Two-Component Molecular Tagging Velocimetry Utilizing NO Fluorescence Lifetime and NO2 Photodissociation Techniques in an Underexpanded Jet Flowfield
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abstract
We report the application of molecular tagging velocimetry (MTV) towards two-component velocimetry demonstrated in an underexpanded free jet flowfield. Two variants of MTV are presented: 1) Electronic excitation of seeded nitric oxide (NO) and gated fluorescence imaging (fluorescence lifetime) and 2) Photodissociation of seeded NO2 followed by NO fluorescence imaging (NO2 photodissociation). The seeded NO fluorescence lifetime technique is advantageous in low quenching, high velocity flowfields, while the photodissociation technique is useful in high quenching, and either high or low velocity flowfields due to long lifetime of the NO photoproduct. Both techniques are viable for single shot measurements, with determined root mean squared results for streamwise and radial velocities of <5%. The study represents the first known application of molecular tagging velocimetry utilizing either the fluorescence lifetime or photodissociation technique towards two-component velocity mapping in a gaseous flowfield. Methods for increasing the spatial resolution to be comparable to particle-based tracking techniques are discussed. Copyright 2009 by Andrea Hsu, Ravi Srinivasan, Rodney Bowersox, and Simon North.
