Numerical simulation for sediment transport using MPS-DEM coupling model.

• The newly developed Lagrange-Lagrange coupling model allows simulating sediment transport under complex moving boundary conditions. • A seepage effect on sediment transport is particularly found around the tip of uprush /backwash waves. • An important role of the DEM-base granular model to evaluation of the bottom shear stress is indicated. Interactions between the uprush and backwash waves around a swash zone cause a complex water surface with wave breaking. Infiltration and exfiltration on a permeable beach face produce significant effects on the bottom shear stress. Abrupt changes of the bottom shear stress induced by uprush waves onto a dry bed have a significant impact on the estimation of sediment flux. In order to simulate, with a high degree of accuracy, a violent flow with wave breaking and complex moving bed boundaries along the on-off shore direction, wave motions are solved by using an enhanced particle method based on the MPS (Moving Particle Semi-implicit) method, while the DEM (Discrete Element Method) is used for a movable bed simulation. Consequently, the high potential of a MPS-DEM coupling model to simulate the swash beach process is clearly demonstrated by comparison with previous experimental results. Furthermore, the significance of the seepage flow in the swash beach process is shown with referring the Nielsen's modified Shields number. [ABSTRACT FROM AUTHOR]