On the shape feature of a single bubble rising in viscous liquids

Three-dimensional direct numerical simulations of the rise motion of a single bubble in viscous liquids are carried out in this study. In the simulation, the level set method is employed to capture the bubble surface and a pseudo single fluid model is used to solve the flow fields of gas and liquid phase. The shape feature for a rising bubble are studied with emphasis over a wide flow range with Eotvos number (O(0)~O(2)) and Morton number (O (-11)~O(2)). The bubble shape and rise velocity predicted by the simulation agree well with a well-known bubble regime diagram in the literature. The simulated results demonstrate that the shape of a rising bubble can be directly concerned with three dimensionless numbers (Eo, Mo and Re). It is also found that the bubble shows a periodical-shape oscillating behavior in a high Re region of the ellipsoidal regime.