Numerical study on the interaction of two bubbles rising side-by-side in viscous liquids

The hydrodynamic interaction of two bubbles released from submerged orifices was simulated using a 3D front-tracking type technique called the Local Front Reconstruction Method (LFRM). The effects of fluid properties and orifice spacing on the bubble trajectory, the interaction between two bubbles, and the vortex shedding pattern were investigated. Different types of interaction behaviors, which were observed in experiments by Kong et al. (2019), could be replicated by varying the liquid viscosity. The simulation results revealed that bubbles at low Reynolds number repel each other because the diffusion of vorticity at the bubble surface is blocked and becomes asymmetric due to the presence of a neighboring bubble. In contrast, at medium and high Reynolds numbers, the bubbles attract each other after their detachment from the orifices, and their subsequent possible bouncing depends on the orifice spacing. The bubble pair will feature a zigzagging motion while rising when double-threaded vortices are generated behind the bubble.