Cluster Formation due to Collisions in Granular Material

Abstract

The role of inelastic collisions in granular hydrodynamics is studied experimentally in a two dimensional system of spherical particles rolling on a smooth surface and driven by a moving wall. Clusters form at high particle densities; the velocity distribution is narrowed, and the collision rate is enhanced within the clusters. The clusters migrate downward in the presence of a very slight tilt, but are not dispersed. A one dimensional model captures the effect of gravitation on the observed statistical distributions.