Simplified read schemes for krypton tagging velocimetry in N₂ and air

The background and results for two simplified read schemes for krypton tagging velocimetry (KTV) are presented. The first scheme utilizes the excitation/re-excitation approach found in the literature but replaces the pulsed dye laser used for the re-excitation step with a continuous wave, narrowband laser diode. The second scheme is a single-laser setup with no read laser where the fluorescence of the tagged Kr is imaged at successive times. Results are presented and compared to historical data for experiments performed in 99%N₂/1% Kr and 95% air/5% Kr underexpanded jets. The approach with the laser diode has a higher signal, while the single-laser approach yields more consistent results. Both schemes maintain an SNR comparable to that in the literature, but with a simpler setup that enables future high-repetition rate KTV experiments.