Coupling of NWT and large-eddy simulation for wave-induced sediment transport

We present the validation and application of a numerical model for the simulation of wave-induced sediment transport. Our approach is a oneway coupling of an inviscid flow model (i.e., a Numerical Wave Tank based on potential flow theory; NWT) to a Navier-Stokes solver, to simulate near bottom wave-induced turbulent boundary layer flows. Only two-dimensional incident wave fields have been considered so far (i.e., long-crested swells), while the near-field wave-induced turbulent flow and sediment transport are fully three-dimensional. Good results are obtained for steady streaming velocities when applying open boundary conditions (i.e., zero velocity gradient), a quarter-wavelength from the edge of the domain without the assumption of periodicity. For turbulent test cases, we solve the Navier-Stokes equations using a large-eddy simulation using an approximate (log-layer) wall boundary condition and a dynamic Smagorinsky subgrid scale model. After validating the model hydrodynamic predictions, we simulate wave-induced sediment transport over an idealized rippled bed, and find reasonable agreement with laboratory results for oscillatory flows over full-scale sand ripples. Both idealized and more realistic test cases are presented. © 2010 by The International Society of Offshore and Polar Engineers (ISOPE)