Numerical study of co-axial bubble coalescence characteristics

Bubble coalescences have a significant role in petroleum and chemical industries for proper mixing, good heat and mass transfer between the gas and liquid phases. In this study, the volume of fluid method has been used to model for investigation of co-axial bubble coalescence dynamic evolution in stagnant fluid. The CSF method was incorporated as a source term in the momentum equation to track the motion of the bubble and liquid interface. The effects of Bond number ranges, Boq similar to 4.09-50 (variation of the surface tension) and Reynolds number range, Re similar to 0.98-120 (variation of the liquid viscosity) were investigated. Significant effects were observed in the process of bubble coalescence on the shape of bubbles when the viscosity ratio ((r)), and density ratio ((r)) were kept constant. The changes in bubble shape with progressing time were validated by the experimental observation of available literature. For low Bo and Re, the late coalescence of the bubbles was found, whereas the shape of the succeeding bubbles had changed significantly. The same ratio of Bo/(r) and Bo/Re does not affect the bubble coalescence process, if Bo, (r) and Re is reduced to 82%. By the study of co-axial coalescence of three bubbles, it is found that the liquid-film rupture and bubble breakup between the middle and third bubble occurs faster for both low and high Re. (c) 2015 Curtin University of Technology and John Wiley & Sons, Ltd.