Numerical simulation of periodic bubble formation at a submerged orifice with constant gas flow rate

Extensive numerical simulations were carried out to study the problem of bubble formation at submerged orifices under constant inflow conditions. A combined volume-of-fluid and level-set method was applied to simulate the formation process, the detachment and the bubble rise above the orifice in axisymmetric coordinates. On the one hand, the operating conditions of the formation process such as orifice flow rate, orifice radius and wettability of the orifice plate were investigated for the working fluids of air and water at 20 °C. On the other hand, the influence of the variation of fluid properties (liquid density and viscosity, surface tension) was examined individually. In this frame, the present work focused on low and medium flow rate conditions, at which the formation takes place in a periodic manner, in contrast to aperiodic or double periodic modes. The results of the computations provide information on the influence of various conditions on the bubble shapes, the bubble volume and the transition from a single to a double periodic formation process. The numerical results were extensively validated with experimental data available in the literature.