On the development of planar laser velocimetry techniques fro cryogenic wind tunnels

Abstract

Two laser-light sheet based planar velocimetry techniques were successfully applied for the first time in two different cryogenic wind tunnel facilities. Particle image velocimetry (PIV) was used in a low speed cryogenic facility for the investigation of wing tip devices at Mach 0.2 and a temperature of 100K. A specially designed Doppler global velocimetry system (DGV, planar Doppler velocimetry) was tested in a high-speed cryogenic facility at Mach 0.3 – 0.8 and pressures of 1.2–2.5 bar. While the PIV application made use of standard oil droplet seeding injected into the tunnel, the DGV system relied on the light scattered by small ice crystals which were generated by injecting a mixture of warm nitrogen and water vapor into the cold flow. As operational and access conditions are quite different between the two facilities both PIV and DGV respectively were the best choice for the non-intrusive measurement of flow fields.