Laser Doppler velocimeter for multicomponent measurements using an electro-optical modulator demonstrated for a two-component optical configuration

Abstract

For a multidimensional velocity measurement in fluids laser Doppler optics were developed which permit the switching of the measuring volume during the transit time of a particle by using an electro‐optical modulator. This enables a multidimensional measurement of the flow velocity from only one Doppler burst. The so‐called multicomponent Doppler burst can be detected and processed by only one photomultiplier and one conventional counter. The new measuring technique is demonstrated for an optical configuration which permits a quasisimultaneous two‐component measurement of flow velocity. Experimental results are presented to verify this measuring principle. This new measuring technique reduces the number of optical components and electronic devices compared with a conventional two‐dimensional measuring system using two colors. The range of detectable velocity vectors for usual fringe numbers is shown. Finally, factors limiting the application of this system are discussed.