Collective motion and solid-liquid-type transitions in vibrated granular layers

TL;DR

This study investigates phase transitions and wave behaviors in vibrated granular layers, revealing a solid-liquid transition at low frequencies and unique bending waves at high frequencies, enhancing understanding of granular dynamics.

Contribution

It introduces the observation of a solid-liquid transition and identifies a new type of bending wave in vibrated granular layers, expanding knowledge of granular material behavior.

Findings

Solid-liquid transition occurs at low excitation frequencies.

Subharmonic standing waves are linked to fluid-like behavior.

Bending waves are observed at high frequencies with minimal grain transfer.

Abstract

From pressure and surface dilation measurements, we show that a solid-liquid-type transition occurs at low excitation frequencies in vertically vibrated granular layers. This transition precedes subharmonic bifurcations from flat surface to standing wave patterns, indicating that these waves are in fact associated with the fluid like behavior of the layer. In the limit of high excitation frequencies, we show that a new kind of subharmonic waves can be distinguished. These waves do not involve any lateral transfer of grains within the layer and correspond to excitations for which the layer slightly bends alternately in time and space. These bending waves have very low amplitude and we observe them in a vibrated two-dimensional layer of photoelastic particles.