Unsteady Flow Investigation around a Pitching Wind Turbine Blade Element

A numerical and experimental investigation is presented studying the unsteady wake and evaluating the unsteady aerodynamic loads for an S822 airfoil in pitching motion, for the case where the maximum dynamic angle of attack is equal to the static angle of maximum lift to drag ratio. Smoke wire flow visualization compares the wakes of static and dynamic cases for Re < 105 and shows the strong dependency of the wake structure on the Reynolds number. Laser Doppler Anemometry (LDA) measures the unsteady wake characteristics of the flow for Re = 10(5) and shows that increasing the amplitude of oscillation increases the boundary layer thickness. For all cases, a numerical simulation with the Transition SST method has been employed as an alternative method and shows good agreement with the experimental results. Finally, the unsteady loading will cause varying rotor loads.