The effect of numerical integration on the finite element approximation of linear functionals |
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Authors: | Ivo?Babu?ka Email author" target="_blank">Uday?BanerjeeEmail author Hengguang?Li |
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Institution: | (1) GM R&D Center, Warren, MI 48090–9055, USA |
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Abstract: | In this paper, we have studied the effect of numerical integration on the finite element method based on piecewise polynomials
of degree k, in the context of approximating linear functionals, which are also known as “quantities of interest”. We have obtained the
optimal order of convergence, O(h2k){\mathcal{O}(h^{2k})}, of the error in the computed functional, when the integrals in the stiffness matrix and the load vector are computed with
a quadrature rule of algebraic precision 2k − 1. However, this result was obtained under an increased regularity assumption on the data, which is more than required
to obtain the optimal order of convergence of the energy norm of the error in the finite element solution with quadrature.
We have obtained a lower bound of the error in the computed functional for a particular problem, which indicates the necessity
of the increased regularity requirement of the data. Numerical experiments have been presented indicating that over-integration
may be necessary to accurately approximate the functional, when the data lack the increased regularity. |
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Keywords: | |
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