Coupled LES and bed morphodynamics of a utility-scale vertical-axis MHK turbine under rigid- and mobile-bed conditions

We present a coupled large-eddy simulation (LES) and bed morphodynamics study to examine the sediment dynamics around a utility-scale vertical-axis marine hydrokinetic (MHK) turbine under two flume bed conditions: rigid and mobile. Carefully comparing the coupled LES and morphodynamics numerical results under the rigid- and mobile-bed conditions, we attempt to quantify the effect of scour development on the wake recovery and power production of the turbine and to gain insight into the formation, development, and migration of dunes over the mobile bed. The sediment dynamics are obtained using the Exner-Polya equation, which is solved until an equilibrium bed morphology is reached. A mass-balance-based sand-slide module is used to ensure that bed deformation angles are physically accurate. The model's flow and sediment transport results are validated using experimental data of adequate Reynolds numbers representing large-scale tidal farms.