Simplification of RELIEF Velocimetry Using Picosecond Tagging and Broad Band Interrogation

Abstract

This work demonstrates the potential for a simplified portable "RELIEF" velocity apparatus, employing the use of a compact, relatively low cost, ~150 pico-second duration Nd:YAG laser to vibrationally excite molecular oxygen in a stimulated Raman scattering, tagging step. The tagged oxygen molecules are interrogated by Laser Induced Fluorescence, utilizing a low cost broadband ArF laser, as a replacement for the injection-seeded ArF laser which has been traditionally employed. The Stokes beam required in the tagging step is generated in both a single and multi-pass Raman Shifting Cell, with the corresponding Raman shift conversion efficiencies reported herein.

Electric field measurements in a dielectric barrier nanosecond pulse discharge with sub-nanosecond time resolution

“…This is due to the effect of stimulated Brillouin scattering (SBS) occurring in the cell. As noted in [24], SBS backscatter dominates over the forward scattering when the coherence length of the pump beam, l c , is on the order of or greater than the focused beam confocal beam parameter, z o ,…”

Applications of 2-D Moiré Deflectometry to Atmospheric Turbulence

“…Optical methods, in general, can be well-suited to measurements directly in the spatial domain and have already been used to study transverse velocity structure functions, including Raman-Excited Laser Induced Electronic Fluorescence (RELIEF) (Frisch 1995;Noullez et al 1997;Miles et al 1991;Webster 2009). Methods such as tracking inertial particles using a high-speed camera or by using the Laser Doppler effect and multiple probes (Lekakis 1996;Journal of Applied Fluid Mechanics, Vol.…”