Interaction between a nonspherical pulsating bubble and a free surface near a solid wall

Abstract

The pulsating bubble near different boundaries demonstrates various dynamics. In this study, the three-dimensional Eulerian finite element method with the adaptive mesh refinement technique was used to investigate the interaction between a bubble and a free surface near a solid wall, including the toroidal bubble motion after the jet impact. The impact pressure on the solid wall was investigated, and the changing trend of pressure peak reverses when the initial depth of the bubble center is between 0.7 and 0.9 times the bubble's maximum radius. Throughout the process, competition occurs between the Bjerknes effects of the free surface and solid wall, which leads to the nonspherical pulsation of the bubble. Different collapsing forms of bubbles, i.e., the strong jet, weak jet, and crescent-type forms, were identified. Greater depth may result in a reduced height of a free surface water column, which is described in a fitting curve. Additionally, inclination of the solid wall can cause the free surface to exhibit a side hump or groove phenomenon. But for a large-scale bubble, no groove phenomenon of the free surface occurred, and the bubble collapsed in a horn-shaped form with two jets in the upward and downward directions.