Internal friction and boundary conditions in lossy fluid seabeds
作者:
Grant B. Deane,
期刊:
The Journal of the Acoustical Society of America
(AIP Available online 1997)
卷期:
Volume 101,
issue 1
页码: 233-240
ISSN:0001-4966
年代: 1997
DOI:10.1121/1.417995
出版商: Acoustical Society of America
关键词: SEA BED;INTERNAL FRICTION;BOUNDARY CONDITIONS;SOUND WAVES;VELOCITY;WAVE PROPAGATION;ABSORPTION
数据来源: AIP
摘要:
There are two distinct mechanisms associated with compressional wave absorption in lossy media, internal relaxation and internal friction. For the special case of propagation in an homogeneous, unbounded medium, both mechanisms can be modeled by adopting the convention of a complex sound speed and are, in this sense, equivalent. For the more realistic case of propagation in a stratified medium, the convention of complex sound speed does not give a correct description for losses which modify the linearized equation of motion, such as internal friction. In the presence of boundaries, internal friction can be modeled by the introduction of a complex quiescent density in addition to complex sound speed. Propagation models which use complex sound speed only in the presence of boundaries make the tacit assumption that seafloor losses are caused by internal relaxations only. A solution is developed for propagation in a lossy Pekeris channel where absorption in the lower fluid is caused by internal friction. The example that has been considered yields a sound level 3 dB less than the standard description over a 50-km path.
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