Simulations of dense granular gases without gravity with impact-velocity-dependent restitution coefficient

TL;DR

This paper presents two-dimensional simulations of vibrated granular materials without gravity, incorporating a velocity-dependent restitution coefficient that captures viscoelastic and plastic deformations, revealing new behaviors in cluster formation and collision dynamics.

Contribution

The study introduces a velocity-dependent restitution coefficient model accounting for viscoelastic and plastic deformations, leading to novel insights into granular gas behavior without gravity.

Findings

Formation of a loose cluster near the fixed wall at large N

Pressure is independent of N and proportional to vibration velocity V

Collision frequency at the vibrating wall is independent of N and V

Abstract

We report two-dimensional simulations of strongly vibrated granular materials without gravity. The coefficient of restitution depends on the impact velocity between particles by taking into account both the viscoelastic and plastic deformations of particles, occurring at low and high velocities respectively. Use of this model of restitution coefficient leads to new unexpected behaviors. When the number of particles N is large, a loose cluster appears near the fixed wall, opposite the vibrating wall. The pressure exerted on the walls becomes independent of N, and linear in the vibration velocity V, quite as the granular temperature. The collision frequency at the vibrating wall becomes independent of both N and V, whereas at the fixed wall, it is linear in both N and V. These behaviors arise because the velocity-dependent restitution coefficient introduces a new time scale related to the collision velocity near the cross over from viscoelastic to plastic deformation.