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Noise generation by a low-Mach-number jet

Published online by Cambridge University Press:  20 April 2006

John Laufer  and
Ta-Chun Yen
John Laufer
Affiliation:
Department of Aerospace Engineering, University of Southern California, Los Angeles, CA 90089-1454
Ta-Chun Yen
Affiliation:
Department of Aerospace Engineering, University of Southern California, Los Angeles, CA 90089-1454 Present address: Beijing University, Beijing, People's Republic of China.
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Abstract

Using a ‘clean’ jet facility the relationship between the jet flow and its radiation field was studied experimentally in the Mach-number range 0.05 < Mj < 0.20 and a Reynolds-number range 6 × 104 < ReD < 2.3 × 105. The various acoustic source parameters such as strength, frequency and Mach number were varied systematically, and the far-field pressure measured simultaneously. On the basis of these measurements the nature of the sources in the initial shear layer could be characterized. The principal results, equally valid for unexcited and excited jets, are as follows: the acoustic sources are not convected but are located within a confined volume fixed with respect to the nozzle even though they are being generated by moving disturbances in the jet; they are associated with the nonlinear saturation of the unstable wave amplitudes of the shear layer occurring at the vortex-pairing locations; the radiation intensity varies nonlinearly with the source strength and is highly directional, exponential in character.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 134 , September 1983 , pp. 1 - 31
Copyright
© 1983 Cambridge University Press

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