Analysis of recovery type a posteriori error estimators for mildly structured grids

Abstract

Some recovery type error estimators for linear finite elements areanalyzed under O(h^{1+α}) (α> 0) regular grids. Superconvergenceof order O(h^{1+ρ}) (0 < ρ\leq α) is established forrecovered gradients by three different methods. As a consequence,a posteriori error estimators based on those recovery methods areasymptotically exact.