Translations and Rotations are correlated in Granular Gases

TL;DR

This paper demonstrates that in granular gases of rough particles, rotational and translational velocities are correlated, with the correlation strength depending on collision dissipation parameters, supported by theory and simulations.

Contribution

The paper introduces a simple theoretical model for velocity correlations in granular gases of rough particles and validates it through extensive numerical simulations.

Findings

Rotational and translational velocities are correlated in granular gases.

Even minimal particle roughness induces significant correlations.

The derived theory accurately predicts the correlation dependence on collision parameters.

Abstract

In a granular gas of rough particles the axis of rotation is shown to be correlated with the translational velocity of the particles. The average relative orientation of angular and linear velocities depends on the parameters which characterise the dissipative nature of the collision. We derive a simple theory for these correlations and validate it with numerical simulations for a wide range of coefficients of normal and tangential restitution. The limit of smooth spheres is shown to be singular: even an arbitrarily small roughness of the particles gives rise to orientational correlations.