Role of defects in the onset of wall-induced granular convection

TL;DR

This study explores how wall-induced convection in vibrated granular materials is affected by defects, showing defects lower the vibration threshold for convection and that nucleation follows an Arrhenius law.

Contribution

It demonstrates the influence of defects on the onset of granular convection and models defect nucleation with an Arrhenius law, combining experiments and simulations.

Findings

Convection occurs within the bouncing bed region.

Defects lower the vibration strength needed for convection.

Defect nucleation follows an Arrhenius law.

Abstract

We investigate the onset of the wall-induced convection in vertically vibrated granular matter by means of experiments and two-dimensional computer simulations. In both simulations and experiments we find that the wall-induced convection occurs inside the bouncing bed region of the parameter space in which the granular bed behaves like a bouncing ball. A good agreement between experiments and simulations is found for the peak vibration acceleration at which convection starts. By comparing the results of simulations initialised with and without defects, we find that the onset of convection occurs at lower vibration strengths in the presence of defects. Furthermore, we find that the convection of granular particles initialised in a perfect hexagonal lattice is related to the nucleation of defects and the process is described by an Arrhenius law.