液体中での音波照射による閉端孔内に存在する複数気柱の排出

In the cleaning and coating processes of product manufacturing, some cases require filling liquid into closed-end holes. We have developed a liquid infiltration method, i.e., gas removal, into closed-end holes by irradiating acoustic waves. The method uses gas oscillation inside the holes; however, the final removal process of break-up gas columns is still unclear. This study observed the multiple gas column oscillation inside a closed-end hole during acoustic wave irradiation and its removal process. We also visualized the liquid flow between columns using the PIV technique. As a result, we found that the gas removal occurrence depends on the size, distance, and the number of gas columns. The removal process shows that the gas columns were approached and coalesced. They were then ejected through capillary wave propagation, necking, break-up, and re-coalescence. The oscillation of the gas column near the hole exit induced the flow between columns and approaching the other gas column. The PIV analysis shows that the long-distance gas column cases induced smaller flow velocities and could not achieve gas removal due to liquid inertia.