Driven low density granular mixtures

TL;DR

This paper investigates the steady state behavior of driven low density granular mixtures in two dimensions, revealing multiple granular temperatures, non-Gaussian velocity distributions, and spatial clustering through analytical and simulation methods.

Contribution

It introduces a detailed analysis of two different energy driving mechanisms and uncovers phenomena like temperature disparities and cluster formation in granular mixtures.

Findings

Presence of two distinct granular temperatures for each species

Overpopulated tails in velocity distribution functions

Non-uniform density and temperature profiles with height

Abstract

We study the steady state properties of a 2D 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 non trivial 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 non uniform 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.