Molecular tagging velocimetry measurements in supersonic microjets

The application of acetone-based molecular tagging velocimetry (MTV) is demonstrated in sonic and supersonic jets produced by a 1-mm-exit-diameter nozzle. Measurements are performed in the static pressure range 1.3-53 mbar, with spatial resolution of approximately 10 pm. The statistical uncertainty (2sigma) in velocity is found to be of order 6-10 m/s, approximately independent of flowfield pressure. Acetone laser-induced fluorescence temporal decay curves were also obtained, with 1/e lifetime found to range from similar to200 ns at 1.3 mbar to less than 50 ns at 24 mbar. These relatively short lifetimes were nonetheless sufficient to obtain MTV data over the entire pressure range.