Experimental Investigation of Vortex Formation over a Delta Wing with Consideration of Pressure Power Spectrum

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 surface of 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 comparing to the canard-off case. Due to the downwash and upwash of the canard, the wing operates at lower effective angles of attack and therefore, the vortex breakdown is delayed. The power spectrum results of the unsteady pressure on 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.