CLUSTER FORMATION DUE TO COLLISIONS IN GRANULAR MATERIAL

The role of inelastic collisions in granular hydrodynamics is studied experimentally in a two dimensional system of spherical particles roll ing on a smooth surface and driven by a moving wall. Clusters form at high particle densities; the velocity distribution is narrowed, and th e 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 ob served statistical distributions.