Research on the collapse process of a near-wall bubble

Abstract

The effect of wall on the bubble collapse is significant. A compressible numerical simulation method based on the state equation was used to numerically calculate the collapse process of bubbles at different leaving wall distances. The results show that when the dimensionless distance between the bubble center and the wall is greater than zero, the bubble generates a high-pressure region at the top of the interface, which induces a jet toward the wall. When the dimensionless distance is less than zero, the jet is generated from the vicinity of the contact position between the bubble and the wall and moves along the wall towards the center axis of the bubble. When the dimensionless distance is equal to zero, that is, the center of the bubble coincides with the center of the wall, the bubble shrinks uniformly, and its collapse process is consistent with that of a single bubble in free space under the same parameter conditions. Comparison of these three typical cases of dimensionless distance from the wall reveals that the presence of the wall induces an asymmetric effect and a pressure gradient effect in the flow field around the bubble, and the farthest point away from the center of the attached wall is a high-pressure region, which induces destabilization of the bubble interface and the occurrence of jets.