Abstract: The process of bubble formation is involved in a lot of gas-liquid reactors and process equipment.It is therefore important to understand bubble formation process and to develop computational models for the accurate prediction of the bubble formation characteristics in different bubbling regimes.Numerical simulation of bubble formation cycle on orifice were carried out using the combined level set and volume-of-fluid method and the predictions were experimentally validated,Effects of gas flow rate and orifice diameter on the bubbling regimes were discussed.Based on the simulation data and experimental data on the transition of bubble formation regimes,Froude and Bond numbers,the inlet gas velocity at orifice decreases with increase in the orifice diameter is presented.