Air vortex detection using the rotational Doppler effect

Abstract

A vortex generated by an air depression in a tube is investigated optically using the rotational Doppler effect. A superposition of Laguerre Gaussian beams with opposite topological charges probes the turbulence along its axis. The scattered light is frequency shifted depending on the charge and is detected and analyzed with a spectrum analyzer. A complete transversal mapping of the turbulence is performed, showing fluid rotation of the order of a few Hertz. Applications to wake turbulences in aircraft safety are then considered.