Optical Flow-Velocity Measurement in Irregularly Shaped Cavities

Summary

A nearly disturbance-free technique for the measurement of the velocity field of viscous liquids in closed and irregularly shaped cavities is described. This method is based on the photochromic effect. Up to now photochromism was used in experimental fluid dynamics to produce dye lines in a fluid with a photoactive additive of very low concentration. The present method uses a totally saturated solution of indolinespiropyran in a mixture of dekahydronaph-thalin and tetrahydronaphthalin. By means of a glass-fiber for the transmission of UV-light of 356 nm it is possible to color small fluid volumes inside the fluid at rest. The motion of the colored spots can be photographed by a movie camera. Thus path-lines of individual particles in the liquid can be determined when the whole body of the liquid is set into motion.