Numerical Simulation of Quasi-Static Bubble Formation from a Submerged Orifice by the Axisymmetric VOSET Method

Abstract

In order to investigate the dynamics of quasi-static bubble formation from a submerged orifice, this paper developed an axisymmetric VOSET method with continuum surface force (CSF) model which can accurately capture the moving phase interface of gas-liquid flow. Test case shows that numerical results are in good agreement with experimental results from the literature. The effects of gas flow rate, orifice size, surface tension, contact angle, liquid density, and gravitational acceleration on bubble shape, departure time and departure volume are investigated and analyzed. It is found that increase in orifice size, surface tension, and contact angle results in the increase in the capillary force resisting bubble detachment, which leads to larger departure time and departure volume. But there is a critical contact angle, and contact angle has no significance effect on the process of bubble formation and detachment, when it is smaller than the critical value. Buoyancy force promoting bubble detachment increases with the increase of liquid density and gravitational acceleration, which results in smaller departure time and departure volume. Also, the forming process of the neck shape of bubble bottom at the bubble detachment stage is observed, and the results show that the position of the smallest part of the neck approximately equals to the orifice radius Rc.