AN IMPROVED TWO-PHASE FLOW MODEL FOR STEADY UNIFORM SHEET-FLOW BASED ON DENSE GRANULAR FLOW RHEOLOGY

The sheet flow regime of sediment transport is associated with very strong flow forcing and very high sediment transport rate. Improving the modelling of this regime is of primarily importance for a better prediction of the morphological evolution of riverine and coastal systems. During the last decades an important research effort has been devoted to the development of process-based models for unidirectional and oscillatory sheet flows. In recent contributions we have developed a novel two-phase sheet flow model and a new experimental set-up to acquire high-resolution measurements of collocated velocity and concentration profiles under unidirectional, steady and uniform sheet flow conditions. The original two-phase flow two-layer model is further developped as a single layer model in the present contribution. This model is based on a mixing length approach for modelling the turbulent Reynolds shear stress and on a modified dense granular flow rheology for the modelling of granular shear and normal stresses. The developped two-phase flow model is compared with the novel dataset presented above in terms of streamwise velocity and concentration profiles demonstrating the relevancy of the proposed modeling approach.