Reynolds number effects on low-speed aerodynamics of a hypersonic configuration

A Collaborative Research Center project is focused on fundamental design aspects of a hypersonic research configuration that consists of a lifting body with a delta planform of aspect ratio 1.1 and rounded leading edges. The aerodynamics of the configuration at Mach numbers below 0.3 are described. The conclusions are based on tests in different subsonic wind tunnels. Pressure distribution measurements were carried out at a Reynolds number range of 3 x 10(6) less than or equal to Re less than or equal to 40 x 10(6) using different wind-tunnel models, Above an angle of attack of 8 deg, the Bow at the suction side changes and a concentrated vortex system (primary and secondary vortices) begins to form, causing local pressure minima in the pressure distribution. On rounded leading edges, the primary separation line is not a priori fixed and the vortex system has less intensity than for delta wings with sharp leading edges, The present investigations show that, in this case, the location of the separation line and the strength and location of the vortex system depend on the Reynolds number. Pressure distribution measurements at higher Reynolds numbers with a large model in the German-Dutch Wind Tunnel supported these observations,In particular, the high spatial resolution allowed a good physical interpretation of the flowfield. Knowledge of the Bow processes was improved by surface oil flow patterns, the laser-light-sheet technique, and particle image velocimetry.