Bulletin of the American Physical Society
APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011; Dallas, Texas
Session Y13: Granular Materials I |
Hide Abstracts |
Sponsoring Units: GSNP DFD Chair: Brian Utter, James Madison University Room: D225/226 |
Friday, March 25, 2011 8:00AM - 8:12AM |
Y13.00001: ABSTRACT WITHDRAWN |
Friday, March 25, 2011 8:12AM - 8:24AM |
Y13.00002: Homogeneous linear shear of a two dimensional granular system Joshua A. Dijksman, Jie Ren, Robert P. Behringer Using a novel shear device, we experimentally study the response of dry granular materials to quasi-static shear. Our apparatus is capable of creating linear strain profiles over the entire width of the two dimensional shear cell. By eliminating the usual tendency of granular shear to localize in non-uniform shear bands, we can study the poorly understood nature of granular flows in great detail. We employ photo elastic particles, fluorescent labelling and high resolution imaging to obtain information about particle positions, rotation and inter particle forces. We discuss our results in the context of the jamming scenario and also look at various measures capable of elucidating the physics of dense granular flows. [Preview Abstract] |
Friday, March 25, 2011 8:24AM - 8:36AM |
Y13.00003: Constitutive relations for granular fluid of smooth inelastic hard spheres, to Burnett order Vinay Gupta, Meheboob Alam In the framework of kinetic theory for dilute granular gases, we have generalized the work of Sela \& Goldhirsch (1998) by including body force (gravity) term in the Boltzmann equation. In order to derive the constitutive relations for flows of smooth inelastic hard spheres in three dimensions, the Boltzmann equation is perturbatively solved by performing generalized Chapman-Enskog (double expansion) in two small parameters, the Knudsen number and the degree of inelasticity. We have derived the constitutive relations till Burnett order (up to second order in small parameters). In this talk I would like to present the methodology for obtaining the constitutive relations.\\[4pt] Ref: Sela, N. \& Goldhirsch, I. 1998 Hydrodynamic equations for rapid flows of smooth inelastic spheres, to Burnett order. \textit{J. Fluid Mech.} \textbf{361}, 41--74. [Preview Abstract] |
Friday, March 25, 2011 8:36AM - 8:48AM |
Y13.00004: Random to ordered granular sphere packings through cyclic shear Andreea Panaitescu, Anki Reddy, Arshad Kudrolli We investigate the structure of a dense granular packing submitted to quasi-static cyclic shear deformations using a fluorescent liquid refractive index matching method. This technique allows us to obtain the three dimensional position of 1mm glass spheres in the bulk during each cycle. The granular packing is observed to evolve towards crystallization over hundreds of thousands of shear cycles and the packing fraction is correspondingly observed to increase from loose packing fraction, 0.59, to above random close packing, 0.634. The appearance and the propagation of the crystalline order was studied using the orientational order metric, Q$_{6}$. In the early stages of nucleation the particles belonging to the nucleating crystallites are predominantly in hexagonal close packed configuration. When the packing volume fraction approaches a value close to random close packing, a rapid increase of the global Q$_{6}$ and the number of particles with local face centered cubic order is observed. Following the evolution of the crystallites, we find the critical nuclei size to be between 10-50 particles, surprisingly consistent with transitions observed with thermal elastic frictionless spheres. A detailed description of the crystalline clusters and their development will be presented. [Preview Abstract] |
Friday, March 25, 2011 8:48AM - 9:00AM |
Y13.00005: Shearbanding Instability and Patterns in Granular Shear Flows Priyanka Shukla, Meheboob Alam When a (dense) granular material is sheared in shear-cell experiments, shearing remains confined to a narrow localized zone (``shearband'') near the moving boundary. Such shear-banding has also been realized in the molecular dynamics simulations of granular plane Couette flow for a range of densities (even without gravity) in the rapid flow regime. In this talk I will present the shear-banding instability of granular shear flow via an order parameter equation. \\[4pt] [1] Weakly nonlinear theory of shear-banding instability in granular plane Couette flow: analytical solution, comparison with numerics and bifurcation, Priyanka Shukla and Meheboob Alam, Journal of Fluid Mechanics 2010, {\bf 665}, p. 1-50. \\[0pt] [2] Landau-type order parameter equation for shear banding in granular Couette flow, Priyanka Shukla and Meheboob Alam, Physical Review Letters, {\bf 103}, 068001, 2009. \\[0pt] [3] Universality of shear-banding instability and crystallization in sheared granular fluid, Meheboob Alam, Priyanka Shukla and Stefan Luding, Journal of Fluid Mechanics, {\bf 615}, p. 293-321, 2008. [Preview Abstract] |
Friday, March 25, 2011 9:00AM - 9:12AM |
Y13.00006: Shearing granular media: from elasticity to compaction Jean-Francois Metayer, Elie Wandersman, Martin Van Hecke, Matthias Schr\"{o}ter A granular system is able to behave like a solid (a sand pile for example) or like a liquid depending on the deformation imposed on the material. Using rheometry measurements we investigate the response of a granular bed to an imposed deformation or an imposed stress as a function of its packing fraction. We observed different regimes: elastic and plastic behaviors, flow regime and finally compaction. The dependence of these regimes on the packing fraction and on the pressure allows us to delineate the phase diagram of granular media. [Preview Abstract] |
Friday, March 25, 2011 9:12AM - 9:24AM |
Y13.00007: Microscopic rearrangements and macroscopic stress fluctuations in dense emulsion flow Dandan Chen, Kenneth W. Desmond, Eric R. Weeks One characteristic of dense granular materials is they can resist small stresses but start to flow under large stresses. During granular flow, the stress exerted on the boundaries of the flow can have large fluctuations. These fluctuations are thought to originate from internal rearrangements and from changes of force chains; however, the connection between these internal microscopic changes and the macroscopic influences seen at the boundaries is not yet clear. We experimentally study the shear flow of oil-in-water emulsion droplets in a Hele-Shaw cell with a hopper shape. Due to the thinness of the Hele-Shaw cell, the droplets are deformed into quasi-2D pancakes, somewhat analogous to soft photoelastic disks. As droplets approach the hopper exit, they shear past one another and droplets are forced to rearrange. We focus on a typical plastic rearrangement called T1 event, where local four particles have neighbor exchanges. Simultaneously, we use the deformation of the droplets to determine the interdroplet forces, which also change as the sample is sheared. These forces fluctuate over large regions as expected. Our analysis of this emulsion system shows a direct and local relationship between microscopic T1 rearrangements and macroscopic stress ?uctuations. [Preview Abstract] |
Friday, March 25, 2011 9:24AM - 9:36AM |
Y13.00008: Flow and Sedimentation of particulate suspensions in Fractures Tak Shing Lo, Joel Koplik Suspended particles are commonly found in reservoir fluids. They alter the rheology of the flowing liquids and may obstruct transport by narrowing flow channels due to gravitational sedimentation. An understanding of the dynamics of particle transport and deposition is, therefore, important to many geological, enviromental and industrial processes. Realistic geological fractures usually have irregular surfaces with self-affine structures, and the surface roughness plays a crucial role in the flow and sedimentation processes. Recently, we have used the lattice Boltzmann method to study the combined effects of sedimentation and transport of particles suspended in a Newtonian fluid in a pressure-driven flow in self-affine channels, which is especially relevant to clogging phenomena where sediments may block fluid flows in narrow constrictions of the channels. The lattice Boltzmann method is flexible and particularly suitable for handling irregular geometry. Our work covers a broad range in Reynolds and buoyancy numbers, and in particle concentrations. In this talk, we focus on the transitions between the ``jammed'' and the ``flow'' states in fractures, and on the effects of nonuniform particle size distributions. [Preview Abstract] |
Friday, March 25, 2011 9:36AM - 9:48AM |
Y13.00009: Dilation of Granular Packings of Spheres and Non-Spherical Particles under Shear Abigail Polin, Bez Laderman, Christopher Peel, John R. Royer, Paul M. Chaikin A parallelepiped shear cell is used to experimentally measure the dilation of particles prepared at different initial volume fractions from relatively loose assemblies to densely packed ones. The samples consist of spherical marbles, plastic ellipsoids and tetrahedral dice at the centimeter scale and specially prepared particles at the millimeter scale. Under quasi-static shear, loosely packed samples compact while densely packed particles dilate, as in previous studies. For small shear amplitudes, both the dilation and compaction of the tetrahedral packings is significantly larger than that of spheres. [Preview Abstract] |
Friday, March 25, 2011 9:48AM - 10:00AM |
Y13.00010: Dynamic crystallization in granular flow Aline Hubard, Mark D. Shattuck We explore dynamic crystallization in simulations of two dimensional (2D) inelastic frictional hard disks as a model for granular materials. Previous simulations and experiments show formation of hexagonal structures in quasi-2D systems under vibration, rotation, and shearing. In experiments of a uniform but non-equilibrium steady-state (UNESS) under constant pressure the gas-crystal transition shows all of the classic signs of a first-order sublimation phase transition including discontinuous change in density, rate dependent hysteresis, and an equation of state consistent with sublimation. We use molecular dynamics to simulate steady shear under a variety of boundary conditions to determine a dynamic equation of state in the in the density range of the crystallization transition. We compare the dynamic equation of state with that found in non-flowing UNESS experiments, simulations, and theory. [Preview Abstract] |
Friday, March 25, 2011 10:00AM - 10:12AM |
Y13.00011: The path to fracture: dynamics of broken-link networks in granular flows Mark Herrera, Shane McCarthy, Steven Slotterback, Michelle Girvan, Wolfgang Losert Capturing the dynamics of granular flows on intermediate length scale can often be difficult. We propose the broken-links network as a new tool to study fracture at the intermediate scale. Using experimental data on the 3D tracks of all particles in a region, we calculate the dynamically evolving broken-links network and observe a second-order, percolation-like phase transition in the formation of the giant component as links are broken. We implement a velocity gradient model of link breakages and find that the model demonstrates a faster growth of the giant component than the data. Surprisingly, the broken-links network formed in the model is also more highly clustered than our empirical observations. [Preview Abstract] |
Friday, March 25, 2011 10:12AM - 10:24AM |
Y13.00012: Hockey night in phase space Kiri Nichol, Karen Daniels In order to explore the possibility of developing a statistical mechanics for dissipative ensembles, we have performed an experiment in which we track the translational and rotational velocities of pucks on an air hockey table. The pucks are driven by bumpers at the boundaries and are bidisperse to prevent crystallization. At packing fractions of 60\% we find that the system distributes rotational and translation energy according to the equipartition theorem. However, as the packing fraction increases, the ratio of rotational energy to translational energy also increases to a value larger than predicted by equipartition. The translational and angular velocity distributions are approximately exponential and the distributions of the translational velocity are the same for both large and small particles. In contrast, the distribution of the angular velocities is broader for the small particles than for the large. [Preview Abstract] |
Friday, March 25, 2011 10:24AM - 10:36AM |
Y13.00013: Rotational statistics in dense granular flows of smooth cylindrical particles Jeffrey Olafsen, Jacob Jantzi We report the results of an experiment to investigate the dissipation in the rotational degree of freedom for smooth cylindrical particles in a dense, driven granular flow. The flow is studied in a rotating drum of radius R = 30 cm for particles of radius r = 0.635 cm while the cell is rotated at speeds between 0.25 and 0.75 Hz. The 2D geometry of the experimental design allows for the measurement of two translational degrees of freedom as well as the rotation of the disks within the driven flow. The rotational velocity statistics demonstrate non-Gaussian behavior as well as a significant amount of energy being dissipated within the flow via the tangential friction between the particles. The results of this experiment are significant in that many driven granular experiments use smooth cylindrical or spherical particles to investigate granular dynamics, but the contribution from the rotational degrees of freedom are often unmeasured. A novel imaging technique is used to extract both the translational and rotational velocity statistics to a high degree of precision in the entire cell during the experiment. [Preview Abstract] |
Friday, March 25, 2011 10:36AM - 10:48AM |
Y13.00014: ABSTRACT WITHDRAWN |
Friday, March 25, 2011 10:48AM - 11:00AM |
Y13.00015: Size Segregation of Granular Materials Anurag Tripathi, D.V. Khakhar Segregation of granular materials due to size difference while flowing/energized is a very well known but poorly understood phenomena. Despite of some good understanding of the mechanism of size segregation, predictive models for size segregation are not available. Size segregation of binary granular mixtures flowing over inclined plane is studied by means of DEM simulations. Buoyant force acting on trace particles of a bigger size is obtained by varying the density of the trace particles rising/sinking in the granular flow. We show that moderately big trace particles of same density as that of the light particles tend to rise because of higher buoyancy forces than the weight of the trace particles. For very big trace particles of same density, however, the buoyant force becomes smaller than the weight of the particles causing the particles to settle down. Drag force on the trace particle is found to be given by Stokes' law. Friction drag is found to almost $10-12\%$ of the weight of the trace particles. Incorporating the Stokes' law and balancing the segregation and diffusion flux of big particles, we are able to predict the number fraction of the big particles in terms of viscosity and diffusivity for moderately dilute binary mixture of different size particles. The proposed theory is tested against DEM simulation results and very good agreement has been found with the simulation results. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2022 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
1 Research Road, Ridge, NY 11961-2701
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700