Dam-break flows of dry granular material on gentle slopes

Abstract

This work examines dam-break flows of dry granular material and investigates the suitability of the depth-averaged models with particular attention being given to the description of the shear stresses and pressure terms. The experimental results of dam-break flows down a gently sloped channel have been reported. Tests were carried out on both a smooth Plexiglas bed as well as a rough one. Measurements of the flow depth profiles and the front wave position were obtained using two digital cameras. In order to compare the prediction of the depth-averaged approach with granular avalanche tests, a specific mathematical and numerical model was implemented. The momentum equation was modified in order to take into account the resistances due to the side walls. The numerical integration of the shallow water equations was carried out through a TVD finite volume method. In order to address the importance of a good estimate of the stress distribution inside the pile, several numerical simulations were performed, calculating with different formulas the pressure coefficient that relates longitudinal and vertical normal stresses in the momentum equation. The simulations present, in general, agree with experimental data. The differences have been outlined between the smooth and rough bed cases.