Visualization of boundary layer separation and passive flow control on airfoils and bodies in wind-tunnel and in-flight experiments

¹ Institute of Thermomechanics, Academy of Sciences of the Czech Republic, Dolejskova 5, Prague 8, Czech Republic
popelka@it.cas.cz ; simurda@it.cas.cz ; natalies@it.cas.cz ; Milan.Matejka@fs.cvut.cz ; uruba@it.cas.cz
² Department of Applied Mathematics, CTU in Prague - Faculty of Transportation Sciences, Konviktska 20, Prague 1, Czech Republic
kuklojan@fd.cvut.cz

Abstract

Infrared camera, Particle Image Velocimetry, smoke-wire, tuft filaments and oil-flow visualization techniques were used for wind-tunnel and in-flight investigation of boundary layer separation, both stall and separation bubbles, related to the low-Reynolds numbers transition mechanism. Airfoils of Wortmann FX66 series and FX66 series wing-fuselage interaction, as well as modern airfoils and their wing-fuselage geometry were subject to study. The presence of previously identified structures in the CFD modelling, such as horse-shoe vortices, was confirmed in the flow.

Wind-tunnels and in-flight measurements on sailplanes were carried out and effect of passive flow control devices - vortex generators - was surveyed; namely counter-rotating vortex generators and Zig-zag type turbulators were applied. Separation suppression and consequent drag coefficient reduction of test aircrafts was reached. PIV investigation was further extended by Time-Resolved techniques.

An important study on structure of the turbulent flow in the lower atmosphere, creating an environment of the soaring flight, was presented.