CANARD-WING INTERACTIONS IN SUBSONIC FLOW

Extensive subsonic wind tunnel tests were conducted on a coplanar wing-canard
configuration at various angles of attack. In these experiments, a 60° swept canard was placed
upstream of a 60° swept main delta wing. This paper deals with the distribution of mean and
fluctuating pressure coefficients on the upper surfaces of both the canard and the wing immersed
in a variety of angles of attack. According to the results, presence of canard postpones the vortex
formation and growth on the wing to higher angles of attack compared to the canard-off case. Due
to the canard downwash field, the wing operates at lower effective angles of attack and therefore,
its vortex breakdown is delayed. The spectral analysis of the unsteady pressure on both the canard
and the wing show the existence of narrow, dominant frequency band containing the majority of
the fluctuation energy. This frequency band is believed to be the natural frequency of the leading
edge vortex. The results show that the dominant frequency of the wing vortex is lower than that of
the canard having the same sweep angle as the wing, which is an indication of the wing vortex
attenuation due to canard downwash field.