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 G18: Fluids V |
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Sponsoring Units: DFD Chair: Balu Nadiga, LANL Room: Room 210 |
Tuesday, March 7, 2023 11:30AM - 11:42AM |
G18.00001: Spontaneous Transport across Locally Nonchaotic Molecular-Sized Outward-Swinging Gates Yu Qiao, Zhaoru Shang, Rui Kou In this research, we investigate an interesting concept: molecular-sized outward-swinging gates, which may be viewed as a locally nonchaotic entropy barrier. Our theoretical analysis, Monte Carlo simulation, and brutal-force solution of governing equations all indicate that across such gates, under the condition of local nonchaoticity, the probability of particle crossing is effectively asymmetric. It was confirmed experimentally by using a nanoporous membrane one-sidedly surface-grafted with bendable organic chains. Remarkably, across the membrane, gas could flow form the low-pressure side to the high-pressure side. The transport process was spontaneous and repeatable. |
Tuesday, March 7, 2023 11:42AM - 11:54AM |
G18.00002: Gait induced self-organization in shape changing active matter Akash Vardhan, Aryaman Jha, Daniel Soto, Ram Avinery, Zeb Rocklin, Daniel I Goldman In a recent study [Vardhan et al. (arxiv: 2206.04782)], we reported the discovery of “gliders”, which are dynamically bound, locomoting excitations that emerge spontaneously from stochastic rigid-body collisions in a shape-changing, programmable active matter system known as “smarticles”. In dense ensembles, these gliders self-assemble into chain-like structures by spontaneously linking with other robots in their vicinity. This results in a long-range spatial order with a characteristic lifetime of 8-10 periods. We study how initially compressed collectives expand to lower density configurations using simulations and experiments and analyze the degree of self-organization for various gaits (i.e., closed loops in the shape space). We measure instantaneous contact and construct a graph where the vertices are the spatial coordinates of each particle and the edges represent the pairwise contacts, hence obtaining the average number of neighbors per gait period for each smarticle. We observe that time-irreversible gaits responsible for producing gliders also give rise to chains with closed loops having 4 neighbors on average. Further, we observe a time-reversible gait produces long, aligned chains with most agents having 2 neighbors on average. The emergent order is thus found to be controlled by gait dynamics. |
Tuesday, March 7, 2023 11:54AM - 12:06PM |
G18.00003: Diffusiophoretic transport and dispersion of colloids across complex landscapes Mobin Alipour, Haoyu Liu, Aditya Pujari, Amir Pahlavan Understanding the transport and dispersion of colloids in heterogeneous environments is essential for a wide range of phenomena, from drug delivery to subsurface energy storage and contaminant removal. The classical description of colloid transport relies on the balance between advection by the background flows and diffusion of particles. However, it is known that colloids can also move in the presence of solute gradients, a phenomenon known as diffusiophoresis. Recent studies have demonstrated the utility of diffusiophoresis in manipulating and steering colloids in simple microfluidic geometries. Yet, it remains a question whether diffusiophoresis could play an important role in more complex environments, where background fluid flows are often present. Here, combining experimental observations and numerical simulations of microfluidic channels patterned with obstacles, we study the competition between phoretic and convective migration of colloids and discuss the implications of the phoretic migration at the pore-scale on the transport and dispersion of colloids at the macroscopic scale. |
Tuesday, March 7, 2023 12:06PM - 12:18PM |
G18.00004: Under Pressure: Fracture and Relaxation in Bulk Cornstarch Suspensions Irmgard Bischofberger, Paul Lilin, Jean Elkhoury, Ivo Peters We probe the fracture and relaxation characteristics of dense cornstarch suspensions, a complex fluid that exhibits discontinuous shear-thickening behavior. We inject air at a constant pressure into suspensions of different mass fractions of cornstarch in water placed in an open three-dimensional container. Because the suspension is opaque, fast X-ray radiography is required to image the growth of the air cavity upon air injection. The X-ray images reveal shapes ranging from smooth bubbles to sharp cracks. By measuring the air thickness, we find that both bubbles and cracks grow at a constant volumetric flow rate that increases linearly with the applied pressure, a remarkably simple behavior for a complex fluid. We show that the air cavity shape and relaxation dynamics strongly depend on the cornstarch mass fraction: sharp cracks relax into bubbles with a relaxation time scale that depends on the mass fraction. This relaxation process will yield new insights into the transition of the material from the discontinuous shear-thickening state to the fluid state. |
Tuesday, March 7, 2023 12:18PM - 12:30PM |
G18.00005: Computer Simulation of the Magnetic Resonance Measurement of Flow of Fluidized Particles Alireza Bordbar, Stefan Benders, Wasif Zia, Alexander Penn, Christopher M Boyce Magnetic resonance velocimetry (MRV) is among the non-invasive measurement techniques for multiphase flow systems that is receiving increasing attention. MRV simulation of flow systems is a subject that has not been dealt with enough in literature, especially for time-varying multiphase flow systems. Such simulations can help in evaluating the accuracy of rapid experimental MRV techniques. This study aims to perform a MRV simulation of an incipiently fluidized bed into which two high velocity side-by-side air jets are injected. The simulation procedure starts from importing results of CFD-DEM into MR simulator and compares the results with actual prior MR measurements. |
Tuesday, March 7, 2023 12:30PM - 12:42PM |
G18.00006: Hydrodynamic focusing in porous media and its ramifications on the critical penetration depth Patrick M Comiskey, Christopher Staszel The effect of hydrodynamic focusing through porous media is analytically investigated to ascertain the critical thickness such that liquids do not completely penetrate the media. The flow field of a single drop impacting a surface with any number of pores is established by solving the Laplace equation resulting from an instantaneous pressure impulse as prescribed by impact dynamics. Complex analysis is utilized to transform the drop into the complex plane via conformal mapping in order to determine the liquid velocity penetrating into the pores. The critical penetration of the drop into the porous media occurs when the kinetic energy of the drop, known as a function of the penetration velocity, is dissipated by viscous friction. It was found that hydrodynamic focusing in multi-pore surfaces occurs, and the liquid penetration velocity rapidly diminishes as the number of pores increases. Moreover, the critical thickness of a porous media also rapidly diminishes as the number of pores increases and importantly, plateaus. Implications for liquids splashing onto garments is discussed. |
Tuesday, March 7, 2023 12:42PM - 12:54PM |
G18.00007: Preferential Flow and Mechanical Stability of Model Sandy Soils Ippolyti Dellatolas, Irmgard Bischofberger Preferential flow occurs as rain permeates a soil, where unstable pathways of enhanced fluid flow coexist with drier regions. The instability is triggered by a competition between gravitational, capillary, and viscous forces that governs the spatial extent and the kinetics of the preferential flow pathways. Preferential flow has been linked to increased occurrence of landslides following heavy rainfall events and earthquakes, yet the mechanism by which preferential pathways trigger failure remains poorly understood. Using a custom-built laboratory-scale experimental setup, we probe the infiltration of water through a porous medium of tunable grain size and grain surface properties. We induce mechanical perturbations to the material to study the failure modes of the wet granular channels. Complementing these experiments with a rheological characterization of a preferentially wetted granular medium, we elucidate the impact of preferential paths on the stability of the granular medium. |
Tuesday, March 7, 2023 12:54PM - 1:06PM |
G18.00008: Impact of large periodic deformations on solute transport in soft porous media Matilde Fiori, Christopher W MacMinn, Satyajit Pramanik From soils to soft biological tissues, there are many examples of materials that can be modelled as highly deformable porous media, characterised by a strong coupling between mechanical stimulation and fluid flow due to complex rearrangements of the pore space. In both contexts – subsurface geomechanics and living-tissue biomechanics or tissue engineering – the effects of large periodic deformations on solute transport and mixing can be of great interest for predicting and/or controlling the motion of contaminants or nutrients. Here, we propose a 1D continuum model based on large-deformation poroelasticiy that links an applied periodic deformation to the resulting solute transport and mixing. Transport occurs through advection, molecular diffusion, and hydrodynamic dispersion, all of which are affected by the deformation in specific ways. We explore the effects of several dimensionless parameters on the problem, focusing on the ones regulating the applied periodic load. We find that the amplitude and period of deformation influence the mechanical response of the material, which can belong to either a linear slow-loading or a nonlinear fast-loading regime. These mechanical regimes directly characterise the resultant movements of solute. |
Tuesday, March 7, 2023 1:06PM - 1:18PM |
G18.00009: Simulation and modeling of settling in polydisperse gas-solid flows Emily Foster, Eric Breard, Ph.D., Sarah Beetham Sedimenting flows occur in a wide range of industrial and natural systems, such as circulating fluidized bed reactors and pyroclastic density currents (PDCs), the most hazardous volcanic process. In systems with sufficiently high mass loading, momentum coupling between the phases gives rise to mesoscale behavior, such as clustering. These structures are then capable of generating and sustaining turbulence in the carrier phase and directly impact large-scale quantities of interest, such as settling time. As an added complexity, many flows of interest consist of a polydisperse particulate phase. In this talk, we characterize the sedimentation behavior of a range of polydisperse gas-solid flows, sampled from a parameter space typically associated with PDCs. Highly resolved data is collected using an Euler-Lagrange framework and polydisperse settling behavior is contrasted with Stokes settling and analogous ensembles of monodisperse particles. Finally, a settling law is proposed which takes into account polydispersity by leveraging the first four moments of the particulate phase distribution. |
Tuesday, March 7, 2023 1:18PM - 1:30PM |
G18.00010: Stochastic Modeling of Sieving in Membrane Filters Binan Gu, Pejman Sanaei, Lou Kondic, Linda J Cummings Membrane filtration of fluids is ubiquitous, and there is increasing interest from industrial practitioners in mathematical models that capture the complex nature of the process. Previous theoretical efforts include studies on material features of the membrane structure, and their connection to fluid mechanical properties and filtering efficiency. In this work, we focus on filtration through membranes whose internal structure is a network of pores through which foulant-laden fluid flows, with two modes of fouling operating simultaneously -- adsorption and sieving. Adsorption involves a slow accretion of foulant particles far smaller than pore sizes on the pore wall, while sieving concerns much larger particles that block pore entrances on a faster time scale. We model sieving as a stochastic process on the network with both a simulation-based approach and a mean-field probabilistic approach. Using each method, we investigate how the two fouling mechanisms interact and affect measures of membrane filter performance such as total throughput and accumulated foulant concentration in the filtrate. In addition, we show how the behavior changes when network geometric parameters are varied. |
Tuesday, March 7, 2023 1:30PM - 1:42PM |
G18.00011: Interactions and Pattern Formation in a Macroscopic Magnetocapillary SALR System Alireza Hooshanginejad, Victoria Spradlin, Jack-William Barotta, Giuseppe Pucci, Daniel M Harris Interaction potentials defined by Short-range Attraction and Long-range Repulsion (SALR), frequently arise in the modeling of colloidal systems. Here, we introduce a new SALR potential that combines capillary attraction and repulsive magnetic forces and can be realized in an accessible tabletop experiment. We develop a simplified model of the pairwise interaction potential that predicts a variety of regimes, including the possibility of a local minimum energy configuration for certain parameters. Experiments confirm that a minimum energy configuration corresponding to a finite equilibrium spacing is possible for a pair of millimetric magnetic floating disks. Quasi-1D experiments and simulations show that beyond a critical packing fraction, the uniform lattice state becomes unstable and localized clusters spontaneously form. Finally, we explore pattern formation at high packing fractions in the two-dimensional magnetocapillary system which exhibits behaviors that are reminiscent of microscopic colloidal systems. |
Tuesday, March 7, 2023 1:42PM - 1:54PM |
G18.00012: Modelling of complex-shaped granular particles using spherical harmonics Mohammad Imaran, James Young, Rosario Capozza, Kevin Stratford, Kevin J Hanley One of the key challenges in the modeling of granular particles is the realistic representation of their shape and implementation of the associated contact laws. A novel simulation technique using spherical harmonics which extends DEM towards modelling arbitrary shaped particles in LAMMPS, is presented. The shape of these particles is represented using spherical harmonics where their radii can be calculated at spherical coordinates [1]. The interaction between these particles depends on the overlap volume, which follows an energy-conserving contact theory [2]. A contact detection algorithm, based on the bounding spheres of the interacting particles, is developed. The overlap volume and other required quantities are calculated using Gaussian quadrature integration of the spherical cap formed by the bounding spheres. The granularity of particles and subsequent computational requirements can thus be controlled by truncating the number of terms in the spherical harmonic expansion [3]. The number of quadrature points and degree of spherical harmonic expansion are shown to affect the precision and computational cost of the simulation, which increases almost quadratically. A simple MPI parallelization results in a significant reduction in the simulation time. The proposed algorithm developed in the form of a user-package in LAMMPS thus aids in the accurate modelling of the motion of complex-shaped particles. |
Tuesday, March 7, 2023 1:54PM - 2:06PM |
G18.00013: Capillary imbibition in lubricant-coated surfaces Sergi G Leyva, Rodrigo Ledesma-Aguilar, Aurora Hernandez-Machado, Ignacio Pagonabarraga We describe spontaneous imbibition processes in lubricant-coated surfaces. This geometry represents a simplified version of experimental realisations like slippery liquid-infused porous surfaces (SLIPS) and lubricant-impregnated surfaces (LIS), where the lubricant eliminates direct contact of both invading and displaced fluids with the solid. We combine a theoretical and computational analysis to clarify the dissipation mechanisms that governs the dynamics of imbibition. The asymmetric distribution of dissipation among the fluid phases results in two limit regimes: When the dissipation is more relevant in the displacing fluid, we find a diffusive advancing of the front, which corresponds the well-known limit in which invading and displaced fluids are in direct contact with the solid. If dissipation takes place preferentially in the lubricant, we find a linear advancing of the front through the entire channel. |
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