Efficient numerical model for sediment transport on vortex ripple bed in wave-induced oscillatory flow

Sediment motion on rippled bed under wave action plays an important role in coastal landforms, but the application of traditional numerical model is limited by large computational work or bottom sediment condition due to unsteady effects. A single-phase model is proposed to maintain low computation and high accuracy for the vortex structure development and suspended sediment motion on vortex rippled bed in wave-induced oscillatory flow. The 2D bottom sediment condition takes into account the acceleration effect and asymmetric boundary layer development under nonlinear waves as well as the sediment phase-lag. The particle inertia and wake flow around sediment particle are considered in sediment turbulence, and the SST k-omega turbulence model which is suitable for inverse pressure gradient flow on rippled bed is selected to close the Reynolds stress. The singlephase model well predicts the velocity on vortex ripples, periodic concentration at fixed points and vertical distribution of averaged sediment concentration. The results show qualitative formation, development and ejection of vortex, and demonstrate quantitative development of vortex center, radius and strength in symmetric and asymmetric flows. In addition, the model well performs the development of sediment cloud referring to vortex structure.

Automated summary

A single-phase model is proposed to predict sediment motion on vortex rippled bed under wave action. The model takes into account the acceleration effect of bottom sediment, the development of asymmetric boundary layer, and the sediment phase-lag, and successfully predicts the velocity, concentration, and development of sediment cloud on vortex ripples.