Granular rotor as a probe for a non-equilibrium bath

TL;DR

This paper demonstrates that a granular rotor can serve as an effective non-equilibrium probe, accurately inferring the local velocity distribution of a granular gas through combined analytical and molecular dynamics methods.

Contribution

It introduces a theoretical framework and simulation validation showing the rotor's ability to map the granular gas's velocity distribution.

Findings

The rotor's angular distribution accurately reflects the granular gas's velocity distribution.

A one-to-one theoretical map between the gas's VDF and rotor's angular distribution is established.

Simulations confirm the rotor's effectiveness as a local non-equilibrium bath probe.

Abstract

This study numerically and analytically investigates the dynamics of a rotor under viscous or dry friction as a non-equilibrium probe of a granular gas. In order to demonstrate the role of the rotor as a probe for a non-equilibrium bath, the molecular dynamics (MD) simulation of the rotor is performed under viscous or dry friction surrounded by a steady granular gas under gravity. A one- to-one map between the velocity distribution function (VDF) of the granular gas and the angular distribution function for the rotor is theoretically derived. The MD simulation demonstrates that the one-to-one map accurately infers the local VDF of the granular gas from the angular VDF of the rotor, and vice versa.