Two-Dimensional Transonic Wind Tunnel Tests of Three 15-Percent Thick Circulation Control Airfoils

Abstract
Two-dimensional transonic wind tunnel tests were conducted on three fifteen percent circulation control elliptic airfoils over the Mach no. range 0. 3 to 0.9. Model configurations included a pure elliptical shape with both jet flap and tangential upper surface trailing edge blowing, plus tangential blowing over an elliptical shape with a rounded trailing edge. Performance of the rounded trailing edge configuration was the best of the three at low speeds, but above M = 0.55, detachment of the Coanda jet caused rapid performance deterioration. Due to its elongated trailing edge and associated larger effective radius downstream of the slot, the tangentially blown pure ellipse was able to extend the jet detachment Mach number to 0.7, where maximum equivalent lift-to-drag ratios of 22 at a two-dimensional lift coefficient of 0.44 were achieved. The jet flaps proved to be inferior to the tangentially blown configurations in all respects except in its ability as a thrusting, drag- reducing body.

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