Large-scale avalanche braking mound and catching dam experiments with snow:: A study of the airborne jet

We report a series of ongoing large-scale experiments to study the interaction of a snow avalanche with a dam and a row of mounds which are of a comparable height to the flow depth. The experimental results indicate that the behaviour of the supercritical flow around the obstacles is governed by the large-scale properties of the flowing avalanche rather than micro-scale properties of the granular current. The experiments show that, similarly to smaller-scale experiments with glass particles, the avalanche detaches from the top of the dam or mound and forms a coherent airborne jet, which can be modelled as a two dimensional ballistic projectile with negligible air resistance. We study the two parameters that define the trajectory of the jet, namely the speed at which the jet is launched from the top of the obstacle and the deflection of the jet by the obstacle, and compare the results with a theory for the deflection of a jet of an ideal fluid.