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An experimental study of simultaneous multipoint measurements in the flowfield and acoustic field of a Mach 1.75 cold-air jet is presented. A series of four optical-deflectometer probes measured turbulent fluctuations in or near the jet flow, and eight microphones recorded the far-field pressure in the direction of peak emission. The correlation methodology involves the coherence between the delay-and-sum beamformer outputs of the optical-deflectometer probes and the microphones. This procedure yields results with greater fidelity and higher coherence levels than obtained with individual optical-deflectometer-to-microphone correlations. With the optical-deflectometer probes in the jet shear layer, there is a significant correlation, on the order of 0.1, between the turbulent fluctuations and farfield noise. As the optical-deflectometer probe moves transversely away from the jet, its correlations with the microphone beamformer first drops and then increases. This trend signifies the transition from hydrodynamic to acoustic pressure fields. In the vicinity of the nozzle exit, the peak coherence between the beamformed optical-deflectometer and microphone signals coincides with the physical location of the optical-deflectometer probe. However, as the shear layer thickens downstream, the peak coherence generally lags the probe location, which is a probable result of acoustic refraction by the mean flow. [ABSTRACT FROM AUTHOR]

Provides information on a study which proposed an empirical model for eddy convection in coaxial supersonic jets. Experimental methods used; Results and discussion; Conclusion.

Provides information on a study which measured the noise radiated from perfectly expanded supersonic coaxial jets in an anechoic chamber for operating conditions with the same total mass flow and thrust and with the same temperature ratio. Experimental method used; Numerical results and calculations; Conclusion.

Presents experimental results on a method that eliminates Mach waves from the exhaust of supersonic jets. Removal of supersonic jet noise; Increase of takeoff thrust with minimal impact on overall fuel consumption; Definition of the principle of Mach wave elimination.