Sharpened bounds for corner singularities and boundary layers in a simple convection–diffusion problem

Abstract

A singularly perturbed convection–diffusion problem posed on the unit square is considered. Its solution may have exponential and parabolic boundary layers, and corner singularities may also be present. Sharpened pointwise bounds on the solution and its derivatives are derived. The bounds improve bounds near an outflow corner of the problem that were derived in an earlier paper of the authors. Application is made to an error analysis of a finite element method for the problem.