Mesure par Diffusion Raman Spontanee de la Masse Volumique Locale dans un Ecoulement Gazeux (Measurement of Local Density in a Gas Flow Using Spontaneous Raman Scattering) (Messung der Oertlichen Dichte in Einer Gasfoermigen Stroemung Durch Spontane Raman-Steuung)
(Englisch)
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The study aims to demonstrate the possibilities and current limitations of spontaneous Raman scattering as a measurement technique when applied to gas dynamics. Three examples are presented. The authors show, in a study of air entrainment by a free jet, that spontaneous Raman scattering combined with LDA is especially well-suited to the study of chemically inert gas mixtures. Local measurements of mean velocity and mean density are used to compute the entrainment rate. Turbulent fluctuations of the concentration in a mixing area are then analyzed. Though it is not yet possible, with today's lasers, to track turbulent fluctuations of density in real time, their frequency spectrum can be determined. The authors do that through correlation of the signal photons from Raman scattering, which gives the density autocorrelation function. From this they compute the mean density, the root mean square of fluctuation, and the power spectral density of that same quantity. Density turbulence is thus known statistically. A few feasibility tests were run at M=2.06 and M=4.38 in a supersonic wind tunnel.
Mesure par Diffusion Raman Spontanee de la Masse Volumique Locale dans un Ecoulement Gazeux (Measurement of Local Density in a Gas Flow Using Spontaneous Raman Scattering) (Messung der Oertlichen Dichte in Einer Gasfoermigen Stroemung Durch Spontane Raman-Steuung)