A Process-Based Sediment Transport Model for Sheet Flows with the Pickup Layer Resolved in an Empirical Way

Abstract

A two-layer process-based model for predicting the sheet-flow sediment transport under wave-current flows is presented. The whole one-dimensional-vertical (1DV) water column is separated into a pick-up layer and a suspension layer. The pick-up layer is resolved through an empirical way, while the suspension layer adopts Reynolds-averaged Navier-Stokes (RANS) equations coupled with a two-equation $k - \omega$ turbulence closure for flow velocity, and a turbulent diffusion equation for sediment concentration. The instantaneous position of sand bed can be modeled as a linear function of Shields parameter, but as a first test of the model, we apply the measured erosion depth as input. The model also includes the hindered velocity effect due to particle-particle interaction, as well as the turbulence damping effect induced by density stratification. The model is firstly validated against the skewed-flow water-tunnel tests published in O’Donoghue and Wright (2004), which have measurements of velocity, concentration, sand flux and net transport rate. A good model-data agreement indicates that the model may be a promising tool to investigate the sheet-flow sediment transport in coastal environments.