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 flo w 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 fl uorescence at various delays after its formation. With seeding levels of 60 0 ppm, signal-to-noise levels are shown to be sufficient for detecting the shifted structure at delays of up to 20 ms. The technique was used to resol ve small scale turbulent flow structures within a quartz cell. (C) 1999 Els evier Science B.V. All rights reserved.