基于正交贴体网格的VTI介质地震波数值模拟

Numerical Simulation of Seismic Wave in VTI Media Based on Orthogonal Body-fitted Grid

为了解决规则网格有限差分法在处理起伏地表自由边界条件时需进行复杂坐标转换和插值运算的问题,以及对起伏地表进行阶梯状离散近似所产生的虚假散射波问题,将计算流体力学中的正交贴体网格生成技术引入到起伏地表下VTI介质的网格剖分中,采用基于同位网格的DRP/opt MacCormack有限差分法模拟起伏地表下VTI介质中的地震波场。网格的正交性使实施自由边界条件时无需做复杂的坐标转换和插值运算。数值算例表明,本文提出的网格剖分法能够有效消除阶梯状网格产生的虚假散射波,从而提高起伏地表下VTI介质地震波数值模拟精度。

In order to solve the complex coordinate transformation and interpolation operations when the regular grid finite difference method deals with the free boundary conditions of irregular surface,as well as the false scattered waves generated by the stepped discrete approximation of irregular surface,the orthogonal body-fitted gird generation technique in computational fluid mechanics was introduced into the mesh generation of VTI media under irregular surface.The DRP/opt MacCormack finite difference method based on the collocated grid was used to simulate seismic waves in VTI media under the irregular surface.The orthogonality of the grid eliminates the need for complex coordinate transformation and interpolation operations in the implementation of free boundary conditions.Numerical examples show that the proposed grid generation method can effectively eliminate the false scattered waves generated by the stepped grid,thus improve the accuracy of seismic numerical simulation in VTI media under the irregular surface.