A multi dimensional two phase flow modeling framework for sediment transport applications
Studying coastal processes is essential for the sustainability of human habitat and vibrancy of coastal economy. Coastal morphological evolution is caused by a wide range of coupled cross shore and alongshore sediment transport processes associated with short waves, infra gravity waves, and wave induced currents. One of the key challenges was that the major transport occurs within bottom boundary layers and it is dictated by turbulence sediment interactions and inter granular interactions. Therefore, this study focuses on numerical investigations of sediment transport in the bottom wave boundary layers on continental shelves and nearshore zones, with emphasis on both fine sediment (mud) and sand transports. On the continental shelves, the sea floor is often covered with fine sediments (with settling velocity no more than a few mm/s) Wave induced resuspension has been identified as one of the major mechanisms in the offshore delivery for fine sediments. A series of turbulence resolving simulations were carried out to study the role of sediment resuspension/deposition on the bottom sediment transport. Specifically, we focus on how the critical shear stress of erosion and the settling velocity can determine the transport modes. At a given wave intensity associated with more energetic muddy shelves, three transport modes, namely the well mixed transport (mode I) two layer like transport with the formation of lutocline (mode II) and laminarized transport (mode III) are obtained by varying the critical shear stress of erosion or the settling velocity. A 2D parametric map is proposed to characterize the transition between transport modes as a function of the critical shear stress and the settling velocity at a fixed wave intensity. In addition, the uncertainties due to hindered settling and particle inertia effects on the transport modes were further studied. Simulation results confirmed that the effect of particle inertia is negligible for fine sediment in typical