MEASUREMENT OF PARTICLE VELOCITIES IN SUPERSONIC GAS STREAMS
NAVAL ORDNANCE TEST STATION CHINA LAKE CA
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A photographic technique was developed to directly measure the velocity of particles as small as 2-3 microndiameter traveling at velocities up to 2,600 ftsec in supersonic gas streams. A double-pulsed explosivekrypton light source was used to provide intense and precisely controlled light pulses that were used both for illuminating and shuttering the event. The particle images were recorded on film as pairs of streaks. The velocities of the particles were determined from the magnification of the camera-lens system, the measured distance between the streaks on the film, and the time interval between flashes. A series of ten runs was made in which the velocity of 3-50 micron particles were measured as they were carried in a 2,900 ftsec helium stream. Particle velocities up to 2,600 ftsec were measured with an accuracy of from 1. 5 to 3.2. By optimizing the technique it should be possible to extend the measurements to higher particle velocities. Particle velocities and sizes were correlated and the results compared with theoretical data calculated using a one-dimensional treatment with constant lag assumptions. Although the data trends correlate well, it appears that particle lag is not as great as predicted by theory.
- Fluid Mechanics