Study on the Evolution of the Yawed Wake of a Floating Offshore Wind Turbine Under Surge Motion

Improving the operational efficiency of floating offshore wind farms through coordinated yaw control is of great importance for enhancing their economic viability. However, the evolution of yawed wakes under platform motions remains insufficiently understood. In this study, large eddy simulation (LES) is employed to investigate the wake characteristics of a floating wind turbine under different yaw angles and surge frequencies. The results show that surge motion slightly promotes wake expansion and significantly increases turbulence intensity, while exerting only a minor influence on the wake centerline deflection. As the yaw angle increases, the wake deflection becomes more pronounced. Compared with a fixed wind turbine, surge motion alleviates the spanwise compression of the wake under yawed conditions. At relatively small yaw angles, the wake dynamics are dominated by periodic streamwise contraction and expansion. With increasing yaw angle, the spanwise component of the thrust induced by surge motion becomes stronger, which further gives rise to pronounced spanwise wake meandering. For the non-yawed turbine, wake lock-in is primarily governed by the periodic contraction–expansion motion of the wake, and the onset of lock-in occurs at a slightly lower frequency (St = 0.2) than that induced by sway motion (St = 0.3). Under yawed conditions, however, wake lock-in is mainly dominated by wake meandering, and the corresponding lock-in frequency becomes closer to that associated with sway-induced wake dynamics.