Wind turbines are installed in the strongly inhomogeneous and unsteady turbulent atmospheric boundary layer. This induces unsteady mechanical loads at different characteristic time scales from seconds to minutes which limit significantly their life time. The present work, supported by the SMARTEOLE ANR project, focuses on the flow control strategies at the blade scale, to manipulate lift and thus alleviate some of these loads. For this purpose, a NACA654-421 airfoil profile has been modified : the trailing edge has been rounded to take advantage of Coanda effects and the camber has been increased to compensate the loss of lift due to the trailing edge modifications. The lift control is obtained by fluidic injection via 42 1x1 mm micro-jets placed at the trailing edge along the entire span of the wing. An experiment has been conducted to identify both static and dynamic performances of the proposed control mechanism.
The experimental campaign consisted in chordwise unsteady pressure measurements as well as aerodymics forces measurements. The preliminary results of the mean quantities indicate that the lift gain obtained is proportional to the fluidic injection, which is of interest when closed-loop control is to be considered. In a second series of measurements, we focus on the step-response of the flow to the actuation. The lift response is shown to behave as a first order dynamics and we show that the response time of lift is of the order of 3 convective time units. This is about three times faster than what is usually observed for boundary layer reattachement process.