DYNAMIC LIFT ENHANCEMENT USING OSCILLATING LEADINGAND TRAILING-EDGE WING FLAPS

THE MAIN INTEREST OF THIS RESEARCH EFFORT FOCUSES ON THE LIFTOVERSHOOT PHENOMENON FOR STRAIGHT AND MODERATELY SWEPT WINGS. ONE PRACTICAL PROBLEM WHEN ONE WANTS TO UTILIZE THE DYNAMIC LIFT AS A MEANS TO ENHANCE AIRCRAFT PERFORMANCE IS THAT THE LIFT-OVERSHOOT IS USUALLY TOO SHORT-LIVED TO BE OF USAGE. A METHOD TO ENHANCE AND PROLONG THE DYNAMIC LIFT BY COORDINATED, SMALL-AMPLITUDE MOVEMENTS OF THE LEADING AND TRAILING EDGE FLAPS IS PROPOSED. OSCILLATION OF THE LEADING EDGE FLAP IS USED TO REDISTRIBUTE THE VORTICITY WHICH NORMALLY GOES INTO A SINGLE STRONG STALL-VORTEX AT THE END OF A PITCH-UP MOTION INTO SMALLER AND WEAKER VORTICES DURING THE COURSE OF THE WING MOTION. COMPARED WITH THE CASE WITH NO FLAP MOTION, THE RESULTING SMALLER LEADING EDGE VORTEX AT THE END OF THE PITCH-UP MOTION WILL TAKE A LONGER TIME TO GROW TO THE CRITICAL STRENGTH FOR DYNAMIC STALL TO OCCUR AND THUS THE ONSET OF STALL IS DELAYED. A COORDINATED OSCILLATION OF THE TRAILING FLAP CAN RESULT IN AN EFFECTIVE CAMBER CHANGE WHICH DELAYS THE CONVECTION OF THESE VORTICES DOWN THE WING SURFACE AND FURTHER INCREASES THE DURATION OF DYNAMIC LIFT ENHANCEMENT. THE GOAL OF THE RESEARCH PROGRAM IS TO DEVELOP AND DEFINE A DYNAMIC FLAP OSCILLATION METHODOLOGY FOR CONTROLLING AND DELAYING WING STALL DURING DYNAMIC SITUATIONS.