Modelling and simulation of powder-snow avalanches

Finite volume release gravity currents of large density contrast on steep slopes, representing powder-snow avalanches, are simulated numerically using a dynamic mesh adaptation technique. This technique allows to treat large Reynolds numbers and large density contrast flows, but it is (presently) restricted to two dimensions. Comparison of numerical results with experiments in the Boussinesq limit shows that 2D simulations capture the essential flow dynamics. The physics of powder-snow avalanches is analysed on hand of the similarity model developed by Rastello and Hopfinger (2004) and briefly reproduced here. The numerical simulations provide the closure parameters required in this model and give access to the flow structure. The non-Boussinesq effect is to decrease substantially the spatial growth in height and to increase the aspect ratio, hence the overall flow structure.