A Study On Recent Trends In High Subsonic Flow Over Delta Wings

摘要

An understanding of the vortical structures and vortex breakdown is essential for the development of highly maneuverable and high angle of attack flight. This is primarily due to the physical limits these phenomena impose on aircraft and missiles at extreme flight conditions. In today's competitive world, demands for more maneuverable and stealthy air vehicles have encouraged the development of new control concepts for separated flo ws and vortex 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 Vortex flo w experiment. 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.Vortex Flow Experiment provided a variety o f experimental data for a 65. swept delta wing sharp and blunt leading edges. Flow details including forces and moments, surface pressures,Pressure Sensitive Paint measurements, and off-surface flow variables from Particle Image Velocimetry were made available for comparisons with computational simulations. This paper concentrates on so me typical problems of delta wings with rounded leadin g edges at subsonic speed: the prediction of the main leading edge separation, the generation of the second inner vortex, the effect of transition, and Reynolds number effects