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  • 1980-1984  (2)
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  • 1
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    Transmitted sound field due to an impulsive line acoustic source bounded by a plate followed by a vortex sheet (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The propagation of sound due to a line acoustic source in the moving stream across a semiinfinite vortex sheet which trails from a rigid plate is examined in a linear theory for the subsonic case. A solution for the transmitted sound field is obtained with the aid of multiple integral transforms and the Wiener-Hopf technique for both the steady state (time harmonic) and initial value (impulsive source) situations. The contour of inverse transform and hence the decomposition of the functions are determined through causality and radiation conditions. The solution obtained satisfies causality and the full Kutta conditions. The transmitted sound field is composed of two waves in both the stady state and initial value problems. One is the wave scattered from the edge of the plate which is associated with the bow wave and the instability wave. These waves exist in the downstream sectors. The other is the wave transmitted through the vortex sheet which is also associated with the instability wave. Regional divisions of the transmitted sound field are identified.
    Keywords: ACOUSTICS
    Type: NASA-CR-166174 , SU-JIAA-TR-27
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Transmission of sound across a vortex layer enclosing a cylindrical column of jet (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An approximate solution to the problem of transmission of sound across a cylindrical vortex was obtained. Results are considerably different from the plane vortex sheet case because of the added role played by the curvature of the jet. In comparison with the plane case, the specularly transmitted waves are more complex and require some numerical integration. Resonance waves are identically predicted for M 2, but there is also a wave field whose modified effect appears to extend the region of resonance just as the instability waves cover a region in space and time. The instability waves are predicted to exist for all Mach numbers but vanish for wavelengths that are large compared to the jet radius. The region of propagation is similarly wavelength dependent.
    Keywords: ACOUSTICS
    Type: NASA-CR-169845 , NAS 1.26:169845 , SU-JIAA-TR-50
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
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