Multiscale simulations of a horizontal axis tidal turbine in a tidal site

We present multiscale simulations of a three-bladed horizontal axis tidal turbine (HATT) in a tidal site. The power and wake generated by the HATT are computed using an Overset Large Eddy Simulation (OLES) technique, where the velocity field is split into a background and a perturbation field. The background flow is a tidal boundary layer with a depth of 10 m, which exhibits a logarithmic distribution for the averaged streamwise velocity. This flow is computed via Large Eddy Simulation for an open channel flow with a time varying pressure gradient. The interaction between this background flow and the HATT is captured using a line actuator model, which generates the perturbation flow representing the turbulent wake. These simulations assume the turbine to have a diameter of 2.5 m and the hub to be located 7.5 m from the bottom floor. The results show the power coefficient to exhibit a cyclical behavior and the power spectral density to have peaks at multiples of one third of the rotational frequency. The turbulent wake exhibits the classical behavior with the near wake dominated by helicoidal vortical structures, and the far wake characterized by diffusion phenomena.