Effect of thickness-to-chord ratio on aerodynamics of non-slender delta wing

Abstract

The effect of thickness-to-chord (t/C) ratio on aerodynamics of a non-slender delta wing with sweep angle of 45 degree is characterized in a low-speed wind tunnel using laser illuminated smoke visualization, surface pressure measurements, particle image velocimetry, and force measurements. The delta wings of t/C ratios varying from 2% to 15% with 45 degree windward beveled leading edges are tested. The results indicate that the effect of t/C ratio on flow structure is quite substantial. Considering the low angles of attack where the wings experience leading edge vortex structure, the strength of the vortex structure increases as the t/C ratio increases. However, low t/C ratio wings have pronounced surface separations at higher angle of attack compared to the wings with high t/C ratios. These results are well supported by the force measurements such that high t/C ratio wings induce higher lift coefficients, CL, at low angles of attack, whereas maximum CL values are higher and appear at higher angle of attack for low t/C ratio wings. This indicates that low t/C ratio wings are more resistive to the stall condition. Considering the lift-to-drag ratio, CL/CD, increase in t/C ratio induces remarkable drop in CL/CD values.