Scaling laws in Aeolian Sand transport
Résumé
We report on wind tunnel measurements on saltating particles in a turbulent boundary layer and provideevidence that over an erodible bed the particle velocity in the saltation layer and the saltation length arealmost invariant with the wind strength, whereas over a nonerodible bed these quantities vary significantlywith the air friction speed. It results that the particle transport rate over an erodible bed does not exhibit acubic dependence with the air friction speed, as predicted by Bagnold, but a quadratic one. This contrastswith saltation over a nonerodible bed where the cubic Bagnold scaling holds. Our findings emphasize thecrucial role of the boundary conditions at the bed and may have important practical consequences foraeolian sand transport in a natural environment.