Improved flow visualization technique for quantitative velocity measurement in small test volumes

Abstract

A flow visualization technique which utilized a photochromic dye in solution was introduced by Popovich and Hummel in 1967. The dye was activated along narrow trace lines by passing sharply focused beams from an ultraviolet light source through the solution. The movement of the dye traces were recorded by high-speed cinematography and velocities were found from analysis of the resulting pictures. Two variations to this basic method are described. These permit more accurate velocity measurements to be made in certain liquid systems where test volumes are small or near physical barriers, and where the flow is two dimensional or is time dependent. Manufacture of a suitable dye and construction of an inexpensive pulse laser which may be used as an ultraviolet light source are discussed.

Drop formation in liquid-liquid systems

“…Thus the integral could be broken into two parts, and the momentum flux could be calculated. The velocity profile exiting nozzle B could not be determined theoretically, so a flow visualization technique described by Johnson et al (1985) was employed. Briefly, a photochromic dye dissolved in the dispersed phase was activated by a pulsed laser directed through the column.…”