Abstract: The convergence analysis of the lower order nonconforming element proposed by Park and Sheen is applied to the second-order elliptic problem under anisotropic meshes. The corresponding error estimation is obtained. Moreover, by using the interpolation postprocessing technique, a global superconvergence property for the discretization error of the postprocessed discrete solution to the solution itself is derived. Numerical results are also given to verify the theoretical analysis.

Key words: nonconforming finite element, anisotropic, error estimate, interpolation postprocessing, superconvergence