Influence of rotations in energy transfer of a particle colliding on a flat surface

Abstract

To understand the influence of rotations on the dissipation of energy in the interaction between a grain and its environment, we investigate the relaxation process of a single particle bouncing on a flat horizontal surface. For this purpose, faceted particles were used to promote the appearance of rotations in each bounce. The evolution of potential, translational and rotational kinetic energies was analysed during the whole relaxation process, particularly focusing on the behaviour just before and after each collision. The rebounding action of an individual grain results in energy dissipation commonly quantified by ϵ, the coefficient of restitution. This coefficient is defined as the ratio of the normal velocity component prior to impact (Vn) to the corresponding component immediately following the collision (V ′ n ), i.e. related to translational kinetic energy associated with motion in the normal direction. We identify a critical impact velocity below which, in certain collisions, ϵ > 1. This phenomenon can be attributed to stored rotational kinetic energy which is transferred to translational kinetic energy during the collision, thereby increasing the normal velocity V ′ n and resulting in the observed high values of ϵ.