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Intensity fluctuations due to the motion of internal solitons in shallow water
Author(s): QIN Jixing, KATSNELSON Boris, LI Zhenglin, ZHANG Renhe, LUO Wenyu, State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Department of Marine Geosciences, School of Marine Sciences, University of Haifa, Haikou Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences
Pages: 145-
153
Year: 2016
Issue:
2
Journal: Acta Acustica
Keyword: 孤立子; 简正波; 声能量; 声场起伏; 声强; 传播路径; 本征函数; 扰动波; 成反比; 声线;
Abstract: Mode coupling plays a dominant role in the fluctuations of sound signals at the receiver for sufficiently large inclination angle of the internal soliton(IS) front relative to the acoustic path.The coupled-mode formulas for sound filed fluctuations are given in this situation.Theoretical analysis is carried out for intensity fluctuations due to the motion of ISs in shallow water,and numerical simulations are also performed using a parabolic equation model.The quasi-periodic variations of intensity can be observed from the numerical results.The peaks in the spectrum of intensity take place at the so called predominant frequency and its higher harmonics.The predominant frequency is proportional to the velocity of the IS motion along the acoustic path and inversely proportional to the scale of interference beating of the interacting modes,which corresponds to the cycle length of the critical ray in the ray theory.The predominant frequency value does not depend on the IS shape.Moreover,the vertical structures of the intensity spectrum are analyzed and shown to correspond the shapes of the modes which contribute significantly to intensity fluctuations.
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