Clustering, Order, and Collapse in a Driven Granular Monolayer

TL;DR

This paper investigates the dynamic behaviors of a vertically shaken granular monolayer, revealing how varying vibration amplitudes lead to different states such as clustering, order, and collapse, with detailed experimental observations.

Contribution

It provides experimental insights into phase transitions and collapse phenomena in driven granular monolayers, highlighting the effects of vibration amplitude on particle correlations and states.

Findings

High amplitude results in short-range correlations similar to equilibrium gases.

Lowering amplitude increases correlations, leading to clustering or ordered states.

Further cooling causes a collapse into a condensate of motionless particles.

Abstract

Steady state dynamics of clustering, long range order, and inelastic collapse are experimentally observed in vertically shaken granular monolayers. At large vibration amplitudes, particle correlations show only short range order like equilibrium 2D hard sphere gases. Lowering the amplitude "cools" the system, resulting in a dramatic increase in correlations leading either to clustering or an ordered state. Further cooling forms a collapse: a condensate of motionless balls co-existing with a less dense gas. Measured velocity distributions are non-Gaussian, showing nearly exponential tails.