2011 年 26 巻 1 号 p. 11-17
It has been claimed in the literature that selective ethanol separation from ethanol-water solution can be made through ultrasonic atomization. The causes of separation were explained in terms of parametric decay instability of capillary waves, accumulating acoustic energy in a highly localized surface of the capillary wave and effecting ultrasonic atomization. In this study, the atomization process is examined visually with some mechanistic view, and the dynamics of interfacial oscillations occurring along the perturbed protrusion or conical “liquid column/fountain jet” over the ultrasonic transducer are analyzed by high-speed imaging. It is found that the atomization process could be initiated by a sudden increase in surface roughness of microscale, which would be viewed as localized surface patches of two-dimensional capillary waves, often associated with contraction expansion sequence of surface to-pology. Such surface patches could bring further instability in generating a swarm of liquid droplets of microscale around the expanded phase of liquid column.