论文标题
计算时空FEM中的跳跃时间以进行任意时间插值
Computing the jump-term in space-time FEM for arbitrary temporal interpolation
论文作者
论文摘要
一种在分析科学和工程学中依赖时间依赖问题问题的方法是一种所谓的时空有限元元素方法,它在时空和时间上都使用了有限元。在这种情况下,一个常见的Ansatz是将网格沿时间方向划分为所谓的时空板,随后通过不连续的Galerkin方法在时间上薄弱地连接。负责在整个时空板上强加弱连续性的相应跳线可能会具有挑战性,尤其是在变形域的背景下。确保在时间方向上符合时空平板的离散化,从而极大地简化了该术语的处理。否则,必须从一个时间级到另一个时间级的计算昂贵且误差的投影。但是,当涉及具有可变形域的模拟时,例如对于自由表面流,确保符合网格非常费力。应对这一挑战的一种可能解决方案是在每个时间步长时间挤出空间网格,从而导致所谓的时间介绍的棱柱形时空(D-PST)方法。但是,此过程仅限于一阶的有限元。我们提出了一种新颖的算法方法,用于通过在每个时间步长时间翻转网格,以任意离散的网格。由于网格总是符合的,因此这种ANSATZ可以简单地评估跳跃期。用节点数量在时间尺度上翻转网格的成本,这使其在计算上比网格的附加更新更便宜,以执行整合或评估投影。我们在没有变形域的各种物理问题上验证方法。
One approach with rising popularity in analyzing time-dependent problems in science and engineering is the so-called space-time finite-element method that utilized finiteelements in both space and time. A common ansatz in this context is to divide the mesh in temporal direction into so-called space-time slabs, which are subsequently weakly connected in time with a Discontinuous Galerkin approach. The corresponding jumpterm, which is responsible for imposing the weak continuity across space-time slabs can be challenging to compute, in particular in the context of deforming domains. Ensuring a conforming discretization of the space-time slab at the top and bottom in time direction simplifies the handling of this term immensely. Otherwise, a computationally expensive and error prone projection of the solution from one time-level to another is necessary. However, when it comes to simulations with deformable domains, e.g. for free-surface flows, ensuring conforming meshes is quite laborious. A possible solution to this challenge is to extrude a spatial mesh in time at each time-step resulting in the so-called time-discontinuous prismatic space-time (D-PST) method. However, this procedure is restricted to finite-elements of 1st order in time. We present a novel algorithmic approach for arbitrarily discretized meshes by flipping the mesh in time-direction for each time-step. This ansatz allows for a simple evaluation of the jump-term as the mesh is always conforming. The cost of flipping the mesh around its symmetry plane in time scales with the number of nodes, which makes it computationally cheaper than an additional update of the mesh to enforce conformity or the evaluation of a projection. We validate the approach on various physical problems with and without deforming domains.