A Study on Cleaning Ability of Oscillating Bubbles Driven by Low-Frequency Ultrasound

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In this paper, we demonstrate the cleaning ability of oscillating bubbles, on the basis of optical observations of bubble behaviors and cleaning process using a high-speed video camera. It was shown that a bubble cluster was formed after the collapse of the initial bubble. The bubble cluster consisted of a main bubble and many small bubbles. In addition, optical observations clearly revealed that the oscillations of these microbubbles removed a thin ink film bonded to the surface of a slide glass. From the analysis of the relationship between bubble oscillation and cleaning effect, it was confirmed that the cleaned area increased with an increasing amplitude of bubble oscillation, although there was a poor correlation between cleaned area and bubble oscillation. Moreover, the observed results suggested that a pressure ranging from several tens kPa to MPa was generated on the slide glass by hydrodynamic phenomena; micro jet and secondary wave were emitted by the oscillating bubble. Our experimental results lead to the understanding of the cleaning mechanism in ultrasonic cleaning techniques.
2010-07-25