Clustering in high Re monodispersed bubbly flows

Figueroa-Espinoza, Bernardo; Zenit, Roberto

doi:10.1063/1.2055487

Cited by 35 publications

(25 citation statements)

References 12 publications

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“…Although this experiment is not the same as our surfactant-contaminated one, the similarity between these experiments is the two-dimensional structure of rising bubbles. In the case of Figueroa-Espinoza & Zenit (2005), the thinness of the channel constrains the bubble motions in a plane, while in our experiment it is the lift force that sustains the two-dimensional structure near the wall. In both cases, these geometric constraints seem to be an important factor for the horizontal bubble clustering.…”

Section: Resultsmentioning

confidence: 96%

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The effects of surfactant on the multiscale structure of bubbly flows

Takagi¹,

Ogasawara²,

Matsumoto³

2008

Phil. Trans. R. Soc. A.

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It is well known that a bubble in contaminated water rises much slower than one in purified water, and the rising velocity in a contaminated system can be less than half that in a purified system. This phenomenon is explained by the so-called Marangoni effect caused by surfactant adsorption on the bubble surface. In other words, while a bubble is rising, there exists a surface concentration distribution of surfactant along the bubble surface because the adsorbed surfactant is swept off from the front part and accumulates in the rear part by advection. Owing to this surfactant accumulation in the rear part, a variation of surface tension appears along the surface and this causes a tangential shear stress on the bubble surface. This shear stress results in the decrease in the rising velocity of the bubble in contaminated liquid. More interestingly, this Marangoni effect influences not only the bubble's rising velocity but also its lateral migration in the presence of mean shear. Together, these influences cause a drastic change of the whole bubbly flow structures. In this paper, we discuss some experimental results related to this drastic change in bubbly flow structure. We show that bubble clustering phenomena are observed in an upward bubbly channel flow under certain conditions of surfactant concentrations. This cluster disappears with an increase in the concentration. We explain this phenomenon by reference to the lift force acting on a bubble in aqueous surfactant solutions. It is shown that the shear-induced lift force acting on a contaminated bubble of 1 mm size can be much smaller than that on a clean bubble.

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Section: Resultsmentioning

confidence: 96%

“…One more thing should be mentioned related to the work of Figueroa-Espinoza & Zenit (2005). They used a very thin channel and observed the horizontal clustering of bubbles.…”

Section: Resultsmentioning

confidence: 99%

The effects of surfactant on the multiscale structure of bubbly flows

Takagi¹,

Ogasawara²,

Matsumoto³

2008

Phil. Trans. R. Soc. A.

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“…At face value, this might also appear to be a reasonable assumption. However, as noted earlier, rising plane waves (which are very difficult to measure experimentally due to the inability to ''look inside'' the flow 1,23,24 ) can also be considered ''homogeneous'' flow. Thus, it is difficult at best to judge the applicability of one-dimensional models to bubblecolumn flows, and the relative importance of the various modifications (such as accounting for bubble deformation or turbulent transport due to ''large-scale'' turbulent fluctuations) that have been suggested to bring them closer to experiments.…”

Section: Introductionmentioning

confidence: 97%

Effect of model formulation on flow‐regime predictions for bubble columns

Monahan

Fox

2006

AIChE Journal

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“…The model of elastic collision among contacting bubbles, which is derived under the potential flow assumption, results in a formation of horizontal bubble clusters (Sangani and Didwania, 1993;Smereka, 1993). The horizontal clusters are observed experimentally (Zenit et al, 2001;Figueroa-Espinoza and Zenit, 2005;Takagi et al, 2008) by adding a small amount of electrolyte or surfactant in order to reduce the bubble coalescence. In the usual bubble column, however, coalescence frequency occurs.…”

Section: Introductionmentioning

confidence: 99%

Motion and coalescence of a pair of bubbles rising side by side

Sanada¹,

Sato²,

Shirota³

et al. 2009

Chemical Engineering Science

119

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Bouncing and coalescence of a pair of slightly deformed bubbles rising side by side in a quiescent liquid are experimentally studied. The trajectories and shapes of the bubbles are investigated in detail by using a high-speed video camera. The wakes of bubbles are visualized by using a photochromic dye that is colored with UV light irradiation. We observe that the patterns of the trajectories of rising bubbles are strongly dependent on the Reynolds number. When the Reynolds number is over the critical region, two bubbles approach each other and then collide. After the collision, two types of motions are observed-coalescence and bouncing. We investigate the critical Reynolds number and Weber number over which the bubbles bounce. In the definitions of these numbers, we use vertical velocity, instead of horizontal one, as the characteristic velocity. We clarify that the critical Weber number is around 2 regardless of the Morton number. The critical Reynolds number decreases with an increase in the Morton number. Moreover, the visualization of the wake of bubbles enables us to observe the vortex separation from the rear surface of the bubbles on collision. We find that the vortex separation from the rear of bouncing bubbles causes a decrease in the rising velocity and an increase in the horizontal speed after their collision. We also observe that the behavior of repeatedly bouncing bubbles is significantly influenced by the wake instability of a single bubble rather than by the bubble-bubble interaction.By applying an existing model for spherical bubble-bubble interaction, we clarify that the revised model accurately describes the trajectory of a pair of slightly deformed bubbles using the restitution coefficient and velocity fluctuation from the experimental results.

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Clustering in high Re monodispersed bubbly flows

Cited by 35 publications

References 12 publications

The effects of surfactant on the multiscale structure of bubbly flows

The effects of surfactant on the multiscale structure of bubbly flows

Effect of model formulation on flow‐regime predictions for bubble columns

Motion and coalescence of a pair of bubbles rising side by side

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