Drag reducer design of wind turbine blade under flap-wise fatigue testing

Wind turbine blade fatigue testing is necessary to verify the reliability of the structure design. A large aerodynamic drag is experienced under flap-wise fatigue testing since the prototype blade under testing moves through the air as a bluff body. An ellipse-sectional drag reducer made of a thin-wall shell is usually installed near the blade tip to alleviate the aerodynamic drag resistance. However, the correlation between drag reducer profile shape and aerodynamic characteristics has not been studied. In addition, the mass and stiffness of the drag reducer also have an adverse influence on the fatigue testing quality. In this study, a shuttle-shaped airfoil is proposed and an optimization design framework is built by a high-efficient aero-structure integrated numerical method. Results indicate that, as compared to the elliptical airfoils, an optimized shuttle-shaped airfoil can more effectively reduce the aerodynamic drag and at the same time improve the prototype blade test reliability.