Modelling tidal current turbine wakes using a coupled RANS-BEMT approach as a tool for analysing power capture of arrays of turbines

The downstream evolution of the wake generated by a rotating tidal energy conversion device influences the performance of the device itself as well as the performance of any downstream device. An improved method is proposed for coupling a blade element momentum theory inner solution for a horizontal axis tidal turbine with an outer domain flow solved using a commercial finite volume computational Fluid Dynamics solver. A mesh sensitivity study is carried out and shows that for wake evolution of distance 10 diameters a high resolution mesh (>10M cells) is required. The importance of swirl is shown in retarding the wake spreading and that the inclusion of a suitable turbulence intensity term is also required to capture the spread of the near wake. A final section demonstrates the use of such a technique for analysing the energy capture of an array of multiple turbines distributed over 1km2 of seabed. The use of staggered lateral position between longitudinal arrays demonstrates a potential for more effective power capture.