3.4 Jet Noise Reduction Scale-model tests of advanced exhaust mixers in a high-fidelity wind tunnel have shown jet noise reduction of 3 decibels for a range of engine types, including separate flow engines. The mixers are exhaust nozzles that have been formed into complex shapes designed to enhance the mixing of the core, bypass, and ambient airflows to reduce jet noise. Although mixers have been in use, the innovation in these results was an improved design method, which incorporated numerically predicted flow physics to guide the noise reduction design and optimize engine performance. Such methods expand the understanding of the mechanisms of noise sources and ultimately extend the benefit of the developed technology to many different applications. In addition to these scale-model test results, a 3-decibel jet noise reduction was also achieved during an Allied-Signal static test of a full-scale engine. The developed technology is being considered for industry designs and will likely be on production engines early this century. Model jet noise reducing advanced exhaust mixer NASA POC: Dennis Huff 216-433-3913 Dennis.L.Huff@grc.nasa.gov

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