Hydrodynamics of a Granular Gas in a Heterogeneous Environment

TL;DR

This paper investigates the transport behavior of granular gases in non-uniform active fluids, demonstrating that Navier-Stokes hydrodynamics accurately describes steady flows even at high inelasticity, with deviations increasing as inelasticity decreases.

Contribution

It introduces a model for granular gas dynamics in a non-uniform active fluid and validates hydrodynamic descriptions through numerical simulations, highlighting novel effects of inelasticity.

Findings

Navier-Stokes hydrodynamics accurately describes steady flow.

Deviations from hydrodynamics increase as inelasticity decreases.

Active fluid modeled with non-uniform fluctuating volume force.

Abstract

We analyze the transport properties of a low density ensemble of identical macroscopic particles immersed in an active fluid. The particles are modeled as inelastic hard spheres (granular gas). The non-homogeneous active fluid is modeled by means of a non-uniform stochastic thermostat. The theoretical results are validated with a numerical solution of the corresponding the kinetic equation (direct simulation Monte Carlo method). We show a steady flow in the system that is accurately described by Navier-Stokes (NS) hydrodynamics, even for high inelasticity. Surprisingly, we find that the deviations from NS hydrodynamics for this flow are stronger as the inelasticity decreases. The active fluid action is modeled here with a non-uniform fluctuating volume force. This is a relevant result given that hydrodynamics of particles in complex environments, such as biological crowded environments, is still a question under intense debate.