Granular Gases - the early stage

TL;DR

This paper studies the early evolution of a granular gas's velocity distribution, revealing how it deviates from Maxwellian behavior and proposing a way to measure its age based on Sonine polynomial analysis.

Contribution

It introduces a novel approach to quantify the deviation of velocity distribution in granular gases using Sonine polynomials and discusses measuring the gas's age.

Findings

The Sonine coefficient a_2(t) exhibits complex time dependence.

Granular gases can be characterized by an 'age' based on velocity distribution.

The method provides insights into the early dynamics before clustering occurs.

Abstract

We investigate the evolution of the velocity distribution function of a granular gas composed of viscoelastic particles in the homogeneous cooling state, i.e. before clustering occurs. The deviation of the velocity distribution function from the Maxwellian distribution is quantified by a Sonine polynomials expansion. The first non-vanishing Sonine coefficient a_2(t), reveals a complex time dependence which allows to assign the granular gas the property of an age. We discuss the possibility to measure the age of a granular gas.