LES-DEM simulations of sediment saltation in a rough-wall turbulent boundary layer

Sediment saltation in a rough-wall turbulent boundary layer was simulated with a coupled model with large eddy simulation and a discrete element model. The aim is to quantify the saltation process using eddy-resolving fluid simulations and Lagrangian particle tracking. The four-way coupling approach in this work considered the fluid–particle, particle–particle, and particle–wall interactions. Five simulations were performed. For comparison, one simulation with the flow field replaced by a simple log-law profile was also performed. The simulated saltation trajectory, velocity, and collision angles were analysed and we found: (1) Turbulent fluctuation and random collision with the bed are two controlling factors for particle trajectory. Without turbulent fluctuation, the loss of saltation information is severer in the streamwise direction than in other directions. In the spanwise direction, bed collision plays a comparable role to turbulent fluctuation. (2) Particle velocities in the streamwise and vertical directions follow skew-normal distributions. (3) Turbulent fluctuations make the incidence angle wider and slightly enhance the correlation between the incidence and reflection angles.