NO flow-tagging by photodissociation of NO2 - a new approach for measuring small-scale flow structures

A new flow tagging technique was developed which visualizes small-scale flow structures by writing a spatial line of NO into an air flow homogeneously seeded with NO2. The NO-line was generated by photodissociation of NO2 at 308 nm using a XeCl excimer laser and was imaged by planar laser-induced fluorescence at various delays after its formation. With seeding levels of 600 ppm signal-to-noise levels are shown to be sufficient to detect the shifted structure at delays up to 20 ms. The technique was applied to resolve small scale turbulent flow structures within a quartz cell.