共查询到19条相似文献，搜索用时 156 毫秒
1.
介绍了完美匹配层(PML)人工边界可以吸收不同频率和任意角度入射波的原理以及PML人工边界的构造方法. 在此基础上,将PML人工边界应用于地震波动数值模拟的速度应力混合有限元格式中,探讨了PML应用的可行性,并通过数值试验研究了PML人工边界的反射率,比较了PML人工边界与多次透射公式(MTF)人工边界应用于体波和面波模拟中数值反射的差异,对两种边界的透射效果进行了分析. 结果表明, 尽管数值离散后PML人工边界不再保持完美匹配特性,但PML人工边界在近场波动数值模拟中可获得比MTF人工边界更为理想的吸收效果,在角点透射、大角度掠射情形下尤为明显;PML人工边界在混合有限元格式的数值算法中,未见失稳等不良反应,比MTF人工边界有更好的稳定性;在合理选择参数的情况下,PML人工边界的运算量可接受. 相似文献
2.
利用有限元软件Ansys二次开发语言apdl进行二次开发,将多次透射边界(MTF边界)和弹阻边界(V-S边界)添加到软件中,从而实现对土-结构动力相互作用问题中无限域场地的模拟。以野外大比例(1/2)土-箱基-框架结构试验模型的牵引释放自由振动试验(波源问题)和爆破震动试验(散射问题)数据为基础,通过有限元数值计算结果和试验结果的对比可知,施加了人工边界的土体模型可以较好地模拟波在无限域土体中的传播,有效地减少有限元计算模拟时的计算规模。同时多次透射边界在计算精度以及散射问题中地震波输入的便捷性方面要优于弹阻边界。 相似文献
3.
局部透射边界的精度 总被引：6，自引：0，他引：6
廖振鹏 《地震工程与工程振动》1993,13(3):1-6
离散局部透射边界和旁轴近似的精度分析表明,它们所以缺乏透射大角度入射波的能力乃是源于采用单一的透射方向。本文提出将边界节点附近的入射波表示为一系列预定入射角的平面波的叠加以消除这一缺点。在这一思想上建立的局部透射边界能够在全部入射角范围内减小反射。通过模拟稳态SH波动简要地阐明了上述思想及其在建立高精度、稳定的局部透射边界中的意义。 相似文献
4.
基于外行简谐波动模型、多项式插值理论和具有解析表达式的外插序列,导出了N阶透射边界及其误差项与收敛的充分条件。利用外插序列的时空坐标满足同一直线方程的几何特征,完成了简谐波动N阶透射边界向任意外行波动阶透射边界的推广。依据外插序列的解析表达式,导出了后者误差项的近似表达式和收敛性的充分条件。N阶透射边界的主部与N阶多次透射公式相同,但误差项的表达式不同,精度与收敛性的分析方法与结果也不同。提出了与虚拟透射边界相关的频率放大倍数概念,认为它们是影响虚拟透射边界精度的关键因素。 相似文献
5.
土—结构相互作用通用程序的改进 总被引：2，自引：0，他引：2
本文提出了用具有工程实用价值的透射边界替换通用程序ＦＬＵＳＨ中一致边界的方法。通过实例证明、二阶透射边界与一致边界具有相当的精度。改进后的程序ＷＭＮＳ－Ｆ１比ＦＬＵＳＨ具有更高的计算效率和实用性。 相似文献
6.
时域高阶双渐近透射边界能够同时模拟层状介质中行波和快衰波的传播,具有很高的计算精度和计算效率.本文将高阶双渐近透射边界推广应用到多层层状地基系统弹性波传播问题的模拟,采用广义特征值分解分析该透射边界的数值稳定性,通过移谱法消除导致数值不稳定的虚假模态.将高阶双渐近透射边界以超单元的形式直接嵌入到近场有限元方程,建立了有限元-高阶双渐近透射边界时域耦合分析模型,并将其应用到重力坝-层状地基动力相互作用分析.数值算例分析结果表明,该时域耦合分析模型具有很高的精度和计算效率,适用于实际重力坝工程的地震响应分析. 相似文献
7.
本文对场地地震波动模拟中透射边界的稳定性问题进行了一系列研究。对已有的透射边界稳定措施做了比较分析,并给出了不同措施的适用性。结合粘弹性边界的物理模型提出了一个新的消除透射边界飘移失稳的措施,参考高频滤波的思路探讨了一种新的消除透射边界葛频振荡失稳的措施,并用数值试验验证了这两种新的透射边界稳定方法的有效性。将显式行限元一有限差分方法结合透射边界的数值解法的计算结果与解析结果作对比分析,验证这弹一套数值解法的计算精度。利用二维模型模拟了自贡土层和山脊地形的场地效应,利用显戈有限元一有限差分方法结合透射边界这套数值解法进行数值模拟计算,应用汶川地震的实示强震观测记录来验证这套数值解法对于实际地震波动模拟的有效性。 相似文献
8.
本文研究了透射边界及相关问题,指出在近源波动的一般情况下,沿人工边界法向传播的外行波动应为曲面波,但在人工边界点的足够小的时空邻域内,可以将曲平面波近似处理为平面波,亦即采用了局部平面波假定。认为对不同的人工边界点,局部平面波模型中的基本变量是时空变量,是影响透射边界近源精度和稳定性的决定性因素。建立了对物理视波速进行优化求解的数学模型,以及相应的1阶和2阶优化透射边界。 相似文献
9.
本文将对多次透射边界在瞬态波动模拟中的精度分析推广到介质中存在多个物理波速的情形，阐明了它模拟成层介质中瞬态波动的适用性，指出多次透射边界的误差随着透射阶数的增加而迅速减小，二阶透射边界已具有足够高的模拟精度。 相似文献
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11.
间断Galerkin有限元法（DG-FEM）作为一种有效的高阶有限元法受到了国内外学者的广泛关注.本文基于任意高阶间断Galerkin有限元法对弹性波方程进行空间离散,并将离散后所得的非齐次线性常微分方程系统齐次化,最后结合针对齐次问题的强稳定性保持龙格库塔（SSP Runge-Kutta）算法,将DG-FEM推广至时间任意高阶精度.另外,借鉴近最佳匹配层（NPML）的思想,基于复频移（CFS）拉伸坐标变换推导了一种新的PML吸收边界条件（简称为CFS-NPML）,该CFS-NPML能够与DG-FEM算法很好地结合,形成有效的起伏地表地震波传播数值模拟技术.数值试验结果表明,DG-FEM具有高阶精度,可以适应任意复杂起伏地表和复杂构造情况下的弹性波传播数值模拟.同时,CFS-NPML对包括面波等震相的人为边界反射都具有良好的吸收效果. 相似文献
12.
模拟地震波传播的三维逐元并行谱元法 总被引：2，自引：0，他引：2
高效地震波场正演模拟对于复杂模型中地震波传播与成像研究至关重要.本文在谱元法原理框架内,对已有逐元谱元法改进,提出一种新的逐元并行谱元法求解三维地震波运动方程,并得到地震波场.逐元并行谱元法的核心思想在于在单元上进行质量矩阵与解向量的乘积运算,并将此运算平均分配至每一个CPU计算核心,此处理有利提升谱元法的并行计算效率.同时,根据Gauss-Lobatto-Legendre(GLL)数值积分点与插值点重合的特点,将稠密单元刚度矩阵的存储转化成单元雅克比矩阵行列式的值及其逆的存储,大幅减少谱元法计算内存开销.此外,在模型边界上利用逐元并行谱元法求解二阶位移形式完美匹配层(PML)吸收边界条件,消除边界截断而引入的虚假反射.通过逐元并行谱元法得到的数值解与解析解对比,以及实际地震波场模拟,数值结果证实了逐元并行谱元法用于地震波场模拟的高效性. 相似文献
13.
A good artificial boundary treatment in a seismic wave grid-based numerical simulation can reduce the size of the computational region and increase the computational efficiency, which is becoming increasingly important for seismic migration and waveform inversion tasks requiring hundreds or thousands of simulations. Two artificial boundary techniques are commonly used: perfectly matched layers (PMLs), which exhibit the excellent absorption performance but impose a greater computational burden by using finite layers to gradually reduce wave amplitudes; and absorbing boundary conditions (ABCs), which have the high computational efficiency but are less effective in absorption because they employ the one-way wave equation at the exterior boundary. Naturally, PMLs have been combined with ABCs to reduce the number of PMLs, thus improving the computational efficiency; many studies have proposed such hybrid PMLs. Depending on the equations from which the ABCs are derived, there are two hybrid PML variants: the PML+unstretched ABC (UABC), in which the ABC is derived from a physical equation; or the PML+stretched ABC (SABC), in which the ABC is derived from the PML equation. Even though all the previous studies concluded that hybrid PMLs can improve the absorption performance, none of them quantified how many PMLs can be removed by combining the PML with the ABC compared with the pure PML. In this paper, we systematically study the absorption performance of the two hybrid PML variants. We develop a method to distinguish the artificial reflections from the PML-interior interface and those caused by the PML exterior boundary to accurately approximate the additional absorption achieved by using the UABC and the SABC. The reflection coefficients based on a theoretical derivation and numerical tests both show that the UABC amplifies most reflections and is not recommended in any situation; conversely, the SABC can always diminish reflections, but the additional absorption achieved by the SABC is relatively poor and cannot effectively reduce the number of PMLs. In contrast, we find that simply increasing the damping parameter improves absorption better than the PML+SABC. Our results show that the improvement in absorption achieved by combining the PML with either the SABC or the UABC is not better than that obtained by simply adjusting the damping profile of the PML; thus, combining the PML with the ABC is not recommended in practice. 相似文献
14.
Xin Liu Yang Liu Zhi-Ming Ren Xiao-Hui Cai Bei Li Shi-Gang Xu Le-Kai Zhou 《应用地球物理》2017,14(2):270-278
Edge reflections are inevitable in numerical modeling of seismic wavefields, and they are usually attenuated by absorbing boundary conditions. However, the commonly used perfectly matched layer (PML) boundary condition requires special treatment for the absorbing zone, and in three-dimensional (3D) modeling, it has to split each variable into three corresponding variables, which increases the computing time and memory storage. In contrast, the hybrid absorbing boundary condition (HABC) has the advantages such as ease of implementation, less computation time, and near-perfect absorption; it is thus able to enhance the computational efficiency of 3D elastic wave modeling. In this study, a HABC is developed from two-dimensional (2D) modeling into 3D modeling based on the 1st Higdon one way wave equations, and a HABC is proposed that is suitable for a 3D elastic wave numerical simulation. Numerical simulation results for a homogenous model and a complex model indicate that the proposed HABC method is more effective and has better absorption than the traditional PML method. 相似文献
15.
流体饱和多孔介质黏弹性动力人工边界 总被引：1，自引：0，他引：1
基于Biot流体饱和多孔介质本构方程，采用平面波和远场散射波经验叠加来反映外行波传播，以经验参数反映人工边界外行波动的衰减和多角度透射特性。在人工边界处分别施加反映固相和液相介质传播效应的弹簧及阻尼来模拟人工边界以外的无限域介质对来自有限域的外行波的能量的吸收作用。从而形成一种流体饱和多孔介质的黏弹性动力人工边界。数值算例表明：边界的精度和稳定性高于现有的黏性边界、黏弹性人工边界及一阶透射边界。 相似文献
16.
Application of the nearly perfectly matched layer for seismic wave propagation in 2D homogeneous isotropic media 总被引：1，自引：0，他引：1
Jingyi Chen 《Geophysical Prospecting》2011,59(4):662-672
Numerical modelling plays an important role in helping us understand the characteristics of seismic wave propagation. The presence of spurious reflections from the boundaries of the truncated computational domain is a prominent problem in finite difference computations. The nearly perfectly matched layer has been proven to be a very effective boundary condition to absorb outgoing waves in both electromagnetic and acoustic media. In this paper, the nearly perfectly matched layer technique is applied to elastic isotropic media to further test the method's absorbing ability. The staggered‐grid finite‐difference method (fourth‐order accuracy in space and second‐order accuracy in time) is used in the numerical simulation of seismic wave propagation in 2D Cartesian coordinates. In the numerical tests, numerical comparisons between the nearly perfectly matched layer and the convolutional perfectly matched layer, which is considered the best absorbing layer boundary condition, is also provided. Three numerical experiments demonstrate that the nearly perfectly matched layer has a similar performance to the convolutional perfectly matched layer and can be a valuable alternative to other absorbing layer boundary conditions. 相似文献
17.
应用高精度人工边界条件可有效提升近场波动数值模拟计算效率.完美匹配层是吸收层形式高精度人工边界条件,匹配层内场方程和界面条件通常分别采用复坐标延伸技术变换强形式无限域内波动方程和界面条件得到,亦曾将无限域界面条件当作匹配层界面条件.场方程和界面条件构建过程相互独立,可能出现匹配不合理而引发数值失稳、计算精度低下等问题.本文提出采用复坐标延伸技术变换弱形式无限域波动方程以构建完美匹配层的方法.弱形式波动方程耦合了波动方程及界面条件,进而规避了变换后所得场方程与界面条件之间的匹配不合理问题.新方法可直接建立弱形式匹配层,在此基础上亦可给出强形式匹配层.弱形式便于有限元离散,强形式便于有限差分离散.基于弱形式完美匹配层,结合勒让德谱元建立了弹性介质近场波动谱元模拟方案.利用算例验证了新方案的精度及数值稳定性.本文工作可直接推广至多相耦合介质近场波动数值模拟. 相似文献
18.
The theory of perfectly matched layer (PML) artificial boundary condition (ABC), which is characterized by absorption any wave motions with arbitrary frequency and arbitrarily incident angle, is introduced. The construc- tion process of PML boundary based on elastodynamic partial differential equation (PDE) system is developed. Combining with velocity-stress hybrid finite element formulation, the applicability of PML boundary is investi- gated and the numerical reflection of PML boundary is estimated. The reflectivity of PML and multi-transmitting formula (MTF) boundary is then compared based on body wave and surface wave simulations. The results show that although PML boundary yields some reflection, its absorption performance is superior to MTF boundary in the numerical simulations of near-fault wave propagation, especially in corner and large angle grazing incidence situations. The PML boundary does not arise any unstable phenomenon and the stability of PML boundary is better than MTF boundary in hybrid finite element method. For a specified problem and analysis tolerance, the computa- tional efficiency of PML boundary is only a little lower than MTF boundary. 相似文献
19.
The complexity of near surface intensifies the diversity of seismic wave fields, which makes study on near surface wavefields important in many aspects. The strong absorption of low velocity layer can affect the resolution of seismic data, and free boundary can cause surface wave. Considering the above problems, we focus on the Rayleigh wavefields simulation using finite-difference wave equation of higher-order staggered grids and PML boundary conditions. Free boundary, buried source and overlying low velocity layer are taken into consideration and point explosion source is adopted. Through some numerical simulation with different parameters, we quantitatively analyze relationship between wave intensity and source depth, as well as the energy variation with propagation and obtain some practical knowledge and conclusions. 相似文献