Experimental investigations on the VFE-2 configuration at DLR, Göttingen, Germany; In Understanding and Modelling Vortical Flows to Improve the Technology Readiness Level for Military Aircraft

Abstract

In the present chapter experimental investigations within the International Vortex Flow Experiment 2 (VFE-2) on a delta wing of 65° sweep angle with sharp as well as with rounded leading edges are described. High resolution surface pressure distributions are measured by means of the Pressure Sensitive Paint (PSP) technique at sub- and transonic speeds (M = 0.4 and 0.8). These tests were complemented by flow field measurements applying Stereo Particle Image Velocimetry (PIV) in different planes above the delta wing. Furthermore, under cryogenic conditions (M less than 0.2) the Infrared (IR) and Temperature Sensitive Paint (TSP) techniques are used for the detection of laminar/turbulent transition in the boundary layer. The results were analysed with respect to the onset of the primary vortex on the delta wing with rounded leading edges, the occurrence of an inner vortex, the development of a vortex system consisting of an inner and outer primary vortex, and under transonic conditions to the sudden occurrence of vortex breakdown above the delta wing. Preliminary results of the transition measurements are available which will be discussed, too.