SHEAR-INDUCED DIFFUSIVE MIXING IN SIMULATIONS OF DENSE COUETTE-FLOW OF ROUGH, INELASTIC HARD-SPHERES

Large-scale numerical simulations of a system of inelastic, rough, har d spheres of volume fraction phi(s) = 0.565, which are initially distr ibuted randomly in a Couette geometry, show clear evidence of the move ment of the particles in directions transverse to the bulk motion, Thi s behavior of the aforementioned system, which has been considered as a model for a granular fluid, is consistent with recent experimental o bservations [Hsiau and Hunt, J. Fluid Mech. 251, 299 (1993)]. Based on the results obtained, there are indications that a bounded rapid gran ular flow could be a diffusive system at volume fractions even higher than 0.56. This finding contradicts earlier computer experiments [Camp bell, J. Fluid Mech. 348, 85 (1997)] which found a rapidly flowing gra nular material is a diffusive system except at large solids concentrat ions (i.e., phi(s) > 0.56). (C) 1998 American Institute of Physics.