Aerodynamic performance and wake characteristics of a semi-submersible floating wind turbine under platform motion

Abstract

Conduct overset-mesh-based CFD simulations to quantitatively investigate the aerodynamic performance and wake evolution of a 5 MW semi-submersible floating offshore wind turbine under forced surge and pitch motions. The results demonstrate that platform motions significantly increase time-averaged power and thrust while inducing pronounced periodic fluctuations.These gains do not follow a linear superposition of the two degrees of freedom, indicating mutual constraints between surge and pitch under dynamic inflow conditions.Regarding wake dynamics, platform motions promote faster velocity recovery by enhancing turbulent mixing and momentum exchange. At a downstream distance of 7 rotor diameters (7D), with a surge amplitude of 4 m and period of 10 s, the mean streamwise velocity recovers to 8.43 m/s, which is 9.34% higher than the fixed-bottom baseline of 7.71 m/s. This result suggests that more compact floating wind farm layouts are potentially feasible.The wake centerline follows a meandering trajectory with asymmetric spatial deflection. Surge motion exerts a stronger modulating effect on wake offset and vorticity dissipation than pitch motion, and low-frequency, high-amplitude oscillations further accelerate vortex decay. Under coupled conditions, the wake velocity and vorticity distributions lie between those of the individual surge and pitch cases, and the overall characteristics are dominated by the surge component. These findings provide quantitative benchmarks for unsteady load assessment and array optimization of floating wind turbines.