Experimental investigation on a 3D wing section hosting multiple SJAs for stall control purpose

Flow control over aerodynamic shapes in order to achieve performance enhancements has been a lively research area for last two decades. Synthetic Jet Actuators (SJAs) are devices able to interact actively with the flow around their hosting structure by providing ejection and suction of fluid from the enclosed cavity containing a piezo-electric oscillating membrane through dedicated orifices. The research presented in this paper concerns the implementation of zero-net-mass-flux SJAs airflow control system on a NACA0015, low aspect ratio wing section prototype. Two arrays with each 10 custom-made SJAs, installed at 10% and 65% of the chord length, make up the actuation system. The sensing system consists of eleven acoustic pressure transducers distributed in the wing upper surface and on the flap, an accelerometer placed in proximity of the wing c.g. and a six-axis force balance for integral load measurement. A dSPACE TM hardware connected to the software environment Matlab/Simulink® and dSPACE Control-Desk® complete the test architecture. Wind tunnel experiments, on the uncontrolled wing (actuators off), are primarily performed for system identification purpose. The open-loop control operation (actuators on but no feedback) of the wing is implemented and tested, obtaining a stall delay of about 2.8 degrees of AOA. Furthermore, a closed-loop strategy, based on the wing upper surface mean pressure chord-wise distributions signature is adopted to characterize the forthcoming boundary layer detachment. This allows for triggering the controller in stall proximity only, for energy saving purpose. Pertinent results and discussion are provided along with concluding remarks and prospects for future research.