Experimental investigation of pitch and surge motion effects on wake characteristics of a floating offshore wind turbine

Investigating the wake flow of floating offshore wind turbines (FOWTs) is crucial for optimizing their structural designs and wind farm layouts. This study used wind tunnel experiments to investigate the wake characteristics of FOWTs under pitching and surge motions. A six-degree-of-freedom (6-DOF) platform was used to simulate the dynamic response of a wind turbine and examine the impacts of turbulence intensity, motion amplitude, and frequency on the wake structure. The pitching motion induced periodic fluctuations in the wind speed within specific regions under uniform inflow conditions. The wake turbulence intensity was more sensitive to changes in pitching amplitude than to frequency changes, with high-amplitude pitching increasing the peak turbulence intensity from 6 % to 8 % at y = 0.2D. Both pitching and surge motions enhanced the energy peaks at the blade tip in the high-frequency band (95 Hz). Additionally, pitching motion caused asymmetric phase differences in the wake, with a negative correlation observed at the mid-blade between contralateral positions. Under turbulent inflow, regions with high correlation (≥0.6) expanded, yet the spectral differences between stationary and motion conditions were small, suggesting that turbulent inflow suppressed motion-induced disturbances across both low and high frequencies. These findings may serve as a reference for the design of offshore floating wind farms.