Phase controlling the yaw motion of floating wind turbines with the helix method to reduce wake interactions: an experimental investigation

The wake interaction between wind turbines causes significant losses in wind farm efficiency that can potentially be alleviated using wake control techniques. We provide detailed experimental evidence on how the coupling between the so-called helix wake control technique and a floating turbine's yaw dynamics can be used to increase wake recovery. Using tomographic particle image velocimetry during wind tunnel experiments, we analysed the wake dynamics and its coupling to a floating wind turbine. The measurements show that ensuring the floating turbine's yaw motion is in phase with the blade pitch dynamics of the helix technique enables an increase of 12 percentage points in available energy in the flow on top of the helix method applied to bottom-fixed turbines. We find that the in-phase scenario results in an earlier interaction between the tip and hub vortices inside the wake, which leads to the desired breakdown of the vortices, thus accelerating the entrainment of energy into the wake.