Vibrated granular media as experimentally realizable Granular Gases

TL;DR

This study uses numerical simulations to explore vibrated granular media, revealing the importance of impact velocity dependent restitution coefficients and showing how system behavior varies with density and gravity, differing from classical theories.

Contribution

The paper introduces a model with impact velocity dependent restitution coefficient, aligning simulations more closely with experimental results and revealing new scaling behaviors.

Findings

Impact velocity dependence is crucial for accurate modeling.

Scaling exponents decrease with increasing particle number.

Gravity influences clustering and scaling behavior.

Abstract

We report numerical simulations of strongly vibrated granular materials designed to mimic recent experiments performed both in presence [1] or absence [2] of gravity. We show that a model with impact velocity dependent restitution coefficient is necessary to bring the simulations into agreement with experiments. We measure the scaling exponents of the granular temperature, collision frequency, impulse and pressure with the vibrating piston velocity. As the system changes from a homogeneous gas state at low density to a clustered state at high density, these exponents are all found to decrease continuously with the particle number. In absence of gravity, a loose cluster appears near the upper wall, opposite the piston, and acts as a buffer for fastest particles leading to unexpected non-extensive scaling exponents ; whereas in presence of gravity, the cluster bounces as a single inelastic body. All these results differ significantly from classical inelastic hard sphere kinetic theory and previous simulations, both based on a constant restitution coefficient.