Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session V48: Jamming and Clogging |
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Sponsoring Units: GSNP Chair: Jonathan Kollmer, North Carolina State Univ Room: LACC 510 |
Thursday, March 8, 2018 2:30PM - 2:42PM |
V48.00001: Soft particle clogging in 2D hoppers Mia Morrell, Haoran Wang, Eric Weeks
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Thursday, March 8, 2018 2:42PM - 2:54PM |
V48.00002: Transition from Jamming to Clogging in Heterogeneous Environments Cynthia Reichhardt, Huba Peter, Andras Libal, Charles Reichhardt Jamming describes a transition from a flowing or liquid state to a solid or rigid state in a loose assembly of particles such as grains [1]. In contrast, clogging describes the ceasing of particulate matter flow through a bottleneck [2]. It is not clear how to distinguish jamming from clogging, nor is it known whether they are distinct phenomena or fundamentally the same. We examine an assembly of disks moving through a random obstacle array and identify a transition from clogging to jamming behavior as the disk density increases. The clogging transition has characteristics of an absorbing phase transition, with the disks evolving into a heterogeneous phase separated clogged state after a critical diverging transient time. In contrast, jamming is a rapid process in which the disks form a homogeneous motionless packing, with a rigidity length scale that diverges as the jamming density is approached. We show how the relaxation times and transient time exponents change at the clogging-jamming boundary and demonstrate that clogged systems reach a stationary state that is independent of the system density while jammed states are strongly dependent on the system density. |
Thursday, March 8, 2018 2:54PM - 3:06PM |
V48.00003: Jamming of Two-Dimensional Systems of Polygonal Grains Cacey Stevens Bester, Hu Zheng, Yiqiu Zhao, Jonathan Bares, Robert Behringer Significant progress has been made in experimental studies of the jamming transition of systems of circular grains. However, grains are rarely circular in real world granular materials. Shape adds complexity to the system-scale behavior of granular systems, which we explore in jamming experiments. We biaxially compress two-dimensional packings of photoelastic polygonal grains, allowing us to visualize internal stresses as the packing shifts to a jammed state. To systematically study the effect of grain shape, regular polygons of varying numbers of sides are used in our experiments. We then measure the contact number evolution and critical packing fraction at jamming, comparing systems of polygons to that of disks. We also explore the influence of features, such as face-face contacts, in connection with the jamming transition. |
Thursday, March 8, 2018 3:06PM - 3:18PM |
V48.00004: Micro-, Meso- and Macroscale Properties of Granular Packings under Cyclic Compression Jonathan Kollmer, Karen Daniels We subject a set of photoelastic particles to repeated cyclic compression. As expected, the load applied to this granular system is focused along force chains which form a network of connections throughout the system. Since a jammed granular system is overconstrained, this force network is not unique and differs for each compression cycle. Using our open source PeGS software we reconstruct the vectorial contact force for all interparticle contacts in the system for thousands of realizations of the force network. We show that the probability distribution function of the contact forces collapses on a single curve for all realizations and packing fractions when scaled by the mean contact force. We further show that fluctuations of the pressure on each particle in the system correlate to the particle's betweenness centrality value extracted from the geometric contact network. Thus we can relate the contact network mesostructure to the individual particle pressures and the statistics of the interparticle forces to the global volume fraction. |
Thursday, March 8, 2018 3:18PM - 3:30PM |
V48.00005: Kinetics and Shape of a Sedimentary Jamming Front Seyyed Muhammad Salili, Douglas Durian Sedimenting grains form a planar jamming front that propagates upward as grains collect into a solid packing at the bottom of a column. The shape of the front may be stationary for tall samples at early times, but at later times this breaks down front interplay between the jamming front and the suspension-supernatant front. Here we obtain the spatiotemporal change of concentration profile for sedimenting non-Brownian particles in an index-matched fluid at low Reynolds numbers using light-sheet fluorescence imaging. Accordingly, shape of the one-dimensional jamming front is measured as a function of initial concentration. The empirically measured shape of the jamming front between sediment and suspension is compared with numerical solution of our formulated nonlinear partial differential sedimentation equation. This equation is based on the permeability of the suspension (a.k.a. the hindered settling function), a nonlocal lubrication force acting in proportion to the spatial gradient in the time derivative of volume fraction, plus gravity and mass conservation [1]. |
Thursday, March 8, 2018 3:30PM - 3:42PM |
V48.00006: Memory of biaxial compression during shear jamming in granular materials Hu Zheng, Dong Wang, David Chen, Robert Behringer We have designed a novel experimental apparatus to probe the jamming features of granular materials based on photoelastic techniques. The experiment consists of a floating layer of photoelastic disks, which is subject to deformation (compression or shearing). We first compress the granular sample to detect the jamming packing fraction of a given systemusing the photoelastic response. This also yields the force chain networks and stresses throughout the material. we decompress the system to a certain distance from the jamming point.We next decompress the system below jamming, and then apply pure shear, lead to a shear jammed state. We compare the force network, coordination number and local density distribution for the states obtained by compression vs. those obtained by shear jamming state when the systems have the same pressure to understand structural similarities in the two types of states. |
Thursday, March 8, 2018 3:42PM - 3:54PM |
V48.00007: Jamming transition in Couette shear Meimei Wang, Hu Zheng, Jonathan Bares, Dong Wang, Robert Behringer We study the jamming transition with a novel Couette experimental apparatus, which allows us to shear an ideal 2D photoelastic granular system. The photoelastic particles are suspended in a density matched fluid, so that there is no basal friction. We simultaneously record the particle positions and photoelastic response over a range of shear rates. The photoelastic data provide grain scale forces on the particles. The macroscale shear stress is obtained by a torque sensor. We study the correlation between the granular scale pressure from the photoelasic response, and macroscale shear stress during the shear jamming transition. We also determine the coarse-grained strain field, which shows novel convective flow over large strains. |
Thursday, March 8, 2018 3:54PM - 4:06PM |
V48.00008: Shear jamming and flow with novel shear profiles Yiqiu Zhao, Jonathan Bares, Hu Zheng, Robert Behringer Bi et al. have shown that, if sheared, a granular material can jam |
Thursday, March 8, 2018 4:06PM - 4:18PM |
V48.00009: How do force chains form in granular materials? Robert Behringer, Dong Wang, Hu Zheng, Jie Ren, Joshua Dijksman Force networks are ubiquitous in dense static and slowly deforming granular materials. A particle is in a strong force chain if it experiences forces at or above the mean. Relatively few particles in a system close to jamming are typically in force chains. This raises the questions, what determines whether a particle becomes part of a force chain, and what controls the evolution of force chains once they have formed? We investigate these questions in the context of shear jamming, where force chains emerge from an initially zero-stress state in response to shear. The shear jamming process causes the mean contact number, Z, to rise above its isostatic value. We identify key structures, groups of three contacting particles (trimers) and intersection points of chains (branches) that respond to shear, so as to create a jammed state. We use experimental data to track all trimers and branches to answer the two questions above. |
Thursday, March 8, 2018 4:18PM - 4:30PM |
V48.00010: Gravity and friction in shear jamming of 3D granular materials David Chen, Robert Behringer Shear jamming occurs in 2D frictional particles over a range of packing fractions below isotropic jamming. Simulations show shear jamming for frictionless spheres, but over a vanishing range as the system size grows. We use packings of submerged hydrogel particles to determine the shear-induced macroscopic response of 3D, low-frictional granular systems near jamming, bridging the gap between frictionless and low-frictional packings. We find that a ~0.4% density-mismatch easily compacts the low frictional (μ ~ 0.03) system, superseding shear jamming and highlighting the importance of gravity. We perform experiments with density-matched high- and low-frictional particles to recover a macroscopic shear jamming response in 3D and elucidate the role of friction in shear jamming. Accompanying DEM simulations corroborate our experimental results. |
Thursday, March 8, 2018 4:30PM - 4:42PM |
V48.00011: Effect of Friction on Shear Jamming Dong Wang, Jonathan Bares, David Chen, Joshua Dijksman, Jie Ren, Hu Zheng, Robert Behringer Shear jamming of granular materials was first found for systems of frictional disks, with a static friction coefficient μ ≈ 0.6 (Bi et al. Nature (2011)). Jamming by shear is obtained by starting from a zero-stress state with a packing fraction Φ between ΦJ (isotropic jamming) and a lowest ΦS for shear jamming. This phenomenon is associated with strong anisotropy in stress and the contact network in the form of force chains, which are stabilized and/or enhanced by the presence of friction. Whether shear jamming occurs for frictionless particles is under debate. The issue we address experimentally is how changing friction affects shear jamming. By applying a homogeneous simple shear, we study the effect of friction by using photoelastic disks either wrapped with Teflon to reduce friction or with fine teeth on the edge to increase friction. Shear jamming is still observed; however, the difference ΦJ - ΦS is smaller with lower friction. In addition, we add a shaking procedure after each quasi-static shear step to remove relatively weak frictional contacts, resulting in dramatically postponing the onset for shear jamming to appear. |
Thursday, March 8, 2018 4:42PM - 4:54PM |
V48.00012: Shear Jamming of Frictional Grains under Oscillatory Shear Michio Otsuki, Hisao Hayakawa Granular materials have rigidity above a critical density [1]. It is well-known that frictionless grains under small strain exhibit a continuous transition of the shear modulus G, while recent studies have revealed that G of frictional grains with harmonic repulsive interaction discontinuously emerges at the critical density [2]. |
Thursday, March 8, 2018 4:54PM - 5:06PM |
V48.00013: Comparison of the Force Network Topology of the 2D and 3D Granular Systems Lenka Kovalcinova, Angelo Taranto, Lou Kondic In this talk, we present results of discrete element simulations and topological data analysis of the force networks in 2D and 3D compressed granular systems. Our numerical setup consists of the system of cylindrical (2D) or spherical (3D) particles placed on a square or cubical grid inside the box with flat walls. Different initial conditions are guaranteed by random assignment of the particle velocities. System dynamics is driven by isotropic compression of the walls interjected by relaxation period to ensure the independence of compression rate. |
Thursday, March 8, 2018 5:06PM - 5:18PM |
V48.00014: Making Jamming more Attractive Dion Koeze, Brian Tighe Numerical and theoretical studies of jamming presume that particles are purely repulsive. In fact emulsion droplets, foam bubbles, and powders typically experience weak cohesive forces. Understanding the consequences of this weak attractive interaction is therefore necessary in order to interpret experimental studies of jamming. I will present the results of simulations of non-Brownian soft spheres with a finite-ranged attractive tail in their pair potential. The distance to the attractive jamming transition can be controlled by systematically varying both packing fraction and the range of the attractive tail. By measuring elastic moduli and identifying rigid clusters using the pebble game, I will demonstrate that attractive jamming displays features reminiscent of both repulsive jamming and rigidity percolation, but lies in a different universality class. |
Thursday, March 8, 2018 5:18PM - 5:30PM |
V48.00015: Scale invariant structures and marginal stability in jammed amorphous solids Hua Tong, Hao Hu, Peng Tan, Ning Xu, Hajime Tanaka A major issue in condensed matter physics is how the structures of amorphous solids are self-organized, which leads to peculiar properties distinct from crystalline counterparts. Due to their disordered nature which is complex and system dependent, there has been no consensus on the existence of amorphous order, not to mention a quantitative description with a firm theoretical basis. Here we derive a new structure indicator, Ψ, from the mechanical aspect of amorphous solids which is universal for systems with different constituents, structures, interactions, and in both 2D and 3D. We find that the distribution of Ψ has a power-law tail, whose exponent shows critical scaling approaching the jamming transition. Such a power-law distribution indicates marginal stability of amorphous solids, even if the system is away from jamming point. Scale invariant structures are identified, which shows long-range correlations and non-trivial fractal dimensions. We argue that this is related to the global organization of force networks under disordered constraint and a link with the long-range stress correlation is discussed. Our findings reveal critically correlated nature of amorphous structures and promote Ψ as a solid starting point for further theoretical description of amorphous solids. |
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