FURTHER DISCUSSION OF NUMERICAL ERRORS IN CFD

The methods of estimating numerical errors given in an earlier paper a re extended in directions that make them useful in actual CFD applicat ions. In particular, the method of estimating convergence error (the e rror due to insufficient iteration) is extended to allow the possibili ty of complex eigenvalues; an ad hoc method that can be applied to any case is also given. For the discretization error, which arises from t he numerical approximation of the differential equation(s), methods th at can be used on non-uniform drids are presented; they can be extende d to unstructured grids as well. The utility of these methods is demon strated for linear problems as well as solutions of the Navier-Stokes equations. The examples show that the estimation of errors is neither difficult nor expensive.