Experimental Investigation on a 3D Wing Section Hosting Multiple SJAs for Stall Control Purpose

Abstract

The control of the flow over aerodynamic shapes in order to achieve performance enhancements, such as improved aircraft maneuverability, has been a lively area of research for last two decades. Active flow control can produce significant performance improvement when combined in a closed-loop control system. Synthetic jet actuators (SJAs) are devices able to interact actively with the flow around a hosting structure by providing ejection and suction of fluid from an orifice. The research presented in this paper concerns the implementation of zero-net-mass-flux SJAs airflow control system on a NACA0015, low aspect ratio (LAR) wing section prototype developed by Clarkson University under the Advancement of Intelligent Aerospace Systems (AIAS) AFOSR Grant FA9550-09-1-0051. Two arrays of custom made SJAs, installed in the proximity of the leading edge and flap of the wing section, make up the actuation system. The sensing system consists of eleven acoustic pressure transducers distributed in the wing upper surface, an accelerometer placed in proximity of the wing center of gravity and a six-axis force balance. A dSPACE hardware connected to the software environment Matlab / Simulink / Control Desk complete the test architecture. Wind tunnel experiments, on the uncontrolled wing, are primarily performed for system identification purpose. The open-loop control of the wing is implemented and tested, obtaining a stall postposition of about 2.8 degrees of angle of attack. A strategy based on the comparison of the mean pressure chord-wise distributions, senses by the acoustic pressure transducers for different angles of attack, on the wing upper surface is adopted to characterize the forthcoming boundary layer detachment. This allows for triggering the closed-loop control in stall proximity only for energy saving purpose. Pertinent results and discussion are provided.