Superconvergence using pointwise interpolation in convection–diffusion problems

Considering a singularly perturbed convection–diffusion problem, we present an analysis for a superconvergence result using pointwise interpolation of Gauß–Lobatto type for higher-order streamline diffusion FEM. We show a useful connection between two different types of interpolation, namely a vertex–edge–cell interpolant and a pointwise interpolant. Moreover, different postprocessing operators are analysed and applied to model problems.