Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session H48: Granular, Porous Media, Multiphase Flows & BubblesFocus

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Sponsoring Units: DFD GSNP Chair: FuLing Yang Room: BCEC 251 
Tuesday, March 5, 2019 2:30PM  2:42PM 
H48.00001: Dynamical model for nonlocal inertialnumber rheology of dense granular flows KengLin Lee, FuLing Yang Dense granular materials present complicated fluid and solid behaviors. The materials flow above a yield stress which is greater than the magnitude when the flow stops, known as hysteresis. Nonlocal flow rheology emerges due to particle cooperative motions, resulting in flowsize dependence in quasistatic regime and longrange collision momentum transport in dense inertial regime. In this talk, we formulate a dynamical GinzburgLandau model of phase transition that can describe these features. We choose the inertial number I as a fluidization order parameter and derive the free energy functional using scaling arguments along with a yieldstress weakening mechanism. The model yields a nonmonotonic flow curve in a homogeneous flow environment, accounting for hysteresis and intermittency in the quasistatic regime. The model shows a generalized Bagnold stress revealing two nonlocal mechanisms: collisions among correlated structures within which fluidization spread. The model captures several salient features in inclined flow configuration including hysteretic starting and stopping heights, Pouliquen's inertial flow rule and flowthickness dependent velocity shapes. 
Tuesday, March 5, 2019 2:42PM  2:54PM 
H48.00002: Boundary Condition for Dense Granular Flows on Smooth Boundary FuLing Yang, ChengChuan Lin When granular material moves relative to a smooth boundary, we often assign a Coulombtype stress boundary condition with a constant effective wall friction coefficient μ_{w}. Recent experimental and numercial (DEM) investigations on both steady and transient flows reveal a roubst trend that that μ_{w} decays monotonically with the distance from a moving boundary such as a free surface, a slip base, or an internal shear band. Individual grain rotation is found to be an internal mechanism to degrade bulk μ_{w}. We discover that grain anular speed is correlated with granular temperatre which has been reported to correlate with bulk slip velocity or shear rate. We integrate the findings to present a boundary condition for dense granular flows with nonzero velocity relative to its boundary. 
Tuesday, March 5, 2019 2:54PM  3:06PM 
H48.00003: Cooperative and uncooperative motions in gravitydriven flows Kerstin Nordstrom, Emma C Thackray, Grace S Cai We present results from experiments and complementary molecular dynamics simulations of 2D gravity driven granular flows. We specifically study silo flow: discharge through an aperture in a rectangular cell. We obtain particlescale data in our experiments using highspeed, highresolution video. We find the presence of cooperatively moving regions and characterize them by their sizes, speeds, and lifetimes. We also find the presence of regions of high nonaffine motion and characterize them similarly. In our analysis, we place particular emphasis on the role of initial packing structure on the resulting bulk flow behavior and microscopic deformations. Our results suggest that the transition from clogging behavior to free flow can be modified by changing the packing structure. 
Tuesday, March 5, 2019 3:06PM  3:18PM 
H48.00004: New concepts for modeling connectivity effects in capillary pressure hysteresis in porous media Zongyu Gu, Amin Amooie, Martin Bazant Continuum models of porous media often characterize microscopic features of the pore space using macroscopic parameters like porosity and tortuosity, and macroscopic state variables like fluid saturations. To account for the effects of porescale connectivity between different sized pores, we propose a new parameter, “porespace accessivity” to contrast serial and parallel arrangements of different sized pores, and a new state variable, “radiusresolved saturation”, to describe the microscopic distribution of fluids. Based on a statistical branching process, we derive a new microscopic constitutive theory of capillary pressure hysteresis for arbitrary drainageimbibition cycles. Expanding on the classical “capillary bundle” picture by means of providing a useful first approximation for connectivity effects in porous media, these concepts may have much broader utility in continuum modeling of porous media in a variety of applications. 
Tuesday, March 5, 2019 3:18PM  3:30PM 
H48.00005: Capillary filling of water in structural defects at fibermatrix interface of unidirectional composite materials Kalpani Galpayage Dona, Sarah E Du, Leif Carlsson

Tuesday, March 5, 2019 3:30PM  3:42PM 
H48.00006: Instabilities of Vertical TimeDependent Miscible Displacements in Homogeneous Porous Media Youssef Elgahawy, Jalel Azaiez Buoyancydriven instabilities develop at the interface between fluids in miscible flow displacements. Such instabilities significantly affect the efficiency of displacement processes encountered in many applications such as enhanced oil recovery and CO_{2} sequestration. Thus, it is imperative to control such instabilities. Most studies on vertical miscible displacements are limited to displacements involving a constant injection rate. However, in some practical processes the injection rate is in fact timedependent. The objective of this study is to investigate the effects of timedependent injection rates on the growth of fingering instabilities. The governing equations are solved numerically using the HartleyPseudospectral method. First, the dynamics of fingering instabilities were examined using nonlinear simulations, under constant injection rates, to determine the criteria for the instability which depends on the mobility ratio, density difference, and the critical injection velocity. Then, utilizing timedependent injection schemes, it was found that the instability can be attenuated depending on the cycle period and velocity amplitude. Moreover, the flow is always less unstable when the displacement is initiated through an extraction stage rather than an injection one. 
Tuesday, March 5, 2019 3:42PM  3:54PM 
H48.00007: ContinuumScale Modeling of Multiphase Flow in Porous Media From a New Microscopic Theory of Hysteresis Amin Amooie, Zongyu Gu, Martin Bazant We present continuum modeling of multiphase flow in macroscopic porous media based on a new microscopic hysteresis theory that provides physicsbased macroscopic parameters and state variables to capture essential porescale features. We propose accessivity to characterize the network connectivity of differentsized pores in a porous medium, and radiusresolved saturations to characterize the distribution of fluid phases within. Developing a statistical theory for quasistatic immiscible drainageimbibition in arbitrary cycles, we arrive at simple models that naturally arrest hysteresis in capillary pressure and relative permeability. Existing models use empirical casebased modifications to capture hysteretic data and rectify the curvatures of their predictions, which fails to make a physical connection to the medium microstructure. Employing the proposed conceptual framework, here we then develop a novel multiphase flow simulator for macroscopic porous media, where the new constitutive relationships for both capillary pressure and relative permeability consistently link the continuum model to the microscopic state of fluid phases in a porous medium of a given microstructure. 
Tuesday, March 5, 2019 3:54PM  4:06PM 
H48.00008: Nonorthogonal multiplerelaxationtime lattice Boltzmann method: theory and its application in multiphase flows Linlin Fei, Kai Hong Luo A threedimensional multiplerelaxationtime lattice Boltzmann method (MRTLBM) is constructed based on a series of nonorthogonal moments. Compared with the widely used orthogonalmomentsbased MRTLBM, the present formulation simplifies the mapping between the discrete velocity space and the moment space, and exhibits better flexibility across different lattices. The proposed method is then extended to simulate multiphase flows with large density ratio and tunable surface tension, and validated via benchmark cases. Finally, we present simulations of several practical and challenging problems using the nonorthogonal MRTLBM to highlight its capability for simulating realistic multiphase flows. 
Tuesday, March 5, 2019 4:06PM  4:18PM 
H48.00009: Cavitation in Boxing: A physical approach Thibault Guillet, Juliette Amauger, David Quere, Caroline Cohen, Christophe Clanet When a closed container filled of water (model of the head) is accelerated by a shock, cavitation bubbles can form and eventually, at their collapse, cause the shattering of the container. Predicting the growth and collapse dynamics of a bubble is crucial in limiting its damages. By conducting simultaneous highspeed imaging of the motion and pressure measurements in the fluid, we show that RayleighPlesset equation accurately predicts the time evolution of the bubble radius. Additionally, we both experimentally and theoretically prove that the pressure distribution in the fluid can be directly derived from the acceleration. Finally, the overall bubble dynamics is found to be governed by the maximal acceleration and the timespan of the shock. 
Tuesday, March 5, 2019 4:18PM  4:30PM 
H48.00010: Cavitation in Boxing : a possible link with Traumatic Brain Injury Juliette Amauger, Thibault Guillet, David Quere, Christophe Clanet, Caroline Cohen Traumatic Brain Injury (TBI) is a major healthcare problem, increasingly occurring in sports like rugby, boxing or football. The occurrence of TBI is dependent on the head acceleration and the duration of the shock, as expressed by the empirical Wayne State Tolerance Curve (WSTC). One of the possible causes of TBI is the formation of cavitation bubbles in the cerebrospinal fluid. To investigate this hypothesis, we experimentally observe the formation of cavitation bubbles due to a shock on a water tank, and we quantify the influence of the acceleration and timespan of the shock on the bubbles dynamics. In the cranial cavity, the cerebrospinal fluid can flow in an out through the spinal cord. Using a flexible membrane to mimic this phenomenon, we show that this motion is a prerequisite for bubble growth. From the prediction of the bubbles sizes, we build a phase diagram of the damaging capacity of the bubbles on the brain as a function of the acceleration profile, in good agreement with the prediction of the WSTC. 
Tuesday, March 5, 2019 4:30PM  4:42PM 
H48.00011: In Situ TEM Imaging of Nanoscale Bubble Collapse and the Resulting Damage Garth Egan, Xavier Lepro Chavez, Edmond Lau, Eric R Schwegler In recent years, it has been suggested that micron and submicron scale cavitation can occur in the human brain during explosive pressure wave, blunt trauma, or sports collision type events and that the resulting bubble collapse could be the main cause of damage leading to traumatic brain injuries. However, the behavior of very small bubbles is not yet well understood because of the challenges associated with imaging on the necessary length and time scales. Here, we present the direct imaging of bubble collapse in a liquid cell using the MovieMode Dynamic Transmission Electron Microscope (MMDTEM) at Lawrence Livermore National Laboratory. Bubbles were induced in ~13 µm of water using laser heating of 60 nm gold particles and typically found to collapse within 200 ns. Polymer coated on the liquid cell substrates served as witnesses to potential damage. The behavior of the system was further explored with molecular dynamic (MD) simulations. 
Tuesday, March 5, 2019 4:42PM  4:54PM 
H48.00012: Magnetic Resonance Imaging of the Interaction of Bubbles and Jets Injected into Fluidized Beds Christopher Boyce, Alexander Penn, Maxim Lehnert, Azin Padash, Klaas P Pruessmann, Christoph R Müller Rapid magnetic resonance imaging (MRI) is used to measure the dynamics of bubbles and jets of gas injected into 3D gasfluidized beds of granular particles. When two bubbles initially of equal volume rise sidebyside, one bubble collapses while the other maintains its size. This phenomenon is attributed to channeling of gas flow through one bubble, leaving the collapsing bubble with insufficient gas flow to maintain its roof and rise velocity via drag force. When two jets of gas are injected sidebyside, bubbles pinch off from the two jets at alternating times, creating a zipperlike pattern. This phenomenon is attributed to the growth of one jet pushing particles toward the second jet, causing bubble pinchoff from the second jet. The second jet subsequently grows, pushing particles toward the first jet, causing a cyclical pattern to form. Different bubble and jet interaction patterns are seen depending on the size of the particles in the fluidized bed; these differences are attributed to the variation in gas permeability through assemblies of granular particles with particle size. 
Tuesday, March 5, 2019 4:54PM  5:06PM 
H48.00013: Bubble collapse and jet formation in corner geometries Ivo Peters, Yoshiyuki Tagawa The collapse of a vapor bubble near a flat solid boundary results in the formation of a jet that is directed towards the boundary. In more complex geometries such as corners, predictions of the collapse cannot be made in a straightforward manner due to the loss of axial symmetry. We experimentally investigate the bubble collapse and jet formation in corners formed of two flat solid boundaries with different opening angles. Using potential flow analysis, we accurately predict the direction of the jet and bubble displacement. We further show that for a corner with an opening angle $\alpha$, there exist analytic solutions that predict the jet direction for all the cases $\alpha=\pi/n$, where $n$ is a natural number. These solutions cover, in discrete steps, the full range of corners from the limiting case of a bubble near a single wall ($n=1$) up to a bubble in between parallel walls ($n\rightarrow\infty$). 
Tuesday, March 5, 2019 5:06PM  5:18PM 
H48.00014: Give it a boost  The shape of a travling long bubble during the transition between two steady states Yingxian Estella Yu, Lailai Zhu, Suin Shim, Jens G Eggers, Howard A Stone When a confined long bubble translates steadily in a cylindrical capillary, with negligible gravity effects, a uniform thin film of fluid separates the bubble surface and the tube wall. Although a wide variety of investigations have been carried out analyzing the relationship between the film thickness profile and the bubble velocity, most of the literature considers the case where the translational velocity is a constant, thus the bubble profile is steady. Instead, in this work, we investigate how this steady state is established by considering the transitional motion of the bubble as it adjusts its film thickness profile between two steady states, characterized by two different bubble speeds. Different sections of the timedependent film profile will be characterized, and we will further discuss how the "travel history" of the bubble is stored in the bubble shape. The theoretical results are further verified both by experiments and numerical simulations. The results can potentially be applied to a tunable insitu particle separation process. 
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