Test Verification of a Transonic Airfoil Design Employing Active Diffusion Control.
Final rept. 13 Jun 74-14 Jun 75,
ADVANCED TECHNOLOGY CENTER INC DALLAS TEX
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Experimental results are presented that show active diffusion control, with its integrated contouringblowing characteristics, to be a viable concept for relaxing transonic airfoil design constraints. The antiseparation tailored contour ATC is the basic device for active diffusion control. A modified 12 thick C-141 section with a trailing edge upper surface ATC, designated as the TEATC12 airfoil, was selected as the proof-of-concept configuration. It incorporates the main features of active diffusion control while providing a reliable baseline for comparison. Previous analytical studies have predicted a near-critical roof-top pressure distribution at the design point and the potential for superior off-design performance. The experimental verification has been obtained in two steps. In the first step, the transonic BLCdiffusion process was modeled in an axisymmetric diffuser facility. Blowing predictions for the ATC geometry were substantiated and interactions between the jet and the mainstream were examined. Experimental verification was completed by testing a TEATC12 airfoil model in the Vought Systems Division High Speed Wind Tunnel. A C-141 model was also tested to provide a direct reference for the TEATC12 results. Wind tunnel data validate the TEATC12 design point at predicted liftblowing and show the design point advantages carrying over to off-design performance. Buffet onset lift coefficients 0.2 higher than those for either shockless supercritical or conventional sections were obtained at M 0.70 and drag divergence was delayed by 0.13 on Mach number relative to comparable conventional sections.
- Fluid Mechanics