Comparative Studies of the Supersonic Jet Noise Generated by Rectangular and Axisymmetric Nozzles

PDFTech ReportDOT-TSC-OST-73-22PB-221 855NoiseAircraft noiseAerodynamicsJet propelled aircraftSupersonic aircraftSound levelMeasurementUnited StatesUnited States. Dept. of Transportation. Office of the SecretaryLow, Khoon CheangLouis, Jean F.Massachusetts Institute of Technology. Dept. of Aeronautics and AstronauticsJohn A. Volpe National Transportation Systems Center, (U.S.)NTL-AVIATION-AVIATIONNTL-AVIATION-Aviation Energy and EnvironmentNTL-ENERGY AND ENVIRONMENT-Aviation Energy and EnvironmentVolpe National Transportation Systems Center, Technical Reference CenterThe main purpose of this study is to develop experimental scaling laws useful for predicting the overall sound power of supersonic jets operating under a range of high stagnation temperatures and pressures and under various exit Mach numbers. A shock tube is used as a flexible tool to provide the range of high stagnation temperatures and pressures associated with the supersonic jets in this investigation. The range of stagnation pressures chosen (for a given temperature and Mach number) correspond to overexpanded, perfectly expanded and underexpanded conditions of the jet. Two different nozzle configurations: a rectangular and an axisymmetric, are examined to determine how a basic difference in shapre of the jet changes the relative importance of the different noise generating mechanisms. Measured sound directivity and Mach waves propagation direction obtsained from shadowgraphs indicate that Mach waves contribute importantly to the noise produced by a rectangular jet