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arXiv 2010.01460math.NAcs.NA
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泊松方程的插值Galerkin有限元法

An interpolated Galerkin finite element method for the Poisson equation

Tatyana Sorokina, Shangyou Zhang

摘要:

在用有限元法求解泊松方程时,我们用一个自由度,用给定的拉普拉斯算子--偏微分方程的右端函数进行插值。有限元解是在较小的向量空间中的伽辽金投影。其思想类似于标准有限元法中边界条件的插值。由于采用逐点插值,我们的方法得到了一个更小的方程组和一个更好的条件数。对于$P_k$($k\ge 3$)有限元,每个单元上的未知数数量从$(k^2+3k+2)/2$显著减少到$3k$。在三角形网格上构造了二维$P_2$协调插值单元和$P_k$($k\ge3$)协调插值单元。证明了这种插值伽辽金有限元法收敛于最优阶。数值试验和与标准有限元的比较,验证了理论和插值伽辽金有限元法的优点。

英文摘要:

When solving the Poisson equation by the finite element method, we use one degree of freedom for interpolation by the given Laplacian - the right hand side function in the partial differential equation. The finite element solution is the Galerkin projection in a smaller vector space. The idea is similar to that of interpolating the boundary condition in the standard finite element method. Due to the pointwise interpolation, our method yields a smaller system of equations and 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 2D $P_2$ conforming and nonconforming, and $P_k$ ($k\ge3$) conforming interpolated Galerkin finite elements on triangular grids. This interpolated Galerkin finite element method is proved to converge at the optimal order. Numerical tests and comparisons with the standard finite elements are presented, verifying the theory and showing advantages of the interpolated Galerkin finite element method.

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