Stress and large-scale spatial structures in dense, driven granular flows

TL;DR

This paper investigates large-scale structures and stress heterogeneities in driven granular flows, revealing chain-like particle formations that influence stress distribution and exhibit slow dynamics near jamming conditions.

Contribution

It introduces a simplified model showing how dynamical heterogeneities and stress chains emerge in dense granular flows, linking these to slow relaxation phenomena.

Findings

Formation of large-scale linear particle structures with high collision frequency.

Dynamical correlation between momentum transfer and collision timing.

Stress heterogeneities grow and decay slowly as flow approaches jamming.

Abstract

We study the appearance of large-scale dynamical heterogeneities in a simplified model of a driven, dissipative granular system. Simulations of steady-state gravity-driven flows of inelastically colliding hard disks show the formation of large-scale linear structures of particles with a high collision frequency. These chains can be shown to carry much of the collisional stress in the system due to a dynamical correlation that develops between the momentum transfer and time between collisions in these "frequently-colliding" particles. The lifetime of these dynamical stress heterogeneities is seen to grow as the flow velocity decreases towards jamming, leading to slowly decaying stress correlations reminiscent of the slow dynamics observed in supercooled liquids.