A $\mathcal{CR}$-rotated $Q_1$ nonconforming finite element method for Stokes interface problems on local anisotropic fitted mixed meshes

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Auteurs principaux: Chenchen, Geng, Wang, Hua, Zou, Fengren
Format: Preprint
Publié: 2025
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author Chenchen, Geng
Wang, Hua
Zou, Fengren
author_facet Chenchen, Geng
Wang, Hua
Zou, Fengren
contents We propose a new nonconforming finite element method for solving Stokes interface problems. The method is constructed on local anisotropic mixed meshes, which are generated by fitting the interface through simple connection of intersection points on an interface-unfitted background mesh, as introduced in \cite{Hu2021optimal}. For triangular elements, we employ the standard $\mathcal{CR}$ element; for quadrilateral elements, a new rotated $Q_1$-type element is used. We prove that this rotated $Q_1$ element remains unisolvent and stable even on degenerate quadrilateral elements. Based on these properties, we further show that the space pair of $\mathcal{CR}$-rotated $Q_1$ elements (for velocity) and piecewise $P_0$ spaces (for pressure) satisfies the inf-sup condition without requiring any stabilization terms. As established in our previous work \cite{Wang2025nonconforming}, the consistency error achieves the optimal convergence order without the need for penalty terms to control it. Finally, several numerical examples are provided to verify our theoretical results.
format Preprint
id arxiv_https___arxiv_org_abs_2507_02741
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle A $\mathcal{CR}$-rotated $Q_1$ nonconforming finite element method for Stokes interface problems on local anisotropic fitted mixed meshes
Chenchen, Geng
Wang, Hua
Zou, Fengren
Numerical Analysis
We propose a new nonconforming finite element method for solving Stokes interface problems. The method is constructed on local anisotropic mixed meshes, which are generated by fitting the interface through simple connection of intersection points on an interface-unfitted background mesh, as introduced in \cite{Hu2021optimal}. For triangular elements, we employ the standard $\mathcal{CR}$ element; for quadrilateral elements, a new rotated $Q_1$-type element is used. We prove that this rotated $Q_1$ element remains unisolvent and stable even on degenerate quadrilateral elements. Based on these properties, we further show that the space pair of $\mathcal{CR}$-rotated $Q_1$ elements (for velocity) and piecewise $P_0$ spaces (for pressure) satisfies the inf-sup condition without requiring any stabilization terms. As established in our previous work \cite{Wang2025nonconforming}, the consistency error achieves the optimal convergence order without the need for penalty terms to control it. Finally, several numerical examples are provided to verify our theoretical results.
title A $\mathcal{CR}$-rotated $Q_1$ nonconforming finite element method for Stokes interface problems on local anisotropic fitted mixed meshes
topic Numerical Analysis
url https://arxiv.org/abs/2507.02741