共查询到17条相似文献，搜索用时 125 毫秒
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本文对地球物理学中的电磁场积分方程正演进行了综述,重点分析和讨论了积分方程正演中的散射场近似求解方法.散射场近似解法可以在保证计算精度的前提下有效的提高计算效率,使积分方程正演突破了传统简单孤立异常体研究的限制,适用于大规模复杂三维电磁场快速正演.本文着重对近年来国内外学者提出的散射场近似求解方法,如扩展Born近似、高阶广义Born近似、准线性(QL)近似和准解析近似(QA)等进行了分析和讨论,指出了各种近似解法的优缺点和适用范围.并在前人工作的基础上总结了地球物理学中的电磁场积分方程正演的基本原理和关键问题及解决方法,包括并矢格林函数、散射场的近似求解方法以及全积分求解方法等.最后,本文提出了积分方程法发展趋势和实际工程应用的前景以及面临的困难和待解决的问题. 相似文献
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为了实现大地电磁测深三维高效快速正演算法,本文研究了大地电磁测深积分方程三维正演模拟的理论与方法.首先详细地推导了Fredholm型积分方程;然后给出积分方程的离散方法、并矢格林函数积分的求解方法以及大型矩阵方程的存储与求解方法;最后,通过理论地电模型的计算检验了方法和程序编制的正确性,并展示了几种理论地电模型的数值计算结果,分析其异常特征.算例结果表明,该正演算法在CPU主频为1.81GHz、内存为1GB的计算机上能正确地模拟多个异常体的异常特征;地表电性不均匀体会使地表视电阻率曲线产生十分严重的畸变;TE模式相对TM模式纵向分辨率比较好,而TM模式的横向分辨率较好;随着异常体埋深的增加,反映异常的分辨能力进一步降低. 相似文献
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采用规则六面体单元和并矢Green函数奇异积分等效积分技术,已有的大地电磁积分正演方法具有不能有效模拟地下复杂地质体和计算精度偏低的缺点.本文提出了一种新的三维大地电磁积分方程正演技术,即采用四面体单元、解析的并矢Green函数奇异积分表达式,达到既能模拟地下复杂异常体,又能有效提高已有积分方程法计算精度的目的.首先,采用四面体网格技术离散地下复杂异常体,获得四面体单元上的大地电磁积分方程.然后,利用针对四面体单元开发的新的奇异值积分的解析表达式,准确计算线性方程中的并矢Green函数的奇异积分,从而获得精确的线性方程.借助于PARDISO高性能并行直接求解器,实现了三维大地电磁问题的高精度求解.最后,基于国际标准3D-1模型和六棱柱模型,通过与其他方法结果的对比分析,验证了本文方法的正确性、处理高电导率对比度的能力(1000:1)和处理复杂模型的能力. 相似文献
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本文对多分层媒质并矢格林函数中的索末菲积分,用Prony方法对其被积函数分式部分用指数函数逼近.利用索末菲恒等式,无穷积分就可化为闭合的级数形式.该闭合形式可看作一串离散镜像在观察点的解.所得结果与数值积分结果吻合很好. 相似文献
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利用积分方程法实现了均匀导电半空间三维大地电磁响应的数值模拟。求取张量格林函数积分时,采用二次剖分算法解决计算中奇异值问题,对于含有贝塞尔函数的积分项,利用结合连分式展开的高斯求积代替常规的快速汉克尔变换方法,确保了张量格林函数的正确计算并提高了计算精度。最后通过数值模拟结果的对比及模型试算验证了算法的正确性,所实现的三维大地电磁数值模拟算法为理论研究三维地电构造的大地电磁响应的分布规律提供了有效的工具,也为研究三维反演算法奠定了基础。 相似文献
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格林函数在解决电磁场和直流电场问题的积分方程法和边界单元法等方法中有着广泛的应用.在应用格林函数时会遇到格林函数奇异性的问题,即其在源区域的内部,当场点和源点重合时,会碰到对格林函数为无穷大,积分为奇异积分.对于不同问题中遇到的不同形式的格林函数奇异性问题的各种处理方法进行了分析和评述.对于标量格林函数奇异性问题处理方法有：挖去法、级数展开法、绕开法和解析法等.对于并矢格林函数奇异性问题处理方法有：分量处理法、源并矢法和拟源并矢法等处理方法.通过对实际工作中所遇到的新方法新问题中的不同形式的格林函数的研究,提供了奇异性问题的处理的方法和途径. 相似文献
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Diffraction of obliquely incident waves by a cylindrical cavity embedded in a layered viscoelastic half-space 总被引：1，自引：0，他引：1
The three-dimensional harmonic response in the vicinity of an infinitely long, cylindrical cavity of circular cross-section buried in a layered, viscoelastic half-space is obtained when the half-space is subjected to homogeneous plane waves and surface waves impinging at an oblique angle with respect to the axis of the cavity. The solution is obtained by an indirect boundary integral method based on the use of moving Green's functions for the viscoelastic half-space. Numerical results describing the motion on the ground surface and the motion and stresses on the wall of the cavity are presented for obliquely incident P-, SV-, SH- and Rayleigh waves with different horizontal angles of incidence. 相似文献
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Green''''s functions for uniformly distributed loads acting on an inclined line in a poroelastic layered site 总被引：4，自引：0，他引：4
Based on one type of practical Biot's equation and the dynamic-stiffness matrices of a poroelastic soil layer and half-space, Green's functions were derived for uniformly distributed loads acting on an inclined line in a poroelastic layered site. This analysis overcomes significant problems in wave scattering due to local soil conditions and dynamic soil-structure interaction. The Green's functions can be reduced to the case of an elastic layered site developed by Wolf in 1985. Parametric studies are then carried out through two example problems. 相似文献
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平面SV波在饱和半空间中沉积谷地周围的散射 总被引：1，自引：0，他引：1
采用一种特殊的间接边界积分方程法,求解了平面SV波在饱和半空间中任意形状沉积谷地周围的二维散射问题。结合饱和半空间中膨胀波源和剪切波源格林函数,由分布在沉积和半空间交界面附近两虚拟波源面上的波源分别构造沉积内外的散射波场,由交界面连续条件建立方程并求解确定虚拟波源密度,总波场反应即可由自由波场和散射波场叠加而得。然后通过边界条件验算、退化解答与现有结果的比较以及稳定性检验,验证了方法的计算精度。通过一组典型算例,研究了平面SV波在饱和半空间中沉积谷地周围散射的基本规律,详细给出了不同参数情况沉积谷地附近地表位移幅值和孔隙水压,着重分析了入射SV波频率和角度、边界渗透条件、沉积孔隙率等因素对场地反应的影响,得出了一些有益的结论。 相似文献
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By using integral transform methods, the Green's functions ofhorizontal harmonic force applied at the interior of the saturated half-space soil are obtained in the paper. The general solutions of the Biot dynamic equations in frequency domain are established through the use of Hankel integral transforms technique. Utilizing the above- mentioned general solutions, and the boundary conditions of the surface of the half-space and the continuous con-ditions at the plane of the horizontal force, the solutions of the boundary value problem can be determined. By the numerical inverse Hankel transforms method, the Green's functions of the harmonic horizontal force are obtainable. The degenerate case of the results deduced from this paper agrees well with the known results. Two numerical examples are given in the paper. 相似文献
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Boundary integral equations for dynamic rupture propagation on vertical complex fault system in half-space:Theory 
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下载免费PDF全文 The boundary integral equation method(BIEM)is now widely used in numerical studies on earthquake rupture dynamics,and is proved to be a powerful tool to deal with problems on complex fault system.However,since this method heavily lies on the specific forms of Green's function and only the Green's function in full-space has a closed analytic expression,it is usually limited to a full-space medium.In this study,as a first step to extend this method to an arbitrary complex fault system in half-space,the boundary integral equations(BIEs)for dynamic strike-slip on vertical complex fault system in half-space are derived based on exact Green's function for isotropic and homogeneous half-space.Effect of the geometry of the complex fault system are dealt with carefully.Final BIEs is composed of two parts:contribution from full-space,which has been thoroughly investigated by Aochi and his co-workers by using the Green's function for full-space,and that from free surface,which is studied in detail in this study. 相似文献