基于垂直灵敏度核函数的浅海尺度海域声层析

发布时间：2018-06-04 08:58

本文选题：浅海声层析 + 射线走时　；参考：《浙江大学》2017年硕士论文

【摘要】：海洋声层析是基于声传播多途效应的一种观测物理海洋的方法,常被用于反演大尺度海域的声速剖面、温度、盐度等物理海洋信息。本文分别用射线声学理论和简正波理论对波动方程求解,在距离无关的海洋环境中,建立基于微扰法建立声速扰动和传播时延扰动之间的线性关系。其中,在基于简正波理论的声层析中,本文引入定量描述传播时延扰动的灵敏度核函数。灵敏度核是关于造成传播时延变化的声速扰动的三维空间分布,其推导是基于格林函数的一阶玻恩近似,将声速扰动和时延扰动之间的非线性关系转化为线性。通过绘制灵敏度核函数的图像,我们可以得到一个类似于高频情况下基于射线理论的声能分布图,发现在低频情况下,传播时延敏感于声线周围的菲涅尔区的声速变化,而不是声线本身的声速变化。此外,我们还可以知道存在正声敏性区域,即经过正声敏性区域的声线有正声速扰动,并且到达波峰的传播时延变大。之后,声层析变成了求解观测方程的逆问题,本文采用正则化约束的最小二乘的方法来反演声速扰动,在微扰小尺度浅海环境和有小尺度涡扰动的浅海环境下分别进行仿真,对比垂直灵敏度核函数浅海声层析和射线走时浅海声层析的反演精度,发现在小尺度浅海低频环境下垂直灵敏度核函数的反演精度远高于射线走时方法。最后,本文提出了一种基于浮标的小型海洋声层析仪,设计其数据采集、数据处理以及远距离通信方法,并实验证明了本文提出的基于浮标实时姿态的远距离通信方法的可靠性。
[Abstract]:Ocean acoustic tomography is a physical ocean observation method based on multipath effect of acoustic propagation. It is often used to retrieve physical ocean information such as sound velocity profile temperature salinity and so on. In this paper, the ray acoustics theory and the normal wave theory are used to solve the wave equation respectively. In the distance independent marine environment, the linear relationship between the acoustic velocity perturbation and the propagation delay disturbance is established based on the perturbation method. Among them, in acoustic tomography based on normal wave theory, a sensitivity kernel function is introduced to describe the propagation delay perturbation quantitatively. The sensitivity kernel is the three-dimensional spatial distribution of the acoustic disturbance which causes the variation of the propagation delay. The derivation of the sensitivity kernel is based on the first order Boone approximation of the Green's function, which converts the nonlinear relation between the acoustic velocity perturbation and the delay disturbance into a linear one. By drawing the image of sensitivity kernel function, we can get a sound energy distribution map similar to that in high frequency case based on ray theory. It is found that in low frequency case, propagation delay is sensitive to the change of sound velocity in Fresnel region around the sound line. And not the speed of sound itself. In addition, we can also know that there are positive acoustic sensitivity regions, that is, the sound lines passing through the positive sound sensitivity region have positive acoustic velocity perturbation, and the propagation delay to the peak becomes longer. After that, acoustic tomography becomes the inverse problem for solving the observation equation. In this paper, the regularization constrained least square method is used to invert the acoustic disturbance, and the simulation is carried out in the perturbation small scale shallow sea environment and the shallow water environment with small scale vortex disturbance, respectively. By comparing the inversion accuracy of vertical sensitivity kernel function in shallow water acoustic tomography with that of ray travel time acoustic tomography, it is found that the inversion accuracy of vertical sensitivity kernel function in small scale shallow sea low frequency environment is much higher than that of ray walking time method. Finally, this paper presents a small marine acoustic tomography instrument based on buoy, which is designed for data acquisition, data processing and long-distance communication. The reliability of the proposed method based on real-time attitude of buoy is proved by experiments.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P714.3;P733.2

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