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

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 gain reached 26 % over the fixed case, although the absolute increase remained moderate because the highly persistent wake, driven by low turbulence and strong thrust of the upstream turbine, resulted in very low baseline power of the downstream turbine. 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. Load increments varied with turbine spacing and alignment, and were more pronounced in sinusoidal motion cases than with wave-induced motions, which also produced increased dynamic loading but with smaller amplitudes. The loads resulting from wave-induced motions exhibited a broad spectral distribution, consistent with the wide frequency content of the wave excitation. Overall, these findings underscore the fact that platform-induced wake dynamics are not a secondary effect but a key driver of wake recovery, downstream turbine performance, and dynamic loading, and must be considered in the design and operation of floating wind farms.