PSP and PIV investigations on the VFE-2 configuration in sub- and transonic flow

An overview is given about investigations on a 65° delta wing using the Pressure Sensitive Paint (PSP) and Particle Image Velocimetry (PIV) techniques, carried out in the framework of the International Vortex Flow Experiment 2 (VFE-2). For the delta wing with rounded leading edges and subsonic flow, the occurrence of a flat vortical structure as well as the onset of the primary vortex and the development of a vortex system consisting of an inner and outer vortex is described in dependency of the angle of attack and the Reynolds number. The Q-criterion is applied to the measured velocity data to estimate the circulation strength of individual vortices allowing for a quantitative description of the vortex developments and interactions. Furthermore, a case at transonic flow speeds ( M = 0.8 ) is described, showing a sudden occurrence of vortex breakdown above the delta wing, most probably induced by a shock wave.