Characterizing a Co-Flow Nozzle for Use in a Filtered Rayleigh Scattering System

Research was conducted on the flow field exiting a co-annular flow nozzle for use in filtered Rayleigh scattering flow visualizations. More specifically, the flow visualizations were of the flow field exiting a coflow nozzle and illuminated by a tunable, nominal 4.2 watt narrow line width Argon laser operating at 514.5nm. ND:YAG lasers are typically used in this application, but some of the properties of a tunable Argon laser make it an attractive alternative. Before generating flow visualizations, the coflow nozzle was characterized both experimentally and computationally. Due to a flow asymmetry in the outer annulus flow field, the nozzle was redesigned using a commercially available computational fluid dynamics program (Fluent) to produce a more homogeneous exit plane velocity profile. The redesigned nozzle was built and experimentally tested through the use of a three dimensional traverse controlled Pitot probe resulting in good relationship between the computational and experimental results. The sharp cutoff molecular iodine filters used to reduce the incident frequency light were tested and the locations of their iodine absorption transitions were determined. Finally, the argon laser was used to produce flow visualizations at both 100 Hz and 1 kHz frame rates.