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Modal content of noise generated by a coaxial jet in a pipeMeasurements of the hydrodynamic pressure fluctuation levels showed that, for circular obstructions with a flow passage diameter less than one-half of the pipe diameter, hydrodynamic pressure fluctuations were small compared with the acoustic pressure, at locations greater than ten pipe diameters downstream of the restrictions. Thus, in the study currently reported, which was concentrated on measurement of the modal characteristics of the sound field downstream of the restrictions, special techniques to avoid contamination by hydrodynamic 'noise' were not necessary. The major results obtained in the study are scaling laws for the shape of the modal pressure spectrum and for the overall efficiency of noise generation. The characteristics of the modal pressure spectra are discussed. It is shown that the primary parameter controlling the spectrum shape is the frequency ratio (Helmholtz number/Strouhal number). The efficiency levels when plotted as a function of Mach number show a strong dependence on restriction size
Document ID
19810052645
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Kerschen, E. J.
(Stanford Univ. CA, United States)
Johnston, J. P.
(Stanford University Stanford, Calif., United States)
Date Acquired
August 11, 2013
Publication Date
May 8, 1981
Publication Information
Publication: Journal of Sound and Vibration
Volume: 76
Subject Category
Acoustics
Accession Number
81A37049
Funding Number(s)
CONTRACT_GRANT: NSF GK-37294
CONTRACT_GRANT: NSF ENG-76-00819
Distribution Limits
Public
Copyright
Other

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