Fundamental turbulence measurements by relief flow tagging

The observation of small-scale velocity structures in high Reynolds number turbulent flowfields is important for the understanding of energy scaling and dissipation phenomena. The Raman excitation plus laser-induced electronic fluorescence (RELIEF) technique is shown to be a promising tool to observe these scales. Lines on the order of 100 μ thick and 1 cm long are written into a contained turbulent jet and observed with a resolution on the order of tens of microns. The images that are recorded give instantaneous velocity profiles it very short time delays between tagging and interrogation are used. This time-of-flight approach is a direct measure of velocity, so approximations such as constant density, constant temperature, or the Taylor hypothesis are not required