Computational modeling of gas-bubble formation through a single submerged orifice

A two-dimensional numerical simulation is carried out to analyze the dynamics of gas-bubble formation from a single submerged orifice in an immiscible Newtonian liquid under the condition of constant gas inflow rate using a finite volume based commercial Computational Fluid Dynamics (CFD) solver ANSYS Fluent. Two conditions for the ambi- ent liquid are considered, namely the liquid in quiescent condition and the liquid as a co-flowing stream with the gas. The full cycle from bubble formation to its detachment and the corresponding dynamics are simulated by using both the Volume of Fluid method (VOF) and Coupled Level Set and Volume of Fluid method (CLSVOF). Although both are front capturing techniques of Eulerian family, they possess some distinct properties in themselves. The CLSVOF method combines the advantages of the level set method with that of the Volume of Fluid method. It is observed that the CLSVOF method is more successful in predicting the interface sharpness in comparison to the VOF method only. The study includes: (i) time sequence profile of bubble formation to clearly represent bubble growth, neck formation, and bubble breakup at given Weber (We), Reynolds (Re), Bond (Bo) numbers, and liquid to gas mean velocity ratio (vr); (ii) bubble growth history for different vr and at constant Re,We, and Bo; (iii) comparison between results obtained by VOF and CLSVOF at given vr, We, Re, and Bo; and (iv) bubble size and bubble formation time, and finally the bubble coalescence phenomenon and technique for its inhibition. © 2017 by Begell House, Inc.