黄泽敏, 袁驷. 线法二阶常微分方程组有限元分析的结点精度修正及其超收敛计算[J]. 工程力学, 2022, 39(S): 9-14, 34. DOI: 10.6052/j.issn.1000-4750.2021.06.S002
引用本文: 黄泽敏, 袁驷. 线法二阶常微分方程组有限元分析的结点精度修正及其超收敛计算[J]. 工程力学, 2022, 39(S): 9-14, 34. DOI: 10.6052/j.issn.1000-4750.2021.06.S002
HUANG Ze-min, YUAN Si. NODAL ACCURACY IMPROVEMENT AND SUPER-CONVERGENT COMPUTATION IN FEM ANALYSIS OF FEMOL SECOND ORDER ODES[J]. Engineering Mechanics, 2022, 39(S): 9-14, 34. DOI: 10.6052/j.issn.1000-4750.2021.06.S002
Citation: HUANG Ze-min, YUAN Si. NODAL ACCURACY IMPROVEMENT AND SUPER-CONVERGENT COMPUTATION IN FEM ANALYSIS OF FEMOL SECOND ORDER ODES[J]. Engineering Mechanics, 2022, 39(S): 9-14, 34. DOI: 10.6052/j.issn.1000-4750.2021.06.S002

线法二阶常微分方程组有限元分析的结点精度修正及其超收敛计算

NODAL ACCURACY IMPROVEMENT AND SUPER-CONVERGENT COMPUTATION IN FEM ANALYSIS OF FEMOL SECOND ORDER ODES

  • 摘要: 采用 m 次单元对线法二阶常微分方程组(ODEs)进行有限元(FEM)求解,其单元内部位移为 m + 1 阶收敛,而端结点位移收敛阶可达 2m 阶。单元能量投影(EEP)超收敛计算恢复的单元内部位移精度一般为\min (m + 2,2m)阶,此收敛阶既受益于也受限于有限元端结点位移的精度。该文提出了一种修正EEP法(M-EEP),利用EEP超收敛解,先对端结点位移进行修正,再用其恢复单元内部位移。广泛的数值试验表明:对端结点位移修正后的收敛阶可达 2m + 2 阶,再次修复的单元内部位移始终可达 m + 2 阶收敛,摆脱了 2m 阶收敛精度的限制。对于线性元,修正后结点位移的精度翻倍,单元内部M-EEP位移亦摆脱了原FEM解2阶收敛精度的限制,升到3阶收敛,基本达到二次元的收敛精度,效果显著。

     

    Abstract: Elements with degree m is used in finite element method (FEM) to solve the second order ordinary differential equations (ODEs) derived from the FEM of lines (FEMOL). The interior displacement of elements generally has a convergence order of m + 1 , while the nodal displacements can achieve a convergence order of 2m . The super-convergence computation using the element energy projection (EEP) method usually has a convergence order of \min (m + 2,2m) , which benefits from the nodal displacements of a higher convergence order but also limits its accuracy by the nodal displacements of elements with lower degrees. In this paper, a modified EEP (M-EEP) method is proposed. With the EEP solution, the nodal displacement accuracy is improved first, and then the interior displacement of elements is recovered, which leads to a modified EEP solution. Numerical experiments show that improved nodal displacements can achieve a convergence order of 2m + 2 , and the interior displacements of elements always have a convergence order of m + 2 without the constraint of order 2m . For linear elements, the interior displacement of M-EEP solution does not have the limitation of second-order convergence from the traditional FEM solution and can achieve the remarkable third-order convergence, equivalent to the convergence order of quadratic elements.

     

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