European_transonic_wind_tunnel
The European transonic wind tunnel (ETW) is a high-Reynolds-number transonic wind tunnel using nitrogen as the test gas.
It is one of the world's largest cryogenic wind tunnels. It is situated in Cologne, Germany. ETW was constructed and is operated by the four European countries France, Germany, Great Britain and The Netherlands. The ETW has been in operation since 1994.[1]
ETW provides real-flight Reynolds numbers by virtue of both increased pressure and decreased temperature. Independent variation of Reynolds number and aero elastic loading can be investigated. They specialize in flight Reynolds number testing for full-span and semi-span models at cruise conditions and extreme borders of the flight envelope.