大陆坡内波环境中声传播模态耦合及强度起伏特征  

Mode coupling and intensity fluctuation of sound propagation over continental slope in presence of internal waves

作　　者：高飞[1,2] 徐芳华 李整林 秦继兴 Gao Fei;Xu Fang-Hua;Li Zheng-Lin;Qin Ji-Xing(Ministry of Education Key Laboratory of Earth System Modeling,Department of Earth System Science,Institute for Global Change Studies,Tsinghua University,Beijing 100084,China;Naval Research Institute,Tianjin 300061,China;School of Ocean Engineering and technology,Sun Yat-Sen University,Zhuhai 519000,China;State Key Laboratory of Acoustics,Institute of Acoustics,Chinese Academy of Sciences,Beijing 100190,China)

机构地区：[1]清华大学全球变化研究院地球系统科学系,地球系统数值模拟教育部重点实验室,北京100084 [2]海军研究院,天津300061 [3]中山大学海洋工程与技术学院,珠海519000 [4]中国科学院声学研究所,声场声信息国家重点实验室,北京100190

出　　处：《物理学报》2022年第20期115-128,共14页Acta Physica Sinica

基　　金：国家重点研发计划(批准号:2020YFA0607900);国家自然科学基金(批准号:42176019,11874061);中国科学院青年创新促进会资助的课题(批准号:2021023)。

摘　　要：大陆坡海域内波普遍存在,其陆坡地形和内波过程都会引起显著的声场起伏.已有研究工作主要关注内波或大陆坡单扰动因子对模态耦合和强度起伏的影响,少见将内波和海底地形起伏同时作为影响因子进行研究.文章考虑孤立子内波和海底地形对声传播的双重影响,首先构建海洋波导模型,然后基于简正波理论数值对比分析各波导模型条件下模态的耦合规律,进而研究声场强度起伏特性及其物理机理.研究结果表明,当声波朝向或远离内波中心传播时,模态耦合在内波与大陆坡的共同作用下出现耦合增强或衰减,高号模态耦合系数振荡;内波扰动的作用使得能量由低号模态耦合至高号模态,提高了声场强度衰减;斜坡的作用使得声波下坡传播时,波导模态数增加、模态强度衰减降低;大陆坡内波环境中的模态强度总和大于内波环境、小于大陆坡环境,且模态组间的能量转移比只有内波或者大陆坡时更强,高号模态从耦合中获得更多能量,使得跃层以上水层能量增强.The topographic variation underwater of the continental slope is one of the main causes for triggering off the formation of internal waves,and the continental slope internal waves are ubiquitous in the ocean.The horizontal variation of waveguide environment,caused by the internal wave and the continental slope,can lead to acoustic normal mode coupling,and then generate sound field fluctuation.Most of the existing research work focused on studying the effect of single perturbation factor of either the internal waves or the continental slope on acoustic mode coupling and intensity fluctuation,while it is hard to find some research work that takes into account both the internal waves and the topographic variations as influencing factors.In this work,numerical simulations for the sound waves to propagate through the internal waves in the downhill direction are performed by using the acoustic coupled normal-mode model in four waveguide environments:thermocline,internal wave,continental slope and continental slope internal wave.And the mode coupling and intensity fluctuation characteristics and their physical mechanisms are studied by comparing and analyzing the simulation results of the four different waveguide environment constructed.Some conclusions are obtained as follows.The intra-mode conduction coefficients are symmetric with respect to the center of the internal wave,while the inter-mode coupling coefficients are antisymmetric around it.As the sound waves propagate toward or away from the center of the internal wave,the acoustic mode coupling becomes enhanced or weakened,and the coupling coefficients curves for large mode oscillate.The influence of internal wave perturbation makes the energy transfer from the smaller modes to the larger modes,which increases the attenuation of sound field intensity.The number of the waveguide modes increases and the mode intensity attenuation decreases,when the sound waves propagate downhill.The total intensity of all modes for the continental slope internal wave environment is

关 键 词：大陆坡 孤立子内波 声场起伏 模态耦合 

分 类 号：P731.24[天文地球—海洋科学]