Incompressible SPH scour model for movable bed dam break flows

•An ISPH erosion model is proposed for the sediment bed scouring.•The concept of pick-up velocity is used to initiate the sediment grains.•Sensitivity analysis is made on the particle spacing and pick-up velocity.•Two-phase velocity and pressure fields are studied near the water–sediment interface.•Vertical profiles of velocity, concentration and two stresses in both phases are analysed.

In this study an incompressible smoothed particle hydrodynamics (ISPH) approach coupled with the sediment erosion model is developed to investigate the sediment bed scour and grain movement under the dam break flows. Two-phase formulations are used in the ISPH numerical algorithms to examine the free surface and bed evolution profiles, in which the entrained sediments are treated as a different fluid component as compared with the water. The sediment bed erosion model is based on the concept of pick-up flow velocity and the sediment is initiated when the local flow velocity exceeds a critical value. The proposed model is used to reproduce the sediment erosion and follow-on entrainment process under an instantaneous dam break flow and the results are compared with those from the weakly compressible moving particle semi-implicit (WCMPS) method as well as the experimental data. It has been demonstrated that the two-phase ISPH model performed well with the experimental data. The study shows that the ISPH modelling approach can accurately predict the dynamic sediment scouring process without the need to use empirical sediment transport formulas.