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有限差分方法广泛应用于求解许多科技领域所涉及的偏微分方程,高阶显式有限差分方法通常用来提高求解精度,已经提出的高阶隐式有限差分方法和截断高阶显式有限差分方法可用来进一步提高模拟精度而不增加计算量。本文首先计算了针对常规网格上的一阶导数和二阶导数、交错网格上的一阶导数的有限差分系数,发现高阶隐式有限差分系数中存在一些小的系数。频散分析结果表明:忽略这些小的差分系数能够近似维持有限差分的精度,但是显著减小了计算量。然后,引入镜像对称边界条件来提高隐式有限差分方法的精度和稳定性,采用混合吸收边界条件来减小来自模型边界所不需要的反射。最后,给出了针对均匀和非均匀介质模型的弹性波模拟例子,表明了本文方法的优点。
The finite difference method is widely used to solve the partial differential equations involved in many fields of science and technology. The high-order explicit finite difference method is usually used to improve the accuracy of the solution. The advanced implicit finite difference method and the truncated high-order explicit finite difference method have been proposed to further improve the simulation accuracy Without increasing the amount of computation. In this paper, we first calculate the finite difference coefficients of the first derivative and the second derivative on a regular grid and stagger the first derivative of the grid. We find that there are some small coefficients in the higher order implicit finite difference coefficients. Dispersion analysis results show that ignoring these small differential coefficients can maintain the accuracy of the finite difference approximately, but reduce the computational complexity significantly. Then, the mirror symmetry boundary condition is introduced to improve the accuracy and stability of the implicit finite difference method. Hybrid absorption boundary conditions are used to reduce the unwanted reflections from the model boundary. Finally, an example of elastic wave simulation for homogeneous and inhomogeneous media is presented, which shows the advantages of the proposed method.