Wake characteristics of a floating wind turbine in yaw under sway motions

In this work, high-fidelity large eddy simulation based on the actuator line model is resorted to investigate the wake of a floating wind turbine with different yaw angles (0°, 10°, 20°, and 30°) under sway motions. The results show that floating motion can enhance wake expansion by about 30%–110% and significantly reduce instantaneous asymmetry. At small yaw angles, the wake is governed by sway motion, resulting in pronounced lateral stretching and an approximately symmetric double-peak probability density function of the instantaneous wake center. At moderate yaw angles, the wake evolution is dominated by both the sway motion and the yaw misalignment, leading to reduced wake deflection and a transition from laterally stretched wake structures to vertically elongated ones, with an obvious asymmetry of the instantaneous wake center. At large yaw angles, the sway-induced effect is suppressed by the yaw misalignment, making the wake structure and instantaneous characteristics similar to those of the fixed turbine. The wake of a yawed floating turbine is highly sensitive to the motion frequency. When the sway frequency approaches the dominant frequency of the wake meandering, lock-in occurs with an amplification factor of the wake meandering ranging from 4 to 10. Wake mixing and recovery increase with the motion amplitude. However, excessive amplitude or off resonance frequency reduces the amplification factor of the wake meandering.