Wind tunnel investigation of wake dynamics of floating offshore wind turbines under different inflow conditions and pitch-surge coupling

Floating offshore wind turbines (FOWTs) experience the coupling of the platform's six-degree-of-freedom (6-DOF) motion and the turbulent wind field, leading to more complex wake characteristics. This study conducted a systematic wind tunnel experiment using a Stewart platform to investigate the nonlinear, periodic, and momentum mixing characteristics of the FOWT wake under different turbulence intensities and pitch-surge coupled motions for in-depth analysis. The results show that under uniform inflow, the pitch-surge coupled motion causes the wind turbine thrust and the wind speed in the wake near the middle of the blade at 2D to exhibit significant periodic fluctuations; however, the mean wind speed deficit remains nearly the same across all motion conditions. The turbulence intensity for high-amplitude motion follows a typical double Gaussian distribution, with the peak increasing to approximately 9 %. Turbulent inflow accelerates wake recovery by enhancing momentum mixing. The coupled motions significantly enhance mesoscale energy (250–750) in the mid-region of the side blade, manifested by a strong amplification of periodic vortex disturbances and enhancement of lateral diffusion. This effect should be emphasized in wind farm design and control strategy. These findings provide a scientific basis for optimizing wind farm layout and designing FOWT control strategies.