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arXiv 2109.07546math.NAcs.NA
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基于凝聚的非线性多重网格法求解多孔介质中两相流动与输运问题

An Aggregation-based Nonlinear Multigrid Solver for Two-phase Flow and Transport in Porous Media

Chak Shing Lee, François P. Hamon, Nicola Castelletto, Panayot S. Vassilevski, Joshua A. White

摘要:

本文提出了一种求解两相流速度-压力-饱和度混合方程的非线性多重网格方法。求解器,这是下的全近似计划(FAS)的框架,扩展了我们以前的工作,非线性多重网格的异质扩散问题。多重网格层次中的粗空间是通过聚合自由度,然后解决一些局部流问题来构造的。混合配方和粗空间的选择,使我们能够组装粗糙的问题,而无需访问更精细的水平在解决阶段,这是至关重要的多重网格方法的可扩展性。具体地,可以使用预先计算的粗略通量基向量直接在粗略水平上评估逆风通量的自然概括。所得到的求解器是适用于一般非结构化网格上离散化的问题。建议的非线性多重网格求解器的性能与标准的单级牛顿法相比,证明通过具有挑战性的数值例子。据观察,建议的求解器是强大的高度非线性问题,并明显优于牛顿法的情况下,高Courant-Friedrichs-Lewy(CFL)号码。

英文摘要:

A nonlinear multigrid solver for two-phase flow and transport in a mixed fractional-flow velocity-pressure-saturation formulation is proposed. The solver, which is under the framework of the full approximation scheme (FAS), extends our previous work on nonlinear multigrid for heterogeneous diffusion problems. The coarse spaces in the multigrid hierarchy are constructed by first aggregating degrees of freedom, and then solving some local flow problems. The mixed formulation and the choice of coarse spaces allow us to assemble the coarse problems without visiting finer levels during the solving phase, which is crucial for the scalability of multigrid methods. Specifically, a natural generalization of the upwind flux can be evaluated directly on coarse levels using the precomputed coarse flux basis vectors. The resulting solver is applicable to problems discretized on general unstructured grids. The performance of the proposed nonlinear multigrid solver in comparison with the standard single level Newton's method is demonstrated through challenging numerical examples. It is observed that the proposed solver is robust for highly nonlinear problems and clearly outperforms Newton's method in the case of high Courant-Friedrichs-Lewy (CFL) numbers.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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