Numerical simulation of flow-sediment dynamics in wave-current bottom boundary layer:I:flow dynamics modelling

Flow dynamics simulation in the bottom boundary layer (BBL) has great theoretical and practical significance in analyzing wave-current interaction and sediment transport. There are many BBL models, however, most of them are for single bed forms. An intra-wave process based 1DV model was established to simulate the flow dynamics in the BBL under the combined action of waves and currents, which is applicable for both vortex rippled beds and flat beds. This model is based on the governing equations of wave-current BBL. The k-ε model was employed to simulate the turbulence over flat beds. The combined vortex and k-ε model was employed for vortex rippled beds, and expressions of the turbulence kinetic energy and turbulence dissipation at the interface between the vortex layer and turbulence layer were derived. A number of experimental datasets were collected to verify the model, which showed that the model could properly simulate the flow dynamics in the wave-current BBL, such as the instantaneous velocity, kinetic energy and shear stress at different phases as well as the wave-induced mean velocity and wave-current mean velocity. Using this model, discussions were made on the patterns of the flow dynamics over different bed forms in combined wave-current conditions. In conclusion, this paper provides a tool for the study of flow dynamics in the BBL. © 2019, Editorial Board of Advances in Water Science. All right reserved.