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arXiv 2302.00337math.NAcs.NA
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重叠网格上的时空CutFEM:简单连续网格运动

Space-Time CutFEM on Overlapping Meshes: Simple Continuous Mesh Motion

Mats G. Larson, Anders Logg, Carl Lundholm

摘要:

本文提出了一种求解热传导方程的切割有限元法,它是在两个重叠的网格上进行的:一个静止的背景网格和一个在其内部或“上面”移动的重叠网格,这里重叠网格被指定为一个简单的连续运动,这意味着它的位置作为时间的函数是连续的和分段线性的。对于离散的函数空间,我们在空间上使用连续的Galerkin,在时间上使用不连续的Galerkin,在两个网格之间的边界上增加一个不连续。的有限元制定是基于Nitsche的方法,还包括一个积分项的时空边界之间的两个网格,模仿标准的不连续Galerkin时间跳跃项。简单的连续网格运动导致时空离散化,标准分析方法失败或不适合。因此,我们采用了一个相对较新的能源分析框架,该框架具有足够的通用性和鲁棒性,可以适用于当前的环境。能量分析包括一个稳定性估计,这是略强于标准的基本和先验的误差估计,这是最佳的顺序相对于时间步长和网格步长。我们还提出了一个问题,在一个空间维度,验证分析误差收敛顺序的数值结果。

英文摘要:

We present a cut finite element method for the heat equation on two overlapping meshes: a stationary background mesh and an overlapping mesh that moves around inside/"on top" of it. Here the overlapping mesh is prescribed a simple continuous motion, meaning that its location as a function of time is continuous and piecewise linear. For the discrete function space, we use continuous Galerkin in space and discontinuous Galerkin in time, with the addition of a discontinuity on the boundary between the two meshes. The finite element formulation is based on Nitsche's method and also includes an integral term over the space-time boundary between the two meshes that mimics the standard discontinuous Galerkin time-jump term. The simple continuous mesh motion results in a space-time discretization for which standard analysis methodologies either fail or are unsuitable. We therefore employ what seems to be a relatively new energy analysis framework that is general and robust enough to be applicable to the current setting. The energy analysis consists of a stability estimate that is slightly stronger than the standard basic one and an a priori error estimate that is of optimal order with respect to both time step and mesh size. We also present numerical results for a problem in one spatial dimension that verify the analytic error convergence orders.

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