Principle of Phase-Doppler Anemometry

The principle of phase-Doppler anemometry (PDA) relies on the Doppler difference method used for conventional laser-Dopler anemometry and was first introduced by Durst and Zare (1975). By using an extended receiving optical System with two or more photo detectors it is possible to measure simultaneously size and velocity of spherical particles. For obtaining the particle size the phase shift of the light scattered by reflection or refraction from the two intersecting laser beams is used.