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M.A. Gageik, I. Klioutchnikov, H. Olivier
Performing a Direct Numerical Simulation (DNS), a mesh study for the transonic flow around the well known NACA 0012 airfoil at a moderate Reynolds number of Re_c= 5·10^5 is presented. The three-dimensional Navier-Stokes equations for an unsteady, compressible flow are discretized in a generalized curvilinear coordinate system. The spatial derivatives of first-order are approximated by a fifth-order WENO scheme, the second-order derivatives by a sixth-order central scheme and the time derivatives by a fourth-order Runge-Kutta scheme. The focus of the investigation is on the demonstration of the applicability of DNS for simulating an airfoil flow at a moderate Reynolds number. At this Reynolds number, theoretical estimations for the necessary number of mesh points are far away from realizable mesh sizes. In the present study five three-dimensional meshes are compared where the largest mesh consists of one billion mesh points (8192 x 512 x 256). This mesh size is close to the practical limit of recent simulations since the numerical effort, expressed in core-hours, is 16 · 10^6 h. The other meshes are gradually coarsened by a factor of 0.25 resulting in only four million mesh points for the coarsest mesh. The mesh study is performed by the comparison of aerodynamical and turbulent quantities. On the one hand the main flow features are studied, which are mostly determined by large flow scales. On the other hand the turbulent intensities are compared, which are influenced by the smallest scales. In this context, the analysis of the energy-spectrum of the turbulent kinetic energy is a useful tool to evaluate the quality of the turbulent boundary layer. Furthermore, pressure waves are studied for all meshes which are generated at the trailing-edge moving upstream.
Deutscher Luft- und Raumfahrtkongress 2014, Augsburg
Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn, 2014
21,0 x 29,7 cm, 10 Seiten
Stichworte zum Inhalt:
airfoil, direct numerical simulation