Modeling Film Drainage and Coalescence of Drops in a Viscous Fluid

Janssen, Pja Pieter; Anderson, Patrick Patrick

doi:10.1002/mame.201000375

Cited by 50 publications

(44 citation statements)

References 89 publications

(132 reference statements)

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“…Burkhart et al [24] showed that the theory of Rother and Davis [15] substantially improves the predictions of the coalescence kinetics as compared to the trajectory analysis. Due to continuous improvements in algorithms and computational power, numerical studies of droplet coalescence and film drainage are appearing [25][26][27]. By using a boundary-integral method, Yoon et al [27] were able to qualitatively match their experimental data for the critical -numbers and critical offsets for systems with a low viscosity ratio.…”

Section: 84mentioning

confidence: 99%

“…By using a boundary-integral method, Yoon et al [27] were able to qualitatively match their experimental data for the critical -numbers and critical offsets for systems with a low viscosity ratio. Nevertheless, there is still no consensus in literature on how to predict a realistic coalescence rate for a given flow type, capillary number and viscosity ratio [25].…”

Section: 84mentioning

confidence: 99%

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The effect of geometrical confinement on coalescence efficiency of droplet pairs in shear flow

Bruyn

Cardinaels

Moldenaers

2013

Journal of Colloid and Interface Science

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This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. 1The effect of geometrical confinement on coalescence efficiency of droplet pairs in shear flow AbstractDroplet coalescence is determined by the combined effect of the collision frequency and the coalescence efficiency of colliding droplets. In the present work, the effect of geometrical confinement on coalescence efficiency in shear flow is experimentally investigated by means of a counter rotating parallel plate device, equipped with a microscope. The model system consisted of Newtonian droplets in a Newtonian matrix. The ratio of droplet diameter to plate spacing ( ) is varied between 0.06 and 0.42, thus covering bulk as well as confined conditions. Droplet interactions are investigated for the complete range of offsets between the droplet centers in the velocity gradient direction. It is observed that due to confinement coalescence is possible up to higher initial offsets. On the other hand, confinement also induces a lower boundary for the initial offset, below which the droplets reverse during their interaction, thus rendering coalescence impossible.Numerical simulations in 2D show that the latter phenomenon is caused by recirculation flows at the front and rear of confined droplet pairs. The lower boundary is independent of , but increases with increasing confinement ratio and droplet size. The overall coalescence efficiency is significantly larger in confined conditions as compared to bulk conditions.

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Section: 84mentioning

confidence: 99%

Section: 84mentioning

confidence: 99%

The effect of geometrical confinement on coalescence efficiency of droplet pairs in shear flow

Bruyn

Cardinaels

Moldenaers

2013

Journal of Colloid and Interface Science

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“…Description of the matrix drainage is a self‐consistent problem due to inter‐droplet circulation and droplet deformation that affect rate of the droplet approach. Therefore, equations describing drainage of the matrix have only numerical solutions for realistic models of the droplet deformation even if Newtonian systems and simple geometry of collisions are considered . Only a limited number of theories of flow induced coalescence provide results applicable to evaluation of the phase structure evolution in flowing polymer blends …”

Section: Introductionmentioning

confidence: 99%

Flow‐Induced Coalescence in Polydisperse Systems

Fortelný

Jůza

2014

Macro Materials & Eng

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The theory of flow‐induced coalescence, based on the switch between the rates of approach of spherical and flattened droplets, is generalized to systems with different droplet radii. Probability, Pc, that the droplet collision will be followed by their fusion is calculated for systems containing droplets with two different droplet radii as a function of the average droplet radius. Analysis of the results obtained shows that Pc is a gradually decreasing function of the average droplet radius, 〈R〉 in broad range of 〈R〉 for systems with a large width of droplet radii distribution. The dependence of Pc for a polydisperse system should be considered also if experimentally determined average particle size is regarded as a result of the competition of the droplet breakup and coalescence in flowing polymer blends.

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“…For a detailed picture, see the review articles by Chesters 5 and Janssen and Anderson 10 and the references therein. The rate limiting step for coalescence in many cases is the drainage of suspending fluid from between the drops when they are in close contact.…”

Section: Introductionmentioning

confidence: 99%

A scaling relation for the capillary-pressure driven drainage of thin films

2013

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The effect of interfacial slip on the rheology of a dilute emulsion of drops for small capillary numbers J. Rheol. 56, 1555 (2012); 10.1122/1.4749836The effect of interfacial slip on the dynamics of a drop in flow: Part I. Stretching, relaxation, and breakup Hydrodynamic interactions between deformable particles such as drops or vesicles are an integral part of the rheology of emulsions and suspensions. In addition, the drainage of the thin film separating two colliding drops or vesicles is crucial for understanding the dynamics of coalescence or adhesion, which can lead to phase separation. However, despite several decades of study, this phenomenon is still not well understood and existing analytical theories do not agree quantitatively with experimental and numerical results. In this article, new scaling arguments are presented to analyze the drainage process, once the film becomes sufficiently thin. In particular, it is shown that the length over which the pressure varies in the film changes as the film drains, and follows a specific scaling relation. The mass balance in the film is then revisited in light of the new scaling for the pressure gradient. Numerical simulations are conducted to test the new scaling arguments and evaluate the revised mass balance. In the case of vesicles, they exhibit an excellent fit with the new scaling theory. The theory is also found to apply well to drops, but only when the flow inside the drops is determined predominantly by the flow in the thin film rather than by the ambient flow. C 2013 AIP Publishing LLC. [http://dx.

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Modeling Film Drainage and Coalescence of Drops in a Viscous Fluid

Cited by 50 publications

References 89 publications

The effect of geometrical confinement on coalescence efficiency of droplet pairs in shear flow

The effect of geometrical confinement on coalescence efficiency of droplet pairs in shear flow

Flow‐Induced Coalescence in Polydisperse Systems

A scaling relation for the capillary-pressure driven drainage of thin films

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