Two-component molecular tagging velocimetry utilizing NO fluorescence lifetime and NO_(2) photodissociation techniques in an underexpanded jet flowfield

摘要

We report the application of molecular tagging velocimetry (MTV) toward two-component velocimetry as demonstrated in an underexpanded free jet flowfield. Two variants of the MTV technique are presented: 1) electronic excitation of seeded nitric oxide (NO) with gated fluorescence imaging (fluorescence lifetime) and 2) photodissociation of seeded NO_(2) followed by NO fluorescence imaging (NO_(2) photodissociation). The seeded NO fluorescence lifetime technique is advantageous in low-quenching, high-velocity flow-fields, while the photodissociation technique is useful in high-quenching environments, 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 approx5percent. This study represents the first known application of MTV utilizing either the fluorescence lifetime or the photodissociation technique toward two-component velocity mapping in a gaseous flow-field. Methods for increasing the spatial resolution to be comparable to particle-based tracking techniques are discussed.