Experimental Investigation Of Air Jets To Control Shock-Induced Dynamic Stall

This paper shows experimental results for dynamic stall control on a dynamically pitching OA209 airfoil at Mach 0.5, with Re=1.9x106 and Re=0.85x106. The control was by supersonic constant blowing on the suction side of the airfoil. Dry compressed air was blown normal to the airfoil chord, from portholes at 10% chord, with diameter 1% chord. Jet spacing along the airfoil breadth was varied from 6.7% chord to 20% chord. At both Reynolds numbers, the OA209 experienced shock-induced stall with a hysteresis in lift and pitching moment around the static values, rather than the overshoot in forces typically associated with a dynamic stall vortex. The forces and the stall control were primarily functions of the maximum angle of attack, with full control of stall possible for maximum angles of attack of 14° and less. For deep dynamic stall with maximum angles of attack 18°, the jet spacing and blowing pressure was varied. A good optimum was found for the jets spaced at 20% chord and Cq=0.004 (Cμ =0.016) resulting in a reduction of the pitching moment peak by 60%.