A posteriori error estimation by postprocessor independent of method of flowfield calculation

We consider a postprocessor that is able to analyze the flow-field generated by an external (unknown) code so as to determine the error of useful functionals. The residuals engendered by the action of a high-order finite-difference stencil on a numerically computed flow-field are used for adjoint based a posteriori error estimation. The method requires information on the physical model (PDE system), flowfield parameters and corresponding grid and may be constructed without availability of detailed information on the numerical method used for the flow computation