A model for collisions in granular gases

TL;DR

This paper introduces a comprehensive collision model for granular gases that accounts for velocity-dependent restitution coefficients, unifying existing theories and revealing complex behaviors based on impact velocity and surface properties.

Contribution

It presents a unified model for granular collisions that incorporates dissipative viscoelastic effects and generalizes classical impact theories.

Findings

Restitution coefficients depend on impact velocity.

Collision type varies with impact velocity and surface properties.

Tangential restitution coefficient shows complex velocity dependence.

Abstract

We propose a model for collisions between particles of a granular material and calculate the restitution coefficients for the normal and tangential motion as functions of the impact velocity from considerations of dissipative viscoelastic collisions. Existing models of impact with dissipation as well as the classical Hertz impact theory are included in the present model as special cases. We find that the type of collision (smooth, reflecting or sticky) is determined by the impact velocity and by the surface properties of the colliding grains. We observe a rather nontrivial dependence of the tangential restitution coefficient on the impact velocity.