Behaviors of bubble(s) exhibiting non-linear shape oscillation under ultrasonic vibration, and their interaction among multiple bubbles are focused. Size of the bubbles interested in the present study is of O(1 mm) in diameter. The bubbles were injected through the micro syringe to the test fluid (water or water/surfactant mixture) filled in the rectangular tank. Ultrasonic vibration were triggered after the detach of the bubble from the tip of the syringe; thus the bubbles were exposed to the periodic oscillation in rising the test fluid. In the case of single bubble, the authors clearly detect a wave with a small wavelength known as Kelvin wavelength emerges on the surface of a bubble under the small-amplitude ultrasonic vibration, and radial and shape oscillations under the large-amplitude vibration by use of high-speed camera. Preferable mode number of the shape oscillation, and the transition process from the radial to the shape oscillation are discussed. In the case of multiple bubbles rising successively, transition of the oscillatory mode and mode interaction between/among these are focused. Effect of the preceding bubbles upon the following ones is described.
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