Abstract
Effects of yawed approaching flows on the wake structure of axial-flow tidal turbines are not fully understood. To obtain a better understanding, numerical studies of a laboratory-scale three-bladed horizontal axis tidal turbine at tip speed ratio TSR=5.2 with yaw angles of zero and 15◦ have been carried out to investigate the wake characteristics of the turbine in the near- and far wake. A hybrid approach coupling Large Eddy Simulation (LES) with Actuator Line Modelling (ALM) has been employed in the present study. The predicted results confirm the asymmetry of the turbine wake in which it is inclined to the direction where the rotor is yawed. This study quantitatively explains the reason of wake deflection and shows that transition occurs earlier on one side of the wake, leading to quicker wake recovery on that side. This study also reveals that at yawed conditions the axial velocity component of flow at the turbine plane unexpectedly varies in the circumferential direction.