Erosion waves: transverse instabilities and fingering

TL;DR

This paper investigates the stability and pattern formation of erosion waves in granular avalanches through laboratory experiments, revealing a common erosion/deposition scenario despite different scales.

Contribution

It demonstrates the existence of a linear instability leading to fingering patterns in granular avalanches, unifying observations across different experimental conditions.

Findings

Identification of a linear instability in avalanche fronts

Observation of coarsening dynamics before fingering

Quantitative agreement in stability diagrams across experiments

Abstract

Two laboratory scale experiments of dry and under-water avalanches of non-cohesive granular materials are investigated. We trigger solitary waves and study the conditions under which the front is transversally stable. We show the existence of a linear instability followed by a coarsening dynamics and finally the onset of a fingering pattern. Due to the different operating conditions, both experiments strongly differ by the spatial and time scales involved. Nevertheless, the quantitative agreement between the stability diagram, the wavelengths selected and the avalanche morphology reveals a common scenario for an erosion/deposition process.