Stretched exponentials and power laws in granular avalanching

TL;DR

This paper presents a model for granular avalanching that captures both stretched exponential and power law behaviors, explaining experimental observations through different transport modes.

Contribution

It introduces a novel model incorporating two transport modes to explain the crossover between avalanche behaviors in granular materials.

Findings

The model reproduces both stretched exponential and power law avalanching.

A change in dominant transport mode explains the observed crossover.

Power law avalanching occurs when clustered surface flow dominates.

Abstract

We introduce a model for granular avalanching which exhibits both stretched exponential and power law avalanching over its parameter range. Two modes of transport are incorporated, a rolling layer consisting of individual particles and the overdamped, sliding motion of particle clusters. The crossover in behaviour observed in experiments on piles of rice is attributed to a change in the dominant mode of transport. We predict that power law avalanching will be observed whenever surface flow is dominated by clustered motion.