Dynamic Measurements of Normal and Tangential Coefficients of Restitution for an Inelastic Billiard

Driven granular media dissipate a large amount of energy in their particle-particle and particle-boundary interactions. As such, our understanding of the fundamental dynamics in these systems is complicated by the velocity-dependent nature of the coefficient of restitution. Even how a driven granular flow jams necessitates a better understanding of the details of this dissipative mechanism. Very sophisticated experiments have sought to better understand and characterize the velocity dependence of the coefficient of restitution by attempting to constrain and control aspects of the collisions. A careful and in-depth analysis for an inelastic billiard moving within a confining boundary allows the velocity-dependence to be measured as the dynamics freely evolve over multiple collisions in the driven system. The shape of the geometry can be varied to tease out details of the dynamics as well as the differences between the normal and tangential coefficients of restitution. The large amount of data generated in this experiment allows the contributions from both the normal and tangential velocity components in the particle-boundary interactions to be examined. Two derivative experiments, one for particle-boundary and the other for particle-particle collisions will also be discussed.