HOMOGENEOUS COOLING OF ROUGH, DISSIPATIVE PARTICLES - THEORY AND SIMULATIONS

We investigate freely cooling systems of rough spheres in two and thre e dimensions. Simulations using an event-driven algorithm are compared with results of an approximate kinetic theory, based on the assumptio n of a generalized homogeneous cooling state. For short times t, trans lational and rotational energy are found to change linearly with t. Fo r large times both energies decay like t(-2) with a ratio independent of time, but not corresponding to equipartition. Good agreement is fou nd between theory and simulations, as long as no clustering instabilit y is observed. System parameters, i.e., density, particle size, and pa rticle mass can be absorbed in a rescaled time, so that the decay of t ranslational and rotational energy is solely determined by normal rest itution and surface roughness.