Presentations

Visualization experiments are performed to examine nucleation, growth, and detachment of bubbles at hydrophobic surfaces of a beer can. Solutions of our concern are carbonated water and beer. The solution under cooling is poured into a (hydrophilic) glass container; the container is then sealed. A piece of a beer can whose inner coating is hydrophobic is inserted inside the container. To trigger gradual growth of bubbles nucleated preferentially at the piece of the beer can, dissolved gas supersaturation is created by heating the solution (with the container being sealed). From the visualization experiments, we report on the evolution of bubble population and size (from the front view) and the shape of attached bubbles (from the side view) at surface, exploring the role of surface tension and proteins in detachment of the bubbles.

We experimentally study the dynamics of near-wall bubbles induced by focusing pulse laser into a gelatin gel. From high-speed video visualization, we examine non-spherical oscillation of the bubble. The visualization result shows that the bubble centroid oscillates toward the wall. This translational oscillation will be caused by inertia and elasticity of the surrounding gel.

We experimentally demonstrate that laser-induced bubble collapse can produce negative pressure in water. Here, we produced a bubble by focusing pulse laser into water. We visualized collapse and rebound stages of the bubble by a high-speed camera. In the collapse stage, the single bubble was found to be split into multiple bubble fragments. Multiple spherical shocks were then emitted from collapse of these bubbles, leading to interaction between the shocks and bubbles. We also measured the emitted pressure using a hydrophone, showing negative pressure generation. This means that tension wave is generated by the shock-bubble interaction after the multiple-bubble collapse.

超音波洗浄の効率化およびエロージョンフリー化を同時に実現するための各種パラメータの最適化に関する解説を行った。超音波洗浄の可視化実験より、低音圧超音波照射下の洗浄面近傍に現れるファインバブルの穏やかな運動が高効率かつダメージレスな洗浄に寄与することを示した。

水中超音波の照射による洗浄メカニズム解明のための超音波キャビテーション流れの可視化技術の紹介をした。

超音波洗浄のエロージョンフリー化への取り組みとして酸素過飽和水を洗浄液とする低音圧超音波照射を提案し、物理洗浄における超音波キャビテーション気泡の運動の役割を解説した。

超音波洗浄のエロージョンフリー化への取り組みとして酸素過飽和水を洗浄液とする低音圧超音波照射を提案し、物理洗浄における超音波キャビテーション気泡の運動の役割を解説した。