Vortex trajectories and breakdown on wing-canard configurations

Abstract

Flow visualization and force measurement experiments are carried out on close-coupled wing-canard and wing-alone configurations. The effects of the canard sweep angle and longitudinal position on the leadingedge vortex trajectories, their breakdown characteristics, and the configuration aerodynamic coefficients, are studied. The effects of highly (75 deg) and moderately (56 deg) swept canards of equal area are compared. Results show that the canard displaces the leading-edge vortex of the wing upward and outboard in the vicinity of the trailing edge. Increasing the angle of attack results in an upward displacement of these vortices. The angle of attack for which the wing-vortex breakdown points cross the trailing edge on the wing-canard configurations is 8-10 deg higher than in the wing-alone configuration. Increasing the longitudinal separation between the canard and the wing reduces the wing-canard interference. Force measurements show that the normal-force coefficient of the wing—highly-swept-canard configuration at high incidence can be smaller than for the appropriate wing-alone coefficients. This may indicate that the strong leading-edge vortices of the highly-swept canard, which at high incidence are very close to the wing surface near the trailing edge, alter the leeside flow structure there and reduce the lift.