Freezing phenomena of supercooled water under impacts of ultrasonic waves

In order to clarify effects of ultrasonic waves on supercoold water, ultrasonic waves were applied to supercooled water. Frequency of the ultrasonic waves applied was 45 kHz, and the intensities of the waves were 0.13 and 0.28 W cm−2, respectively. Four cases of experimental conditions were selected; a case of a free surface, a case of an oil-water surface, a case of a free surface with a dipped metal bar and a case of an oil–water surface with a dipped metal bar. For each experimental condition, water was cooled at a constant cooling rate and the ultrasonic wave was applied from underneath until the water in a test tube solidified. It was found that in the case of 0.28 W cm−2, the ultrasonic wave had distinct effects on freezing of supercooled water for all experimental conditions. On the other hand, in the case of 0.13 W cm−2, the ultrasonic wave had an effect on freezing of supercooled water only under existence of a free surface and a metal bar.