Fluctuating hydrodynamics for driven granular gases

TL;DR

This paper develops a microscopic fluctuating hydrodynamics framework for driven granular gases heated by a stochastic thermostat, deriving the noise characteristics and analyzing the velocity fluctuations.

Contribution

It constructs a Boltzmann-Langevin equation for driven granular gases and explicitly derives the noise terms and their amplitudes in the hydrodynamic limit.

Findings

The noise in driven granular gases is white, unlike in free cooling cases.

The amplitude of the Langevin force is explicitly evaluated.

A spectrum analysis of the linearized Boltzmann-Fokker-Planck operator is performed.

Abstract

We study a granular gas heated by a stochastic thermostat in the dilute limit. Starting from the kinetic equations governing the evolution of the correlation functions, a Boltzmann-Langevin equation is constructed. The spectrum of the corresponding linearized Boltzmann-Fokker-Planck operator is analyzed, and the equation for the fluctuating transverse velocity is derived in the hydrodynamic limit. The noise term (Langevin force) is thus known microscopically and contains two terms: one coming from the thermostat and the other from the fluctuating pressure tensor. At variance with the free cooling situation, the noise is found to be white and its amplitude is evaluated.