A Spectrally-resolved Rayleigh scattering setup to measure velocity and temperature in high-speed flows

摘要

Two variations of a spectroscopic setup to analyze Rayleigh scattered light from a high-speed jet were created at the NASA Ames Research Center for simultaneous measurement of velocity, temperature and density. The point-measurement arrangement used a narrow linewidth CW laser and analyzed the scattered light to resolve the Rayleigh-Brillouin spectrum. In one variation the scattered light was collected on an optical fiber and transmitted to an air-spaced, planar, Fabry-Perot interferometer. In the second the probe volume was directly imaged through a solid etalon. A new software program was developed in the Matlab® platform to model the fringes produced by the incident laser light and the Rayleigh scattered light. The former generated the instrument function, which was then used to convolve the Rayleigh-Brillouin spectrum to model the Rayleigh image. The high-speed jet was supplied by filtered, particle-free clean air, and was surrounded by a clean, low-speed co-flow. While both setup produced fairly accurate measurements, the uncertainties produced by the direct-imaging setup was lower, partly due to a more efficient use of the scattered light. Data collected over a Mach number range of 0