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A HYBRID RANS-LES SOLUTION OF THE FLOW AROUND AN AIRFOIL-FLAP CONFIGURATION

Qinyin Zhang
Institute of Aerodynamics, RWTH Aachen University Wüllnerstr. zw. 5 u. 7, D-52062 Aachen, Germany

Wolfgang Schroder
Institute of Aerodynamics RWTH Aachen University Wullnerstr. 5a, 52062 Aachen, Germany

Matthias Meinke
Aerodynamisches Institut, RWTH Aachen, Wullnerstrasse zw. 5 und 7, D-52062 Aachen, Germany

Abstract

High Reynolds number flows are particularly challenging problems for large eddy simulations (LES). This is due to the resolution of small-scale structures in the thin and often transitional boundary layers. For airfoil flow in high-lift configuration, in which separation regions exist, the range and the disparity of the scales are enormous. For this reason, the prediction of high Reynolds number airfoil flow with LES, which cover the whole configuration, still requires huge computer resources. A hybrid zonal RANS-LES method for the flow over an airfoil in high-lift configuration at Rec = 1.0 · 106 is presented in this paper. The solution is obtained by first carrying out a 2D RANS solution, from which boundary conditions are formulated for a zonal domain for the LES, which comprises the flap and only a part of the main airfoil. The turbulent boundary layers at the inflow region of the LES domain on both sides of the main airfoil are generated by using controlled forcing terms which use the turbulent shear stress profiles obtained from the RANS solution. A comparison with an LES for the full domain and also experimental data shows good agreement of all results. Compared to the LES for the full domain the computational effort for the hybrid RANS-LES solution is reduced to about 50%.