Abstract
We measured the amount of hydroxyl radicals and sonoluminescence to investigate the condition of ultrasonic cavitation. The generation of OH· radicals and sonoluminescence upon ultrasonic radiation occurred with the same trend at various concentrations of N2 and O2 in water, so we found that sonoluminescence can be used to measure the amount of cavities as well as radicals. In the investigation of the cavity-generating area, in degassed water, cavities were generated at water surface, and in gas-dissolved water, cavities were weakly generated from the entire volume of water. As the result of varying the N2 concentration or the dissolving condition at the water surface, we found that cavities were generated maximally at a certain gas concentration, and then decreased with excess dissolved gases. Cavitation did not occur in the degassed water, but occurred when gases dissolved from the water surface.
