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Augmented adiabatic mode theory for upslope propagation from a point source in variable‐depth shallow water overlying a fluid bottom

 

作者: Allan D. Pierce,  

 

期刊: The Journal of the Acoustical Society of America  (AIP Available online 1983)
卷期: Volume 74, issue 6  

页码: 1837-1847

 

ISSN:0001-4966

 

年代: 1983

 

DOI:10.1121/1.390271

 

出版商: Acoustical Society of America

 

关键词: water;sound waves;wave propagation;depth;asymptotic solutions

 

数据来源: AIP

 

摘要:

A uniform asymptotic solution is presented for sound propagation from a constant frequency point source in shallow water whose depthH(r) decreases monotonically with cylindrical distancer. The water has constant sound speedc1and density ρ1; the bottom fluid extends indefinitely in depth and has sound speedc2and density ρ2, wherec2>c1. The interface depth has constant valueH0up to ranger0and thereafter decreases linearly to zero. The solution appears as a sum of modal terms, each such mode eventually encountering a critical depthHc(n) (at which modal phase velocity equalsc2) at a critical rangerc(n). A previously derived local solution for a modal term near its critical range is modified such that it automatically reduces to the adiabatic mode solution at nearer ranges and such that it is valid at arbitrary distances beyond the critical range. Bulk attenuation is incorporated into the model using an appropriate modal average over depth. Numerical results are compared with four parabolic equation computations supplied by Jensen. In these four cases only single mode propagation is considered andr0is 0. The two theories agree well, with discrepancies typically less than 1 dB. Additional comparisons with parabolic equation computations (simultaneous propagation of three and two modes) presented by Jensen and Kuperman [J. Acoust. Soc. Am.67, 1564–1566 (1980)] show comparable agreement, but for the higher modes there are marked discrepancies in the directions at which sound is beamed into the bottom fluid from regions encompassing those mode’s critical ranges. This is attributed to the progressive deterioration of the present theory with increasing mode number.

 

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