Visualization of Bubble Dissolution As a Means to Measure Dissolved Nitrogen Concentration

In ultrasonic cleaning, violent cavitation bubble dynamics causes material damage to cleaning surfaces, which is called cavitation erosion. The control of the dissolved gas concentration in cleaning liquid is effective to avoid cavitation erosion. The dissolved oxygen (DO) concentration is easily measured by a commercial DO meter, but the dissolved nitrogen (DN) concentration in water where multiple gas species are dissolved cannot be accurately measured with a commercially available DN meter. Therefore, it is important to construct a new method of measurement of DN concentration. In this study, we visualize the diffusion driven dissolution of bubble in air-saturated water and degassed water. The Epstein-Plesset theory considering multiple gas species is derived and compared with the experimental result where the DN concentration is treated as a fitting parameter in order to estimate the unknown DN concentration. Results indicates that the DN concentration can be measured by comparison between the theory and the relatively slow dissolution of bubble.