Flow visualization techniques often enable the first insight into the investigated problem. Generally, the particle image velocimetry, smoke-wire, tuft filaments and oil-flow visualization techniques are used for wind-tunnel investigation. Considering the phenomenon of boundary layer separation bubble related to the low-Reynolds number's transition, these methods face several difficulties mainly with imposed influence to the sensitive flow mechanism. Infrared imaging allowing non-invasive visualization of the afore-mentioned investigations is one of the techniques currently undergoing further promising development in terms of resolution, device size, and price. In the presented paper, the focus was placed on validation of the infrared imaging as a standard visualization technique for wind-tunnel investigation of boundary layer development along an airfoil and its usage for roughness-due-to-insect investigation.

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.

No abstract

ABSTRACT