Laser Induced Photochromic Flow Visualization

The photochromic flow visualization technique has been utilized to study several different liquid flows. The technique utilizes radiachromic dyes that can be dissolved in a number of liquids. The resulting dye-solvent solutions remain colorless in the absence of ultraviolet radiation; however, the solutions turn dark blue when exposed to ultraviolet light. A nitrogen pulse laser has been constructed for use as source of ultraviolet radiation. When sharply focused, the emitted beam of ultraviolet light produces a very narrow, well defined line in a solvent-dye solution. The subsequent motion of the “activated trace” can then be recorded with high-speed photography. Digitization of the resulting movies allows one to quantify the flow field of interest. Several interesting flows have been studied using the photochromic flow visualization technique. This paper begins with a brief summary of several of these past studies. The remainder of the text concerns a set of experiments that were conducted to ascertain the rigidity of liquid-liquid interfaces. The experimental apparatus used to obtain high-speed movies will first be described. Next, the quantitative evaluation of these movies will be explained. Finally, typical results of the quantitative analysis will be presented.