Use of Large-Eddy Simulation for the bed shear stress estimation over a dune

摘要

Environmental flows are generally characterized by complex bed morphology and high current speeds.Such configurations favor the formation of vortex structures that strongly affect hydrody-namics and sediment transport.Large-Eddy Simulation(LES)enables investigation of the dynam-ics of the largest turbulence scales and,thanks to enhanced calculation resources,has now become applicable for simulating environmental flows.In this paper,a LES approach is developed in a CFD code(TELEMAC-3D),which was originally developed to simulate free surface flows using RANS methods.The present developments involve implementing subgrid models,boundary con-ditions and numerical schemes suitable for LES.The LES version of TELEMAC-3D was validated by comparing results on the model with experimental data for flow past a cylinder.Then,the model was applied to a test case representing flow over dunes.After validating the hydrodynamics,the model was used to assess the bottom shear stress,using both a RANS and a LES approach.Com-parison highlighted the potential contribution of LES to investigating the hydrodynamic forces acting on the bottom.