| Abstract: | In this paper we produce tight guaranteed bounds for the error in the pointwise values of the derivatives of a post‐processed finite element solution to a potential flow problem, in which the boundary condition is purely normal velocity. Our approach has to be modified for the problems with Dirichlet boundary conditions. The aim is to produce a tight envelope of certainty within which the exact value is guaranteed to lie. Our numerical experiments produce narrow envelopes at interior points and at points close to or on the boundary. Copyright © 1999 John Wiley & Sons, Ltd. |
