Modélisation physique de l'interaction entre avalanches aérosols et les structures de protection

Physical modeling between powder avalanches and defense structures

¹ U.R ETNA Cemagref, 2 rue de la papeterie BP 76, 38402 Saint-Martin d'Hères / France
² WLS-BOKU Institute of Torrent and Avalanche Control University of Bodenkultur Peter-Jordanstraβe 82, 1190 Vienna / Austria

Auteur de correspondance : florence.naaim@cemagref.fr

Abstract

In order to better understand the interaction between powder avalanche and defense structures, we realized physical experiments on small-scale models. The powder snow avalanche was simulated by a " heavy " salt solution in a water tank. Quasi two-dimensional and three-dimensional experiments have been carried out with different breaking dams heights. For the reference avalanche, the velocity just behind the nose in the head is greater than the front velocity. For 2D configuration, the ratio Umax/UF could be 1.6 but depends on the height. For 3D configuration, this ratio differs a little and it is even greater (up to 1.8). The vertical velocity goes up to 106 % of the front velocity for 3D simulation and 74 % for 2D simulation. The reduction in flow velocity due to presence of dams is an increasing function of dam's height. But this reduction depends on topography : dams are more efficient on an open slope avalanche (3D configuration). The ratio Umax/UF is an increasing function of dam's height and can reach a value of 1.9. That is why the front velocity is not relevant to determine the efficiency of dams. The obstacle leads to a reduction in vertical velocity dawnstream the vortex zone.