Towards the understanding of bubble-bubble interaction upon formation at submerged orifices: A numerical approach

•We present the bubble-bubble interaction patterns when emerged from submerged orifices.•Three distinct patterns of bubble release dependent on mutual spacing of the orifices are reported.•Hydrodynamic reasons of different merging regimes are described using velocity vectors around the bubbles.•A map of different zones as a function of Mo, orifice diameter and spacing has been proposed.•Effect of van der Waals force has been established in connection of bridge thinning by virtue of gas inertia.

Present study reports numerical investigations on the bubble evolution at submerged orifices and their mutual interactions in quiescent liquid under constant inflow condition of air. In finite volume based 3D domain, breaking and making of interfaces are tracked using volume of fluid (VOF) solver. Binary interaction dynamics is studied for a wide range of fluid properties (3.85 × 10−11 < Mo < 4.645 × 10−6), orifice diameters (1, 1.5 and 2 mm) and spacings (2-10 mm). Apart from observed coalescence and non-coalescence, fusion of bubbles before and after pinch off from orifice mouth at different Mo are presented. Using velocity patterns inside the bubble, explanation of different merging pattern is proposed. A 3D map for distinct behaviour while merging, in terms of Mo, orifice diameter and spacing is also tried. Finally, effect of velocity of gaseous phase on merging between sister bubbles are assessed numerically.