Numerical study of co‐axial bubble coalescence characteristics

Abstract

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, Bo~4.09-50 (variation of the surface tension) and Reynolds number range, Re~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 (μ r ), and density ratio (ρ 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/μ r and Bo/Re does not affect the bubble coalescence process, if Bo, μ 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. Figure 4. Predicted two co-axial bubble coalescence for (a) Re = 12, Bo = 50, r = 1000, r = 100 (Case 2) and (b) Re = 10, Bo = 50, r = 850, r = 100 (Chen et al. [16] ).Asia-Pacific Journal of Chemical Engineering NUMERICAL STUDY OF CO-AXIAL BUBBLE COALESCENCE 675 Bo = 5 ; (1st) Bo = 5 ; (2nd) Bo = 5 ; (3rd) Bo = 50 ; (1st) Bo = 50 ; (2nd) Bo = 50 ; (3rd) Figure 9. Effect of Bond number on three co-axial bubble rising history for Re = 12, r = 1000 and r = 100. Figure 10. Predicted three co-axial bubbles coalescence for r = 1000 and r = 100. (a) Re = 1.2, Bo = 50. (b) Re = 120, Bo = 50. MD. T. ISLAM ET AL. Asia-Pacific Journal of Chemical Engineering 678

Interaction of two differently sized bubbles in a viscous liquid

“…Figure displays the shape evolution, together with the numerical prediction in Islam et al and the experimental observation in Manasseh et al As computation starts, bubbles become ellipsoidal because of the pressure difference between the top and bottom surfaces. A liquid jet is generated by a circulation of liquid around the bubble, pushing the bottom surfaces of bubbles.…”

“…Besides, the detachment of satellite bubble is not predicted by the coarse mesh. Therefore, a mesh density of 80 cells/ d o is employed in this work, which has a much finer grid resolution than many previous numerical studies . In addition, based on a temporal convergence study, a dimensionless time step of Δ t = 1 × 10 −4 is adopted thereafter, which is comparable to that in Chakraborty et al…”

“…A validation test concerning two equal‐sized, coaxial bubbles is performed. The conditional parameters are Eo = 5, Ga = 12, and S = 2.36, which has been simulated by Chen et al and Islam et al…”

“…Following Chen et al, Hasan and Zakaria pointed out that the coalescence process is governed by Eo / Ga under fixed η and λ . On the basis of the studies of Chen et al and Hasan and Zakaria, Islam et al further argued that the bubble coalescence time can be estimated by Eo / λ and Eo / Ga .…”

Methane bubble formation and dynamics in a rectangular bubble column: A CFD study

“…The state of bubble development changes with the alteration in bubble terminal velocity, coalescence and break-up of bubbles [15][16][17][18][19][20]. The air bubble dynamics i.e., bubble shapes, bubble terminal velocity, the wake structure of bubble and coalescence of two and three bubbles in a bubble column filled with different quiescent liquid e.g., water, glycerol-water solution have been extensively studied [21][22][23][24].…”