Effect of the vertical wake deflection on the response of a 12MW semisubmersible FWT

Abstract

Abstract The need to understand the interaction of floating wind turbines operating in the marine boundary layer with other surrounding turbines is of increasing importance as wind farms and rotor sizes get larger. For low wind speed conditions, the wake deflects upwards due to the floating wind turbine built-in rotor tilt and the platform pitch angle. Furthermore, based on field data from the North Sea, a convective atmosphere is likely to occur, especially for lower wind speeds. It is therefore key to understand the combined effect of meandering, wake deflection and atmospheric stability for low wind speed conditions on the floating wind turbines in a wind farm. In this work, to account for atmospheric stability, data from large-eddy simulation (LES) for a 7.5m/s wind speed scenario and three atmospheric stability conditions, are used as input to FAST. Farm to study the effect of the wake deflection upwards on a 12 MW semisubmersible placed 8 rotor diameters (D) downwind of a stationary wind turbine. Three built-in shaft tilt angles cases are considered for the fixed upwind turbine: 12°, 6° and no tilt angle. The main effects of the wake deflection are on the power output of the floating wind turbine in the wake, and on the tower top yaw moment. For stable conditions, the mean tower top yaw moment increases by more than three times. The findings of this work contribute to the investigation of the wake deflection as a control strategy to minimize wake losses in floating wind farms.