Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session S15: Granular, Porous Media, & Multiphase Flows II |
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Sponsoring Units: DFD GSNP Chair: Nathan Keim, California Polytechnic State University Room: 210/212 |
Thursday, March 5, 2020 11:15AM - 11:51AM |
S15.00001: Nonlinear acoustic resonance and wave-induced softening in dense granular matter through flow heterogeneities Charles Lieou, Jerome Laurent, Paul A Johnson, Xiaoping Jia We report a series of experiments on the softening and compaction of a dense granular pack through traveling acoustic pressure and shear waves. Softening is manifested by a reduction the traveling-wave speed, as the amplitude of the disturbance increases beyond some threshold. We explain these seemingly contradictory observations using a theoretical model, based on shear transformation zones (STZs), that directly attributes these observations to dynamical heterogeneities and slipping contacts in the granular pack. Softening is accounted for by the increase of the fraction of STZs or slipping contacts as a function of increasing strain amplitude, while compaction is explained by an Ising-like correlation between STZs in the subyield regime. In so doing, we demonstrate the fundamental connection between nonaffine granular rearrangements, mesoscopic glassy dynamics, jamming and unjamming, and matter-wave interactions. |
Thursday, March 5, 2020 11:51AM - 12:03PM |
S15.00002: Scaling and dynamics of impacts into cornstarch and water suspensions Marc Brassard, Neil Causley, Joshua Dijksman, Abe Clark Impacts into dense suspensions, which consist of micron-scale particles suspended in a Newtonian fluid, undergo a dramatic solidification when subjected to sudden impact. Recent work has shown that the forces during the initial moments of impact are too large to be described by discontinuous shear thickening (DST), which is a steady-state description. Other descriptions, such as the added mass model proposed by Waitukaitis and Jaeger, capture some aspects of the dynamics well but fail to predict certain features. Here, we show results from experimental impacts into dense suspensions consisting of cornstarch particles and water. We vary the size, speed, mass, and shape of the projectile as well as the density of the suspension. We quantify the forces as a function of time using high-speed imaging and other sensors. We use scaling analysis to probe the underlying physical mechanisms and compare our results to existing descriptions. |
Thursday, March 5, 2020 12:03PM - 12:15PM |
S15.00003: Peak Force Scaling During Impacts into Wet and Dry Granular Materials Neil Causley, Nasser F Krizou, Marc Brassard, Joshua Dijksman, Abe Clark Impacts into granular materials, both wet and dry, are common in engineering and nature, but a fundamental description of the forces during impact is still lacking. Certain drag laws (e.g., Poncelet laws) and other rheological descriptions (e.g., inertial rheology for dry grains or discontinuous shear thickening for suspensions) are often successful in describing certain aspects of the forces, but these descriptions typically fail to capture the largest forces during the initial moments of impact. Here, we use experiments and simulations to study early time dynamics of impacts into wet and dry granular materials. We show that the magnitude and time scales of the peak forces obey power law scaling that is similar across the different types of materials we study, and we use dimensional analysis to isolate the relevant physical mechanisms. We find that existing models do not predict many of the scaling laws we observe, suggesting the need for new models to describe this process. |
Thursday, March 5, 2020 12:15PM - 12:27PM |
S15.00004: Proper Spatial Average Operators in a Heterogeneous Porous Medium Ehsan Taghizadeh, Brian David Wood In this work, we explore a wide range of kernel functions commonly used in Bayesian statistics to evaluate their functionality in attenuating geometrical fluctuations arising from sudden change in the porosity in a heterogeneous porous medium. Boxcar; single-, double-, and triple-convoluted boxcar; Epanechnikov; Tricube; Gaussian; Cosine; Logistic; Sigmoid; and Silverman are among weighting functions we examined for the cases where (1) a periodic homogeneous medium, (2) a quasi-periodic heterogeneous medium with a gradual porosity change, (3) a quasi-periodic heterogeneous material with a discontinuous jump in porosity, and (4) a disordered heterogeneous porous medium with a discontinuous jump in the porosity exist. We use an extended porous material’s diffusion model developed based on volume averaging method recently reported by Battiato et al 2019 [1]. The model retains the zero- and first-order terms in the closure problem and neglects the second-order Taylor series. Results are promising in a sense that mollified version of some of those weighting functions can improve divergence of Taylor series approximation of the average flux of mass through the porous material. |
Thursday, March 5, 2020 12:27PM - 12:39PM |
S15.00005: Fluid Flow with Suspended Soft Particles in Porous Media Shuaijun Li, Jing Fan Transport of soft particles with flow in porous media is ubiquitous in many natural and engineering processes. For example, preformed-particle-gel (PPG) treatment is a common technique in enhanced oil recovery. While the measurable properties in this process are at the microscale, such as gel size, properties, and the macroscopic permeability directly correlates with the overall recovery efficiency. Therefore, it is desirable to find the quantitative relation between the macroscopic permeability and the relevant microscopic properties. However, this remains an unsolved problem. In this work, we study transport of mono-dispersed suspended soft particles in porous media. We start from analyzing a soft particle transport through a single pore throat and find the correlation between injection pressure and the properties of the soft particle. Based on this result, we then expand the analysis to macroscale. we find a quantitative relation between the macroscopic permeability and pore-scale properties in the presence of pore blockage. The work significantly improves our understanding on transport of soft particles in porous media and directly benefits the relevant industrial applications. |
Thursday, March 5, 2020 12:39PM - 12:51PM |
S15.00006: Granular packings with sliding, rolling and twisting friction Andrew Santos, Ishan Srivastava, Dan Stefan Bolintineanu, Jeremy Lechman, Gary Grest, Leo Silbert Intuition tells us that a rolling or spinning sphere will eventually stop due to the presence of friction. The resistance to rolling and spinning/twisting that stops one sphere also changes the microstructure of a granular packing of frictional spheres. Isostatic constraint counting allows packings of 3d spheres to span an average number of contacts per sphere between 6 to 2, depending on the types of frictional constraints. We perform discrete element modeling simulations to construct sphere packings implementing a range of frictional constraints under a stress-controlled protocol. The simulated granular packings are tested against the isostatic conjecture and are compared to experimental values. Stable packings are achievable at low volume fractions and average coordination numbers, circa 0.52 and 2.6 respectively, when the particles experience high resistance to sliding, rolling and twisting. |
Thursday, March 5, 2020 12:51PM - 1:03PM |
S15.00007: Elastogranular Buckling of a Slender Ring David Schunter, Jr., Douglas Holmes Thin flexible-walled structures provide utilitarian geometries in a variety of biological and engineering contexts. Whether describing the origins of certain vascular disorders, the mechanics of thin membranes, or in constructing domed architectures, understanding how these thin objects respond due to external forcing is crucial. Previous work has focused on thin structures deforming within media that, in general, have both compositional and mechanical homogeneity. In comparison, much less is known about the behavior of slender structures embedded in active or driven matter, such as a vibrating granular monolayer. By placing a thin elastic ring within a horizontally driven 2D granular bed, we investigate the phase space of buckling morphologies that arises under gradual compression of this coupled system. Varying the compression rate U, we see a crossover between two distinct regimes, with ring buckling geometries reflecting the degree of granular force homogeneity. These results will bring new insight into how flexible structures deform & pack within complex media, and will be relevant for geometric approaches to cell mechanics, the design of soft robots, the modeling of animal movements, and developing responsive, directable medical devices. |
Thursday, March 5, 2020 1:03PM - 1:15PM |
S15.00008: Using time-dependent random resistor networks to capture the dynamics of flow in disordered porous media Ahmad Zareei, Shima Parsa, David A Weitz, Ariel Amir The heterogeneous microstructure of a disordered porous medium determines the pore-level flow. Any changes to the micro-structure in a porous medium, such as solute retention during polymer flow (effectively "clogging" some pores in the network), affects the pore-level flow and alters the bulk behavior. In order to better understand the effect of microstructure on flow behavior, we study a model based on a disordered network of tubes, mathematically equivalent to a random resistor network. We show that this approximate model captures the observed velocity distribution in experiments on glass beadpack. We model the dynamics of structural changes during polymer retention, and show that the (dynamic) resistor network produces flow velocity distributions and bulk properties consistent with the experiments. |
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