Effect of floating wind turbine wakes on the thrust dynamics of a downstream turbine

Abstract

Floating offshore wind turbines (FOWTs) experience platform-induced motions that modulate power and rotor thrust and can imprint coherent disturbances on the wake, with potential implications for both wind farm yields and fatigue of downstream turbines. Control strategies such as dynamic yawing can also improve wind farm performance at the expense of increased fatigue. This work presents wind tunnel experiments investigating how imposed surge, pitch, and yaw motions of an upstream model turbine affect the thrust response of a downstream turbine operating in the wake under low-turbulence inflow conditions (TI ≃ 2%). Two identical performance-scaled models of the DTU 10MW turbine are arranged in tandem at spacings of 2–5D. The upstream turbine is subjected to prescribed harmonic motions characterized by the Strouhal number and normalized motion velocity (surge/pitch) or yaw amplitude (yaw). Results show that low-frequency surge and pitch motions produce a clear periodic response in downstream thrust, whereas higher-frequency surge/pitch cases do not yield discernible peaks at the imposed motion frequency. For prescribed yawing motions, an increase in mean downstream thrust is observed with increasing Strouhal number and yaw amplitude, while spectral signatures appear primarily as sidebands around the rotor frequency. These findings help clarify which motion-induced disturbances persist through the wake in low-TI conditions and provide a baseline for future studies at higher ambient turbulence and with additional floating degrees of freedom.