Laser light scattering diagnostic for measurement of flow velocityin vicinity of propagating shock waves

摘要

A laser light scattering diagnostic for measurement of dynamicflow velocity at a point is described. The instrument is being developedfor use in the study of propagating shock waves and detonation waves inpulse detonation engines under development at the NASA Glenn ResearchCenter (GRC). The approach uses a Fabry-Perot interferometer to measurethe Doppler shift of laser light scattered from small (submicron)particles in the flow. The high-speed detection system required toresolve the transient response as a shock wave crosses the probe volumeuses fast response photodetectors and a PC based data acquisitionsystem. Preliminary results of measurements made in the GRC Mach 4,10×25 cm supersonic wind tunnel are presented. Spontaneouscondensation of water vapor in the flow is used as seed. The tunnel issupplied with continuous air flow at up to 45 psia; the flow isexhausted into the GRC laboratory-wide altitude exhaust system atpressures down to 0.3 psia