Comparisons of spark-charge bubble dynamics near the elastic and rigid boundaries.

The objective of this paper is to apply experimental methods to investigate the dynamics of spark-induced bubbles in the vicinity of the elastic and rigid boundary. In the experiment, the temporal evolution of the bubble is recorded by the high-speed camera at the 25,000 frames per second, as well as corresponding data such as normalized collapse position, the time of bubble collapse, and the velocity of the high-speed liquid jet. Results are presented for a single bubble generated over the elastic and rigid plates, under a wide range of normalized standoff distance from 0.5 to 3.0. The results show that the high-speed jet emitted by non-spherical bubble collapse near the boundary is one of the important factors to cause the destructive erosion pit. With the increase of the standoff distance, the expansion, shrink, jet formation, and rebound of the bubbles vary evidently adjacent to the different boundary conditions. Compared with the rigid boundary cases, the normalized first collapsed position and the time of bubble collapse are much smaller near the elastic boundary. The formation of the high-speed liquid jet in the neighborhood of the elastic/rigid boundary is founded in two different mechanisms. Furthermore, the normalized maximum velocity near the rigid plate is always larger than that near the elastic plate.