Numerical simulation of sediment transport using a free-surface resolving Eulerian–Lagrangian approach

In this study, a diffusion-averaged Volume of Fluid–Discrete Element Method model was developed to investigate sheet flow sediment transport under surface waves and dambreak-induced swash. The model was validated against large wave flume experiments of non-breaking monochromatic wave-induced sheet flow. The model successfully predicted the sediment concentration profiles, as well as the net-onshore dominated sediment transport rate under velocity-skewed waves. Visualization of vortical structures revealed the existence of bed-penetrating Kelvin–Helmholtz rollers within the upper section of the sheet flow layer thickness. The onset of momentary bed failure in this study was recorded at periods when the Sleath parameter, S> 0.53. For dambreak-induced swash, the under-prediction of the maximum shoreline limit, as well as the swash depth and velocity at the shoreward limit, is attributed to enhanced infiltration in the gravel bed from random-closed packing. Simulated intra-swash sediment flux compared well with the measured data, with discrepancies primarily due to the smoothing length and the location of the initial shoreline.