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    Martínez-Lera, P. Schram, C. Bériot, H. and Hallez, R. 2014. An approach to aerodynamic sound prediction based on incompressible-flow pressure. Journal of Sound and Vibration, Vol. 333, Issue. 1, p. 132.

  • Journal of Fluid Mechanics, Volume 690
  • January 2012, pp. 441-460

The effects of viscosity on sound radiation near solid surfaces

  • C. L. Morfey (a1), S. V. Sorokin (a2) and G. Gabard (a1)
  • DOI:
  • Published online: 01 December 2011

Although the acoustic analogy developed by Lighthill, Curle, and Ffowcs Williams and Hawkings for sound generation by unsteady flow past solid surfaces is formally exact, it has become accepted practice in aeroacoustics to use an approximate version in which viscous quadrupoles are neglected. Here we show that, when sound is radiated by non-rigid surfaces, and the smallest dimension is comparable to or less than the viscous penetration depth, neglect of the viscous-quadrupole term can cause large errors in the sound field. In addition, the interpretation of the viscous quadrupoles as contributing only to sound absorption is shown to be inaccurate. Comparisons are made with the scalar wave equation for linear waves in a viscous fluid, which is extended using generalized functions to describe the effects of solid surfaces. Results are also presented for two model problems, one in a half-space and one with simple cylindrical geometry, for which analytical solutions are available.

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1.D. G. Crighton 1975 Basic principles of aerodynamic noise generation. Prog. Aerosp. Sci. 16 (1), 3196.

2.N. Curle 1955 The influence of solid boundaries on aerodynamic sound. Proc. R. Soc. Lond. 231, 505514.

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6.J. E. Ffowcs Williams & D. L. Hawkings 1969 Sound generation by turbulence and surfaces in arbitrary motion. Phil. Trans. R. Soc. Lond. A 264, 321342.

8.F. Irgens 2008 Continuum Mechanics. Springer.

9.M. J. Lighthill 1952 On sound generated aerodynamically I. General theory. Proc. R. Soc. Lond. 211, 564587.

10.C. L. Morfey , C. J. Powles & M. C. M. Wright 2011 Green’s function in computational aeroacoustics. Intl J. Aeroacoust. 10, 117160.

11.P. M. Morse & K. U. Ingard 1968 Theoretical Acoustics. McGraw-Hill.

13.K. Shariff & M. Wang 2005 A numerical experiment to determine whether surface shear-stress fluctuations are a true sound source. Phys. Fluids 17, 107–105.

14.J.-Z. Wu , H.-Y. Ma & M.-D. Zhou 2006 Vorticity and Vortex Dynamics. Springer.

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Journal of Fluid Mechanics
  • ISSN: 0022-1120
  • EISSN: 1469-7645
  • URL: /core/journals/journal-of-fluid-mechanics
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