1. Institute of Fluid Mechanics, Technische Universität Braunschweig, D-38108 Braunschweig, Germany
2. Institute of Aerodynamics and Flow Technology, DLR, German Aerospace Center, D-38108 Braunschweig, Germany
3. Institute of Aerodynamics and Flow Technology, DLR, German Aerospace Center, D-37073 Göttingen, Germany