Experimental investigation of the effects of floating wind turbine motion on a downstream turbine performance and loads

Abstract. This study investigates how the motion of a floating wind turbine affects the aerodynamic performance and dynamic loading of a downstream turbine operating in its wake. Wind tunnel experiments were conducted using a two-turbine setup, where the upstream turbine was subjected to controlled platform motions (both sinusoidal and wave driven) while the downstream turbine remained fixed and was tested in multiple relative positions. Results show that large-amplitude, low-frequency, sinusoidal motions of the upstream turbine, especially in crosswind and yaw directions, can increase the power output of the downstream turbine under low-turbulence conditions and at short turbine spacing (3–5 rotor diameters). The largest relative power gain reached 26 % over the fixed case, although absolute gains remained moderate. The gains obtained under idealized sinusoidal motions were replicated in cases with realistic-wave-driven motions when wind and waves were aligned, but not when wind–wave misalignment introduced crosswind movements of the upstream wind turbine. In parallel, motion of the upstream turbine increased the dynamic loading on the waked turbine. These effects varied with turbine spacing and alignment, and were more pronounced in sinusoidal motion cases. Still, similar mechanisms were observed under wave-induced motion. Overall, these findings underscore that platform-induced wake dynamics are not a secondary effect, but a key driver that must be considered in the design and operation of floating wind farms.