Dr. Gregg Lois

Physics Department

University of California-Santa Barbara

Abstract: Granular materials, such as sand in an hourglass, have recently emerged as an ideal system to study dynamical processes occurring far from equilibrium.  Of particular interest are flows of granular materials, which play an important role in many diverse natural and technological processes, including the frictional properties of earthquake faults, the transport of pharmaceutical or chemical products, and the formation of galaxies.  Here we study granular shear flow using simulation.  By increasing the density of the granular material we observe a spontaneous transition from a dilute regime, where interactions consist of only binary collisions, to a dense regime characterized by large force networks and collective motions.  This transition results from a tendency for interacting grains to cluster, due to the dissipative nature of collisions, and can be quantified by measuring correlations between grains.  In the dilute regime, generalizations of kinetic theory are useful and make accurate predictions.  In the dense regime we introduce theories, based on the nature of the force networks, that successfully predict constitutive relations.

                                   Monday, January 9, 2006

                                   Mason Lab 107, 2:30 – 3:30pm

                                   Host:  Professor Corey O'Hern