Raman Doppler velocimetry: a unified approach for measuring molecular flow velocity, temperature, and pressure

Absorption, Scattering, and Fluorescence Techniques for Hypersonic Flow Measurements

“…The Doppler shift is actually obtained through the difference in frequency shift between the forward and backward scattered Raman peaks and, in addition, the two line shapes jointly determine the gas translational temperature, T, and pressure, P. In this manner, all three parameters (V,P,T) can be determined from frequency :lifference measurements independent of intensity or absolute frequency considerations. rhis technique was initially employed in a concentric IRS mode (Ar+ probe, tunable pulsed dye amplified pump) and successfully demonstrated that the complex optical configuration would work in a major wind tunnel environment and geometry [7,8]. The system has more recently been reconfigured in the SRGS mode (tunable dye laser probe, Nd:YAG pump) in order to take advantage of the increased energy per pulse available using a narrow-line Single Axial Mode (SAM) Nd:YAG laser.…”

Aerothermodynamics and Transition in High-Speed Wind Tunnels at NASA Langley

“…Now, there is renewed interest in such diagnostics. One example is a prototype system for simultaneously measuring velocity, translational temperature, and pressure that was recently developed for and demonstrated in the UPWT by Exton & Hillard (1986). This system has been refined con siderably in the laboratory since its first application and is scheduled to be used in the near future to survey the vortex system for a delta wing in the UPWT.…”

Properties of the iodine molecule relevant to laser-induced fluorescence experiments in gas flows

“…2. Saturation of the PI3/R15 (43, 0) B-X transition of iodine vs. static gas pressure, with the static gas temperature as parameter; the saturation intensity is calculated for narrow-band excitation at line center scattering (Exton and Hillard 1986;Long et al 1985), laserinduced fluorescence is a much more efficient process so that the signal levels are orders of magnitude higher. The laser beam can be generously expanded into a wide sheet to illuminate an entire plane.…”