The physics of liquid jets has been attracting scientists' interest for many decades. Previous works have focused on various aspects of jets dynamics including instability, self-similarity, etc. We propose a new criterion to classify liquid jets dynamics based on a non-dimensionalization of Navier-Stokes equations, which generalises well-established scalings. We employ such framework to describe specific dynamics, e.g. breakup characteristics, drop formation and dripping-jetting transition, and identify the driving physical mechanisms of different regimes. We compare the proposed classification with experimental results. [Preview Abstract] |
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1A.00021: Characterization of synthetic jet actuators used for jet noise reduction by flow control Alexis Zelenyak, Zachary Berger, Matthew Berry, Patrick Shea, Mark Glauser The issue of jet noise introduces various opportunities for advancements in flow control and fluid dynamics. One such method for jet noise reduction involves the use of synthetic jet actuators as shear layer excitation on the flow produced by a fully compressible, turbulent jet. A set of eight zero-net-mass flux actuators are organized around the periphery of the jet in an actuation glove fitting on the nozzle. As some noise reduction has been achieved through the use of this actuation system, further characterization of the system is necessary to fully quantify its capabilities and understand its effect on the flow physics in the shear layer. The synthetic jet actuators are driven by several different frequencies based on the Helmholtz resonance of the cavities, with measurements taken at several locations along the actuator orifice. Velocity profiles are then constructed from the measured response using hot wire anemometry. Such experimental results provide vital insight into the flow field created by the synthetic jet actuator system, allowing for more effective modification to the actuation glove. [Preview Abstract] |
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1A.00022: Heater Applications for High Speed Jets Jack Rossetti, Zachary Berger, Matthew Berry, Andre Hall, Mark Glauser In this investigation, we study a high speed jet flow for noise reduction techniques. Here we specifically examine a heated jet for practical jet noise applications. Experiments are conducted in the Syracuse University anechoic chamber at the Skytop campus. This 206 m3 facility is lined with fiberglass wedges having a cutoff frequency of 150 Hz. Far-field microphones and near-field pressure sensors measure the acoustics and hydrodynamics, respectively. A 470 kW Chromalox heating unit is used to heat the flow to 1000$^{\circ}$F at the nozzle exit. The controller for the heating unit has an associated time lag based on the Mach number and temperature. Therefore, this study will primarily focus on the heat transfer between the heating elements and the nozzle flow. Optimization of the heater's controller will allow for sufficient run time for data acquisition capabilities. Previous investigations at Syracuse University indicate significant differences between heated and cold jets, with regards to the acoustics and potential core characteristics (Hall et al. 2009). [Preview Abstract] |
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1A.00023: Statistical Comparison of Far-Field Noise Events in a Controlled Flow Ma=0.6 Jet Graham Freedland, Jacques Lewalle We compare distributions of acoustic events in controlled and uncontrolled high speed jets. By examining far-field acoustic signals from three microphones and using continuous wavelets, sources of noise can be identified through cross-correlation of the different far-field signals. From the events found, four properties (wavelet magnitude, Strouhal number and lags between two pairs of microphones) were tabulated. Each test gives over 10,000 events, which were sorted into histograms that approximate the statistical distributions of properties. This is used to determine what influence the addition of synthetic jet actuators has on the properties of the flow of the jet. A qualitative analysis of the distributions using quantile-quantile plots helps in the understanding of the distributions of sources. A quantitative analysis using the Anderson-Darling and Kolmogorov-Smirnov tests establishes statistically significant differences between the baseline and control cases. The authors thank Dr. Mark Glauser, Dr. Kerwin Low and the Syracuse Jet Group for the use of their data, Professor Dongliang Wang of Upstate Medical University for his suggestion of statistical methods, and Spectral Energies LLC (through an SBIR grant from AFRL) for their support. [Preview Abstract] |
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1A.00024: Focusing of cylindrical liquid jets into droplets Kristen Edwards, Amy McCleney, Philippe Bardet Upward angled water jets discharging in quiescent air are studied experimentally with time varying forcing. The jets issue from a 2 mm diameter tube, while highly controllable forcing is accomplished with a magnetic linear motor coupled with an arbitrary waveform generator. In particular, regimes of jet focusing are generated at various injection rates. The jets result in large droplets that can be created at various elevations. This type of flow mimics the spray generated by an Archer fish. Actual forcing functions were monitored using LDT. [Preview Abstract] |
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1A.00025: BIOLOGICAL, MICRO AND COMPLEX FLUIDS . [Preview Abstract] |
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1A.00026: Thin-Film Drainage and Droplet Adhesion in a Microfluidic Channel Jonathan Hui, Wei Wang, Peter Huang In many multiphase fluid processes, such as in petroleum extraction and biochemical analysis, one often sees the lodging of immiscible droplets that block flow in a conduit. The absence of a thin-film lubrication layer surrounding adhered droplets significantly increases the threshold pressure gradient required to induce bulk flows. In this work, we investigate the thin-film drainage process that leads to droplet adhesion and study how coating droplets with charged surfactants or solid particles can prevent direct contact between the droplets and channel wall. We report on our current computational and experimental results of an oversized gas droplet in a water-filled flow channel under the influence of surface tension and interfacial electrostatic repulsion. [Preview Abstract] |
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1A.00027: On the heat transfer and flow of a non-homogenous fluid Joseph Fiordilino, Ashwin Vaidya, Mehrdad Massoudi In this study, we consider the flow of a complex fluid such as coal-water slurry or biomass. We assume the suspension can be modeled as a non-homogenous viscous fluid whose viscosity is a function of space and temperature. We study the heat transfer and the steady fully developed flow of this complex fluid between two long horizontal plates subject to the no-slip condition at the plates. Two different correlations are proposed for the viscosity and the thermal conductivity and analytical and numerical results are presented for the velocity, temperature and the volumetric flow rate. [Preview Abstract] |
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1A.00028: Remote recoil between waves and vortices in superfluids Yuan Guo, Oliver Buhler This is a theoretical and numerical study of a particular wave-vortex interaction effect in superfluids, which extends previous work in classical compressible fluid mechanics. The fundamental modeling assumption is that both waves and vortices can be described by the defocusing nonlinear Schr\"odinger equation. At play is the refraction of small-scale waves by inhomogeneous straining flows due to one or several line vortices and the concomitant back-reaction, the``remote recoil", that is felt at the vortex locations. The remoteness is meant to highlight that the waves and the vortices are far from each other, and do not overlap in physical space. This recoil is of second order in wave amplitude and can be computed from the pseudomomentum budget of the waves. The recoil force and the scattering angle are computed both for finite and infinite wavetrains and the results are cross-checked against numerical integration of the relevant ray-tracing equations. We also consider the peculiar case of a wavetrain collapsing onto a single vortex, in which the wave-vortex interactions are not remote anymore. For some parameter values the WKB theory underlying ray tracing may retain its validity during the wave collapse. This would be a novel form of singular absorption of waves by a vortex. [Preview Abstract] |
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1A.00029: Computational models for fluid-structure interaction with a poroelastic structure Rana Zakerzadeh, Paolo Zunino, Martina Bukac, Ivan Yotov In the context of hemodynamics, we model blood flow in arteries as an incompressible Newtonian fluid confined by a multilayered poroelastic wall. We consider a two layer model for the arterial wall, where the inner layers behave as a thin structure modeled as a linearly elastic membrane, while the outer part of the artery is described by the Biot model. We propose and analyze a splitting strategy, which allows solving the Navier-Stokes and Biot equations separately. In this way, we uncouple the original problem into two parts defined on separate subregions, leading to a more efficient calculation of the numerical solution. The theoretical results will be complemented by numerical simulations. We numerically investigate the effects of porosity to the structure displacement. Namely, we distinguish a high storativity and a high permeability case in the Darcy equations, and compare them to the results obtained using a purely elastic model. A physical interpretation of the observed phenomena will be discussed. Indeed, the role of the proroelastic parameters on the pressure wave propagation in arteries emerges from the analysis of an equivalent formulation of the Biot system, where all the equations are condensed into a single one. [Preview Abstract] |
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1A.00030: Engineered Asymmetric Synthetic Vesicles Li Lu, Paul Chiarot Synthetic vesicles are small, fluid-filled spheres that are enclosed by a bilayer of lipid molecules. They can be used as models for investigating membrane biology and as delivery vehicles for pharmaceuticals. In practice, it is difficult to simultaneously control membrane asymmetry, unilamellarity, vesicle size, vesicle-to-vesicle uniformity, and luminal content. Membrane asymmetry, where each leaflet of the bilayer is composed of different lipids, is of particular importance as it is a feature of most natural membranes. In this study, we leverage microfluidic technology to build asymmetric vesicles at high-throughput. We use the precise flow control offered by microfluidic devices to make highly uniform emulsions, with controlled internal content, that serve as templates to build the synthetic vesicles. Flow focusing, dielectrophoretic steering, and interfacial lipid self-assembly are critical procedures performed on-chip to produce the vesicles. Fluorescent and confocal microscopy are used to evaluate the vesicle characteristics. [Preview Abstract] |
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1A.00031: Fluid Mechanics of the Vascular Basement Membrane in the Brain Mikhail Coloma, Jonathan Hui, Paul Chiarot, Peter Huang, Roxana Carare, Kenneth McLeod, David Schaffer Beta-amyloid is a normal product of brain metabolic function and is found within the interstitial fluid of the brain. Failure of the clearance of beta-amyloid from the aging brain leads to its accumulation within the walls of arteries and to Alzheimer's disease. The vascular basement membrane (VBM) within the walls of cerebral arteries surrounds the spirally arranged smooth muscle cells and represents an essential pathway for removal of beta-amyloid from the brain. This process fails with the stiffening of arterial walls associated with aging. In this study we hypothesize that the deformation of the VBM associated with arterial pulsations drives the interstitial fluid to drain in the direction opposite of the arterial blood flow. This hypothesis is theoretically investigated by modeling the VBM as a thin, coaxial, fluid-filled porous medium surrounding a periodically deforming cylindrical tube. Flow and boundary conditions required to achieve such a backward clearance are derived through a control volume analysis of mass, momentum, and energy. [Preview Abstract] |
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1A.00032: A simple microfluidic-inspired extensional flow device for observation of small aquatic organisms: design and implementation Neil Thomas, Rachel Pepper, Dorian Liepmann, M.A.R. Koehl We present a simple method for trapping microscopic particles and organisms around 100 $\mu$m in size. Using a laser-cut acrylic device and gravity-fed flow, single particles or organisms are trapped in a stagnation point formed at the center of intersecting channels, where they are observed under a microscope. Objects can be trapped by controlling the flow along the extensional axis, which is achieved by varying the outflow rate of one exit channel. We show results from applying this method to study the response of marine larvae (of the sea slug, \textit{Phestilla sibogae}) to varying accelerations. We also present details of the simple and inexpensive fabrication technique used to create such small devices. Overall, this fabrication technique allows for the generalization of microfluidic devices to micro- and millimeter scale applications. [Preview Abstract] |
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1A.00033: Mathematical Model and Simulation of Particle Flow around Choanoflagellates Using the Method of Regularized Stokeslets Niti Nararidh Choanoflagellates are unicellular organisms whose intriguing morphology includes a set of collars/microvilli emanating from the cell body, surrounding the beating flagellum. We investigated the role of the microvilli in the feeding and swimming behavior of the organism using a three-dimensional model based on the method of regularized Stokeslets. This model allows us to examine the velocity generated around the feeding organism tethered in place, as well as to predict the paths of surrounding free flowing particles. In particular, we can depict the effective capture of nutritional particles and bacteria in the fluid, showing the hydrodynamic cooperation between the cell, flagellum, and microvilli of the organism. [Preview Abstract] |
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1A.00034: Surface Patterning: Controlling Fluid Flow Through Dolphin and Shark Skin Biomimicry Lawren Gamble, Amy Lang, Michael Bradshaw, Eric McVay Dolphin skin is characterized by circumferential ridges, perpendicular to fluid flow, present from the crest of the head until the tail fluke. When observing a cross section of skin, the ridges have a sinusoidal pattern. Sinusoidal grooves have been proven to induce vortices in the cavities that can help control flow separation which can reduce pressure drag. Shark skin, however, is patterned with flexible scales that bristle up to 50 degrees with reversed flow. Both dolphin ridges and shark scales are thought to help control fluid flow and increase swimming efficiency by delaying the separation of the boundary layer. This study investigates how flow characteristics can be altered with bio-inspired surface patterning. A NACA 4412 hydrofoil was entirely patterned with transverse sinusoidal grooves, inspired by dolphin skin but scaled so the cavities on the model have the same Reynolds number as the cavities on a swimming shark. Static tests were conducted at a Reynolds number of approximately 100,000 and at varying angles of attack. The results were compared to the smooth hydrofoil case. The flow data was quantified using Digital Particle Image Velocimetry (DPIV). The results of this study demonstrated that the patterned hydrofoil experienced greater separation than the smooth hydrofoil. It is hypothesize that this could be remediated if the pattern was placed only after the maximum thickness of the hydrofoil. [Preview Abstract] |
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1A.00035: Vortex Formation on a Plunging Plate with Butterfly Inspired Surface Patterning Preston Powell, Amy Lang, Michael Bradshaw Previous research has shown that butterfly wings are covered in scales (100 microns in length) that are aligned in rows. When these scales are removed, butterflies require more energy and flaps per second to fly. These scales are pivotal to a butterfly's flying efficiency and are the inspiration for this study. This study examined whether improved efficiency is a result of the prolonged attachment of the leading-edge vortex (LEV) due to the arrangement of these rows. Efficiency is important for any system, however, this type of flight is quite similar to that of an MAV. A long flat plate was lifted at various Reynolds numbers to generate tip vortices on the bottom side. Three test plates were used: one flat plate as a control, one with length-wise ridges, and one with width-wise ridges. These ridges act as a simplistic model of butterfly scales while maintaining flow similarity. DPIV was used to measure the circulation and attachment of the leading-edge vortex for each plate. This experiment tested the hypothesis that the width-wise ridges will exhibit the longest attachment of the LEV which corresponds to increased lift. Also, the plate with length-wise ridges will have the quickest shedding of the LEV and decreased lift. [Preview Abstract] |
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1A.00036: TURBULENCE, STABILITY AND FLUID-STRUCTURE INTERACTION . [Preview Abstract] |
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1A.00037: Equilibrium Configurations of a Fiber in a Flow Pamela Guerron, Christopher Berghout, Bogdan Nita, Ashwin Vaidya The aim of this study is to understand the coupled dynamics of flexible fibers in a~ fluid flow. In particular, we examine the equilibrium configurations of the fiber with changing Reynolds numbers, orientations and lengths of the fiber. Our study is motivated by biological phenomena such as ciliary bending, flexing of plants and trees in winds etc.~ Our approach to resolving this problem has been threefold: experimental, numerical and theoretical.~ In our experiments we create physical models of variable length fibers inserted into a basal body structure, which is then suspended in a flow tank and positioned at different angles. The structure (fibers) are subjected to different velocities of water flow, ranging from 0m/s to 0.53 m/s in increments of 0.038 m/s. The results of the experiment were analyzed using Adobe Photoshop and the effect of the above mentioned parameters upon the shape of the fiber is analyzed. In addition, we also simulate this problem using the software Comsol and also create a simple, toy mathematical model incorporating the competing effects of tension and fluid drag on the fiber to obtain a closed form expression. Our various approaches point to consistent results. [Preview Abstract] |
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1A.00038: Properties of the plasma sheath edge above a rectangular depression in DONUT Thomas E. Steinberger, T.E. Sheridan Plasma is a gas consisting of positively and negatively charged particles, such as electrons and positive ions. The electric field inside a plasma is very small since plasma is a conductor. When plasma is in contact with a material boundary (i.e., a ``wall'') a boundary layer called the plasma sheath forms. The electric field inside the sheath is large and points away from the wall. The sheath electric field reduces the loss of highly mobile electrons, while accelerating ions out of the plasma, so that in steady state the electron and ion loss rates balance. The shape of the sheath edge is determined by the shape of the wall and the width of the sheath. We report experimental measurements of sheath conformation to a rectangular depression in a flat horizontal electrode (i.e., ``the wall'') in the Dusty Ohio Northern University experimenT (DONUT) for various aspect ratios. Clusters of two microscopic dust particles float above the depression at the sheath edge. The horizontal shape of the sheath edge is determined from the horizontal center-of-mass frequencies for the dust particles. The vertical electric field is found from the force balance on the dust particles, and the local charge density is measured using the vertical center-of-mass frequency. [Preview Abstract] |
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1A.00039: Partially-Averaged Navier-Stokes Modeling of Turbulent Swirling Flow Hosein Foroutan, Savas Yavuzkurt A Partially-Averaged Navier-Stokes (PANS) model is developed in this study and tested for the simulation of turbulent swirling flow. In the PANS approach, the extent of partial averaging is controlled by the unresolved-to-total ratios of turbulent kinetic energy, $k$, and turbulent dissipation rate, $\varepsilon $, which depend upon the computational grid spacing. Therefore, PANS closure model can be used at any grid resolution ranging from Reynolds-Averaged Navier-Stokes (RANS) to Direct Numerical Simulation (DNS). The present PANS model is derived from the extended $k-\varepsilon $ turbulence model of Chen and Kim (1987), where an extra time scale of the production is included in the turbulent dissipation rate transport equation. The new model is applied to the simulation of turbulent confined swirling flow through an abrupt expansion with Re$=$30,000 and swirl number of 0.6. The results are compared to the available experimental data, as well as those obtained using RANS and Detached Eddy Simulation (DES) on the same grid resolution. [Preview Abstract] |
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1A.00040: Pressure Driven Turbulent Flow in a Channel with Superhyrophobic Riblets Arian Yousefi, Ilenia Battiato In the past decades, many studies have focused on the ability of micro-patterned surfaces to reduce the fluid resistance in micro-fluidic applications. They revealed that micro-structures treated with hydrophobic coatings can significantly reduce skin drag in both laminar and turbulent regimes. We study pressure driven Navier-Stokes flow through and over a periodic rectangular array of alternating ribs and grooves parallel to the flow direction. The fluids inside and above the grooved surface are air and water, respectively. We employ the method of eigenfunction expansion combined with a domain decomposition approach to obtain a semi-analytical solution for the flow velocity within and above the grooves. The local and mean velocity profiles inside the grooves, the slip length and the slip velocity are determined for a number of different scenarios. Finally, we compare our semi-analytical solution with experimental data. [Preview Abstract] |
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1A.00041: Hydrodynamic Simulations of Steady-State Density Inversion in Vertically Shaken Granular Layers Farheen Syeda, Josh Panfil, Jon Bougie We investigate density inversion in shaken granular layers using three-dimensional, time-dependent continuum simulations to Navier-Stokes order for a layer of uniform, inelastic, frictionless spheres on a vertically oscillating plate. For given shaking strength, these simulations show cyclic time dependence of the granular layer correlated with the time-dependent oscillation of the plate for low accelerational amplitude. In such cases, the highest density region can be found near the plate during portions of the cycle. When the accelerational amplitude exceeds a critical value, the layer exhibits a steady-state density inversion, in which a high-density region is found far from the plate, supported by a lower-density, gas-like region below. For a variety of dimensionless shaking strengths $S$, we study the transition from a time-dependent, non-density-inverted state to a steady-state density inversion as a function of the dimensionless accelerational amplitude $\Gamma$. In each case, the density profile of the layer exhibits a cyclic oscillation at the driving frequency for low $\Gamma$ and the response frequency matches the driving frequency through the transition. However, the amplitude of time-dependent response drops as $\Gamma$ exceeds a critical value. [Preview Abstract] |
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1A.00042: Proposed Mechanism for Shock-Driven Stripe Patterns in Vertically Oscillated Granular Systems Alex Gilman, Stefanie Moertl, Jon Bougie We investigate vertically shaken granular systems using numerical solutions of continuum equations to Navier-Stokes order for uniform, frictionless, inelastic spheres. When layers of particles are oscillated at accelerational amplitudes greater than that of gravity, the layers leave the plate, and shocks are created upon re-established contact with the plate. Additionally, standing-wave patterns form when the accelerational amplitude exceeds a critical value. We demonstrate relationships between properties associated with shocks and properties associated with standing wave patterns, and propose a mechanism by which a non-uniform shock front drives standing-wave configurations. For a given layer depth and accelerational amplitude, varying driving frequency alters the shock strength as well as pattern wavelength; increasing layer depth produces stronger shocks and longer wavelengths for a given frequency. We use non-dimensional versions of the Navier-Stokes equations to mathematically derive relationships between these variables. We compare these mathematical relationships to those found empirically through simulations conducted at various layer depths and frequencies. [Preview Abstract] |
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1A.00043: ABSTRACT WITHDRAWN |
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1A.00044: An Alternative Nondimensional Vibration Frequency for Spanwise Tensioned Membranes in Low Re Flow Zheng Zhang, Andrew Wrist, James P. Hubner, Lawrence Ukeiley For the fixed flexible membrane wing at low Reynolds number (Re \textless\ 100,000), the membrane vibration interacts with the separated shear layer emanating from the leading edge, increasing the momentum transfer and reducing the flow separation. This investigation proposes an alternative vibration frequency scaling for the membrane wing. Compared to the traditional Strouhal scaling, the proposed nondimensional vibration frequency combines effects of the aerodynamically-induced tension, applied tension and membrane properties. A simplified aerodynamically-induced strain model is introduced through assuming uniform aerodynamic loading on the membrane. To verify the vibration frequency scaling and the accuracy of the aero-strain model, high-speed deformation measurement and force measurement of two-dimensional free leading- and trailing- edge membrane wings are performed in the low speed wind tunnel at Re $\sim$ 50,000. The preliminary data show that the proposed scaling is more appropriate than Strouhal scaling when the flow was driven by the membrane motion but not the shedding vortex. [Preview Abstract] |
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1A.00045: Numerical simulation of Rayleigh-Bernard convection in a cylindrical container Norma Y. Sanchez-Torres, Erick J. Lopez-Sanchez, Sergio Hernandez-Zapata, Gerardo Ruiz-Chavarria The heat transport by natural convection is a central mechanism in the explanation of many natural phenomena. Despite many works that treat the Rayleigh-Benard convection, most of them describe the phenomenon by making a two-dimensional approach. The purpose of this work is to use a cylindrical geometry. The study further extends to convection driven by evaporation which actually is an open subject. In this work we use a numerical methods to solve the Navier-Stokes, continuity and energy equations: a finite differences method for time, r and z coordinates; and a Fourier spectral method for the angular coordinate. In this manner the numerical code can be parallelized. The boundary conditions are the usual on solid walls, i.e. non-slip for velocity. The system starts at rest. The results are compared with experimental results and data reported in the literature. [Preview Abstract] |
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1A.00046: Simulating the motion of micro-capsules in complex geometries Lailai Zhu, Luca Brandt We develop a code to resolve the fluid-structure interaction of capsules in low-Reynolds-number flow, in $3$D general geometries. We use an accelerated boundary-integral method, the general geometry Ewald method (GGEM) to solve the Stokes flow in the framework of the Navier-Stokes solver NEK5000 based on the spectral element method. A global spectral interpolation employing spherical harmonics is incorporated simultaneously to resolve the membrane dynamics. Two cases are investigated to illustrate the generality of our implementation. Firstly we simulate a capsule transported in a $3D$ channel and/or duct with a corner, for a better understanding of moving soft objects in geometrically complex configurations. We examine the effect of capsule elasticity and wall confinement in detail. Our results give useful hints for the design of micro-devices. As a second case, we simulate the capsule flowing past a cylindrical obstacle with and without confinement, representing two popular cell separation configurations, pinched flow fractionation (PFF) and deterministic lateral displacement (DLL) respectively. In contrast to the original methodology using fluid inertia, particle size or steric effect, we numerically demonstrate the pure-elasticity-driven cell separation in such devices. [Preview Abstract] |
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1A.00047: Examining Dynamic Stall for an Oscillating NACA 4412 Hydrofoil Eric McVay, Amy Lang, Lawren Gamble, Michael Bradshaw Dynamic stall is unsteady separation that occurs when a hydrofoil pitches through the static stall angle while simultaneously experiencing a rapid change in angle of attack. The NACA 4412 hydrofoil was selected for this research because it has strong trailing edge turbulent boundary layer separation characteristics. General dynamic stall angle of attack for approximately symmetric airfoils has been recorded to occur at 24 degrees, with separation beginning at about 16 degrees. It is predicted that the boundary layer will stay attached at a higher angle of attack because of the cambered geometry of the hydrofoil. It is also hypothesized that the boundary layer separation occurs closer to the trailing edge and that the dynamic stall angle of attack occurs somewhere between 24 and 28 degrees for the oscillating NACA 4412 hydrofoil. This research was conducted in a water tunnel facility using Time Resolved Digital Particle Image Velocimetry (TR-DPIV). The hydrofoil was pitched up from 0 to 30 degrees at Reynolds numbers of 60,000, 80,000 and 100,000. Flow characteristics, dynamic stall angles of attack, and points of boundary layer separation were compared at each velocity with both tripped and un-tripped surfaces. Follow-on research will be conducted using flow control techniques from sharks and dolphins to examine the potential benefits of these natural designs for separation control. [Preview Abstract] |
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1A.00048: Interacting Hairpin Vortices Rijan Maharjan, Daniel Sabatino The generation mechanism for hairpin vortices is most commonly described as an autogeneration process in which an isolated vortex induces the formation of additional vortices. However, the interaction of two or more vortices can be another generation mechanism. The present work examines the interaction of two artificially generated hairpin vortices in a free-surface water channel. The hairpins are formed by direct injection at different streamwise locations. The different modes of interaction are categorized by the strength and relative position of the vortices at the time of interaction. One of the interaction modes causes the generation of a third hairpin vortex in a process similar to the autogeneration process of isolated hairpins. A comparison of the isolated and interacting generation processes is presented using visualizations and PIV measurements. [Preview Abstract] |
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1A.00049: VISCOUS FLOWS |
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1A.00050: Measurement of traction forces exerted by the foot in motion Maria Fernanda Lugo-Bolanos, Shreyas Mandre, Madhusudhan Venkadesan, Mahesh Bandi When walking and running, the foot acts like a flexible viscoelastic object that cushions impact and stores elastic energy. To characterize the functioning of the foot as a spatially extended and flexible object, we require all components of the ground traction forces to be measured with sufficient spatial and temporal resolution. We present here the theoretical underpinnings of a method based on photoelasticity to measure these traction forces with millimeter scale spatial, and millisecond temporal resolution. [Preview Abstract] |
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1A.00051: The Influence of Dome Size, Parent Vessel Angle, and Coil Packing Density on Coil Embolization Treatment in Cerebral Aneurysms David H. Frakes, Aprinda Indahlastari, Justin Ryan, M. Haithem Babiker, Priya Nair, Varsha Parthas Intracranial aneurysms (ICAs) are dilated cerebral blood vessels. Treating ICAs effectively prior rupture is crucial since their association with 45{\%} mortality rate. Embolic coiling is the most effective ICA treatment. Series of embolic coils are deployed into the aneurysm with the intent of reaching a sufficient packing density (PD) to help seal off the ICA from circulation. While coiling is effective, treatment failures have been associated with basilar tip aneurysms (BTAs), perhaps because of their geometry. The aim of this study was to examine the effect of dome size, parent vessel (PV) angle, and PD on intraaneurysmal (IA) velocity, crossneck (CN) flow and low wall shear stress (WSS) area using simulations and experiments in idealized BTA models. IA velocity and CN flow decreased after coiling, while low WSS area increased. With increasing PD, IA velocity and CN flow were further reduced, but low WSS area had a minimal change. Coil PD had the greatest impact on post-treatment flow while dome size had a greater impact than PV angle. Overall, the role of aneurysmal geometries may vary depending on treatment goal and timing e.g., high coil PD may reduce IA velocity more effectively during early aneurysmal growth when the dome size is small. [Preview Abstract] |
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