The numerical simulation of the non-cohesive sediment transport in a turbulent channel flow with a high concentration is a challenging but practical task. A modified coherent dynamic eddy model of the Large Eddy Simulation (LES) with a pick-up function is used in the present study to simulate the sediment erosion and the deposition in a turbulent channel flow. The rough wall model is used instead of the LES with the near-wall resolution to obtain the reasonable turbulent flow characteristics while avoiding the high costs in the computation. Good results are obtained, and are used to analyze the sediment transport properties. The results show that the streamwise vortices play an important role in the riverbed erosion and the sediment pick-up, which may serve as guidelines for the sediment management and the water environment protection engineering.
A modified large-eddy simulation model,the dynamic coherent eddy model(DCEM)is employed to simulate the generation and propagation of internal solitary waves(ISWs)of both depression and elevation type,with wave amplitudes ranging from small,medium to large scales.The simulation results agree well with the existing experimental data.The generation process of ISWs is successfully captured by the DCEM method.Shear instabilities and diapycnal mixing in the initial wave generation phase are observed.The dissipation rate is not equal at different locations of an ISW.ISW-induced velocity field is analyzed in the present study.The structure of the bottom boundary layer(BBL)of internal wave packets is found to be different from that of a single ISW.A reverse boundary jet instead of a separation bubble exists behind the leading internal wave while separation bubbles appear in other parts of the wave-induced velocity field.The boundary jet flow resulting from the adverse pressure gradients has distinctive dynamics compared with free shear jets.
