Optical and Acoustic Observations of Bubble Adhered to Piezoelectric Transducer under Ultrasound Field: Pressure Signal Caused by Bubble Behavior

概要

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In order to clarify the mechanical effects caused by micro-bubbles in liquids, the detailed behavior of a single bubble adhered to a solid surface was observed optically using an ultra high-speed video camera (maximum recording rate: 1,000,000 frames/s). Making use of a thin piezoelectric transducer on the solid surface, the pressure signal caused by the bubble behavior was simultaneously observed. In addition, the influence of the initial bubble radius $R_{0}$ on mechanical effects was investigated. It was confirmed that a micro-jet was generated from the center of the bubble, which was followed by a counter-jet, in the range of $R_{0}/R_{\text{res}}\approx 0.65--1.10$ ($R_{\text{res}}$: the resonance radius of the free bubble). An impulsive positive pressure to the surface was also observed synchronously with the momentary increase of bubble volume acceleration. Moreover, it was found that the strength of the impulsive pressure was connected to the peak value of volume acceleration. The pressure amplitude showed a maximum value when $R_{0}/R_{\text{res}}$ was approximately 0.9.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2008-05-25