Boundary Layer Transition, Separation and Flow Control on Airfoils, Wings and Bodies in Numerical, Wind-Tunnel and In-Flight Studies

Abstract

Abstract

Particle Image Velocimetry (PIV), smoke-wire, tuft filaments and oil-flow visualization techniques were used for wind-tunnel and in-flight investigations of boundary layer separation, both stall and separation bubbles, related to the low-Reynolds number transition mechanism.  Airfoils of three Czech-designed sailplanes and their wing-fuselage interaction were studied.  The combination of experimental results with those of numerical modeling (computational fluid dynamics, CFD) greatly facilitated the understanding of the various phenomena.  The effects of several passive flow control devices, vortex generators, counter-rotating vortex generators, and zig-zag type turbulators were considered. Separation suppression was reached and corresponding drag coefficient reduction occurred for test aircraft measured in flight. Investigations were extended by the PIV time-resolved technique.