Nonparticle laser anemometry: propagating and nonpropagating fluctuations

Abstract

Laser anemometry - as it is commonly applied - requires particles. However, in certain types of high-speed flows and plasma flows no particles are present. Collective light scattering may then be applied to measure fluid or plasma velocity. A new hybrid scheme has been proposed; the scheme allows for better axial resolution than what has previously been demonstrated. The effects of propagating and nonpropagating fluctuations on the expected crosscorrelation functions are investigated. The correlation function will in general be asymmetric and will consist of three identifiable peaks; two caused by (counter) propagating fluctuations and one caused by nonpropagating fluctuations. Thermal diffusivity cases the maximum of the 'nonpropagating peak' to be displace relative to the case of no diffusivity.