Impact of Blade-Flapping Vibration on Aerodynamic Characteristics of Wind Turbines under Yaw Conditions.

Although the aerodynamic loading of wind turbine blades under various conditions has been widely studied, the radial distribution of load along the blade under various yaw conditions and with blade flapping phenomena is poorly understood. This study aims to investigate the effects of second-order flapwise vibration on the mean and fluctuation characteristics of the torque and axial thrust of wind turbines under yaw conditions using computational fluid dynamics (CFD). In the CFD model, the blades are segmented radially to comprehensively analyze the distribution patterns of torque, axial load, and tangential load. The following results are obtained. (i) After applying flapwise vibration, the torque and axial thrust of wind turbines decrease in relation to those of the rigid model, with significantly increased fluctuations. (ii) Flapwise vibration causes the blades to reciprocate along the axial direction, altering the local angle of attack and velocity of the blades relative to the incoming wind flow. This results in the contraction of the torque region from a circular shape to a complex “gear” shape, which is accompanied by evident oscillations. (iii) Compared to the tangential load, the axial load on the blades is more sensitive to flapwise vibration although both exhibit significantly enhanced fluctuations. This study not only reveals the impact of flapwise vibration on wind turbine blade performance, including the reduction of torque and axial thrust and increased operational fluctuations, but also clarifies the radial distribution patterns of blade aerodynamic characteristics, which is of great significance for optimizing wind turbine blade design and reducing fatigue risks. [ABSTRACT FROM AUTHOR]