Turbulent structure measurements by RELIEF flow tagging

Molecular tagging by Raman excitation + laser-induced electronic fluorescence (RELIEF) is applied to an isotropically turbulent air flow to demonstrate the utility of the technique for measurements of fundamental turbulence parameters. Lines which are 120 μm in diameter are written into the flow and their displacement is recorded after several microseconds. From these images, the average flow velocity profile, the average turbulence intensity profile, and the lateral velocity correlation function are computed. The lines themselves can be examined for coherent structure, eddy diffusion, line stretching, curvature, etc.