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 A18: Fluids I |
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Sponsoring Units: DFD Chair: Ildoo Kim, KonKuk Univ Room: Room 210 |
Monday, March 6, 2023 8:00AM - 8:12AM |
A18.00001: Impact of dynamic permeability reduction on flow distribution in porous media Andres O Gonzalez, Shima Parsa Precipitation of minerals, adsorption of nanoparticles, and trapping of immiscible fluids in porous media result in changes in the available flow paths and modify the permeability of the medium. We use confocal microscopy and bulk transport measurements to probe the local flow and permeability of the medium in 3D porous micromodels. Our experimental measurements show that depending on the time allowed for changes in the structure due to the deposition of a polymer, the structure of the medium changes in response to the flow. Nevertheless, the probability distribution of fluid velocities retains the same shape. We find that at a constant volumetric flow rate, the modified structure of the medium has an intrinsic length-scale that can be estimated from the bulk permeability of the medium. |
Monday, March 6, 2023 8:12AM - 8:24AM |
A18.00002: Impact of interfacial adsorption of nanoparticles on transport properties of two-phase flow in porous media Shima Parsa, Samaneh Farokhirad We study the transport and adsorption of nanoparticles in partially saturated porous media experimentally. Using fluorescent microscopy in two-dimensional model porous media we measure the distribution and breakthrough of nanoparticles at small flow rates. Our results show that at large Peclet numbers, nanoparticles primarily follow the major flow paths while they tend to diffuse close to the interfaces and solid structure at small Peclet numbers. Comparing the breakthrough of nanoparticles in a fully saturated porous medium with a medium partially saturated with a second immiscible fluid shows that by increasing the number of interfaces a smaller number of nanoparticles are discharged from the medium. The impact of interfacial adsorption of nanoparticles strongly depends on the nanoparticle charges and wettability of the medium. |
Monday, March 6, 2023 8:24AM - 8:36AM |
A18.00003: Blocking out Voids in Percolating Media with Impentrable Cores Donald J Priour We examine structurally disordered comprised of interpenetrating polyhedral impenetrable grains with randomly selected shapes and sizes. With fluid and/or charge transport confined to voids among impentrable grains, connected interstitial volumes form system spanning networks below a crtical grain concentration per unit volume. The latter marks the phase boundary between among systems which percolate on macroscopic scales (for lower grain concentrations) and those which do not (for higher grain concentrations). With large-scale Monte Carlo simulations based on dynamical infiltration of void volume networks with virtual tracer particles, we calculate critical indices, including the percolation transition. Subdividing the system into voxels (small cube shaped volumes) fulfills a pragmatic role in minimizing computational effort and memory usage, allowing for the examination of systems with as many as a billion voxels volumes, each of which is occupied by or is contact with on the order of a dozen impenetrable grains. In addition, we exploit the voxel volumes as a more efficient way to find the percolation transition than the root mean square distance traversed by virtual tracers due to higher scaling exponents with tracer dwell time for the mean number of voxel volumes visited over the course of a dynamical infiltration trajectory. In studying porous media comprised of highly irregular angular grains, we consider systems made of up polyhedra cleaved many times with randomly oriented slicing planes where the mean number of fragmentation events is a tunable parameter. We find that the critical porosity increases monotonically and ultimately saturates at about 5.5% with increasing average number of slices per grain. This saturation of the critical porosity occurs in spite of the fact that the range of grain volumes ultimately expands to span several orders of magnitude even as the shape distribution tends to a limiting profile and ceases to evolve. |
Monday, March 6, 2023 8:36AM - 8:48AM |
A18.00004: Simulation Insights into Self-Propelling Chiral Auto-Chemotactic Particles Chung Wing Chan, Zecheng Gan, Rui Zhang Chemotaxis and auto-chemotaxis are ubiquitous in living systems. On the one hand, these mechanisms are important in communications and interactions among constituents (e.g., bacteria) in many active matter systems, the dynamics of which are strongly coupled with its environment in terms of chemical fields or nutrient landscapes. On the other hand, hydrodynamic flows emerged in active matter systems may substantially modify the chemical field and further affect the locomotion dynamics of active particles. In this work, we couple active Brownian dynamics simulations with an advection-diffusion equation to examine the dynamics of self-propelling chiral particles, which exhibit auto-chemotaxis to its own established chemical field. Our two-dimensional simulations can reproduce trajectories characteristic of chiral auto-chemotactic droplets in experiments. We further quantitatively elucidate how the interplay of activity, chirality, and chemical force dictates the geometry of the particle trajectories. Our work leads to a more quantitative understanding of living active matter. |
Monday, March 6, 2023 8:48AM - 9:00AM |
A18.00005: Size-dependent swimming behaviors of bacteria and the role of multiflagellarity Xiang Cheng, Shashank Kamdar, Dipanjan Ghosh, Wanho Lee, Maria Tatulea-Codrean, Supriya Ghosh, Youngjun Kim, Tejesh Cheepuru, Eric Lauga, Sookkyung Lim, Yongsam Kim Flagella are a crucial organelle of bacteria enabling their motility and often adapted in two arrangements, i.e., monotrichous bacteria with a single polar flagellum and peritrichous bacteria with multiple flagella forming a rotating bundle. Although the adaptation of bacterial cellular features are under strong evolutionary pressure, studies have shown that multiflagellarity confers no noticeable benefit to the swimming of bacteria in bulk fluids. The puzzling finding poses a long-standing question: why does multiflagellarity emerge given the high metabolic cost of flagellar synthesis? Contrary to the common view that its benefit lies beyond the basic function of flagella in steady swimming, here we show that multiflagellarity indeed provides a significant selective advantage to bacteria in their swimming ability, allowing bacteria of different body sizes to maintain a constant swimming speed. By synergizing experiments, modeling and simulations, we reveal how bacteria utilize the increasing number of flagella to regulate the flagellar motor load, which leads to faster flagellar rotation neutralizing the higher fluid drag on their larger bodies. Without such a balancing mechanism, the swimming speed of monotrichous bacteria decreases with increasing size. Taken together, our study sheds light on the origin of multiflagellarity. Our findings are important for understanding environmental influence on bacterial morphology and useful for designing artificial flagellated microswimmers. |
Monday, March 6, 2023 9:00AM - 9:12AM |
A18.00006: Adaptive Motility in the Simplest Marine Micro-animals Praneet Prakash, Raymond E Goldstein Marine micro-animals live in a highly fluctuating environment. They face a barrage of life threatening situations during their life cycle and survive in a low-nutrient resource bath. Navigating under such conditions requires perpetual adaptation to the local habitat. Here we examine the motility of one of the simplest marine micro-animals by carefully manipulating the local physio-chemical conditions. We find that they optimise their motility by switching between fast and slow mobility states. The adaptive motility behaviour is mapped to a physio-chemical phase space, and a theoretical model explaining these phenomena is proposed. |
Monday, March 6, 2023 9:12AM - 9:24AM |
A18.00007: Bound states of spheroidal squirmers William E Uspal, Ruben Poehnl The “squirmer model” is a classical hydrodynamic model for the motion of interfacially-driven microswimmers, such as self-phoretic colloids or volvocine green algae. To date, most studies using the squirmer model have considered spherical particles. Recently, we generalized the squirmer model to particles with spheroidal shape and axisymmetric distribution of the surface slip. Additionally, in a recent collaboration, we predicted that discoidal particles moving by induced-charged electrophoresis can form “head-to-head” bound pairs. Here, we develop a general approach to the pairing and scattering dynamics of two spheroidal squirmers. We assume that the direction of motion of the squirmers is restricted to a plane, which is approximately realized in many experimental systems. In the framework of an analytically tractable kinetic model, we predict that, for identical squirmers, a “head-to-head” configuration is stable only when the particles have oblate shape and a non-axisymmetric distribution of surface slip. We also obtain conditions for stability of a “head-to-tail” configuration: for instance, the two particles must have unequal self-propulsion velocities. Our analytical predictions are compared against detailed numerical calculations obtained using the boundary element method. |
Monday, March 6, 2023 9:24AM - 9:36AM |
A18.00008: Deformation Dynamics of Semiflexible Colloidal Chains Sibani Lisa Biswal We present the dynamics of semiflexible Brownian filaments under various flow fields. The filaments under consideration are composed of linked colloidal particles that form bead spring-like chains. Non-local hydrodynamic interactions cause the filaments to bend and rotate to align their end-to-end direction perpendicular to the forcing direction. Different reorientation mechanisms are varied for different regimes of flexibility. The competition between the reorientation mechanisms and the Brownian effects results in normal distributions of the orientation of the chains. When the chains are stiff, these fluctuations cause the chains to flow faster than their reciprocal non-Brownian cases. With increasing flexibility, thermal fluctuations lead to more compact configurations of the chains and higher average settling velocity. Chain flexibility also plays an important role when considering lateral chain motion. The interplay between elastic, gravitational, and thermal forces leads to important secondary influences on the flow dynamics of semiflexible chains. |
Monday, March 6, 2023 9:36AM - 9:48AM |
A18.00009: Elastic flow instability enhances solute mixing in 3D porous media Christopher A Browne, Sujit S Datta Polymer solutions are often injected in porous media for applications such as groundwater remediation, column chromatography, or packed bed reactions. In these settings, it is often important to mix solutes in initially separated streams. For Newtonian fluids, the flow is typically laminar, limiting mixing to the dispersion inherent to the disordered pore space. However, it remains unknown how polymer solutions modify this mixing. Here, we directly visualize the mixing of two fluorescently dyed streams within a transparent 3D porous medium. We find that, above a threshold flow rate, the mixing rate increases above the expected laminar dispersion. By imaging the pore-scale velocity field, we demonstrate that the increase in solute mixing rate is concomitant with the onset of an elastic instability in which the flow exhibits strong spatio-temporal fluctuations reminiscent of inertial turbulence, despite the vanishingly small Reynolds number. This elastic instability produces a spectrum of solute concentration fluctuations that follow power-law scalings consistent with Batchelor mixing. Thus, by linking macro-scale mixing to the pore-scale unstable flow, our work provides generally-applicable guidelines to control mixing of passive scalars in disordered porous media. |
Monday, March 6, 2023 9:48AM - 10:00AM |
A18.00010: Printing weakly viscous filaments in microgel suspensions Jae Hyung Cho, Emilie Dressaire Embedded three-dimensional (3D) printing is a direct-ink-writing technique that enables fabrication of complex 3D structures by the deposition of inks in a bath of yield stress fluid. Due to its solid-like resistance to flow under small stresses, the yield stress fluid retains the structure and the position of the printed filaments, thus allowing for the use of runny ink materials. We investigate the printability of weakly viscous, water-based Newtonian inks in baths of dense aqueous microgel suspensions. Far less viscous than typical polymer- or colloid-based ink materials, these Newtonian inks readily penetrate into the fluidized region of the yield stress fluid behind the nozzle, making it challenging to control the shape of printed structures. We find that a higher concentration of the microgel suspension results in more unstable deposition of the inks that often leads to the formation of finger-like patterns, despite the stronger resistance of the bath fluid to flow. We explore how this instability may be correlated with the transient rheological responses of the bath fluid. |
Monday, March 6, 2023 10:00AM - 10:12AM |
A18.00011: Drop impact of dense suspensions: shear jamming with free surfaces Michelle R Driscoll, Brian C Seper, Phalguni Shah, Srishti Arora Dense suspensions exhibit a variety of exotic flow behaviors under high stresses, such as shear thickening and shear jamming. Here, I will show how we can utilize ultrahigh-speed imaging and the free-surface geometry in drop impact as a new tool for studying the flow of dense colloidal suspensions. This system offers a unique lens with which to study shear-thickening fluids, allowing us to obtain flow information in a spatially-localized manner, so that we can observe coexisting solid and liquid phases. Furthermore, we capture shear jamming as it occurs via a solidification front traveling from the impact point, and show that the speed of this front is set by how far the impact conditions are beyond the shear thickening transition. We are currently investigating how jamming and solidification are altered when the suspension is composed of rod-like particles, as well how these jammed systems re-fluidize. |
Monday, March 6, 2023 10:12AM - 10:24AM |
A18.00012: Sheet happens: instabilities in polymeric fluid sheets, and the distinct roles of rheology and microstructure Carly E Galvin, Brendan C Blackwell, Michelle R Driscoll We encounter fragmentation in fluid sheets whenever we visit a waterfall or hold our thumb over the end of a garden hose. Because of their 2D geometry, these sheets present a unique opportunity to explore material instabilities. Newtonian fluid sheets have been well characterized; we are working toward an analogous understanding of complex fluid sheets, where the viscosity of the material depends on the applied stress. Fragmentation patterns in polymeric fluid sheets in particular demonstrate the distinct effects of rheology and microstructure on material stability. In our experiments, we generate the sheets via the collision of two liquid jets and film their dynamics using high-speed photography. Our findings indicate that quickly-expanding sheets are less stable than slowly flowing sheets, and that higher viscosities generate thicker and more stable sheets. Jet velocity, jet diameter, and the investigated fluid's rheological properties are all important in setting the observed instabilities, but polymeric fluids such as Carbopol 940 which self-assemble into microgels have unique fragmentation patterns. Adding sugar alcohols to these solutions changes the microstructure of the fluid without changing its rheology, which allows us to separately examine the roles of these two parameters. |
Monday, March 6, 2023 10:24AM - 10:36AM |
A18.00013: Stripe Instabilities and Disclinations in Freely Suspended Films of Lyotropic Chromonic Liquid Crystals under Oscillatory Shear Flow Angel Martinez Lyotropic chromonic liquid crystals have received a wide interest in recent years because their fundamental viscoelastic properties are relatively not well understood and due to their utility for new technologies in optics and biological sensors. These materials are composed of self-assembled plank-like molecules that form liquid crystal phases uniquely characterized by a huge viscoelastic anisotropy. We study the structural response of a thin, freely suspended nematic film of the chromonic DSCG to oscillatory shear flow. Oscillating shear flows are generated via a suspended magnetic needle driven by an oscillating magnetic field. At shear strain amplitudes below ~0.15, we observe the formation of stripe instabilities with a spatial frequency that depends on shear rate. In this regime, the instabilities are cyclic—twisting and untwisting in response to the cyclic shear. At amplitudes larger than ~0.22, we see the formation of disclinations that store elastic energy and advect away from the needle in a manner reminiscent of elastic turbulence. Rather than exhibiting cyclic reversibility, these disclinations are persistent and grow with the number of shear cycles. At shear strains in between, the instabilities first begin to persist between cycles before ultimately proliferating and transitioning into disclinations. Understanding these materials under large and unsteady strains is a step toward bulk processing, to enable applications such as paintable polarizers and other deformable optics. |
Monday, March 6, 2023 10:36AM - 10:48AM |
A18.00014: Modeling Sheared Frictional Liquid Crystals Christopher Quinones, Peter D Olmsted Recent experiments [1] on sheared suspensions of rigid rods in the dense, non-Brownian regime in rotational geometries have found that the nematic director tilts out of the shear plane into the positive vorticity direction. This state is not "flow-aligned", and may be a kind of previously unobserved kayaking state. We show that at the level of a director or second order tensor model, neither the effect of the flow curvature or Frank elasticity can account for this tilting: both fiber models like Advani-Tucker and liquid crystal models like Doi-Edwards predict stable flow-alignment at high Peclet (i.e. non-Brownian) number. To model this "vorticity tilting", we also consider another feature of dense suspensions: inter-particle contacts. We construct a Rayleighian that includes the additional dissipation due to the relative motion of frictionally contacting rods, and then minimize this to produce a modified Smoluchowski equation, which we use to calculate dynamical equations for the tensor describing rod orientations. We treat both a form of "lubricated" friction, which is proportional to the magnitude of velocity at contact, and a Coulomb-like kinetic friction, which is proportional to the direction of contact velocity. |
Monday, March 6, 2023 10:48AM - 11:00AM |
A18.00015: Extensional Rheology of Protein-Polysaccharide Mixtures Karim Al Zahabi, Lena Hassan, Ramiro Maldonado, Vivek Sharma Many food formulations that replace animal-based proteins with vegan, plant-sourced proteins contain polysaccharides as rheology modifiers which influence ropiness, stringiness and dispensing behavior. It is becoming increasingly recognized that properties associated with heuristic terms like stringiness, stretchiness, or ropiness are correlated with the extensional rheology of these formulations. However, quantitative measurements of macromolecular responses to streamwise velocity gradients for these complex systems has been a longstanding challenge. In this talk, we characterize the pinching dynamics and extensional rheology of different mixtures of proteins and polysaccharides found in several vegan food foams and emulsions via dripping-onto-substrate (DoS) rheometry. We elucidate how complexation transforms the perceived stringiness and responses to both shear and extensional deformations. |
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