Granular Brownian Motors: role of gas anisotropy and inelasticity

TL;DR

This paper studies how gas anisotropy and inelastic collisions influence the steady-state drift of a wedge-shaped granular Brownian motor, revealing significant effects on motion and equipartition breaking.

Contribution

It introduces the role of gas anisotropy and inelasticity in granular Brownian motors, highlighting a key dimensionless parameter affecting drift and equipartition.

Findings

Gas anisotropy significantly affects motor drift.

A dimensionless parameter links shape, mass, inelasticity, and anisotropy.

Anisotropy causes a dramatic breaking of equipartition.

Abstract

We investigate the motion of a wedge-shaped object (a granular Brownian motor), which is restricted to move along the x-axis and cannot rotate, as gas particles collide with it. We show that its steady-state drift, resulting from inelastic gas-motor collisions, is dramatically affected by anisotropy in the velocity distribution of the gas. We identify the dimensionless parameter providing the dependence of this drift on shape, masses, inelasticity, and anisotropy: the anisotropy leads to a dramatic breaking of equipartition, which should easily be visible in experimental realizations.