Effect of the vibration profile on shallow granular systems

TL;DR

This study investigates how asymmetric vibration profiles influence the collective behavior, phase separation, and transition order in shallow granular systems of inelastic spheres, revealing that asymmetry promotes phase separation at lower densities.

Contribution

It demonstrates that asymmetric vibration profiles significantly affect phase space dynamics and phase separation in shallow granular systems, a novel insight into granular behavior under non-symmetric forcing.

Findings

Asymmetric vibrations increase the size of chaotic regions in phase space.

Phase separation occurs at lower densities with asymmetric vibration profiles.

The order parameter of the transition is larger under asymmetric forcing.

Abstract

We describe the collective behavior of a system of many inelastic spherical particles inside a box which is being periodically vibrated. The box is shallow, with large horizontal dimensions, while the height is less than two particle diameters. The vibrations are not symmetric: the time the box is moving up is, in general, different to the time it is moving down. The limit cycles of isolated grains are largely affected by the asymmetry of the vibration mode, increasing the size in phase space of the chaotic regions. When many grains are placed in the box, the phase separation between dense, solid-like regions, coexisting with fluid-like regions takes place at smaller global densities for asymmetric vibration profiles. Besides, the order parameter of the transition takes larger values when asymmetric forcing is used.