Interaction of a pair of horizontally aligned bubbles in gravity field

Both large deformation and strong discontinuity problems exist in the process of bubble-bubble interaction. The lattice Boltzmann method which is based on the microscopic level has naturally comparative advantage to describe tiny changes in multiphase flow system. A three-dimensional lattice Boltzmann (LB) model of two horizontally aligned bubbles is presented to explore the bubble movement, topological transformation and bubbles interaction characteristics. In this model, the viscous effect is easily considered, and surface tension effect is realized by introducing a discrete LB body force term. To provide a reference, the isolated bubble dynamics driven by gravity is simulated firstly, and the surface tension effect is studied. Then the effect of gap distance and interface width on the coalescence of two stable bubbles is discussed. Finally, the interaction of two horizontal bubbles with different size ratio in gravity field is explored carefully. The results not only show the detailed coupling and coalescence process of two rising bubbles, but expose that the relative size ratio plays an important role in the interaction. The opposite phenomenon can be seen. When bubbles are of different size, the coalescence phenomenon will happen, but when they are in the same size, the rejection phenomenon will replace it.