Granular Rayleigh-Taylor Instability: Experiments and Simulations

TL;DR

This study investigates the gravity-driven Rayleigh-Taylor instability in granular materials through experiments and simulations, revealing pattern formation, coarsening dynamics, and scale invariance in granular flows.

Contribution

It provides a combined experimental and numerical analysis of granular Rayleigh-Taylor instability, highlighting pattern evolution and scale invariance in granular flows.

Findings

Pattern formation of granular fingers and air bubbles observed.

Coarsening dynamics characterized by finger merging and growth.

Quantitative agreement between experiments and simulations achieved.

Abstract

A granular instability driven by gravity is studied experimentally and numerically. The instability arises as grains fall in a closed Hele-Shaw cell where a layer of dense granular material is positioned above a layer of air. The initially flat front defined by the grains subsequently develops into a pattern of falling granular fingers separated by rising bubbles of air. A transient coarsening of the front is observed right from the start by a finger merging process. The coarsening is later stabilized by new fingers growing from the center of the rising bubbles. The structures are quantified by means of Fourier analysis and quantitative agreement between experiment and computation is shown. This analysis also reveals scale invariance of the flow structures under overall change of spatial scale.