This paper summarizes on-going experimental research associated with efforts to achieve aero-performance efficient noise reduction of supersonic jet mixing and shock noise for military style supersonic nozzle exhausts. The baseline supersonic nozzle under investigation is one that is designed with a sharp throat radius of curvature and conical convergent and divergent sections with flat seals. Relevant baseline geometries are defined by the supersonic nozzle exhaust ducts on the F101, F110, F414, and F119 engines. Acoustic suppression technology being investigated utilizes corrugated surface topology for the divergent section of a supersonic nozzle, divergent sections with bevelled exhaust, and high pressure water drop injection from the nozzle nacelle trailing edge. Acoustic measurements were acquired for a small scale model, nominally 10 % scale, supersonic nozzle with baseline and suppressed configurations. These nozzles have a nominal exhaust diameter of 5 cm. The suppression concepts are all aero-performance efficient designs that achieve substantial jet mixing noise reduction and elimination of shock generated noise. In the current round of testing, a twin jet nozzle nacelle was designed and fabricated. The twin jet model scale experimental measurements have indicated that corrugated divergent surface topology can suppress mixing noise by 4 dB relative to the baseline and completely eliminate shock generated noise. The reduction in jet mixing noise improves to 5.5 to 6 dB when bypass flow is ported through the interior of the corrugated seal.
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