Communications on Applied Mathematics and Computation ›› 2026, Vol. 8 ›› Issue (2): 765-777.doi: 10.1007/s42967-024-00473-z

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Interpolated Galerkin Finite Elements on Rectangular and Cuboid Meshes for the Biharmonic Equation

Mengjiao Pan1, Tatyana Sorokina2, Shangyou Zhang3   

  1. 1. School of Science, East China Jiaotong University, Nanchang, 330013, Jiangxi, China;
    2. Department of Mathematics, Towson University, Towson, MD, 21252, USA;
    3. Department of Mathematical Sciences, University of Delaware, Newark, DE, 19716, USA
  • 收稿日期:2024-11-28 修回日期:2024-12-15 出版日期:2026-04-07 发布日期:2026-04-07
  • 通讯作者: Shangyou Zhang,E-mail:szhang@udel.edu E-mail:szhang@udel.edu

Interpolated Galerkin Finite Elements on Rectangular and Cuboid Meshes for the Biharmonic Equation

Mengjiao Pan1, Tatyana Sorokina2, Shangyou Zhang3   

  1. 1. School of Science, East China Jiaotong University, Nanchang, 330013, Jiangxi, China;
    2. Department of Mathematics, Towson University, Towson, MD, 21252, USA;
    3. Department of Mathematical Sciences, University of Delaware, Newark, DE, 19716, USA
  • Received:2024-11-28 Revised:2024-12-15 Online:2026-04-07 Published:2026-04-07
  • Contact: Shangyou Zhang,E-mail:szhang@udel.edu E-mail:szhang@udel.edu

摘要: A new Galerkin finite element for the biharmonic equation is constructed on 2D rectangular and 3D cuboid meshes. In this \begin{document}$ C^1 $\end{document}-\begin{document}$ Q_k $\end{document} (\begin{document}$ k\geqslant 4 $\end{document}) interpolated Galerkin finite element construction, all unknowns associated with the interior of each element are determined by the direct interpolation of the right-hand-side function, and the rest of the unknowns, associated with the boundary of each element, are determined by solving the remaining linear equations of the Galerkin projection. In comparison with the traditional finite element method in two dimensions, our method reduces the number of unknowns from \begin{document}$ O(k^2) $\end{document} to O(k). Additionally, the method reduces the condition number drastically as it requires only 1% of the computer time, compared with the standard finite elements, in several numerical tests. We prove the existence and uniqueness of the solution and the optimal order of convergence. We confirm the theory by numerical tests in two dimensions and three dimensions.

关键词: Finite element, Interpolated finite element, Rectangular grid, Biharmonic equation, Tensor product

Abstract: A new Galerkin finite element for the biharmonic equation is constructed on 2D rectangular and 3D cuboid meshes. In this \begin{document}$ C^1 $\end{document}-\begin{document}$ Q_k $\end{document} (\begin{document}$ k\geqslant 4 $\end{document}) interpolated Galerkin finite element construction, all unknowns associated with the interior of each element are determined by the direct interpolation of the right-hand-side function, and the rest of the unknowns, associated with the boundary of each element, are determined by solving the remaining linear equations of the Galerkin projection. In comparison with the traditional finite element method in two dimensions, our method reduces the number of unknowns from \begin{document}$ O(k^2) $\end{document} to O(k). Additionally, the method reduces the condition number drastically as it requires only 1% of the computer time, compared with the standard finite elements, in several numerical tests. We prove the existence and uniqueness of the solution and the optimal order of convergence. We confirm the theory by numerical tests in two dimensions and three dimensions.

Key words: Finite element, Interpolated finite element, Rectangular grid, Biharmonic equation, Tensor product

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