Granular Gas Cooling and Relaxation to the Steady State in Regard to the Overpopulated Tail of the Velocity Distribution

TL;DR

This paper provides a universal description of the velocity distribution in granular gases, highlighting the impact of the high-energy tail on cooling dynamics and relaxation times through simulations and kinetic theory.

Contribution

It introduces a comprehensive model capturing the velocity distribution across all velocities, emphasizing the tail's role in granular gas behavior.

Findings

The velocity distribution exhibits an exponential tail at high velocities.

Deviations from Maxwell distribution affect the cooling coefficient.

Relaxation times are significantly larger due to tail effects.

Abstract

We present a universal description of the velocity distribution function of granular gases, $f(v)$, valid for both, small and intermediate velocities where $v$ is close to the thermal velocity and also for large $v$ where the distribution function reveals an exponentially decaying tail. By means of large-scale Monte Carlo simulations and by kinetic theory we show that the deviation from the Maxwell distribution in the high-energy tail leads to small but detectable variation of the cooling coefficient and to extraordinary large relaxation time.