1989-09-01

Low-Speed Aerodynamic Characteristics of a Powered Nasp-Like Configuration in Ground Effect 892312

An investigation was conducted in the Langley 14- By 22-Foot Subsonic Tunnel to determine the low-speed aerodynamic characteristics of a powered generic NASP-like configuration in ground effect. The model was a simplified configuration consisting of a triangular wedge forebody, a rectangular mid-section which housed the propulsion simulation system, and a rectangular wedge aftbody. Additional model components included a delta wing, exhaust flow deflectors, and aftbody fences.Six-component force and moment data were obtained over an angle of attack range from −4° to 18° while model height above the tunnel floor was varied from 1/4 inch to 6 feet. Variations in freestream dynamic pressure, from 10 psf to 80 psf, and engine ejector pressure yielded a range of thrust coefficients from 0 to 0.8.Flow visualization was obtained by injecting water into the engine simulator inlets and using a laser light sheet to illuminate the resulting exhaust flow. This investigation technique allowed diagnostic analysis of the exhaust flow and aided in interpreting the force and moment data.The effect of the engine simulator flow field (both inlet and exhaust flows) as it was constrained between the large undersurface of the configuration and the tunnel floor produced significant power-on ground effects. Where lift increased with decreasing ground height during power-off testing, significant lift losses were noted in ground effect as thrust was increased. Variations in angle of attack as well as the presence of aftbody fences also had a substantial influence on the ground effects during power-on testing, Further results indicated that adding a wing to the configuration reduced, but did not eliminate, the power-on lift losses in ground effect.

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