Numerical Investigation of the Aerodynamic Properties of a Flying Wing Configuration

Kurzfassung

The main objective of this study is to contribute towards a more comprehensive understanding of the vortex dominated flow over the DLR-F17E configuration with varying leading edge radii as part of the DLR UCAV2010 project. The vortical flow over sharp edges delta wings is mainly understood though the need has arisen to further extend the knowledge about the vortex system behaviour over blunt edged delta wings. This work aims to determine the effect of Reynolds number and Mach number variation over the DLR-F17E configuration. For the numerical investigation the DLR flow solver TAU, solving for the compressible, three-dimensional, time-accurate Reynolds-Averaged Navier-Stokes equations, is used. The configuration was meshed using the unstructured-hybrid grid generator Centaur. Experimental data on the SACCON in the NWB Braunschweig, gathered prior to this work, serves as comparative data for the numerical outcomes. For low Mach numbers at low angles of attack the numerical outcomes matched the experiment data quite well. However for higher angles of attack the flow solver failed to give a near real world representation of the vortex systems as observed during the experiment. With increasing angle of attack the tip vortex moves towards the apex and at high angles of attack a large high suction region over the entire wing is observed. Further it was found that with increasing Mach number the apex vortex gains in strength and the tip vortex moves towards the apex. The tip vortex develops to a huge outer vortex which introduces a high suction area initializing a nose down pitching moment of the configuration at M=0.4 up to M=0.6. The Reynolds number effect on the configuration was found to be minor. Though, it was possible to determine that the tip vortex gains in strength with increasing Reynolds number. Also the tip vortex slightly increased its size towards the trailing edge with increasing Reynolds number. Experimental investigations on the DLR-F17E model are currently being planned in order to compare these here conducted numerical results, as part of the FaUSST project. Furthermore numerical investigations using the cell-centered approach are being conducted.