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Title

ACTIVE FLOW CONTROL OF DYNAMIC STALL BY MEANS OF JET FLOW AT HIGH REYNOLDS NUMBER 1×106

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Abstract

 IN THIS STUDY, WE HAVE PROVIDED A CRITERION FOR JET SLOT LOCATION IN DYNAMIC STALL MOTION OF AN AIRFOIL AT HIGH REYNOLDS NUMBER 1´106, FOR ACTIVE FLOW CONTROL (AFC) PURPOSES. THE AIRFOIL IS SYMMETRICAL NACA 0012 WITH A PITCHING MOTION BETWEEN AOAS 5 DEG. AND 25 DEG. ABOUT ITS QUARTER-CHORD WITH A SINUSOIDAL MOTION. WE HAVE UTILIZED COMPUTATIONAL FLUID DYNAMICS (CFD) TOOL TO NUMERICALLY DETECT DYNAMIC STALL VORTEX (DSV) ON THE VERGE OF ITS FORMATION. THEN, WE HAVE PLACED THE JET SLOT AT THE SEPARATION POINT UPSTREAM THE DSV AND SOME OTHER LOCATIONS NEARBY TO PERFORM SENSITIVITY ANALYSIS. OUR RESULTS SHOWED THAT PLACING THE JET SLOT WITHIN A VERY SMALL RANGE UPSTREAM THE LOCATION OF SEPARATION POINT HAS TREMENDOUS EFFECTS ON BOTH LIFT AND DRAG, SUCH THAT MAXIMUM DRAG WHICH OCCURS AT MAXIMUM INCIDENCES REDUCED BY 80%. THERE WAS ANOTHER UNIQUE OBSERVATION: PUTTING JET AT SEPARATION POINT LEADS TO AN INVERSE BEHAVIOR OF DRAG HYSTERESIS CURVE IN UPSTROKE AND DOWNSTROKE MOTIONS. DRAG IN DOWNSTROKE MOTION IS SIGNIFICANTLY LOWER THAN UPSTROKE MOTION, WHEREAS IN UNCONTROLLED CASE THE CONVERSE IS TRUE. IN ADDITION, BY IMPLEMENTING JET FLOW LIFT IS SIGNIFICANTLY ENHANCED DURING BOTH UPSTROKE AND DOWNSTROKE MOTIONS. FINALLY, IT SHOULD BE INDICATED THAT THIS STUDY PROVIDES INITIAL STEPS IN INVESTIGATIONS OF APPLYING SYNTHETIC JET ACTUATOR (SJA) ON A PITCHING AIRFOIL AT HIGH REYNOLDS NUMBER 1´106 WITH EFFECTS OF CHANGING MOMENTUM RATIO AND SJA FREQUENCY, WHICH WILL BE PRESENTED IN THE NEAR FUTURE.

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