The effects of grain shape and frustration in a granular column near jamming

TL;DR

This paper explores how grain shape and frustration influence the jamming behavior of granular columns, identifying four dynamical regimes and highlighting the impact of shape effects near different frustration levels.

Contribution

It introduces a comprehensive phase diagram of granular jamming considering grain shape and frustration, revealing the interplay between these factors and dynamical regimes.

Findings

Four dynamical regimes identified: ballistic, logarithmic, activated, glassy.

Shape effects are significant at strong and weak frustration levels.

Shape effects diminish near a mean-field point.

Abstract

We investigate the full phase diagram of a column of grains near jamming, as a function of varying levels of frustration. Frustration is modelled by the effect of two opposing fields on a grain, due respectively to grains above and below it. The resulting four dynamical regimes (ballistic, logarithmic, activated and glassy) are characterised by means of the jamming time of zero-temperature dynamics, and of the statistics of attractors reached by the latter. Shape effects are most pronounced in the cases of strong and weak frustration, and essentially disappear around a mean-field point.