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 W18: Fluids XII |
Hide Abstracts |
Sponsoring Units: DFD Chair: Maziyar Jalaal, University of Amsterdam Room: Room 210 |
Thursday, March 9, 2023 3:00PM - 3:12PM |
W18.00001: Evolution of a two-layer film with large viscosity ratio Ensela Mema, Linda J Cummings, Lou Kondic This work focuses on developing a mathematical model that describes the evolution of two immiscible Newtonian liquid layers: the lower layer rests on a solid substrate and the upper layer rests on top of the lower layer. Our model assumes that the bottom liquid is more viscous than the top. Using the lubrication approximation scalings, we reduce the model into a system of two partial differential equations that describe the evolution of the liquid-liquid and liquid-gas interface over time. Numerical methods are used to gain insight into which conditions lead to dewetting/rupture of the film followed by a comparison of our work with existing models in literature. |
Thursday, March 9, 2023 3:12PM - 3:24PM |
W18.00002: Instability and Jetting of a Charged Milimeter-Scale Water Drop Evaporating in a Strong Electric Field John J Lee, Fahad Obaid, Sabyasachi Paul, Yong Chan Cho, Geun Woo Lee, Michael P SanSoucie, Robert W Hyers The stability of a charged liquid drop has been an interesting topic for more than a century due to its wide implications such as sprays, aerosols, ink-jet printing, and lightning in a cloud. In 1882, Rayleigh developed a mathematical model to predict the instability of a charged liquid drop. Decades later, Taylor studied the breakup of an uncharged water drop in an electric field. Recently, Shrimpton combined both Rayleigh and Taylor to consider both the drop charge and the external electric field simultaneously. Almost all experimental studies so far have been conducted with micron-scale liquid drops, which makes it extremely difficult to capture the dynamics of a drop. This presentation summarizes our efforts to visualize the instability of a charged millimeter-scale water drop in a strong electric field and identify the mechanism of the observed prematured jetting. A series of experiments were conducted using the Solution Electrostatic Levitator (SEL) developed at Iowa State University. SEL levitates a charged (~400 pC) liquid drop of 2.5-3.5 mm in diameter within a strong (~105 V·m-1) electric field. As the levitated drop evaporates, its diameter decreases down to ~0.5 mm and the surface charge density increases. As the coulomb force between surface charges approaches to the surface tension force, the drop becomes unstable and deforms into a prolate spheroid. Upon further evaporation, when the surface charge density reaches the jetting limit, some of surface charge is ejected by jetting and the drop regains its near-spherical shape. The changes in drop size and drop charge were measured as a function of time and relative humidity. In the presentation the mechanism of drop charge, the cause of charge loss, and the influence of a strong electric field on drop jetting will be discussed. |
Thursday, March 9, 2023 3:24PM - 3:36PM |
W18.00003: Influence of fluid viscosity on elastocapillary coiling JP P Raimondi, Sara Gonzalez, Emilie Dressaire A typical spider web is composed of many different types of silk, each designed for a specific |
Thursday, March 9, 2023 3:36PM - 3:48PM |
W18.00004: Molecular dynamics investigation into the spreading of water on completely wetting surfaces Mesfin Tsige, Selemon Bekele The spreading of water droplets of varying sizes on a completely wetting surface is modeled for the first time using atomistic molecular dynamics simulations. In the early stage of droplet spreading, the inertia of the drop resists the capillary driven motion and in the final stages, the effect of viscous forces acting in the neighborhood of the three-phase contact line become relevant and the competition between surface tension and viscous forces results in extremely slow spreading dynamics. The spreading observed is characterized by the bulk part of a droplet spreading over a high-density monolayer of water that forms within tens of picoseconds after the droplet is placed on the surface. The monolayer exhibits two spreading regimes, each following a power law in time with different exponents, and the late stage is faster than that predicted by Tanner’s law. We will show that a first principle model based on hydrodynamic theory describes the spreading data rather well in the regime where the low contact angle approximation holds and, overall, the simulation results qualitatively agree with recent experimental data. |
Thursday, March 9, 2023 3:48PM - 4:00PM |
W18.00005: The Limits to Bubble Capture through Porous Aerophilic Membranes Bert Vandereydt, Saurabh Nath, Jack Lake, Tal Joseph, Kripa K Varanasi Hydrophobic membranes are a common tool used to capture unwanted bubbles in applications ranging from microfluidics to anti-foaming. In these, rapid bubble capture on the order of milliseconds is required as longer bubble capture times will lead to bottlenecks. For example, in microfluidics a larger channel would be required to capture sufficient gas fluxes ; while in the anti-foaming case, foaming will not be prevented if the sparging rate exceeds to bubble capture rate. Hence, in this work we seek out the mechanisms behind transport of a bubble in contact with a hydrophobic membrane. For this, we fabricated super-hydrophobic membranes with with variable dimensions. Through altering physical parameters of the membrane, we have identified three different limiting regimes of bubble capture through a membrane. With the use of scaling laws, we can predict the transition between regimes. At the high end, bubble capture times under 1ms have been recorded for a 3.5mm diameter bubble. This work elucidates the limiting factors behind bubble transport through a membrane, and its results can be translated to applications where bubble capture is required. |
Thursday, March 9, 2023 4:00PM - 4:12PM |
W18.00006: Mixing droplets in the wind Jessica L Wilson, Howard A Stone Drops on fibers in crossflows have complex dynamics. At an intermediate Reynolds number, the imposed crossflow leads to a wake asymmetry which induces translation along the fiber. As the drops move, they deposit thin films on the fiber. These thin films can be picked up by other drops, representing a possible mechanism for mixing. Using fluorescent dye and a laser light sheet, we image mixing in the drops. We compare the mixing with other mixing flows and aim to rationalize it with analytical and numerical models for the internal flows.
|
Thursday, March 9, 2023 4:12PM - 4:24PM Author not Attending |
W18.00007: Intertwined effects of solidification and impact: Instability, fingering, and satellite drop ejection Peiwen Yan, Pirouz Kavehpour Upon impact of a liquid drop on a smooth solid surface, lamella spreads and sequentially detaches from bulk contact line. Fingering and ejecting a thin-liquid sheet and satellite drops render those phenomena aesthetically pleasing and mathematically challenging. Though vast literature investigates isothermal splashing dynamics, this study explores lamella extension and its levitation affected by solidification mechanism, an interplay of fluid dynamics, heat transfer, and phase transition with its broad occurrence in nature and industry. Phenomenological observations and theoretical explanation are presented on the high-resolution spatiotemporal splashing physics at the proximity to dynamical contact line. Here, impacting hexadecane droplets on subcooled glass surfaces are experimentally studied with ranges of Weber number from 10.0 to 800 and Stefan number from 0.01 to 0.15. While adjusting substrate temperature, splashing dynamics is controlled and yield unique patterns from thin-sheet to prompt splash, but suppressed eventually with increasingly elevated Stefan number. We - Ste nomogram is constructed based on splash outcomes and instability threshold determined. This work aims to ultimately reveal how solidification interferes with splashing dynamics. |
Thursday, March 9, 2023 4:24PM - 4:36PM |
W18.00008: Reciprocal swimming at intermediate Reynolds number Nicholas J Derr, Thomas Dombrowski, Chris Rycroft, Daphne Klotsa In Stokes flow, Purcell's scallop theorem forbids objects with time-reversible (reciprocal) swimming strokes from moving. In the presence of inertia, this restriction is eased and reciprocally deforming bodies can swim. A number of recent works have investigated dimer models that swim reciprocally at intermediate Reynolds numbers Re ≈ 1–1000. These show interesting results (e.g. switches of the swim direction as a function of inertia) but the results vary and seem to be case-specific. Here, we introduce a general model and investigate the behaviour of an asymmetric spherical dimer of oscillating length for small-amplitude motion at intermediate Re. In our analysis we make the important distinction between particle and fluid inertia. We asymptotically expand the Navier-Stokes equations in the small amplitude limit to obtain a system of linear PDEs. Using a combination of numerical and analytical methods we solve the system to obtain the dimer's swim speed and show that there are two mechanisms that give rise to motion: an effective slip velocity on the boundary and Reynolds stresses in the bulk. Each mechanism is driven by two classes of sphere–sphere interactions, between one sphere's motion and 1) the oscillating background flow induced by the other's motion, and 2) the geometric asymmetry stemming from the other's presence. We can thus unify and explain behaviors observed in other works. Our results show how sensitive, counter-intuitive and rich motility is in the parameter space of finite inertia of particles and fluid. |
Thursday, March 9, 2023 4:36PM - 4:48PM |
W18.00009: Brownian dynamics simulations of interacting magnetic tri-axial ellipsoids Daniel H Duke, Isaac Torres Diaz Magnetic nanorobots have immense potential for medical treatment at the cellular level. Colloidal nanorobots with independent locomotion and multi-actuating capabilities controlled by electromagnetic fields are still challenging. Our approach to fabricate nanorobots uses the dipolar interaction between anisotropic particles with different shapes and materials to generate tunable configurations between particles. Quantifying the high-dimensional dependence of dipolar interactions of tri-axial particles in position and orientation is crucial to model magnetic nanorobots. We report the analytical expressions for the interaction dipolar forces and torques between permanently magnetized tri-axial ellipsoids with different shapes and materials. We combine the novel ellipsoid-dipole model with unit quaternions to parameterize the orientational space. The analytical expressions capture the established behavior of uniform magnetic spheres. Additionally, we report Brownian dynamics simulations of interacting permanently magnetized ellipsoids under the influence of time-varying magnetic fields. We will show simulation results for binary systems composed of tri-axial ellipsoids with different shapes and sizes. We characterize the relative dynamic patterns between particles in the relative particle space. Simulation results show a synchronous particle rotation for small dipolar interactions; however, results show coupling rotation dynamics for strong dipolar interactions. |
Thursday, March 9, 2023 4:48PM - 5:00PM |
W18.00010: Velocity fluctuations in the sedimentation of active suspensions Bryan O Maldonado, Shravan Pradeep, Paulo E Arratia, Douglas J Jerolmack Sedimentation of active matter is found in many natural and industrial processes, such as ocean's biological pump and wastewater treatment. Sedimentation processes are usually characterized by studying the concentration profiles, hindered settling functions, and velocity fluctuations. In passive systems, previous results show that the correlation length of colloidal particles in the direction parallel to sedimentation decreases exponentially with distance. These correlations depend on the concentration and size of the dispersed particles. However, biological activity, due to the presence of motile bacteria or other swimmers, affect the correlation lengths of settling passive particles is a question that remains unanswered. To address it, we experimentally investigate the effects of bacteria activity on the sedimentation process of dilute suspensions of spherical colloids. By tracking individual particles in an active suspension, results show that the presence of swimming bacteria (E. coli) disturbs the sedimentation particles trajectories. We find an enhancement particle mean-square displacement in the lateral direction once activity is introduced in the system. This leads to a significant difference in the correlation lengths between passive and active systems. |
Thursday, March 9, 2023 5:00PM - 5:12PM |
W18.00011: Helical Locomotion in Yield Stress Fluids Farshad Nazarinasrabad, Hadi Mohammadigoushki Microorganism’s locomotion is common in various biological environments and affects several aspects of our life, including reproduction and infection. We report experiments on the locomotion of a helical swimmer in yield stress fluids. The swimmer must overcome two thresholds to be able to swim forward. Above a critical yield strain εy≈10%, the swimmer is able to overcome the yield barrier and create rotational motion. However, exceeding the first threshold is not sufficient for locomotion. Only below a critical Bingham number (Bic ≈ 0.6), when the rotational motion forces the material to yield far away from the swimmer, forward motion will occur. These critical thresholds do not depend on the swimmer geometry and the fluid rheological properties. Below the critical Bic, and at low pitch angles (12° ≤ ψ ≤ 37°), the yield stress to Newtonian swimming speed ratio is below unity. Remarkably, this speed ratio can increase well beyond one (up to 10) at larger pitch angles, indicating that yield stress may facilitate the locomotion. Flow visualizations indicated that the fluid deformation is highly localized and the swimming speed is controlled by a balance between propulsion inside the tail and bulk deformation around the head. |
Thursday, March 9, 2023 5:12PM - 5:24PM |
W18.00012: Tuning biflagellar dominance in a robotic model of phototactic algae Tommie L Robinson, Kelimar Diaz, Kirsty Y Wan, Daniel I Goldman Microscopic algae use their flagella to generate diverse locomotive behaviors, such as goal-directed motion. In particular, phototaxis is a light-triggered response during which algae swim toward a light source to carry out photosynthesis. While the biological mechanism regarding the algae’s photoreceptor is well understood, less is known about how the flagellar dynamics lead to phototaxis. In Chlamydomonas, one possible mechanism of phototactic turning is achieved via either differences in beating frequency or amplitude between the cis (closest to the eyespot) and trans flagellum (farthest from the eyespot) (Witman, 1996). To test this, we developed a macroscopic motor-driven robophysical model that swims in a viscous fluid (glycerin, 1,100 cSt) to replicate low Reynolds number swimming. We implemented turning via differential-beating with varying flagellar (1) frequencies and (2) amplitudes. Differential-beating frequencies led to greater net turning with a maximum turning rate of 3.75±0.33 degrees per cycle (deg/cyc), compared to differential-beating amplitude with a maximum of 2.08±0.06 deg/cyc. Further, we observed that turning performance was sensitive to the flagellar waveforms. Based on these insights, we propose a mechanistic model of sensorimotor coupling in which phototaxis is achieved by controlling the functional asymmetry between the two flagella in response to light. |
Thursday, March 9, 2023 5:24PM - 5:36PM |
W18.00013: Using calibrated numerical models as a noninvasive probe to study bacterial motility Bruce E Rodenborn, Hoa Nguyen, Orrin Shindell, Frank Healy, Kathleen M Brown, Brianna Tilley The evolutionary pressures that cause morphological changes in bacteria are often difficult to determine because we lack precise information about fluid-structure interactions when bacteria are motile. Numerical modeling provides insights, but the models are often calibrated using biological measurements that have large uncertainties. Instead, our collaborative project (NSF POLS - 2210610) uses dynamically similar tabletop experiments to precisely calibrate the method of regularized Stokeslets (MRS) and the method of images for regularized Stokeslets (MIRS) to extract quantitatively accurate values of forces and torques on model bacteria moving near a boundary. The experiments also provide the first validation of theories for torque on cylinders (Jeffrey and Onishi 1981) and torque on spheres (O'Neil 1964) moving near a boundary. The simulations then serve as a noninvasive probe to measure swimming metrics such as the Purcell efficiency, energy per distance, and our new metabolic energy cost measure. We have shown that our method provides unique insights into how cylindrical body shape affects swimming performance measures near a boundary (Shindell et al., Fluids, 2021). This work also shows that the wavelength of a helical flagellum seems to be selected independently of body shape. See the related talk by Orrin Shindell for more details. |
Thursday, March 9, 2023 5:36PM - 5:48PM |
W18.00014: Computing the Dynamics of Motile Bacteria from Experimental Data Orrin Shindell, Hoa Nguyen, Frank Healy, Bruce E Rodenborn The motile bacterium Pseudomonas aeruginosa consists of a rod shaped body and a single polar flagellum. A molecular motor connects the helical flagellar filament to the cell body and generates a toque to propel the cell through its low Reynolds number environment. To determine the torque generated by the P. aeruginosa motor, we measure the motion of individual bacteria and input their trajectories into the computational method of regularized Stokeslets (Cortez 2001). The computational method is calibrated using dynamically similar table-top experiments to ensure accurate torque values. In this presentation, we present our method and the results of our torque measurements. See the accompanying talk by Bruce Rodenborn for details of table-top experiments and the calibration method. |
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. |
© 2024 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