EVALUATION OF NUMERICAL DIFFUSION EFFECTS IN VISCOUS-FLOW CALCULATIONS

A method for estimating the amount of numerical diffusion present in a solution of the Reynolds-averaged Navier-Stokes (RANS) equations is d escribed. The method is demonstrated in particular for those RANS algo rithms which achieve numerical stability by the direct addition of num erical smoothing terms. Results are shown for laminar flow around an a erofoil, with effects of grid quality and certain algorithm parameters investigated. It is shown that the estimate of the numerical diffusio n can be successfully used to guide automatic grid adaptation in this case. Some features and implications of the results, such as the effec tiveness of the numerical smoothing algorithm and the appropriateness of its form, are discussed and related to other work. Some implication s for general cases, particularly the need for an improved form of the numerical smoothing algorithm, are inferred.