Creeping Avalanches of Brownian Granular Suspensions

TL;DR

This paper investigates the unique creeping avalanche behavior of Brownian granular suspensions in rotating drums, revealing slow, logarithmic relaxation dynamics influenced by thermal agitation, and proposes a Kramer's escape rate model.

Contribution

It introduces the first detailed study of creep avalanches in Brownian granular suspensions and develops a simple theoretical model to explain the observed slow flow behavior.

Findings

Avalanches do not stop at a finite angle of repose.

A creep regime exists below a critical angle where piles slowly flow and relax logarithmically.

The relaxation rate depends on the ratio of grain weight to thermal energy.

Abstract

We study the avalanche dynamics of a pile of micron-sized silica grains in miniaturized rotating drums filled with water. Contrary to what is expected for classical granular materials, the avalanches do not stop at a finite angle of repose. Below an angle $\theta$\_c, we observe a creep regime where the piles slowly flow until they become flat. In this regime, the relaxation is logarithmic in time and is slower when the ratio between the weight of the grains and the thermal agitation is increased. We propose a simple 1D model based on Kramer's escape rate to describe this flow.