“Partially Fluidized Granular Flows: Continuum Theory and MD Simulations ”

Professor Lev S. Tsimring
Institute for Nonlinear Science
UC San Diego

DATE: Thursday, June 3, 2004
TIME: 4:00 p.m.
PLACE: Engineering II, Room 3361

ABSTRACT

A continuum theory of partially fluidized granular flows is developed. The theory is based on a combination of the equations for the flow velocity and shear stresses coupled with the order parameter equation which describes the transition between flowing and static components of the granular system. The order parameter is introduced as a fraction of persistent contacts among total number of contacts between particles. We demonstrate that the shear stress tensor can be represented as a sum of "fluid part" depending on the strain rate tensor, and a "static part" depending on the order parameter. Based on the hysteretic bifurcation diagram for a thin shear granular layer obtained in soft particle MD simulations, we construct the equation for the order parameter. The theory is applied to several granular problems: avalanches in shallow inclined layers, shear granular flows and granular friction. The theoretical results are compared with 2D soft particle molecular dynamics simulations and available experimental data.