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arXiv 2006.00435math.NAcs.NA
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Stokes流动系统非拟合间断Galerkin方法的等高阶分析

Equal higher order analysis of an unfitted discontinuous Galerkin method for Stokes flow systems

Aikaterini Aretaki, Efthymios N. Karatzas, Georgios Katsouleas

摘要:

在这项工作中,我们分析了一个不适合的不连续Galerkin离散的数值解的Stokes系统的基础上,相等的高阶不连续的速度和压力。这种方法结合了两个方面的优点,首先是分段不连续高阶精确近似的优点,其次是不适合可能复杂物体和/或几何变形周围的真实几何网格的优点。利用一个虚构的域框架,感兴趣的物理域被嵌入在一个不适合的背景网格和几何不适合的离散化是建立在对称的内部惩罚不连续Galerkin制定。为了提高稳定性,我们丰富的离散变分公式与压力稳定项。此外,本文采用高阶鬼惩罚策略来解决由小截断单元相对于未拟合边界引起的系统矩阵的病态。受连续非拟合FEM [21,74,75]以及基于不连续空间[10,44,45,73]的其他非拟合网格调查的启发,我们使用在切割单元面上定义的适当速度和压力重影罚分来建立一种鲁棒的高阶方法,尽管通常在dG方法上应用单元聚集技术。目前的介绍应证明有价值的工程应用中,特别强调的是放在最佳的有效近似实现更小的相对误差在较粗的网格。研究了该方法的Inf-sup稳定性、最优收敛阶和条件数对割集的敏感性。数值算例验证了理论结果。

英文摘要:

In this work, we analyze an unfitted discontinuous Galerkin discretization for the numerical solution of the Stokes system based on equal higher-order discontinuous velocities and pressures. This approach combines the best from both worlds, firstly the advantages of a piece-wise discontinuous high-order accurate approximation and secondly the advantages of an unfitted to the true geometry grid around possibly complex objects and/or geometrical deformations. Utilizing a fictitious domain framework, the physical domain of interest is embedded in an unfitted background mesh and the geometrically unfitted discretization is built upon symmetric interior penalty discontinuous Galerkin formulation. To enhance stability we enrich the discrete variational formulation with a pressure stabilization term. Moreover, the present contribution adopts high order ghost penalty strategies to address the ill conditioning of the system matrix caused by small truncated elements with respect to the unfitted boundary. Motivated by continuous unfitted FEM [21,74,75] along with other unfitted mesh surveys grounded on discontinuous spaces [10,44,45,73], we use proper velocity and pressure ghost penalties defined on faces of cut cells to establish a robust high-order method, in spite of the cell agglomeration technique usually applied on dG methods. The current presentation should prove valuable in engineering applications where special emphasis is placed on the optimal effective approximation attaining much smaller relative errors in coarser meshes. Inf-sup stability, the optimal order of convergence, and the condition number sensitivity with respect to cut configuration are investigated. Numerical examples verify the theoretical results.

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