The Development and Application of Optical Measurement Techniques for High Reynolds Number Testing in Cryogenic Environment

The European Transonic Windtunnel (ETW) is a pressurised cryogenic facility suitable to achieve flight conditions for cruise and high lift configurations of aircraft models. Becoming involved in the design process of new aircrafts or providing high quality data for the validation of CFD codes requires the availability of qualified measurement tech niques for flow field analysis and model surface diagnostics. Over the past decade ETW has developed special instrumentation and installations, together with optical methods for flow visualization or model deformation measurements in order to fulfil the requirements of high Reynolds number aerodynamic testing. This paper gives an overview on the relevant optical tools operated under severe test conditions and presents new techniques under development. Gained experiences are addressed and achievements and maturity are documented.