QQ客服 官方微博 反馈留言

题名	地声界面波传播及其对掩埋目标散射特性研究
作者	郭新毅
学位类别	博士
答辩日期	2008-05-26
授予单位	中国科学院声学研究所
授予地点	声学研究所
关键词	地声学 界面波 散射 探测掩埋目标
其他题名	Study on Geo-acoustics Interface wave Propagation and Scattering Associate with Buried Objects
学位专业	声学
中文摘要	在海洋声学研究领域中，海底界面波作为声场结构中的渐消模式在声场分析中通常被省略掉。然而界面波运动相对于体波有着鲜明的特点，其传播方向与介质界面平行，幅度随深度迅速衰减，介质水平和垂向运动存在偏振特性。本文旨在研究并利用界面波的运动特性，为海滩和浅海地区的探雷方法开辟一个新的思路。 文中首先分析界面波的传播特点，介绍了界面波在弹性半空间中的一些传播特性。对于分层介质来说，界面波传播存在频散特性，因此可以用模式分析方法研究界面波的传播模型。针对一种典型的分层结构模型，文中计算出界面波传播模式，以此构造界面波传播Green函数。对于介质中存在掩埋目标的情况，文中推导了界面波散射积分方程，并利用计算机模拟介质中界面波散射声场。推导界面波散射公式首先从弹性波散射积分方程出发，根据波动方程基本解中Green函数的界面波项，将散射积分方程分解为水平方向积分和垂直方向积分两部分。经过数学变化和推导，得到一个适合于界面波散射问题的积分方程简单表达式，通过迭代求解这个表达式可以解决介质中掩埋物对界面波的散射问题。为检验该算法，文中根据界面波传播计算中使用的海底分层模型，采用界面波第一阶模式计算沉积层中掩埋物的散射位移场。从计算中可以看出该方法收敛速度较快，并且可以获得界面波对掩埋物散射位移场的强度。另外对于介质中存在多个掩埋目标的情况，利用含多个异质体弹性动力学的散射积分思路，将前文中界面波散射迭代公式推广到对多目标的散射分析当中，计算界面波对多个掩埋目标的散射声场，同时给出了高阶模式的散射情况。 为了验证界面波探雷方法的可行性，论文对界面波探测掩埋目标方法做了实验分析。文中首先就界面波信号提取、传播速度和传播衰减等几个传播方面的问题进行了分析。然后通过掩埋目标和检波器阵列以及震源位置的几何关系推算出直达波和回波的时间差，在接收信号中观察回波信号。 论文理论研究和实验工作的主要创新点有： （1） 文中将弹性波散射公式推广到界面波散射计算中，用界面波在介质中传播的Green函数构造散射迭代积分，通过数值计算得到界面波散射的声场分布，用来预报界面波散射的目标强度； （2） 根据弹性动力学中弹性波对多散射体的散射理论，引申出界面波对多散射体的散射算法，文中给出了数值解； （3） 论文对界面波高阶模式的散射情况做出了分析，以往的理论认为界面波第一阶模式占传播能量的主要部分，文中对高阶模式的求解将有助于分析散射声场的精细结构； （4） 文中利用界面波散射探测浅层掩埋目标的实验研究在国内尚属首次； （5） 实验中界面波利用三分量检波器接收并通过矢量偏振滤波方式提取界面波成分，数据分析结果表明，这种方法能够有效地利用界面波特性； （6） 文中对信号中界面波成分的传播速度，衰减和对目标的回波特征分别做出了详细的分析，并对比了掩埋物目标强度的理论值和实验结果。
英文摘要	Abstract: In research of the ocean acoustics, interface waves in sediment are generally neglected because it is the evanescent mode in acoustics field. However, interface wave has unique motion compared with body wave. The propagation direction of interface wave parallel with medium’s interface and amplitude attenuate rapidly with depth. The horizontal and vertical motions of interface wave are polarization. The main purpose of this thesis are researching and using the characterization of interface and supply a new method for anti-mine operation in surf-zone and shallow sea. In the first place, this thesis introduces the propagation characterization of interface wave in elastic half space. In the layer medium, frequency dispersion exists and propagation model of interface wave can be researched using mode analysis. For a typical layer structure model, the propagation modes of interface wave can be calculated and the Green’s function can be obtained using propagation modes. In practical problem, there are buried objects in medium. Interface wave scattering integral equation is derived, and scattering interface wave field can be simulated by computer. A sample integral equation for scattering of interface wave has been deduce based on the fundamental solution of wave equation and elastic wave scattering theory. The advantage of this method is that the volume integral can be separated into a combination of a plane integral and a vertical integral. This method can deal with scattering of interface wave from buried objects by iteration. For checking for this arithmetic, using solved propagation modes of interface wave, the scattering displacement field can be calculated using the first mode of interface wave. The convergence rapidity of the method has been proved very high by some practical example, and the scattering strength can be obtained simultaneously. Sometimes, there are buried multi-objects in medium, therefore, the interface wave scattering integral equation can be spread into calculation multi-objects scattering problem by the integral equation of the scattering elastic wave field associate with multi-inhomogeneities. In this paper, the high mode scattering of interface wave can be calculated also. In order to achieve the detection mine using interface wave, there is an experience for verifying this method. In this experience, the interface wave signal extraction, propagation velocity, propagation attenuation, and several other aspects are analyzed. The time difference between direct wave and echo wave in the received signal can be obtained according to the geometry relationship of buried objects, source and geophone array locations. Echo signal exists in received signal. The main new innovative points of theory and experiment are as following: (1) The formula of elastic wave scattering is extended into calculation interface wave scattering. In this paper, the scattering alternation integral are established by Green’s function of interface wave propagation in medium. The interface wave scattering field can be calculated using numerical method, and the result will predict the target strength; (2) Based on the theory of elastic wave scattering associated with multi-objects, the interface wave scattering associated with multi-objects can be derived, and the numerical results can be obtained at the same time; (3) The high model scattering of interface wave is analyzed in this paper. In the past theory, the first model of interface wave occupies the main palace of propagation energy. The high model scattering results conduce to analysis fine structure of scattering wave field; (4) The experiment of detection buried objects using interface wave scattering is initiation interiorly; (5) In the experiment, the three components geophones can be used to incept signal, and vector polarization filter method is used to extract interface wave from the signal. Through analyzing data, this method shows a good effect; (6) In this thesis, the propagation velocity, attenuation and echo of interface wave component in the signal are analyzed separately, and the target strength can be calculated and compared with theory result at the same time.
语种	中文
公开日期	2011-05-07
页码	129
内容类型	学位论文
源URL	[http://159.226.59.140/handle/311008/288]
专题	声学研究所_声学所博硕士学位论文_1981-2009博硕士学位论文
推荐引用方式 GB/T 7714	郭新毅. 地声界面波传播及其对掩埋目标散射特性研究[D]. 声学研究所. 中国科学院声学研究所. 2008.

个性服务

查看访问统计

相关权益政策

暂无数据

收藏/分享

除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。