Hostname: page-component-5b777bbd6c-7mr9c Total loading time: 0 Render date: 2025-06-24T10:33:02.779Z Has data issue: false hasContentIssue false
  • English
  • Français

Measurements of subsonic jet noise and comparison with theory

Published online by Cambridge University Press:  29 March 2006

P. A. Lush
P. A. Lush
Affiliation:
Institute of Sound and Vibration Research, University of Southampton
Get access Rights & Permissions [Opens in a new window]

Abstract

Measurements of the noise field from a 25 mm diameter subsonic air jet are presented. These results are analysed in some detail by determining both the jet velocity dependence and the directivity of the intensity of the radiation in 1/3-octave bands at particular values of the frequency parameter, \[ (fD/V_J)(1-M_c\cos\theta). \] This procedure should ensure that a particular source in a geometrically similar position in the jet is always observed, whatever the jet velocity, diameter and emission angle.

These results are compared with the predictions of Lighthil's (1952) theory of convected quadrupoles. It is shown that the theory predicts the variation of the intensity with jet velocity and emission angle provided that the observed frequency is below a certain critical value, which depends on jet diameter and emission angle and is independent of jet velocity. Above this critical frequency, the predicted variations overestimate the measurements and it appears that the convective amplification predicted by the theory is much reduced. The variation of this critical frequency is explained by assuming that substantial interaction occurs between the radiated sound and the jet flow when the wavelength of the sound becomes shorter than the sound path length in the jet flow.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 46 , Issue 3 , 13 April 1971 , pp. 477 - 500
Copyright
© 1971 Cambridge University Press

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

Article purchase

Temporarily unavailable

References

Davies, P. O. A. L., Fisher, M. J. & Barratt, M. J. 1963 The characteristics of the turbulence in the mixing region of a round jet J. Fluid Mech. 15, 337–367.Google Scholar
Ffowcs Williams, J. E. 1963 The noise from turbulence convected at high speed. Phil. Trans. Roy. Soc A 255, 469–503.Google Scholar
Lighthill, M. J. 1952 On sound generated aerodynamically. 1. General theory. Proc. Roy. Soc A 211, 564–587.Google Scholar
Lighthill, M. J. 1962 Sound generated aerodynamically. Proc. Roy. Soc A 267, 147–182.Google Scholar
Lighthill, M. J. 1963 Jet noise A.I.A.A. J. 1, 1507–1517.Google Scholar