Reducing Dynamic Stall Effects and Load Fluctuations on Wind Turbine Blades using Trailing Edge Flap

Dynamic stall on wind turbine blades often leads to severe fatigue and high load fluctuations that tend to decrease the lifespan of the blades. In this study the influence of trailing edge flap (TEF) on dynamic stall effects are investigated on an oscillating S833 airfoil with a chord length of 178 mm at a Reynolds number of 1.8×10⁵ and a reduced frequency of k= 0.06 and 0.1. Surface pressure measurements along with strain at the blade support are collected for all cases inside a 0.61 m square wind tunnel . The static lift and moment coefficients will be presented for different pitch and flap angles. The lift and moments curves are then presented for the dynamic stall cases for a mean pitch angle of 0° and 10° to represent stall onset and deep stall cases. The flap is also oscillating at the same pitch frequency but with different phase lags to study the influence of flap motion. The curves clearly show the leading edge vortex formation and convection and how it is influenced by the TEF. The coefficient of pressure for different cases are also presented in a contour plot to illustrate how the pressure along the airfoil chord changes for the pitching cycle. Finally a conclusion is presented on how the TEF can control the load fluctuation experienced by the blades.