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An Interpolated Galerkin Finite Element Method for the Poisson Equation

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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.

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Correspondence to Tatyana Sorokina.

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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

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  • DOI: https://doi.org/10.1007/s10915-022-01903-x

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