FINGERING INSTABILITY IN A WATER-SAND MIXTURE

The temporal evolution of a water-sand interface driven by gravity is experimentally investigated. By means of a Fourier analysis of the evo lving interface the growth rates are determined for the different mode s appearing in the developing front. To model the observed behavior we apply the idea of the Rayleigh-Taylor instability for two stratified fluids. Carrying out a linear stability analysis we calculate the grow th rates from the corresponding dispersion relations for finite and in finite cell sizes. Based on the theoretical results the viscosity of t he suspension is estimated to be approximately 100 times higher than t hat of pure water, in agreement with other experimental findings.