VORTEX DYNAMICS ON A PITCHING DELTA WING

A study of the dynamic behavior of the leading-edge vortices on a delta wing undergoing oscillatory pitching motions is presented, A sharp-edged, flat-plate, delta wing having a sweep angle of 70 deg was used in this investigation. The wing was sinusoidally pitched about its one-half chord position at reduced frequencies ranging from k = 2πfc/u = 0.05 to 0.30 at root chord Reynolds numbers between 9 × 104 and 3.5 × 105, for angle-ofattack ranges of α = 29 to 39 deg and α = 0 to 45 deg. During these dynamic motions, visualization of the leadingedge vortices was obtained by injecting TiCl4 through ports located near the model apex. The location of vortex breakdown was recorded using high-speed motion-picture photography. The motion-picture records were analyzed to determine the vortex trajectory and breakdown position as a function of angle of attack. When the wing was sinusoidally pitched, hysteresis was observed in the location of the breakdown position. This hysteresis increased with reduced frequency. The velocity of breakdown propagation along the wing and the phase-lag between model motion and breakdown location were also determined. Detailed information was also obtained on the oscillation of breakdown position in both static and dynamic cases. © 1990 by R. C. Nelson. © The American Institute of Aeronautics and Astronautics, Inc. All rights reserved.