No 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 ([Formula: see text]). 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 [Formula: see text] 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.

No abstract

Wind turbines operate predominantly in relatively unsteady flow conditions and are typically misaligned with the incoming wind. Based on the literature review, controlling a section of the trailing edge of the turbine blade is found to reduce load fluctuations on wind turbine blades. Here, a detailed experimental setup describes a 3.5 m diameter wind turbine equipped with a trailing edge flap (TEF). The instrumentation of the compact blade was capable of measuring surface pressure and root bending moment, as well as controlling a TEF simultaneously and in time-resolved fashion. The blade is of constant pitch and chord of 178 mm while the TEF covers 20% of the chord and 22% of the 1.47 m aerodynamic blade span. The turbine was tested in a controlled wind generation facility large enough to house the turbine with less than 7% blockage. The wind turbine was tested for a range of tip speed ratios, blade pitch angles, flap angles and yaw cases. Although the turbine blade is capable of cyclically and dynamically change the blade pitch and flap angle, this paper only investigates constant pitch and flap angles. The results show that changes to the flap or pitch angle are capable of manipulating the coefficient of power, root bending moment and normal force coefficient. The results also show that the flap demonstrates similar control authority to that of the pitch system with the flap occupying just 4% of the blade surface area without reducing the power output of the turbine.

Dynamic stall on wind turbine blades often leads to severe fatigue that tends to decrease the lifespan of the blades. To mitigate cyclic loading on the blades, trailing edge flaps (TEF) may be used to control the energy captured by the blades. In this study the influence of a TEF on a pitching S833 cambered airfoil is investigated at a Reynolds number of 170,000 and reduced frequencies of k = 0.06 and 0.1. The lift and moment hysteresis cycles are presented for mean pitch angles of 0 • and 10 • to represent stall onset and deep stall. The flap, hinged at 0.8 chord, is pitching with different phase lags to study the influence of flap motion. Coefficient of pressure contour plots presented here, clearly indicate the leading edge vortex (LEV) formation and convection. It is concluded that even though the TEF was not capable of controlling the