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On the noise sources of the unsuppressed high-speed jet

Published online by Cambridge University Press:  29 March 2006

K. A. Bishop ,
J. E. Ffowcs Williams  and
W. Smith
K. A. Bishop
Affiliation:
Rolls-Royce Ltd, Bristol Engine Division
J. E. Ffowcs Williams
Affiliation:
Rolls-Royce Ltd, Bristol Engine Division
W. Smith
Affiliation:
Rolls-Royce Ltd, Bristol Engine Division
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Abstract

The paper describes an interpretation of jet-noise theory and scale-model experiments to highlight physical properties of jet-noise sources at very high speed. The study is prompted by current efforts to suppress the noise of supersonic transport aircraft.

The principal noise sources are shown to be very large-scale wave-like undulations of the jet flow that travel downstream at supersonic speed for a distance of several jet diameters. These motions are relatively well ordered and are probably more akin to recognizable instabilities of a laminar flow than the confused small-scale turbulence. Because of this we postulate a model of the noise generating motions as the instability products of a jet flow of low equivalent Reynolds number. This Reynolds number is based on an eddy viscosity and can be further reduced by artificially increasing the small-scale turbulence level. This step would tend to stabilize the flow and inhibit the formation of large-scale noise producing eddies.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 50 , Issue 1 , 15 November 1971 , pp. 21 - 31
Copyright
© 1971 Cambridge University Press

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References

Bradshaw, P., Ferris, D. H. & Johnson, R. F. 1964 Turbulence in the noise-producing region of a circular jet. J. Fluid Mech. 19, 591.Google Scholar
Crow, S. C. 1968 Viscoelastic properties of fine-grained incompressible turbulence. J. Fluid Mech. 33, 1.Google Scholar
Davies, P. O. A. L., Fisher, M. J. & Barratt, M. J. 1963 The characteristics of turbulence in the mixing region of a round jet. J. Fluid Mech. 15, 337.Google Scholar
Ffowcs Williams, J. E. 1963 The noise from turbulence convected at high speed. Phil. Trans. A 255, 469–503.Google Scholar
Ffowcs Williams, J. E. 1965 On the development of Mach waves radiated by small disturbances. J. Fluid Mech. 22, 49–55.Google Scholar
Ffowcs Williams, J. E. 1969 Jet noise at very low and very high speed. Chapter in Aerodynamic Noise(ed. H. S. Ribner). University of Toronto Press.
Ffowcs Williams, J. E. & Hawkings, D. L. 1968 Shallow water wave generation by unsteady flow. J. Fluid Mech. 31, 779.Google Scholar
Ffowcs Williams, J. E. & Hawings, D. L. 1969 Sound generation by turbulence and surfaces in arbitrary motion. Phil. Trans. A 264, 321–342.Google Scholar
Landahl, M. T. 1967 A wave guide model for turbulent shear flow. J. Fluid Mech. 29, 441.Google Scholar
Ligethill, M. J. 1969 The outlook for a wave theory of turbulent shear flows. In Computation of Turbulent Boundary Layers, vol. 1 (ed. S. J. Kline et al.). Stanford University Report.
Lighthill, M. J. 1970 Turbulence. In Osborne Reynolds and Engineering Today (ed. D. M. McDowell & J. D. Jackson). Manchester University Press.
Lilley, G. M. 1958 On the noise from air jets. Aero. Res. Counc. 20 376, N. 40.
Miles, J. W. 1958 On the disturbed motion of a plane vortex sheet. J. Fluid Mech. 4, 538.Google Scholar
Ribner, H. S. 1958 On tho strength distribution of noise sources along a jet. University of Toronto Institute of Aerospace Studies U.T.I.A. Report 51 and J. Acouat. Soc. Am. 30, 9, 876.Google Scholar
Trevett, E. G. 1968 Velocity measurement in a jet from a convergent nozzle. Rolls-Royce Report AP. 5531.
Webster, R. B. 1970 Jet noise simulation on shallow water. J. Fluid Mech. 40, 423.Google Scholar