Spontaneous Ratchet Effect in a Granular Gas

TL;DR

This paper demonstrates how spontaneous clustering in a vibrofluidized granular gas leads to directed transport phenomena, including convection and ratchet effects, driven by collective symmetry breaking without intrinsic anisotropy.

Contribution

It introduces the concept of a spontaneous ratchet effect in granular gases and models these phenomena quantitatively through a flux-based approach.

Findings

Observation of spontaneous convection rolls in granular fountain

Detection of spontaneous particle current in granular ratchet

Quantitative agreement between experiments, simulations, and flux model

Abstract

The spontaneous clustering of a vibrofluidized granular gas is employed to generate directed transport in two different compartmentalized systems: a "granular fountain" in which the transport takes the form of convection rolls, and a "granular ratchet" with a spontaneous particle current perpendicular to the direction of energy input. In both instances, transport is not due to any system-intrinsic anisotropy, but arises as a spontaneous collective symmetry breaking effect of many interacting granular particles. The experimental and numerical results are quantitatively accounted for within a flux model.