几种自由边界实施方法在完全 匹配层条件下的对比研究

Comparative study among implementations of several free-surface boundaries with perfectly matched layer conditions

  • 摘要: 传统的完全匹配层技术是一种能够较为有效地消除边界反射的边界条件,但是当表层为泊松比较高的自由表面时,该技术可能会产生不稳定的现象.针对传统的完全匹配层技术固有的不稳定和掠射情况下吸收效果不佳等缺陷,发展了多轴完全匹配层、卷积完全匹配层以及将两者结合的多轴卷积完全匹配层等3种边界条件.本文介绍了水平自由表面的不同处理方法以及传统、多轴、卷积和多轴卷积等4种完全匹配层条件的原理,通过二维半无限空间模型的交错网格有限差分正演模拟对比,分析了几种自由边界实施方法在这几种完全匹配层条件下的稳定性,并通过提取单道波形与解析解进行对比,定性分析了水平自由表面几种不同处理方法的准确性以及各自的适用条件. 结果表明,泊松比和水平自由表面实施方法对波场模拟效果及其稳定性有重要影响.

     

    Abstract: Classical perfectly matched layer (PML) absorbing boundary is certified an efficient method to suppress spurious edge reflections in seismic modeling. However, when modeling Rayleigh waves with the existence of free surface, the classical PML algorithm may become unstable in the case that Poisson’s ratio of the medium is high. On the basis of defects of classical PML, such as its inherent instability and the effects of grazing incidence, multiaxial perfectly matched layer, convolutional perfectly matched layer and multiaxial convolutional perfectly matched layer are developed. Six implementations of planar free-surface boundary conditions and principles of four perfectly matched layer methods are introduced, and forward modeling of 2D half-infinite model using staggered grid finite-difference method are given to study the stability of different methods. Through the comparison of waveform between numerical solution and analytical solution, we can illustrate the accuracy and applicability of these methods in this paper. The results show that Poisson’s ratio and implementations of planar free-surface have an important influence on the effects and stability of wavefield simulation.

     

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