Energy dissipation of a particle colliding on a flat surface

Abstract

To gain an understanding of the factors affecting the interaction of one grain with its environment as it reaches equilibrium, we study a particle bouncing off a flat surface. The bouncing of the particle leads to dissipation that is usually characterized with the coefficient of restitution, defined as the ratio between the velocity component that is normal to the contact surface just before impact (Vn) and the same component, but immediately after the collision (Vn'), i.e. related to a kinetic energy corresponding to motion in the normal direction. We will show how the coeffcient of restitution is affected by energy stored in other degrees of freedom and transferred to kinetic energy that leads to an increase in normal velocity after the impact Vn', and therefore to the coeffcient of restitution is larger than 1. For this purpose, the evolution of potential, translational kinetic energy and rotational kinetic energy is analysed during the whole relaxation process and just before and after each collision for two different types of particle, a disk and a faceted particle.