Abstract
We develop a new approach to construct finite element methods to solve the Poisson equation. The idea is to use the pointwise Laplacian as a degree of freedom followed by interpolating the solution at the degree of freedom by the given right-hand side function in the partial differential equation. The finite element solution is then the Galerkin projection in a smaller vector space. This idea is similar to that of interpolating the boundary condition in the standard finite element method. Our approach results in a smaller system of equations and of a better condition number. The number of unknowns on each element is reduced significantly from \((k^2+3k+2)/2\) to 3k for the \(P_k\) (\(k\ge 3\)) finite element. We construct bivariate \(P_2\) conforming and nonconforming, and \(P_k\) (\(k\ge 3\)) conforming interpolated Galerkin finite elements on triangular grids; prove their optimal order of convergence; and confirm our findings by numerical tests.
Similar content being viewed by others
Data Availability
Enquiries about data availability should be directed to the authors.
References
Alfeld, P., Sorokina, T.: Linear Differential Operators on Bivariate Spline Spaces and Spline Vector Fields. BIT Numer. Math. 56(1), 15–32 (2016)
Arnold, D.N., Boffi, D., Falk, R.S.: Approximation by quadrilateral finite elements. Math. Comp. 71(239), 909–922 (2002)
Bramble, J.H., Hilbert, S.R.: Estimation of linear functionals on Sobolev spaces with applications to Fourier transforms and spline interpolation. SIAM J. Numer. Anal. 7, 113–124 (1970)
Brenner, S. C., Scott, L. R.: The mathematical theory of finite element methods. Third edition. Texts in Applied Mathematics, 15. Springer, New York (2008)
Falk, R.S., Gatto, P., Monk, P.: Hexahedral H(div) and H(curl) finite elements. ESAIM Math. Model. Numer. Anal. 45(1), 115–143 (2011)
Hu, J., Huang, Y., Zhang, S.: The lowest order differentiable finite element on rectangular grids. SIAM Num. Anal. 49(4), 1350–1368 (2011)
Hu, J., Zhang, S.: The minimal conforming \(H^k\) finite element spaces on \(R^n\) rectangular grids. Math. Comp. 84(292), 563–579 (2015)
Hu, J., Zhang, S.: Finite element approximations of symmetric tensors on simplicial grids in \(R^n\): the lower order case. Math. Models Methods Appl. Sci. 26(9), 1649–1669 (2016)
Huang, Y., Zhang, S.: Supercloseness of the divergence-free finite element solutions on rectangular grids. Commun. Math. Stat. 1(2), 143–162 (2013)
Lai, M.-J., Schumaker, L.L.: Spline functions on triangulations. Cambridge University Press, Cambridge (2007)
Li, M., Mao, S., Zhang, S.: New error estimates of nonconforming mixed finite element methods for the Stokes problem. Math. Methods Appl. Sci. 37(7), 937–951 (2014)
Schumaker, L.L., Sorokina, T., Worsey, A.J.: A C1 quadratic trivariate macro-element space defined over arbitrary tetrahedral partitions. J. Approx. Theory 158(1), 126–142 (2009)
Scott, L.R., Zhang, S.: Finite element interpolation of nonsmooth functions satisfying boundary conditions. Math. Comp. 54, 483–493 (1990)
Sorokina, T., Zhang, S.: Conforming harmonic finite elements on the Hsieh-Clough-Tocher split of a triangle. Int. J. Numer. Anal. Model. 17(1), 54–67 (2020)
Sorokina, T., Zhang, S.: Conforming and nonconforming harmonic finite elements, Applicable Analysis. Appl. Anal. 99(4), 569–584 (2020)
Wang, C., Zhang, S., Shangyou, Chen, J.: A unified mortar condition for nonconforming finite elements, J. Sci. Comput. 62(1), 179–197 (2015)
Zhang, M., Zhang, S.: A 3D conforming-nonconforming mixed finite element for solving symmetric stress Stokes equations. Int. J. Numer. Anal. Model. 14(4–5), 730–743 (2017)
Zhang, S.: A C1-P2 finite element without nodal basis, M2AN 42 175–192 (2008)
Zhang, S.: A family of 3D continuously differentiable finite elements on tetrahedral grids. Appl. Numer. Math. 59(1), 219–233 (2009)
Zhang, S.: A family of differentiable finite elements on simplicial grids in four space dimensions, (Chinese) Math. Numer. Sin. 38(3), 309–324 (2016)
Zhang, S.: Coefficient jump-independent approximation of the conforming and nonconforming finite element solutions. Adv. Appl. Math. Mech. 8(5), 722–736 (2016)
Zhang, S.: A P4 bubble enriched P3 divergence-free finite element on triangular grids. Comput. Math. Appl. 74(11), 2710–2722 (2017)
Funding
The authors have not disclosed any funding.
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Competing Interests
The authors have not disclosed any competing interests.
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.
Rights and permissions
About this article
Cite this article
Sorokina, T., Zhang, S. An Interpolated Galerkin Finite Element Method for the Poisson Equation. J Sci Comput 92, 47 (2022). https://doi.org/10.1007/s10915-022-01903-x
Received:
Revised:
Accepted:
Published:
DOI: https://doi.org/10.1007/s10915-022-01903-x