FLOW VISUALIZATION STUDY OF DELTA WINGS IN WING-ROCK MOTION

MODERN FIGHTER AIRCRAFT ARE OPERATING IN A FLIGHT REGIME WITH INCREASING DEMANDS FOR MANEUVERABILITY AND CONTROLLABILITY TO BE EFFECTIVE IN THE COMBAT AREANA. ONE OF THE LIMITATIONS TO THAT EFFECTIVENESS IS THE INABILITY TO ACCURATELY TRACK TARGETS FOR GUN OR MISSILE SHOTS DUE TO THE DEGRADING CHARACTERISTIC OF WING ROCK, A SELF-INDUCED, LIMIT-CYCLE OSCILLATION IN ROLL, SOMETIMES ACCOMPANIED BY COUPLED OSCILLATIONS IN YAW, THAT OCCURS NEAR THE STALL ANGLE OF ATTACK. THE PURPOSE OF THIS STUDY IS TO DEVELOP THE CAPABILITY FOR PERFORMING EXPERIMENTS IN A WATER TUNNEL TO VISUALIZE THE COMPLEX VORTEX FLOW FIELDS OF AIRCRAFT-LIKE MODELS UNDERGOING OSCILLATIONS IN ROLL. EXPERIMENTS WILL BE PERFORMED TO VISUALIZE THE INTERACTION OF LEADING EDGE VORTICES WITH EACH OTHER AND WITH THE WING SURFACE USING DELTA WING MODELS VARYING IN SWEEP FROM 70 DEGREES TO 85 DEGREES. A FORCED-OSCILLATION-IN-ROLL APPARATUS WILL BE DEVELOPED. THE EFFECTS OF SWEEP ANGLE, LEADING EDGE RADIUS, OSCILLATION AMPLITUDE AND FREQUENCY, AND ANGLE OF ATTACK WILL BE EVALUATED. MOTION HISTORIES OF THE MODEL AND FLOW RESPONSE WILL BE RECORDED ON VIDEO TAPE. ATTEMPTS WILL BE MADE TO CORRELATE THE MOTION OF THE MODEL AND THE CHANGING STRUCTURE OF THE VORTEX FLOW FIELD. SUCCESSFUL DEMONSTRATION OF THE TECHNIQUE WILL LEAD TO FURTHER STUDIES OF MORE COMPLEX AIRPLANE CONFIGURATIONS AND THE DEVELOPMENT OF OTHER APPARATUSES FOR ANALYSIS OF OSCILLATORY MODEL MOTIONS, SUCH AS PITCH, YAW AND CONTINUOUS ROLL ABOUT THE FREESTREAM VELOCITY VECTOR (CONING MOTION).