Effect of the surge motion on wake characteristics of a floating offshore wind turbine

Understanding how platform surge motion influences wake dynamics and downstream power availability of floating offshore wind turbines is essential for improving offshore wind energy efficiency. Previous studies have primarily focused on uniform inflow conditions, leaving the frequency-dependent wake behavior in a realistic atmospheric boundary layer unexplored. This study performs high-fidelity, GPU-accelerated large-eddy simulations of a NREL 5 MW reference turbine in an atmospheric boundary layer to investigate the effect of surge motion at different frequencies on wake dynamics. Results reveal a strong frequency dependence in velocity deficit, turbulence statistics, and coherent-structure dynamics. Within an effective reduced-frequency range (Strouhal number between 0.26 and 0.65), surge motion generates large-scale coherent structures that enhance momentum transport and accelerate wake recovery. An optimal frequency is identified at a Strouhal number of 0.39, at which the coherent structures achieve a favorable balance between spatial scale, persistence, and turbulent interaction, leading to the strongest wake recovery. At higher frequencies, the structures become smaller and more susceptible to turbulent dissipation, remaining confined near the rotor and contributing less effectively to downstream momentum transport. These results reveal a clear frequency-dependent mechanism by which surge motion modifies wake dynamics through its interaction with background ABL turbulence. These findings provide new physical insight into surge-induced wake dynamics in realistic ABL conditions and offer guidance for optimizing floating wind farm performance.