Investigation of airfoil and wing performance with leading edge contamination

ibis paper presents a summary of the efforts conducted at Bombardier over the past 10 years to understand and predict the effects of leading edge roughness on the aerodynamic performance of three-dimensional wings Two dimensional and three-dimensional wind tunnel tests and dedicated flight tests were conducted, showing that these effects vary with the Ope and texture of the applied roughness. In order-to develop a predictive tool, an attempt was made to find a relationship between randomly distributed roughness using cylinders of different heights and densities, roughness using ballotini, and equivalent sand grain roughness. A CFD method based on the Cebeci-Chang roughness model was used to generate correlations with experimental data It was found that the variation of the size and density of individual roughness elements could be represented using one roughness parameter, R-p, which is equivalent to the sand grain roughness parameter used in the Cebeci-Chang model. Numerical predictions using this approach correlate well with two-dimensional test results The roughness parameter R-p can be used as a relative scale of roughness intensity for ground icing or frost-type roughness A systematic investigation was conducted with the CFD code varying airfoil geometric parameters such as thickness, camber and leading edge radius, in order to evaluate their effects on the airfoils' sensitivity to a nominal roughness intensity and coverage. The results of this investigation can be used in modifying airfoils to achieve a compromise between their optimum clean aerodynamic performance and their operational service requirements.