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    复杂地质条件的间断有限元地震波数值模拟及GPU加速

    A discontinuous Galerkin finite-element method of seismic modeling in complex media using GPUs

    • 摘要: 间断Galerkin有限元方法(DGFEM)是一种具有较高模拟精度的有限元方法,但其算法编程难度大,其针对各类复杂介质的波动方程的算法目前未见统一的计算格式。为此,基于三角形非结构化网格以及局部Lax-Friedrichs数值流,构建了针对复杂介质波动方程模拟的DGFEM编程计算矩阵,并进一步得出了适用于各类复杂介质模拟的单一波场分量的通用计算格式。该通用计算格式能够有效提升DGFEM算法编程的可拓展性。基于该格式给出了DGFEM的通用CUDA核函数的构建方法,并形成CPU+GPU的二维DGFEM并行计算程序框架。通用CUDA核函数可以将DGFEM算法进一步延伸到更加复杂的介质以及三维情况。理论模型和复杂山地模型的数值实验结果表明,构建的通用计算格式和CUDA核函数可以准确模拟声波、弹性波、粘弹性波、孔隙弹性波方程描述的纵波、横波以及慢纵波等波现象。相比单核CPU模拟,二维DGFEM弹性波GPU计算加速比平均在100倍左右。同时,弹性波、粘弹性波、孔隙弹性波模拟耗时约为声波模拟的1.7,2.3,3.0倍。此结果可以指导复杂介质耦合条件模拟时多进程的负载平衡。

       

      Abstract: The discontinuous Galerkin finite-element method (DGFEM), which is a high-order finite element method adapting to complex surface conditions, has attracted extensive attention. Based on triangular unstructured meshes and local Lax-Friedrichs flux, the matrix forms of DGFEM calculation using elastic, viscoelastic, and poroelastic wave equations are established, and the general calculation format for single wave field components is developed, which improves the scalability of DGFEM programming. Based on this format, the procedure to construct a universal CUDA kernel is developed, which can be easily extended for more complex media and 3D cases, and the CPU+GPU parallel computing framework of 2D DGFEM is established. The results of a theoretical model and a complex mountain model reveal that the general calculation format and CUDA kernels constructed in this paper can accurately simulate P-waves, S-waves, and slow P-waves described by using acoustic, elastic, viscoelastic, and poroelastic wave equations. Compared to single-core CPU simulation, the speedup ratio of 2D DGFEM elastic-wave GPU calculation is about 100 on the average. Meanwhile, the simulation time for elastic, viscoelastic, and poroelastic waves is approximately 1.7, 2.3, and 3.0 times that of acoustic wave simulation, respectively. This result can be used to guide multi-process load balancing in the simulation of complex coupled media.

       

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