Applicability of entrainment formulas to modelling of geomorphic outburst flows

This paper presents a non-capacity coupled model of dam-break induced geomorphic flows which couples hydrodynamic model, morphodynamic model and bed evolution. An upwind Godunov-type scheme with a modified Roe’s Riemann Solver is implemented to solve the hyperbolic system. As the key closure equation for non-equilibrium sediment transport model, a wide range of previous empirical, semi-empirical or theoretical entrainment functions are summarized and their performance is investigated by application to three dam-break flow cases with a range of different Shields’ parameters. The sensitivity of the parameters in the entrainment formulas is also evaluated. Many of the existing entrainment formulas have rarely been verified thoroughly due to difficulty of validation in the situation of high-magnitude outburst flows. For non-capacity models of dam-break transient flows, an appropriate and applicable entrainment relationship should be selected and applied thoroughly according to different hydraulic conditions.