31th Congress of the International Council of the Aeronautical Sciences

03.1 - Aerodynamics - CFD Methods and Validation


J.J. Broekhuijsen¹, G. Vidjaja², J.W. van der Burg², H.W.M. Hoeijmakers¹; ¹University of Twente, Netherlands ;²Airbus Operations GMBH, Germany

High-lift performance of modern transport aircraft has a major influence on the efficiency, sizing, economics, take-off and landing performance, fuel consumption and noise emissions. To satisfy the constantly increasing requirements, the diameter of jet engines is larger for every new generation of jet engines. Therefore, the engines are closely coupled to the wing, which requires a cut-out of the slat to allow installing the pylon-nacelle. The slat cut-out leads to aerodynamic interaction which renders the flow in the wing area downstream of the nacelle more sensitive to flow separation, i.e. nacelle wake separation.rnTo overcome this drawback in this critical wing area, in 1971 Kerker and Wells of McDonnell-Douglas1 introduced mounting a pair of strakes, on the forward top of each nacelle. In landing and take-off configuration the presence of the nacelle strake results in a strong streamwise vortex which travels along the upper side of the wing.rnThis vortex interacts with the vortices from the slat cut-out as well as with the boundary layer on the wing such that the onset of flow separation on the wing upper surface is delayed. The nacelle strake vortex recovers a part of the lift loss caused by the presence of the nacelle. This is the nacelle strake effect, characterized by an increase in CL,max and in ?CL,max.rnAlso, it is of considerable interest to be able to capture the effect of the nacelle strake on maximum lift co¬ef¬fi¬ci-ent. The com¬plex interaction phenomena in the non-linear range of the lift curve provide a great challenge to CFD to ac¬cu¬rately and reliably predict the nacelle strake effect.rnThe main objective of the proposed paper is to answer the question: can CFD predict the nacelle strake effect? To answer this question it is necessary to test and evaluate the application of new CFD practices. To that aim, a comprehen

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