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arXiv 1406.6573math.NAcs.CEcs.NA
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非线性斯托克斯方程在非配准和各向异性网格上高阶有限元离散的解法,及其在冰盖动力学中的应用

Solution of nonlinear Stokes equations discretized by high-order finite elements on nonconforming and anisotropic meshes, with application to ice sheet dynamics

Institute for Computational Engineering & Sciences, The University of Texas at Austin(德克萨斯大学奥斯汀分校计算工程与科学研究所);Courant Institute of Mathematical Sciences, New York University(纽约大学库朗数学科学研究所)

Tobin Isaac, Georg Stadler, Omar Ghattas

AI总结:

本文设计了高阶有限元离散方法和可扩展求解器,用于求解非线性不可压缩斯托克斯方程,应用于冰盖动力学中的幂律和剪薄流变学模型,并在各向异性网格上实现高效求解。

摘要:

受极地冰盖动力学高效准确模拟需求的启发,我们设计了高阶有限元离散方法和可扩展求解器,用于求解非线性不可压缩斯托克斯方程。我们关注用于冰动力学和其他地球物理流体建模的幂律和剪薄流变学。我们使用非配准六面体网格和符合的inf-sup稳定有限元速度-压力配对$\mathbb{Q}_k\times \mathbb{Q}^\text{disc}_{k-2}$或$\mathbb{Q}_k \times \mathbb{P}^\text{disc}_{k-1}$。为了解非线性方程,我们提出了一种牛顿-克罗内克方法,配以块上三角预条件器用于线性化斯托克斯系统。该预条件器的对角块是(1,1)-块及其施尔补的稀疏近似。(1,1)-块通过基于高阶离散化节点的线性有限元进行近似,其逆应用通过代数多重网格与不完全因子化平滑器进行近似。该预条件器设计为在各向异性网格上高效,这些网格是匹配冰盖典型高长宽比域所必需的。我们开发并公开了两个库的扩展——p4est并行AMR库的混合网格生成方案,以及PETSc的修改平滑聚合方案,以提高其在高长宽比域中求解PDEs的支持。在数值研究中,我们发现我们的求解器在元素长宽比、非配准界面和网格细化方面具有独立快速收敛性,仅弱依赖于多项式有限元阶数。我们模拟了基于实地数据的南极冰盖的真实冰流动,并研究了我们的求解器在高达383M未知数问题中的并行可扩展性。

英文摘要:

Motivated by the need for efficient and accurate simulation of the dynamics of the polar ice sheets, we design high-order finite element discretizations and scalable solvers for the solution of nonlinear incompressible Stokes equations. We focus on power-law, shear thinning rheologies used in modeling ice dynamics and other geophysical flows. We use nonconforming hexahedral meshes and the conforming inf-sup stable finite element velocity-pressure pairings $\mathbb{Q}_k\times \mathbb{Q}^\text{disc}_{k-2}$ or $\mathbb{Q}_k \times \mathbb{P}^\text{disc}_{k-1}$. To solve the nonlinear equations, we propose a Newton-Krylov method with a block upper triangular preconditioner for the linearized Stokes systems. The diagonal blocks of this preconditioner are sparse approximations of the (1,1)-block and of its Schur complement. The (1,1)-block is approximated using linear finite elements based on the nodes of the high-order discretization, and the application of its inverse is approximated using algebraic multigrid with an incomplete factorization smoother. This preconditioner is designed to be efficient on anisotropic meshes, which are necessary to match the high aspect ratio domains typical for ice sheets. We develop and make available extensions to two libraries---a hybrid meshing scheme for the p4est parallel AMR library, and a modified smoothed aggregation scheme for PETSc---to improve their support for solving PDEs in high aspect ratio domains. In a numerical study, we find that our solver yields fast convergence that is independent of the element aspect ratio, the occurrence of nonconforming interfaces, and of mesh refinement, and that depends only weakly on the polynomial finite element order. We simulate the ice flow in a realistic description of the Antarctic ice sheet derived from field data, and study the parallel scalability of our solver for problems with up to 383M unknowns.

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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