In this article, a study of residual based a posteriori error estimation is presented for the partition of unity finite element method (PUFEM) for three-dimensional (3D) transient heat diffusion problems. The proposed error estimate is independent of the heuristically selected enrichment functions and provides a useful and reliable upper bound for the discretization errors of the PUFEM solutions. Numerical results show that the presented error estimate efficiently captures the effect of h-refinement and q-refinement on the performance of PUFEM solutions. It also efficiently reflects the effect of ill-conditioning of the stiffness matrix that is typically experienced in the partition of unity based finite element methods. For a problem with a known exact solution, the error estimate is shown to capture the same solution trends as obtained by the classical L 2 norm error. For problems with no known analytical solutions, the proposed estimate is shown to be used as a reliable and efficient tool to predict the numerical errors in the PUFEM solutions of 3D transient heat diffusion problems.
K E Y W O R D Sdiffusion problems, enrichment functions, error estimate, GFEM, PUFEM
INTRODUCTIONDifferent numerical methods evolved over the years to reduce the computational cost and memory requirements for complex engineering problems. One of the features of all these numerical methods is that they are subjected to various sources of numerical errors, 1 which can question the reliability of their results. Babuška and Strouboulis 2 emphasized on the reliability of the finite element method (FEM) computations and mentioned that unreliable finite element results can lead to very serious consequences. Over the years, numerous researchers devised different methods for the error estimation of h, p, and hp versions of FEM. [3][4][5] The basic mathematical theory of FEM and its error estimation can be found in the book of Babuška et al. 6 A comprehensive explanation of the error estimation procedures and their theory is also presented by Ainsworth and Oden. 7Int J Numer Methods Eng. 2020;121:2727-2746. wileyonlinelibrary.com/journal/nme