Towards enhanced monopile offshore wind turbine resilience against tornadoes: Synergistic effects of yaw and pitch control on rotor aerodynamic performance

Tornadoes can impose severe transient aerodynamic loads on offshore wind turbines, threatening their structural resilience and operational safety. While previous studies have primarily focused on global structural responses, rotor-level aerodynamic load mechanisms and mitigation strategies under tornado conditions remain insufficiently understood. This study experimentally investigates the aerodynamic performance of a monopile offshore wind turbine rotor subjected to tornado-like vortices over a range of swirl ratios, radial positions, yaw angles, and blade pitch angles. The results identify the z-direction force and x-direction torque as the dominant load components governing rotor response. Mean aerodynamic force coefficients exhibit quasi-sinusoidal variations with yaw angle, enabling simplified characterization of tornado-induced load evolution. A yaw angle near 0° reduces the dominant force by more than 90%, whereas the dominant torque shows limited sensitivity to yaw regulation, with reductions below 15%. In contrast, blade pitch regulation reduces the dominant torque by up to 90% and compensates for the limitations of yaw control. Consequently, coordinated yaw–pitch control provides more comprehensive mitigation of tornado-induced loads, thereby enhancing turbine survivability. Furthermore, integrating this approach into emergency control strategies can improve the ability of wind turbines to respond to evolving loads throughout tornado exposure.