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The filtered Rayleigh scattering (FRS) technique, extended by the method of frequency scanning, is a powerful tool to characterize thermodynamic, as well as aerodynamic, properties of technical flows. In this Letter, we report on the first application of an FRS velocimeter, which is capable of acquiring time-averaged planar pressure, temperature, and three-component velocity distributions simultaneously. The method is validated by characterizing the near-field, as well as the far-field, of a turbulent jet.

Frequency scanning filtered Rayleigh scattering is able to simultaneously provide time-averaged measurements of pressure, temperature and velocity in gaseous flows. By extending the underlying mathematical model, a robust alternative to existing approaches is introduced. Present and proposed model functions are then characterized during a detailed uncertainty analysis. Deviations between the analytical solution of a jet flow experiment and measured results could be related to laser-induced background radiation as well as the Rayleigh scattering’s spectral distribution. In applying a background correction method and by replacing the standard lineshape model by an empirical formulation, detrimental effects on pressure, temperature and velocity accuracies could be reduced below 15 hPa, 2.5 K and 2.7 m s−1.

The pendulum motion of electrons in a hollow cathode discharge accelerated in the cathode fall is demonstrated with the use of a femtosecond laser pulse and the so-called fast optogalvanic effect. The signals are described quantitatively using a Monte Carlo model for various pressure and current levels. As a result the discharge can be described by the model from start-up to high-current operation.