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The effect of mean velocity variations on jet noise

Published online by Cambridge University Press:  28 March 2006

G. T. Csanady
G. T. Csanady
Affiliation:
University of Waterloo, Waterloo, Ontario
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Abstract

Experimental evidence suggests that it may be profitable to separate the discussion of the high-frequency components of jet noise from low-frequency components. Theory then leads one to the recognition that the physical mechanism of noise generation is slightly different for the two components and for this reason one may speak of high-frequency ‘self noise’ and low-frequency ‘shear noise’ (Lilley 1958; Ribner 1964).

Both theory and experiment indicate that mean-flow refraction effects on self noise are appreciable. Using geometrical acoustics a description of the far-field radiation pattern of the high-frequency end of the jet-noise spectrum is obtained, in good qualitative agreement with observations. A conservation law of acoustic energy, applying between the frame of reference in which the sound sources move, and the fixed frame in which the observations are carried out, results in the absence of the convection amplification effect (over and above the U8 law) for total sound power at high frequencies, a result which helps explain the uniform validity of the U8 law.

An analysis of the shear-noise source term suggests that this part of the sound radiation is due to a combination of quadrupoles which have at least one axis parallel to the jet. This then explains the observed concentration of low-frequency noise around the jet axis.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 26 , Issue 1 , September 1966 , pp. 183 - 197
Copyright
© 1966 Cambridge University Press

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References

Atvars, G., Schubert, L. K. & Ribner, H. S. 1965 J. Acoust. Soc. Am. 37, 16.
Blokhintsev, D. I. 1946 Acoustics of a nonhomogeneous moving medium. NACA TM no. 1399 (Translation).Google Scholar
Friedlander, F. G. 1958 Sound Pulses. Cambridge University Press.
Howes, W. L. 1960 Similarity of far noise field of jets. NASA TR no. R-52.Google Scholar
Lighthill, M. J. 1952 On sound generated aerodynamically. Proc. Roy. Soc., A 211, 564–587.Google Scholar
Lighthill, M. J. 1953 On the energy scattered from the interaction of turbulence with sound on shock waves. Proc. Camb. Phil. Soc. 49, 531–551.Google Scholar
Lighthill, M. J. 1954 On sound generated aerodynamically. Proc. Roy. Soc., A 222, 1–32.Google Scholar
Lighthill, M. J. 1962 Sound generated aerodynamically. Proc. Roy. Soc., A 267, 147–182.Google Scholar
Lilley, G. M. 1958 On the noise from air jets. ARC 20, no. 376-N40-FM 2724.Google Scholar
Mollö-Christensen, E., Kolpin, M. A. & Martucelli, J. R. 1964 Experiments on jet flows and jet noise, far-field spectra and directivity patterns. J. Fluid Mech. 18, 285–301.Google Scholar
Mollö-Christensen, E. & Narasimha, R. 1960 Sound emission from jets at high subsonic velocities. J. Fluid Mech. 8, 49–60.Google Scholar
Proudman, I. 1953 The generation of noise by isotropic turbulence. Proc. Roy. Soc., A 214, 119–132.Google Scholar
Ribner, H. S. 1958 Note on acoustic energy flow in a moving medium. UTIA TN no. 21.Google Scholar
Ribner, H. S. 1964 The generation of sound by turbulent jets. Adv. Appl. Mech. 8, 103–182.Google Scholar
Townsend, A. A. 1956 The Structure of Turbulent Shear Flow. Cambridge University Press.
Williams, J. E. F. 1963 The noise from turbulence convected at high speed. Phil. Trans. Roy. Soc., A 255, 469–503.Google Scholar
Wills, J. A. B. 1964 On convection velocities in turbulent shear flows. J. Fluid Mech. 20, 417–432.Google Scholar