Role of roughness on the hydrodynamic homogeneous base state of inelastic spheres

TL;DR

This paper investigates how surface roughness influences the relaxation dynamics and velocity correlations in a gas of inelastic rough spheres, revealing that roughness significantly affects the approach to hydrodynamics and velocity distribution distortions.

Contribution

It provides a detailed analysis of the impact of roughness on relaxation times and velocity correlations using a Grad-like solution and simulations, highlighting the role of roughness in non-Maxwellian behavior.

Findings

Relaxation time is largely unaffected by inelasticity but increases with decreasing roughness.

Velocity correlations are accurately described at all times.

Roughness can induce significant deviations from Maxwellian velocity distributions.

Abstract

A gas of inelastic rough spheres admits a spatially homogeneous base state which turns into a hydrodynamic state after a finite relaxation time. We show that this relaxation time is hardly dependent on the degree of inelasticity but increases dramatically with decreasing roughness. An accurate description of translational-rotational velocity correlations at all times is also provided. At a given inelasticity, the roughness parameter can be tuned to produce a huge distortion from the Maxwellian distribution function. The results are obtained from a Grad-like solution of the Boltzmann-Enskog equation complemented by Monte Carlo and molecular dynamics simulations.