Application of a Statistical Vortex Generator Model Approach on the Short-Chord Flap of a Three-Element Airfoil

Authors: von Stillfried, , Wallin, S.W., Johansson, A.V.J.
Document Type: Article
Pubstate: Published
Journal: KATnet II conference on Key Aerodynamic Technologies, Bremen, Germany, 2009
Year: 2009


Current flap designs on civil transport-type aircraft comprise approximately 30% of the undeployed wing chord. The objective of the short-chord flap project HELIX (Innovative aerodynamic high lift concepts, 2001-2005) within the Fifth framework program by the European Commission was to reduce the trailing edge flaps to 20% chord or less. The benefits of such a short-flap airfoil are e.g. increased fuel tank capacity within the wing, weight savings due to lighter flap track fairings and drag reduction during cruise flight. The major challenge for a short-chord flap airfoil to overcome is the higher flap deflection angle during take-off and landing phases in order to maintain the same amount of lift as for an airfoil with conventional flap size. Flow control devices such as stationary passive vortex generators (VGs) that are mounted on such a short-chord flap can alleviate or even totally avoid flow separation at high deflection angles. A sound computational fluid dynamics investigation of such a flow case requires an adequate grid with a corresponding large number of grid points around such VGs in order to obtain an accurate solution. This, in turn, leads to a time-demanding grid generation which often comes along with lots of practical challenges during the creation. An effective way to get around this time-consuming process is to introduce a modeling of the VGs and to add their physical effects to the governing equations rather than resolving their geometries in the computational grid. FOI, the Swedish Defence Research Agency, and KTH, the Royal Institute of Technology Stockholm, have developed computational tools for VG modeling that make it possible to simulate and to add the additional physical effects of modeled VGs in wall-bounded flows whereas the need for a local mesh refinement in the vicinity of such modeled VGs is no longer required. A method to statistically model VGs is presented and applied in this paper. Experimental and computational results are compared for the HELIX short-chord airfoil take-off configuration for different VG model parameter settings.