COMPARISION BETWEEN MODELS USED TO SIMULATE DAM BREAK FLOWS OVER A MOBILE BED MADE OF DIFFERENT MATERIALS

Fent, Ilaria [UCL] Van Emelen, Sylvie [ECAM] Soares Frazao, Sandra [UCL]

The hydrodynamic and morphodynamic processes are very important aspects in the study of dam break flow over mobile bed. It is possible to simulate and thus to forecast the water and sediment movements thanks to appropriate models. The hydrodynamics is well represented by the Saint-Venant shallow water equations that constitute a simple hyperbolic system and for which different numerical models exist. The inclusion of the morphodynamics introduces additional difficulties, so different solutions have been developed in order to better represent the movement of sediments and the associated changes to the morphology. Several models with different approaches have been developed and are available in the literature: (i) the clear water layer model, representing one layer of clear water flowing over a mobile sediment bed; (ii) the mixture layer model, considering one layer of a variable density mixture of sediment and water; (iii) the two-layer model, which distinguishes the upper clear water layer from the lower moving sediment layer, where the bed load transport takes place and (iv) the two-phase model, which considers the water and the sediments as two immiscible phases characterized by different velocities. This paper aims at assessing the performances of these models using two different test cases of dam-break flow over mobile bed, for which experimental data exist. The results from the different models are compared to data measured in dam-break flow experiments over mobile bed composed by (i) coarse sand for the first case and (ii) light PVC pellets for the second case.