Two-phase modelling of total sediment load in fast geomorphictransients

Sediment transport may occur during fast geomorphic transients as a consequence of strong upward momentum fluxes due to turbulence and/or of intense erosion of a loose bed. Under these circumstances, sediments will move with the distinctive features of bed-load in the region close to the bottom, whereas suspended sediment will follow the carrying fluid in the upper region of the flow. The paper presents a two-phase model able to describe both bed and suspended loads. While bed-load dynamics is modeled considering the particle-bottom and particle-particle collisions and drag received by the fluid, the suspended one is considered just advected by carrying flow. The model is applied to analyzed the dam-break waves over erodible beds of light sediment. The numerical results reproduce the main features of the experiment, putting in evidence the different dynamics of bed and suspended loads