Ordering phenomena in cooling granular mixtures

TL;DR

This paper investigates two phenomena during the free cooling of a 2D granular mixture: a change in kinetic energy ratio due to velocity correlations and a late-stage segregation with domain formation.

Contribution

It reveals how velocity correlations alter energy distribution and uncovers a new segregation effect with domain growth in cooling granular mixtures.

Findings

Kinetic energy ratio approaches mass ratio during cooling.

Segregation domains emerge in late cooling stages.

Spectral analysis shows increasing characteristic length.

Abstract

We report two phenomena, induced by dynamical correlations, that occur during the free cooling of a two-dimensional mixture of inelastic hard disks. First, we show that, due to the onset of velocity correlations, the ratio of the kinetic energies associated with the two species changes from the value corresponding to the homogeneous cooling state to a value approximately given by the mass ratio m_1/m_2 of the two species. Second, we report a novel segregation effect that occurs in the late stage of cooling, where interconnected domains appear. Spectral analysis of the composition field reveals the emergence of a growing characteristic length.