Coalescence and rising behavior of co‐axial and lateral bubbles in viscous fluid: a CFD study

Bubble breakup is a common in the multiphase flow, and the breakup result will influence the performance of the gas-liquid reactor, in which liquid jetting is a typical way in breaking the bubble. In present work, based on the comparison with the experimental results, large eddy simulation and volume of fluid method are coupled to simulate processes of the deformation and breakup of a single bubble in the liquid jet flow. The trajectory of mother bubble, number of daughter bubbles, variation of bubble surface area, and the forces acting on the bubble surface were analyzed. It was found that the shear force at the bubble neck was significantly larger compared with that in the stage of undeformed, and the critical condition for bubble breakup was when the total turbulent pressure on bubble surface was greater than the surface force of bubble. Based on the velocity difference on the upstream and downstream of the bubble, a modified critical Weber number was proposed for a better description of the breakup condition of the single bubble in the liquid jet flow.

Section: Introductionmentioning

confidence: 81%

Single bubble breakup in the flow field induced by a horizontal jet—The numerical simulation

Cao

Huang

et al. 2019

“…For computation, the glycerine solution is selected as the viscous liquid phase, and the air is used as the gas phase. The properties of glycerine solution (80% glycerine + 20% water) are as follows: density, ρ L = 1,205 kg/m 3 ; viscosity, μ L = 0.075 Pa·s; and surface tension, σ = 0.064 N/m.…”

Section: Cfd Modelmentioning

confidence: 99%

A numerical study of single air bubble formation comparison between in viscous liquid and in water

Islam

Ganesan

Billah

et al. 2019

Self Cite

The performance of bubble column reactors is dependent on bubble size that is formed through a sparger. Here, a single air bubble formation (BF) using an orifice in the viscous liquid is modeled by using the volume of fluid method. The interface between the air and the liquid phase is calculated by using the continuum surface force equation. Detailed characteristics of BF such as the instantaneous contact angle, bubble departure volume, bond number due to orifice size and surface tension, and capillary number are examined for different orifice sizes at constant air flow rate boundary condition. The numerical results are validated with available correlation and experimental data for orifice bond number reported in the literature. A comparison of BF characteristics between in the viscous liquid and in the water is examined. The instantaneous contact angle decreases steeply for the orifice with small size than a large orifice. The bubble volume increases with increasing contact angle and decreasing the orifice bond number. In comparison with water, a decreasing detachment time and dome width of bubble and an increasing bubble neck elongation are found in viscous liquid and decrease with increasing bond number. Moreover, there is a minimum capillary number, where the bubble neck elongation height and breakup processes are relatively fast. This study can helpful in designing a coarse gas sparger to develop pseudo‐homogeneous bubbly flow regime at lower superficial gas velocity conditions.

“…QUICK schemes are based on a weighted average of second‐order‐upwind and central interpolations of the variable. To get a rapid convergence without a significant reduction on accuracy and stability for transient problems, the pressure implicit with splitting operators algorithm is adopted for the pressure–velocity coupling . An implicit body force treatment is included to promote the convergence by accounting for the partial equilibrium of the pressure gradient and body forces in the momentum equations.…”

Section: Numerical Aspectsmentioning

confidence: 99%

Interaction of two differently sized bubbles in a viscous liquid

Zhang

Chen

You

et al. 2018

Interaction of two in-line bubbles with different size in a viscous liquid is studied using volume-of-fluid method. Simulations are performed on initially spherical bubbles starting from rest. The influences of size ratio 0.5 ≤ R ≥ 1 and initial distance ratio 1.7 ≤ S ≥ 3 are investigated with fixed Eötvös number Eo = 50, Galilei number Ga = 100, density ratio η = 1,000, and viscosity ratio λ = 100. Two arrangement patterns are considered, the small-big arrangement (SBA) and big-small arrangement (BSA). Two distinct evolution regimes are defined: coalescence and penetration. The bubble-bubble interaction is intensified by increasing R and decreasing S, promoting the possibility of coalescence. Penetration is more prone to occur in BSA than in SBA, and it is absent in BSA when R ≤ 0.625 regardless of S. The ascending velocity of the leading bubble (LB) is nearly independent of size ratio, initial distance ratio, and arrangement pattern, since the motion of the LB is little influenced by the trailing bubble (TB). Meanwhile, the ascending velocity of the TB increases with increasing R and decreasing S. The LB usually plays a dominant role in the interaction, especially in BSA.KEYWORDS arrangement pattern, bubble-bubble interaction, initial distance ratio, size ratio, VOF