Flow-tagging velocimetry using UV-photodissociation of water vapor
1991; Linguagem: Inglês
10.2514/6.1991-355
AutoresLarry Goss, T. Chen, D. D. Trump, B. Sarka, Abdi Nejad,
Tópico(s)Gas Dynamics and Kinetic Theory
ResumoThe need to s tudy high-speed f lows fo r advanced propulsion systems has spurred the development of uon-particle laser-velocimetry techniques since techniques which rely upon seed particles, e.g., Laser Doppler Velocimetry, cannot he applied to this environment because of aerodynamic drag. OH-Flow-Tagging Velocimetry is capable of velocity measurements in highand low-speed flow systems. The technique involves photodissociation of the water molecule (a natural seed in most wind tunnels), resulting in the formation of the OH photofragment which marks the flowfield. The displacement of the OH-photofragment is then measured as a function of time by laser-induced fluorescence. Because of the long chemical lifetime of the OH-photofragment (150 ps, ambient), a wide range of velocity flowfields can be studied with the technique. Spectroscopic studies of water vapor and the OH-photofragment have been utilized to determine the optimum pumpand probe-laser wavelengths. Application of the technique to a high-speed underexpanded jet is demons t r a t ed . I n t r o d u c t i o n Presently, three types of velocity-measurement techniques are being employed for aerodynamic s tudies : 1) par t ic le -based methods (Laser Doppler Veloc imet ry and Par t ic le Imaging Velocimetry), 2) molecular Doppler-shift techniques (with Planar Laser-Induced Fluorescence detection), and 3) flow-tagging methods (RELIEF *Chief Scientist, Optical Diagnos., Member AIAA
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