Wall-Resolved Large-Eddy Simulation of a Three-Element High-Lift Airfoil

This work deals with a highly resolved large-eddy simulation of a three-element high-lift airfoil with a deployed slat and flap. The aim of this simulation is twofold: the first objective is to perform a detailed flow analysis and identify the physical flow mechanisms responsible for noise generation; the second objective is to provide an important numerical database that may be used to assess more affordable numerical approaches based, for instance, on hybrid Reynolds-averaged Navier-Stokes/large-eddy simulation (LES) methods. The assessment of the present LES relies on an extensive database, which was collected during a campaign performed in the ONERA F2 wind tunnel in the framework of LEISA2: a joint ONERA/DLR, German Aerospace Center project. The results of the present LES show an overall agreement with the measurements that is generally within the experimental uncertainty, especially in the slat and flap coves. Differences between the LES and the experiments are present on the flap suction side, where the flow is observed to be very sensitive to slight modifications of the numerical or experimental conditions. The simulation confirms that a large-scale coupled self-sustained oscillations mechanism is present between the slat and flap cavities. Some insight about the transition process on the main wing suction side is also discussed in the paper.