Deep dynamic stall and active aerodynamic modification on a S833 airfoil using pitching trailing edge flap

Abstract

Due to the dynamic nature of the wind resource, wind turbine blades are subjected to significant variation in flow parameters, such as the angle of attack ( $\alpha$ ). In some cases, the occurrence of dynamic stall on wind turbine blades causes load fluctuation which leads to material fatigue that tends to decrease the life span of the blades. In this study, the influence of a trailing edge flap on dynamic stall effects is investigated at high $\alpha$ typical of wind turbines but atypical elsewhere. Pitching of the trailing edge flap was found to have a significant impact on the dynamic stall hysteresis loops responsible for the load fluctuation. Frequency analysis showed that the trailing edge flap was capable of reducing the cyclic fluctuation in the coefficient of lift and root bending moment by at least 26% and 24%, respectively. These results are a significant contribution toward understanding the advantages of using trailing edge flaps and how implementing them will reduce wind turbine blade load fluctuations.