Granular gases under extreme driving

TL;DR

This paper investigates how extreme energy injection influences the steady-state behavior of inelastic granular gases, revealing power-law velocity distributions and energy cascade phenomena through molecular dynamics simulations.

Contribution

It demonstrates that rare, powerful energy injections produce a well-mixed granular gas with a power-law velocity distribution, providing new insights into nonequilibrium steady states.

Findings

Velocity distribution exhibits a power-law tail under extreme driving.

The power-law exponent matches kinetic theory predictions.

When injection rate is high, the tail becomes stretched exponential.

Abstract

We study inelastic gases in two dimensions using event-driven molecular dynamics simulations. Our focus is the nature of the stationary state attained by rare injection of large amounts of energy to balance the dissipation due to collisions. We find that under such extreme driving, with the injection rate much smaller than the collision rate, the velocity distribution has a power-law high energy tail. The numerically measured exponent characterizing this tail is in excellent agreement with predictions of kinetic theory over a wide range of system parameters. We conclude that driving by rare but powerful energy injection leads to a well-mixed gas and constitutes an alternative mechanism for agitating granular matter. In this distinct nonequilibrium steady-state, energy cascades from large to small scales. Our simulations also show that when the injection rate is comparable with the collision rate, the velocity distribution has a stretched exponential tail.