Numerical study of the central breakup behaviors of a large bubble rising in quiescent liquid

In this paper, we conduct three dimensional (3D) simulation on the central breakup of large bubbles rising in quiescent liquid. The liquid jet resulting from the pressure difference between the top and bottom of the bubble penetrates the bubble. A protrusion is formed on the top of the bubble after the central breakup. The density and viscosity ratio affect the formation of the toroidal bubble. The influence of the initial bubble shape on the bubble dynamics is studied. For aspect ratio E = 0.3, the collision of the liquid jet with the bottom of the bubble creates a high pressure region, which increases the pressure difference between the top and bottom of the bubble, thus increasing the jet velocity. For two inline bubbles with a distance of 1.5d, the leading bubble elongates the trailing bubble. The pinch off of the trailing bubble leads to the formation of the third toroidal bubble.