Mesh-free SPH modeling of sediment scouring and flushing

•A multiphase SPH model is developed for study of water-sediment two-phase system.•Effect of rheological model and yield criteria is investigated.•Test cases of this study are (1) scouring downstream of a wall-jet, and (2) reservoir sediment flushing.•Laboratory experiments are conducted to provide the required data for evaluation of the developed numerical model.•The developed model and proposed modifications predicted the bed and water profiles quite compatible with those of experimental measurements. A two-phase mesh-free Lagrangian model, based on the Smoothed Particle Hydrodynamics (SPH) method, is developed and evaluated for the continuum-based study of sediment-water system (a dense submerged granular flow system). The case studies are (a) sediment scouring downstream of a wall-jet, and (b) reservoir sediment flushing, both of great interest of engineers and researchers. The mesh-free Lagrangian nature of the SPH method makes the model capable of dealing with the large interfacial deformations involved in these complex water-sediment flow systems. Water and sediment materials are both treated as continuum and the governing equation of their motion are solved on a Lagrangian frame using SPH formulation. A pressure-dependent viscoplastic rheological model is used to describe the behavior of the sediment phase. A combination of Mohr–Coulomb and Shields yielding criteria (in place of commonly used Mohr–Coulomb yield criteria) is employed to determine the critical stress above which the sediment material behaves as a viscous fluid. Effect of this combination on the model results is investigated. To validate the developed numerical model, this study also provides some original experimental measurements for the test cases of this study. The results show the good compatibility of the numerical and experimental water and bed profiles. The sediment feature such as scouring and deposition areas (for wall-jet scouring case) and the sediment failure slope (for the flushing test case) are reproduced by the developed SPH model, with a good degree of accuracy. The numerical results as well as experimental measurements of this study not only provide an insight into better understanding of the complicated mechanism of sediment transport induced by rapid flow discharge, but also provide a reliable numerical tool and benchmark for simulation of such problems.