Impulse distributions in dense granular flows: signatures of large-scale spatial structures

TL;DR

This study uses simulations to analyze impulse distributions in dense granular flows, revealing flow-velocity invariance for large impulses and cluster formation at low velocities, providing insights into dynamic force chains.

Contribution

It introduces a model linking impulse distributions to cluster sizes and velocities, enhancing understanding of force chain formation in granular flows.

Findings

Impulse distribution P(I) is flow-velocity-invariant for large impulses.

Small impulses decrease with flow velocity due to frequent collisions.

Large clusters form as flow velocity decreases, influencing impulse behavior.

Abstract

In this paper we report the results of simulations of a 2D gravity driven, dissipative granular flow through a hopper system. Measurements of impulse distributions P(I) on the simulated system show flow-velocity-invariant behavior of the distribution for impulses larger than the average impulse <I>. For small impulses, however, P(I) decreases significantly with flow velocity, a phenomenon which can be attributed exclusively to collisions between grains undergoing frequent collisions. Visualizations of the system also show that these frequently colliding particles tend to form increasingly large linear clusters as the flow velocity decreases. A model is proposed for the form of P(I), given distributions of cluster size and velocity, which accurately predicts the observed form of the distribution. Thus the impulse distribution provides some insight into the formation and properties of these ``dynamic'' force chains.