Wind turbines generally suffer from unsteady inflow caused by yaw misalignment, gusts, and turbulence which induce fatigue loads. Spanwise distributed active micro-tabs at the mid and outer blade regions are able to countervail these unsteady loads. However, during the actuation process of these devices, transient effects play an important role. This work aims to give a deeper insight in the process of the tab deployment and retraction to evaluate the effectiveness of active micro-tabs for load control on wind turbines. Wind tunnel experiments on a two-dimensional NACA 0018 airfoil with an active micro-tab were conducted. The tab deployment- and retraction time was varied for an application on the suction or the pressure side of the airfoil. Time resolved surface pressure measurements were performed at Reynolds numbers of Re = 7 · 105 and 1 · 106. Transient responses showed a significant delay and post deployment behavior of the lift which strongly depend on the actuation time.

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