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The leaking mode problem in atmospheric acoustic-gravity wave propagationThe problem of predicting the transient acoustic pressure pulse at long horizontal distances from large explosions in the atmosphere is examined. Account is taken of poles off the real axis and of branch line integrals in the general integral governing the transient waveform. Perturbation techniques are described for the computation of the imaginary ordinate of the poles and numerical studies are described for a model atmosphere terminated by a halfspace with c = 478 m/sec above 125 km. For frequencies less than 0.0125 rad/sec, the GR sub 1 mode, for example, is found to have a frequency dependent amplitude decay of the order of 0.0001 nepers/km. Examples of numerically synthesized transient waveforms are exhibited with and without the inclusion of leaking modes. The inclusion of leaking modes results in waveforms with a more marked beginning rather than a low frequency oscillating precursor of gradually increasing amplitude. Also, the revised computations indicate that waveforms invariably begin with a pressure rise, a result supported by other theoretical considerations and by experimental data.
Document ID
19770003381
Document Type
Conference Paper
Authors
Kinney, W. A.
(Georgia Inst. of Tech. Atlanta, GA, United States)
Pierce, A. D.
(Georgia Inst. of Tech. Atlanta, GA, United States)
Date Acquired
August 8, 2013
Publication Date
January 1, 1976
Publication Information
Publication: NASA. Langley Res. Center Advan. in Eng. Sci., Vol. 3
Subject Category
Acoustics
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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IDRelationTitle19770003363Analytic PrimaryAdvances in Engineering Science, Volume 3