Two-Point Dynamic Rayleigh Scattering Measurements in a Free Jet

摘要

A molecular Rayleigh scattering based measurement technique is advanced to measure dynamic gas density and velocity simultaneously at two spatial points in a free jet facility at NASA Glenn Research Center. The gas density is measured by detecting the total scattered light via photomultiplier tubes operated in the photon counting mode providing dynamic measurements at 10kHz data rates. The gas velocity is measured by using a Fabry-Perot interferometer to analyze the spectrum of the scattered light. The interference fringe patterns are detected with a low noise CCD camera providing time-average measurements of velocity at this time. The effort serves as a preliminary step in designing an image dissector system that along with photon counting via photomultiplier tubes will provide simultaneous density and velocity measurements at high data rates. The importance of the development of this non-intrusive two-point dynamic measurement system lies in the promise for obtaining high-quality space-time correlations of density and velocities that are useful in aeroacoustic computational models.