Development of a Circulation Control Wing for UAVs

Circulation Control, which was discovered accidentally by Henry Coanda in 1935, is proven to be an efficient lift augmentation method at low Mach numbers. The objective of this research is to design and develop a Circulation Control Wing (CCW) that will provide increased lift to a fixed-wing Unmanned Aerial Vehicle (UAV). The configuration (the curvature of the trailing edge on a Clark-Y airfoil) that gives high lift augmentation ratios for reasonably low blowing rates is investigated. Wind tunnel tests are conducted on 11.7% thick circulation control airfoil with upper surface blowing capability. Different trailing edges (Coanda surfaces) have been tested at moment coefficients from 0.0 to 0.04. Test data are collected at Mach numbers of 0.021; 0.024; 0.029 and 0.030 at Reynolds numbers of 1.0 × 10⁵ to 1.5 × 10⁵. It is found that the smaller Coanda surface configuration is more effective. At M = 0.021 and α = 13°, the (2.1) Coanda surface gave the maximum ΔC_L = 0.42 at a C_μ = 0.04. The maximum lift enhancement (up to 155%) at zero angle-of-attack, is achieved by using the same Coanda surface(2.1) at C_μ = 0.04 and M = 0.03.