2-COLOR PARTICLE-IMAGING VELOCIMETRY USING A SINGLE ARGON-ION LASER

A swept-beam, two-color particle-imaging velocimetry (PIV) technique h as been developed which utilizes a single argon-ion laser for illumina ting the seed particles in a flowfield. In previous two-color PIV tech niques two pulsed lasers were employed as the different-color light so urces. In the present experiment the particles in a two-dimensional sh ear-layer flow were illuminated using a rotating mirror to sweep the 4 88.0-nm (blue) and 514.5-nm (green) lines of the argon-ion laser throu gh a test section. The blue- and green-particle positions were recorde d on color film with a 35-mm camera. The unique color coding eliminate s the directional ambiguities associated with single-color techniques because the order in which the particle images are produced is known. Analysis of these two-color PIV images involved digitizing the exposed film to obtain the blue and green-particle image fields and processin g the digitized images with velocity-displacement software. Argon-ion lasers are available in many laboratories; with the addition of a rota ting mirror and a few optical components, it is possible to conduct fl ow-visualization experiments and make quantitative velocity measuremen ts in many flow facilities.