Development of a Fluidic Actuator for Adaptive Flow Control on a Thick Wind Turbine Airfoil

Abstract

Wind turbines are exposed to unsteady incident flow conditions such as gusts or tower interference. These cause a change in the blades' local angle of attack, which often leads to flow separation at the inner rotor sections. Recirculation areas and dynamic stall may occur, which lead to an uneven load distribution along the blade. In this work, a fluidic actuator is developed that reduces flow separation. The functional principle is adapted from a fluidic amplifier. High pressure air fed by an external supply flows into the interaction region of the actuator. Two control ports, oriented perpendicular to the inlet, allow for a steering of the actuation flow. One of the control ports is connected to the suction side, the other to the pressure side of the airfoil. Depending on the pressure difference that varies with the angle of attack, the actuation air is directed into one of four outlet channels. These guide the air to different chordwise exit locations on the airfoil's suction side. The appropriate actuation location adjusts automatically according to the pressure difference between the control ports and therefore incidence. Suction side flow separation is delayed as the boundary layer is enriched with kinetic energy. Experiments were conducted on a DU97W300 airfoil at Re = 2.2 أ— 105. Compared to the baseline, lift variations due to varying angles of attack were reduced by an order of magnitude. A Fast/Aerodyn simulation of a full wind turbine rotor was performed to show the real world load reduction potential. Additionally, system integration is discussed, which includes suggestions on producibility and operational details.