Granular Rayleigh-Taylor Instability

Jan Ludvig Vinningland (1) , Øistein Johnsen (1) , Eirik Grude Flekkøy (2) , Renaud Toussaint (3) , Knut Jørgen Måløy (1)

1 Department of Physics [Oslo]
2 PoreLab [Oslo]
3 IPGS - Institut de physique du globe de Strasbourg

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.

Keywords: granular flow; Rayleigh-Taylor instability; pattern formation; size invariance; simulation

Domains: Condensed Matter [cond-mat]; Geophysics [physics.geo-ph]

Jan Ludvig Vinningland, Øistein Johnsen, Eirik Grude Flekkøy, Renaud Toussaint, Knut Jørgen Måløy. Granular Rayleigh-Taylor Instability. AIP Conference Proceedings, 2009, 1145, pp.1067. ⟨insu-02378051⟩