Driven low density granular mixtures

We study the steady state properties of a two-dimensional granular mixture in the presence of energy driving by employing simple analytical estimates and direct simulation Monte Carlo. We adopt two different driving mechanisms, (a) a homogeneous heat bath with friction and (b) a vibrating boundary (thermal or harmonic) in the presence of gravity. The main findings are the appearance of two different granular temperatures, one for each species; the existence of overpopulated tails in the velocity distribution functions and of nontrivial spatial correlations indicating the spontaneous formation of cluster aggregates. In the case of a fluid subject to gravity and to a vibrating boundary, both densities and temperatures display nonuniform profiles along the direction normal to the wall, in particular, the temperature profiles are different for the two species while the temperature ratio is almost constant with the height. Finally, we obtained the velocity distributions at different heights and verified the non-Gaussianity of the resulting distributions.