K. Pengel

Capsulated liquid crystals are a useful and proven tool for surface flow visualization for hypersonic flows as shown by H. Schöler in the DFVLR Ludwig Tube facilities. They change their colours by temperature variations. The temperature distribution obtained from the flow visualization is related to the wall shear stress distribution. Certain non-capsulated liquid crystals react directly to shear forces, resulting in a wave length variation of the reflected light. The colour changes towards the blue end of the spectrum as the shear forces increase. In several investigations the reaction of these "temperature insensitive" liquid crystals to variations in the shear stress distribution was observed in the German-Dutch Wind Tunnel (DNW), a low-speed wind tunnel. The analysis of the pictures lead to information about the wall shear stress distribution on an Airbus wing and in particular to the detection of the laminar to turbulent boundary layer transition. During the test continuously recorded video images present a chronological sequence of events corresponding to variating model configuration and tunnel conditions. Repetitions of several configurations show that all colour changes are reproducible.

DGLR-Workshop, Markdorf, 1988

Conference Paper

englisch

21,0 x 29,7 cm, 10 Seiten

DGLR-Bericht, 1988, 1988-04, 2D-Meßtechnik; S.223-232; 1988; Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn

NA

aerodynamics

Bibliothek

1988