Bulletin of the American Physical Society
2005 APS March Meeting
Monday–Friday, March 21–25, 2005; Los Angeles, CA
Session V6: Jamming in Granular Media, Colloidal Suspensions and Glasses |
Hide Abstracts |
Sponsoring Units: GSNP Chair: Eric Weeks, Emory University Room: LACC 502A |
Thursday, March 24, 2005 11:15AM - 11:51AM |
V6.00001: Random close packing revisited: How many ways can we pack smooth, spherical grains? Invited Speaker: We create jammed packings of smooth, spherical particles using an algorithm in which we successively compress or expand soft particles and minimize the total energy of the system at each step until the particles are just at contact. We focus on small systems and thus are able to find (nearly) all of the jammed states. We decompose the probability for obtaining a jammed state at a particular volume fraction into two composite functions: 1) the density of jammed states, which only depends on geometry and 2) the basin of attraction for each jammed state, which depends on the protocol used to create them. By studying the density of states and basins of attraction separately, we are able to show why it is relatively easy to create random close-packed states in 3D monodisperse and 2D bidisperse systems but not in 2D monodisperse systems. \newline \newline Co-authors are Ning Xu and Jerzy Blawzdziewicz, Department of Mechanical Engineering, Yale University. [Preview Abstract] |
Thursday, March 24, 2005 11:51AM - 12:27PM |
V6.00002: Scaling behavior of drag forces in shallow granular media Invited Speaker: The drag forces on intruders slowly moving through shallow beds of granular media show different scaling behavior depending on the direction of motion. Plunging into the medium results in considerably more resistance than horizontal motion or withdrawing, and for beds of glass beads, the resistive force scales supralinearly with immersion depth. For sand, and unlike glass beads, significant shear- hardening is observed as the intruder moves through a freshly poured bed. The force on compact shapes, such as spheres and cubes scales with the intruder's volume. A simple model based upon the contact forces at the intruder's surface is used to estimate the enhancement of the local pressure ahead of the moving intruder. [Preview Abstract] |
Thursday, March 24, 2005 12:27PM - 1:03PM |
V6.00003: Rotation of magnetic clusters near the colloidal glass transition Invited Speaker: Colloidal suspensions are a model system that exhibits a glass transition as the particle concentration is increased. Using confocal microscopy we follow the motion of the colloidal particles to study the microscopic behavior of the system as the glass transition is approached. In particular, we embed a small number of paramagnetic beads into dense colloidal suspension of PMMA particles. Sometimes pairs of beads stick together to form dimers. Using an external permanent magnet we exert magnetic force on the dimer causing the dimer to rotate. Such a rotating dimer perturbs the colloidal particles. We study how such perturbations induced by the rotating dimer vary with sample concentration and the dimer rotational speed. Our studies provide further insight in the nature of the glass transition. [Preview Abstract] |
Thursday, March 24, 2005 1:03PM - 1:39PM |
V6.00004: Jamming in long rod-like granular materials Invited Speaker: The physics of large aspect-ratio (L/D$>>$10) granular materials is relatively unexplored. Such materials form connected networks significantly more rigid than those found in ordinary round granular materials, a feature well-known to anyone who has moved hay with a pitchfork. I will describe recent experiments that investigate the response of two- and three-dimensional piles to an object forced through the pile, with an emphasis on the transition to a jammed state in which the pile acts as a solid body. In 2D the spatial extent of the disturbance scales with particle length and grows linearly with packing fraction. When the disturbance size becomes comparable with the container, solid-body motion occurs in piles of larger aspect ratio particles. In 3D the transition from stick-slip to solid-body occurs through an intermediate region where the time scale of particle rearrangements becomes comparable with that for the test object to move an appreciable distance. This behavior depends both on particle length, aspect ratio, and container dimension, and we are mapping out the behavior in the multi-dimensional parameter space. [Preview Abstract] |
Thursday, March 24, 2005 1:39PM - 2:15PM |
V6.00005: Models of tensorial rheology of disordered soft materials Invited Speaker: Peter Sollich In recent years, the paradigm of `soft glassy matter' has been used to describe diverse nonergodic materials exhibiting strong local disorder and slow mesoscopic rearrangements. As so far formulated, however, the resulting `soft glassy rheology' (SGR) model treats the shear stress in isolation, effectively `scalarizing' the stress and strain rate tensors. Here we offer generalizations of the SGR model that combine its nontrivial aging and yield properties with a tensorial structure that can be specifically adapted, for example, to the description of fluid film assemblies or disordered emulsions and foams. [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. |
© 2024 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
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700