Application of a Hybrid RANS-LES Method to Free Shear Layers

This paper presents the application of the XLES (eXtra Large Eddy Simulation) method to relevant test-cases. The mixing between two boundary layers and between a wake and a boundary layer are discussed. The first test case considers the mixing layer that forms at the end of a splitting plate. Two boundary layers with different free-stream velocities flow on the upper and lower side of a flat plate and join at the trailing edge forming a free shear layer. The second test case represents a mixing between the 2-D wake originating downstream an airfoil and the 2-D boundary layer developing over a flat plate placed beneath the airfoil. This application is representative of flows over multi-element configurations where the wake coming from the slat merges with the boundary layer of the main component. The method has shown to be effective reducing the modelled turbulence and providing resolved turbulence in the regions of the field treated in LES mode. The “grey-area” issue has been highlighted. This is likely connected to the stochastic character of the model.