Survey of recent flow visualization studies in U.S.A. and Canada

Three major categories of flow-visualization techniques in the United States and Canada are identified: (1) the addition of foreign materials, (2) optical methods, and (3) combined compatible-noninterfering methods. The first group is further discussed with reference to direct injection methods (smoke, small particles and droplets, and dye), tufts and surface-tracing techniques, electrical control methods (smoke wire, hydrogen bubbles), chemical methods (electrolytic and photochemical dye production) and cavitation. The optical methods available are shadowgraphs, schlieren techniques, interferometry, and holography. The combined compatible-noninterfering techniques discussed include optical (shadowgraph and schlieren) and surface-indicator (oil field) methods, a vapor screen method using a CW laser, and a reversible dye technique.