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Acoustic and Mean Flow Measurements of High-Speed, Helium-Air Mixture Jets

The effectiveness of using helium-air mixture jets to simulate heated jets at both subsonic and supersonic velocities is investigated. Particular emphasis is placed on replicating the aeroacoustic properties of heated jets. Acoustic directivity and spectral measurements of helium-air mixture jets are compared to existing heated jet data. Results typically indicate agreement within 2 dB with some discrepancy attributable to facility and run condition differences. In addition, mean flowfield measurements indicate a shortening of the potential core and a slight decrease in jet spreading with the addition of helium – the same trends observed for heated jets. The similarities in acoustic and mean flow behavior indicate that helium-air mixture jet experiments provide a viable low-cost alternative to heated jet experiments.