Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session M18: Fluids VII |
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Sponsoring Units: DFD Chair: Binan Gu, Worcester Polytechnic Institute Room: Room 210 |
Wednesday, March 8, 2023 8:00AM - 8:12AM |
M18.00001: The effects of geometry on the propulsion of neutrobots: a minimal model Herve Nganguia, James Della-Giustina, Ummul Aymen, Ebru Demir Recent advances in drug delivery have used nanoparticles-driven gels as drug delivery systems [Zhang et al., Sci Robot. 6, 2021]. Referred as neutrobots because the controlled gels are phagocytized by neutrophils to evade immune attacks by the body's natural response, these systems have been successfully deployed in-vivo. Inspired by these advances, we propose a minimal model that accounts for the effects of various neutrobots' geometry. We aim to determine numerically the propulsion speed and other performance metrics of the components that make up the neutrobots, and analyze the system based on various configurations that may arise. In this talk, we report our findings regarding the dependence of the swimming performance on the shapes of the neutrobots. We conclude with a discussion about future extensions to more accurately model the in-vivo dynamics of the neutrobots as well as suggestions for ways to design efficient micro-robots for drug delivery. |
Wednesday, March 8, 2023 8:12AM - 8:24AM |
M18.00002: Behavior plasticity in free swimming coral larvae via long term tracking microscopy Ian Ho, Elora López-Nandam, Rebecca Albright, Manu Prakash The larval stage of coral is the only motile stage in its developmental cycle. As a result, the ability of coral larvae to navigate towards reefs and find a suitable settlement location is crucial to their survival. While the effect of external cues such as chemicals, light or sound on larval swimming has been studied, and order of magnitude estimates of swimming speeds have also been measured, observing the free-swimming behavior of larvae at ecologically relevant scales has remained a technological challenge. Here, we use a novel scale-free vertical-tracking microscope (Krishnamurthy et al. 2020) to resolve the swimming behavior of the coral species Acropora millepora at the meter scale. Our experimental results quantify the behavioral modes of larvae both as a function of their diverse shapes and as a function of their developmental cycle. We observe dramatic, short time-scale shape change during swimming that is coupled to a change in swimming velocity. Finally, we also observe that the introduction of symbiotic algae significantly affects the gravitaxis behavior of coral larvae. |
Wednesday, March 8, 2023 8:24AM - 8:36AM |
M18.00003: Exceptional amphibious locomotive capabilities of tiny water walkers Johnathan O'Neil, PANKAJ ROHILLA, Victor M Ortega-Jimenez, Xingwan Zhu, Saad Bhamla Unlike larger animals, small insects such as Microvelia exhibit exceptional water walking abilities by leveraging surface tension. Strikingly, not only are Microvelia able to walk on water, but they can also walk on land with comparable speeds. Microvelia achieve this feat through the alternating tripod gait, commonly found in terrestrial insects such as ants. To understand their outstanding amphibious locomoting capabilities, we use high-speed imaging to study the biomechanics of these organisms on both land and water. Using DeepLabCut, we track the leg tarsi and joints to calculate their speed, acceleration, stroke frequency, and stroke amplitude on water and different terrains. Further, we used Particle Image Velocimetry (PIV) to visualize and quantify the dynamics of vortices generated from the power strokes of the middle and hind legs. Interestingly, the spatio-temporal dynamics of their legs result in the phenomenon of “vortex recapture” wherein the hind legs capture the vortices generated by the middle legs, thereby re-energizing them. We investigate the role of vortex recapture on the interfacial locomotion of these organisms by correlating the vortex circulation and their kinematics. This work not only advances the current knowledge of interfacial locomotion of small water walkers, but also has a potential in influencing designs of amphibious robots. |
Wednesday, March 8, 2023 8:36AM - 8:48AM |
M18.00004: Impact of vortex recapture in water-walking Microvelia using a physical model and computational fluid dynamics PANKAJ ROHILLA, Johnathan O'Neil, Victor M Ortega-Jimenez, Prateek Sehgal, Saad Bhamla Microvelia, one of the genus of water striders, locomote on water and land using an alternating tripod gait. During their gait, the middle legs generate a pair of counter-rotating vortices during their power strokes. Further, the hind legs step into these vortices and re-energize them. Using a physical model and Computational Fluid Dynamics (CFD) modeling, we study the interactions of vortices from the middle and hind legs. We also investigated the fluid-structure interaction between the hind leg and the vortex shed from the middle leg. Overall, this study aims to uncover the role of vortex recapture on the kinematics of Microvelia. We systematically studied the effect of stroke amplitude, leg speed, and stroke frequency of the middle and hind legs on the energetics of Microvelia’s interfacial locomotion. In addition to an in-depth understanding of the fluid dynamics involved in the locomotion of these organisms, these results may guide the designs of water-walking micro-robots. |
Wednesday, March 8, 2023 8:48AM - 9:00AM |
M18.00005: Taxis in density gradients Vaseem A Shaik, Gwynn J Elfring Many organisms inhabit inhomogeneous environments such as those with gradients of heat, light, nutrients, fluid viscosity or density. They react to these inhomogeneities by reorienting and changing speed, often exhibiting a directed migration termed taxis. For instance, E. coli reorients to swim up nutrient gradients but swims down light or viscosity gradients. Here, we demonstrate a new, relatively unexplored taxis in density gradients, which are prevalent in oceans, lakes, and ponds. This taxi is sensitive to whether the organisms generate thrust in front (so-called pullers) or back (pushers). Pullers, like Chlamydomonas reinhardtii for instance, reorient to swim up or down the gradients, depending on the initial orientation. But pushers, like E. coli, rotate to swim normal to the gradients. This densitaxis could help explain organism behaviors in the ocean or be leveraged to sort or organize a suspension of organisms. |
Wednesday, March 8, 2023 9:00AM - 9:12AM |
M18.00006: Towards controlling the rheological properties of suspension systems using fully differentiable unsteady Navier-Stokes flow solvers mohammed alhashim, Michael P Brenner Variations in the microstructure of freely suspended particles leads to diverse rheological |
Wednesday, March 8, 2023 9:12AM - 9:24AM |
M18.00007: Nonlinear analysis of thermal convection and chaos in hybrid nanofluid layer. Jean Bio Chabi Orou Abstract : |
Wednesday, March 8, 2023 9:24AM - 9:36AM |
M18.00008: Influence of geometric ordering on viscoelastic flow instabilities in 3D porous media Emily Chen, Christopher A Browne, Simon J Haward, Amy Q Shen, Sujit S Datta Many applications involve flow of viscoelastic polymer solutions in geometrically complex 3D porous media. Polymers accumulate elastic stresses as they navigate the pore space, leading to a flow instability characterized by spatiotemporally chaotic flow fluctuations. Our previous studies in disordered 3D media suggested that this instability onset is highly sensitive to medium geometry; however, how exactly geometry influences the flow instability remains unclear. We address this gap by directly imaging flow in microfabricated 3D porous media with precisely controlled geometries consisting of body-centered cuboid or simple-cubic arrays of spheres. Unexpectedly, in both cases, the flow instability is generated upstream of the contact regions between spheres rather than at sphere surfaces—suggesting that the consolidation of solid grains, inherent in naturally-occurring media, may play a pivotal role in establishing the flow instability in field settings. Further, the characteristics of the flow instability strongly depend on the unit cell geometry, and we quantify how the pore-scale flow features control the macroscopic flow resistance across the entire medium. Our work thus provides a key step towards elucidating how porous medium geometry shapes viscoelastic flow behavior. |
Wednesday, March 8, 2023 9:36AM - 9:48AM |
M18.00009: Viscous fingering in polymeric fluids Paresh Chokshi, Pooja Jangir, Ratan Mohan The flow displacement process, through microchannel or porous media, suffers from a fingering phenomenon that manifests in the form of finger-like patterns around the interface region. Viscous fingering instability can be controlled by adding polymers to either displacing or displaced fluid which alters the fluid viscosity, the cause of viscous fingering. The shear-rate-dependent viscosity and elasticity of polymeric fluids influence the growth of fingers mainly due to non-uniform viscosity distribution. To investigate the role of rheological properties on instability, the miscible flow displacement is studied experimentally using the Hele-Shaw cell. The aqueous solutions of polyethylene oxide (PEO) of varying concentrations and molecular weights are used as one of the fluids. The visualization of fingers shows that displacement of PEO solutions at high concentration or high molecular weight leads to more complex and fractal-like patterns with tip-splitting and side-branching mechanisms. For similar viscosity contrast between two fluids, the finger formation is found to be more intensified when displaced fluid is polymeric in nature as compared to displacing fluid being polymeric fluid. The shear-thinning behavior strengthens shielding behavior whereas fluid elasticity leads to tip-spitting, irrespective of the flow arrangement. |
Wednesday, March 8, 2023 9:48AM - 10:00AM |
M18.00010: Evolution of microfluidic droplets in ternary systems Thomas Cubaud The microflow behavior of liquid-liquid dispersions is experimentally investigated in the presence of miscible solvents. Original microfluidic methods are developed to characterize out-of-equilibrium fluid interactions resulting from the interplay of interfacial tension and diffusion phenomena. In particular, we examine the dynamic response of viscous droplets to a sharp decrease of interfacial tension resulting from the sequential injections of miscible solvents. Various flow configurations and fluid combinations are examined to clarify the role of liquid solubility on the fundamentals of multiphase flows and advance predictive knowledge of spontaneous emulsification phenomena in microgeometries. |
Wednesday, March 8, 2023 10:00AM - 10:12AM |
M18.00011: Numerical simulations of liquid jetting with solid inclusions Arnab Ghosh, Alessandro Gabbana, Herman Wijshoff, Federico Toschi In this work we study the formation of droplets, in the prospect of inkjet printing, via fully resolved jetting simulations. We employ a color-gradient lattice Boltzmann method, which allows efficient large-scale simulations of the jetting process that compares quantitatively well with experimental data. We focus on the influence of small solid impurities on the jetting process. These impurities, often found in real-life applications, lead to non-trivial interactions which can affect the symmetry of the jet, in turn hampering the overall print quality. We investigate the impact of the relevant parameters, such as size, density, and initial position of a particle on the asymmetries which develop during a jetting cycle. |
Wednesday, March 8, 2023 10:12AM - 10:24AM |
M18.00012: Hydraulic parallel design for microfluidic ultraviscous droplets Hyeon Ho Kim, Seungwoo Lee, YongDeok Cho, Dongjae Baek, Sung Hun Park, Kyung Hun Rho Over the past decades, droplet microfluidic designs have been developed to simultaneously achieve monodisperse particles and high production rates. However, most of these advancements are targeting a low viscous fluid (viscosity about 10-2–10-3 Pa·s) so that microfluidic designs are oriented to increase the channel numbers. This study designs and presents a droplet microfluidic device that can generate uniform droplets of an ultraviscous fluid (viscosity about 3.5 Pa·s). To emulsify an ultraviscous fluid into a uniform and high-throughput droplet, it is necessary to increase the channel numbers and control the channel resistance of the dispersed phase. In this work, the microfluidic devices were divided into 16, 32, and 64 specific designed T-junctions each from one single inlet, and divided junctions were connected into a single post-flow of the continuous phase. At 64 junctions of the microfluidic device, it can emulsify the ultraviscous fluid into ~ 330,000 droplets per hour. The generated droplet has a 2~3% coefficient of variation (CV) at a diameter of about 100μm. In addition, on the account of the fully 2-dimensional branched design, just one soft lithography experiment is enough to fabricate the microfluidic chip which is especially favorable to newcomers. |
Wednesday, March 8, 2023 10:24AM - 10:36AM |
M18.00013: One-dimensional modeling of pressure-driven droplet pinch-off Darsh K Nathawani, Matthew G Knepley The aim of this research is to develop a mathematical model to simulate the effects of shear force on droplet formation. Droplet formation has been an interest of study since the seventeenth-century [L. Rayleigh, "On the instability of jets," Proceedings of the London mathematical society, vol. 1, no. 1, pp. 4–13, 1878]. Droplets are seen in applications like emulsion, spraying, ink-jet printing, atomization and entrainment, and many more. Understanding the droplet dynamics is crucial to improve the efficacy of these processes. The self-similar nature of the flow with a singularity at the pinch-off requires accurate modeling of the curvature. We present a one-dimensional model to simulate the droplet pinch-off in a quiescent environment using front tracking [D. K. Nathawani and M. G. Knepley, "Droplet formation simulation using mixed finite elements", Physics of Fluids, vol. 34, no. 6, p. 064105, 2022]. The model is verified using the method of manufactured solution and validated against laboratory experiments. We propose a self-consistent algorithm with an adaptively refined mesh. Furthermore, we expand the model for droplets in a pressure-driven continuous outer flow to incorporate the effects of shear force on droplet evolution. |
Wednesday, March 8, 2023 10:36AM - 10:48AM |
M18.00014: Simultaneous rheology and impedance measurements on conductive colloidal suspensions Yilin Wang, Tanver Hossain, Shatakshi Gupta, Randy H Ewoldt The development of renewable energy requires energy storage technologies, among which semi-solid redox flow batteries using conductive colloids are promising because of scalability. Understanding the flow and conductive properties of these colloidal suspensions is crucial in designing flow channels and optimizing operating conditions. However, the rheology and conductivity of colloidal suspensions are coupled and highly depend on the shear-induced structure, and these complex properties and the underlying microstructural origins are poorly understood due to a lack of appropriate instrumentation. To address this, we introduce a bespoke attachment to the stress-controlled (combined-motor-transducer) rotational rheometer which can measure rheology and electrical impedance under shear simultaneously. Using this rheo-impedance setup, we measure the thixotropy, anti-thixotropy, shear-dependent conductivity, and anisotropy of carbon black suspensions. We use the results to further propose a microstructure model to explain the measured bulk properties. |
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