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arXiv 1602.01703math.NAcs.NA
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在移动非共形无结构网格上直接任意拉格朗日-欧拉有限体积方案

Direct Arbitrary-Lagrangian-Eulerian finite volume schemes on moving nonconforming unstructured meshes

University of Trento(特伦托大学);University of Málaga(马拉加大学)

Elena Gaburro, Michael Dumbser, Manuel J. Castro

AI总结:

本文提出一种第二阶精度的非共形多边形网格任意拉格朗日-欧拉有限体积方案,通过自动检测非共形元素界面避免剪切流引起的网格畸变,同时保持高精度和稳定性。

摘要:

本文提出了一种第二阶精度的任意拉格朗日-欧拉(ALE)有限体积方案,用于移动非共形多边形网格,以避免典型剪切流引起的网格畸变。新方法中,非共形元素界面不由用户定义,而是由算法自动检测,当元素界面的切向速度差足够大时。远离剪切波的网格节点使用标准节点求解器移动,而在界面处插入一组可滑动的新节点。这样,剪切波两侧的元素可以以不同速度移动,而不会产生高度畸变的元素。该方法的核心是使用空间-时间守恒公式构建最终的有限体积方案,完全避免了额外的重映射阶段,并确保几何守恒定律(GCL)自动满足。此外,网格质量保持高,因此时间步长在时间上几乎恒定,即使在高度剪切的涡流中也是如此。新方案的精度进一步通过引入特殊的良好平衡技术来提高,该技术能够将所支配PDE系统的特定静止解维持到机器精度。为了检查新方法的精度和鲁棒性,进行了大量数值测试。特别是,我们比较了在标准共形ALE方法和新非共形ALE方案中求解的平衡涡流结果,以显示新非共形方案能够避免网格畸变,即使在非常长的模拟时间后也是如此。

英文摘要:

In this paper, we present a novel second-order accurate Arbitrary-Lagrangian-Eulerian (ALE) finite volume scheme on moving nonconforming polygonal grids, in order to avoid the typical mesh distortion caused by shear flows in Lagrangian-type methods. In our new approach the nonconforming element interfaces are not defined by the user, but they are automatically detected by the algorithm if the tangential velocity difference across an element interface is sufficiently large. The grid nodes that are sufficiently far away from a shear wave are moved with a standard node solver, while at the interface we insert a new set of nodes that can slide in a nonconforming manner. In this way, the elements on both sides of the shear wave can move with a different velocity, without producing highly distorted elements. The core of the proposed method is the use of a space-time conservation formulation in the construction of the final finite volume scheme, which completely avoids the need of an additional remapping stage and ensures that the geometric conservation law (GCL) is automatically satisfied. Moreover, the mesh quality remains high and, as a direct consequence, also the time step remains almost constant in time, even for highly sheared vortex flows. The accuracy of the new scheme has been further improved by incorporating a special well balancing technique that is able to maintain particular stationary solutions of the governing PDE system up to machine precision. A large set of numerical tests has been carried out in order to check the accuracy and the robustness of the new method. In particular we have compared the results for a steady vortex in equilibrium solved with a standard conforming ALE method and with our new nonconforming ALE scheme, to show that the new nonconforming scheme is able to avoid mesh distortion even after very long simulation times.

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