Advanced Measurement Techniques for Cryogenic Testing

Abstract

Future generations of aircraft will be developed applying “High Reynolds Number Design”, using advanced computational aerodynamics and industry-scale cryogenic wind tunnels which enable aerodynamic optimization tests for flight Reynolds numbers on scaled models. For validation purposes and to further improve the computational techniques, accurate aerodynamic field-data must be supplied during the design process including transition locations, surface pressure distributions, velocity fields and acoustic field data. Thus, modern, image based measurement techniques commonly used in “warm” industrial wind tunnels have to be made also available for productive testing in cryogenic wind tunnels. For example, the method of Temperature-Sensitive Paint (TSP) for transition detection at in a cryogenic wind tunnel (cryoTSP) has been optimized within the last years and is now ready to use for productive testing. In the European Transonic Windtunnel (ETW), cryoTSP now has substituted a highly sophisticated, cryogenic infrared camera. Transition patterns gathered by cryoTSP on full models at transonic Mach numbers, as well as on half models in high lift configuration at low speed Mach numbers (Fig.2), clearly can show the complex structure of laminarto-turbulent boundary layer transition and further exhibit additional information about transition zone length and underlying instability.