深海声层析传播时延敏感核方法

发布时间：2018-11-02 16:28

【摘要】：1979年W.Munk等人提出利用声学方法对中尺度海洋环境进行监测的海洋声层析方法,解决逆介质问题。该方法利用传播时延等声传播观测量反演经过海域的声速与流速等海洋参数。声层析是结合了海洋测量、声传播建模和声学逆问题的多维问题,传统的声层析方法是基于射线模型的微扰法。微扰法利用从声源到接收阵元的多径信号走时来反演垂直分层的声速剖面。声线路径与路径上慢度(声速的倒数)的线性积分关系构成了声学逆介质问题的基本方程,通过最小二乘等逆问题求解方法可以估计出实际的声速剖面。但受发射信号传播时延测量的分辨力与射线模型的高频近似制约,在低频深海环境下微扰法的分辨力和精度都有所不足。本文提出的传播时延敏感核声层析方法从波动理论与波恩近似推导出声速扰动与传播时延的三维积分关系,可以利用两节点间的低频声信号反演海域中任意位置的声速扰动。传播时延敏感核方法利用信号的波峰时延替代多路径波包,增加了信号的观测量；同时,三维的传播时延敏感核函数将声线路径积分提升到三维的空间积分,提高了观测的空间分辨力。针对传播时延敏感核声层析方法,本文研究了核函数的理论推导、波峰模板匹配以及声层析逆问题的求解方法。首先在宽带模型下,用简正波模型推导出三维核函数表达；然后提出了基于相关的波形模板匹配方法,能有效分辨出匹配的波峰；最后,针对不同的海洋声扰动环境,提出了带有平滑约束的最小二乘方法、截断SVD方法以及凸优化方法,来求解声层析逆问题。本文对传统微扰法声层析与传播时延敏感核方法声层析分别进行了实验仿真,并比较了两者的声速反演结果,验证了传播时延敏感核方法能有效提高精度与分辨力。并在以上研究结果的基础上,开发出一套海洋声层析软件。
[Abstract]:In 1979 W.Munk et al proposed an acoustic tomography method to monitor the mesoscale marine environment using acoustic method to solve the problem of inverse medium. In this method, the ocean parameters such as velocity and velocity of sound passing through the sea area are inversed by equal-acoustic propagation observations with propagation delay. Acoustic tomography is a multidimensional problem which combines ocean measurement, acoustic propagation modeling and acoustic inverse problem. The traditional acoustic tomography method is based on the perturbation method of ray model. The multipath signal travel time from the sound source to the receiving array element is used to retrieve the vertical stratified sound velocity profile by the perturbation method. The linear integral relation between sound path and slowness (reciprocal of sound velocity) constitutes the basic equation of acoustic inverse medium problem. The actual sound velocity profile can be estimated by solving inverse problem such as least square method. However, due to the resolution of transmission delay measurement and the high frequency approximation of the ray model, the resolution and accuracy of the perturbation method in the low-frequency deep-sea environment are insufficient. The propagation delay-sensitive nuclear acoustic tomography proposed in this paper deduces the three-dimensional integral relationship between the acoustic velocity disturbance and the propagation delay from the wave theory and the Bonn approximation. The low-frequency acoustic signal between the two nodes can be used to retrieve the acoustic disturbance at any position in the sea area. The propagating delay sensitive kernel method uses the wave peak delay of the signal to replace the multipath wave packet, which increases the observation quantity of the signal. At the same time, the three-dimension propagation delay sensitive kernel function promotes the acoustic path integral to the three-dimensional spatial integral, which improves the spatial resolution of the observation. In this paper, the theoretical derivation of kernel function, the matching of wave peak template and the solution of inverse problem of acoustic tomography are studied for propagation delay sensitive nuclear acoustic tomography. Firstly, the expression of 3D kernel function is deduced by using the normal wave model under the wideband model, and then the correlation-based waveform template matching method is proposed, which can effectively distinguish the matching peak. Finally, for different ocean acoustic disturbance environments, a least square method with smooth constraints, a truncated SVD method and a convex optimization method are proposed to solve the inverse problem of acoustic tomography. In this paper, the acoustic tomography of the traditional perturbation method and the propagating delay sensitive kernel method are simulated, and the results of the acoustic velocity inversion are compared. The results show that the propagating delay sensitive kernel method can effectively improve the accuracy and resolution. On the basis of the above research results, a set of ocean acoustic tomography software is developed.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：P733.2

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