Experimental Investigation of the DLR-F23 Configuration at Transonic Speeds using Fast-Response Pressure-Sensitive Paint

Abstract

Modern, high-agility aircraft configurations cover an extensive flight envelope, consisting of flight conditions with high maneuverability at subsonic speeds as well as flight conditions with high-level performance in the transonic and supersonic flow regime. In this study, the DLR-F23 hybrid-delta-wing configuration, consisting of a low aspect-ratio triple-delta-wing planform, is investigated in the Transonic Wind Tunnel Göttingen (DNW-TWG). The measurements are performed at Mach numbers between Ma = 0.55 and Ma = 1.15 in the angle of attack (AoA) range from AoA 0° to AoA 30°. Fast-response pressure-sensitive paint measurements (iPSP) are conducted to analyze the aerodynamic surface pressure distribution and the pressure fluctuations. The iPSP measurements are validated with unsteady pressure transducers. A special focus is on the analysis of vortex-vortex and vortex-shock interactions, as well as shock-induced vortex breakdown for three selected cases for subsonic, transonic, and supersonic flow conditions. Proper Orthogonal Decomposition (POD), as an advanced data analysis method, is used to reduce the high-dimensional iPSP data into a series of orthogonal modes arranged according to their energy content. For the subsonic flow case, vortex-vortex interactions can be observed, which results in vortex merging. Shock-induced vortex breakdown is identified in the transonic flow regime. The supersonic case is characterized by multiple vortex-shock interactions. Several strong cross-flow shocks along the vortex trajectories of the primary vortices deeply influence the surface pressure distribution on the wing.