Film drainage between two captive drops: PEO–water in silicon oil

Zdravkov, AN Alexander; Peters, Gwm Gerrit; Meijer, Heh Han

doi:10.1016/s0021-9797(03)00466-1

Cited by 29 publications

(25 citation statements)

References 26 publications

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“…(14)] is much larger than the pressure drop caused by interfacial tension p ∼ λ/ D and dominates the film drainage process. Before this (t < 0.8, say), the drainage can be approximately described by a power-law: h min ∝ t −0.8 , which is somewhat faster than the Newtonian scaling h min ∝ t −2/3 predicted by lubrication theory for "partially mobile" interfaces [19]. In this power-law regime, our value of h min is within 20% of the Newtonian prediction.…”

Section: Role Of Viscoelasticity In Coalescencesupporting

confidence: 56%

“…The thinning of this film, via the drainage of the matrix fluid through the narrowing conduit, determines the time scale of coalescence. The drainage requires a high pressure in the middle of the film, which produces a "dimpled shape" for the interface [19], with the minimum film thickness not at the middle point but farther out toward the sides. Rupture of the film at those locations traps a filament of the matrix fluid inside the resultant large drop.…”

Section: Drop Coalescence After Head-on Collisionmentioning

confidence: 99%

“…In contrast, we have found only two experimental studies that used polymer solutions. Zdravkov et al [19] measured the minimum film thickness as a function of time during coalescence between two viscoelastic drops in a Newtonian matrix. Perhaps because of adsorption of polymer molecules on the interface, the drops are to a large extent immobilized.…”

Section: Role Of Viscoelasticity In Coalescencementioning

confidence: 99%

See 2 more Smart Citations

Diffuse-interface simulations of drop coalescence and retraction in viscoelastic fluids

Yue

Feng

et al. 2005

Journal of Non-Newtonian Fluid Mechanics

130

111

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Drop dynamics plays a central role in defining the interfacial morphology in two-phase complex fluids such as emulsions and polymer blends. In such materials, the components are often microstructured complex fluids themselves. To model and simulate drop behavior in such systems, one has to deal with the dual complexity of non-Newtonian rheology and evolving interfaces. Recently, we developed a diffuse-interface formulation which incorporates complex rheology and interfacial dynamics in a unified framework. This paper uses a twodimensional implementation of the method to simulate drop coalescence after head-on collision and drop retraction from an elongated initial shape in a quiescent matrix. One of the two phases is a viscoelastic fluid modeled by an Oldroyd-B equation and the other is Newtonian. For the parameter values examined here, numerical results show that after drop collision, film drainage is enhanced when either phase is viscoelastic and drop coalescence happens more readily than in a comparable Newtonian system. The last stage of coalescence is dominated by a short-range molecular force in the model that is comparable to van der Waals force. The retraction of drops from an initial state of zero-velocity and zero-stress is hastened at first, but later resisted by viscoelasticity in either component. When retracting from an initial state with pre-existing stress, produced by cessation of steady shearing, viscoelasticity in the matrix hinders retraction from the beginning while that in the drop initially enhances retraction but later resists it. These results and the physical mechanisms that they reveal are consistent with prior experimental observations.

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Section: Role Of Viscoelasticity In Coalescencesupporting

confidence: 56%

Section: Drop Coalescence After Head-on Collisionmentioning

confidence: 99%

Section: Role Of Viscoelasticity In Coalescencementioning

confidence: 99%

See 1 more Smart Citation

Diffuse-interface simulations of drop coalescence and retraction in viscoelastic fluids

Yue

Feng

et al. 2005

Journal of Non-Newtonian Fluid Mechanics

130

111

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“…Furthermore, a high purity of the fluids is mandatory, as already minor impurities may have a significant impact on the properties of the interface and consequently on the coalescence process (Soika and Pfennig, 2005;Wegener et al, 2009). Published values for the critical film rupture thickness differ from tens (Radoev et al, 1983;Vrij, 1966) to hundreds of nanometres (Zdravkov et al, 2003) although theoretical examination predicts a range of around 1 nanometre (Chesters, 1991;Vrij, 1966). The time span of confluence of the two droplets (or film rupture time) varies from hundreds of microseconds to milliseconds (Aryafar and Kavehpour, 2006;Thoroddsen et al, 2005) whereas the drainage time (or contact time) of the film between two interfaces, which has to elapse for coalescence to occur, has a broad distribution from milliseconds (Sagert and Quinn, 1978;Scheele and Leng, 1971) over seconds (Vijayan and Ponter, 1975) to infinity for stable emulsions (Carroll, 1976).…”

mentioning

confidence: 99%

Influence of drop size and superimposed mass transfer on coalescence in liquid/liquid dispersions – Test cell design for single drop investigations

Kamp¹,

Kraume²

2014

Chemical Engineering Research and Design

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Postprint: Kamp, J. & Kraume, M.: Influence of drop size and superimposed mass transfer on coalescence in liquid/liquid dispersions -Test cell design for single drop investigations, Chem. Eng. Res. Des., Elsevier, 2014, 92, 635-643 http://dx.doi.org/10.1016/j.cherd.2013 1 Influence of drop size and superimposed mass transfer on coalescence in liquid/liquid dispersions -Test cell design for single drop investigationsJohannes Kamp a *, Matthias Kraume a a Chair of Chemical & Process Engineering, Technische Universität Berlin, FH 6-1, Fraunhoferstr. 33-36, 10587 Berlin * Corresponding author, e-mail: johannes.kamp@tu-berlin.de, phone: +49 30 314 23171 The detailed understanding of droplet coalescence is important for the accurate description of liquid/liquid dispersions. A test cell is designed which enables serial examinations of the random coalescence process with high repetition rate, good observability and accuracy of experimental parameters. Within this rectangular test cell a rising droplet collides with a pendant one, while recorded by a high speed camera. The gained experimental data allows a validation and further development of appropriate models. The investigated parameters in this work are the drop size and the superimposed mass transfer influencing the coalescence probability. These examinations were carried out in the EFCE standard test system toluene / acetone / water. The effect of varying the drop size seems to be interfered by the different rising velocities due to buoyancy. Introducing a transferring component has a significant impact on the coalescence process. A transfer direction from disperse to continuous phase results in a coalescence probability of almost 100%, whereas the reverse mass transfer direction induces a repulsion of nearly all droplets. Keywords coalescence; test cell; single drop; mass transfer; drop size; coalescence probability IntroductionDispersions of at least two liquids showing a miscibility gap are an integral part of several unit operations. Therefore, a detailed understanding and quantitative description of the characteristics and conditions of these systems is important for various technical applications. The most important characteristic of an emulsion is the drop size distribution which affects e.g. the interfacial area and settling time. The drop size distribution is determined by the phenomena breakage and coalescence of single droplets. Thus, these interactions determine the macroscopic behaviour of an emulsion directly. Although various models are available in literature for both phenomena Lucas, 2010, 2009), the prediction of the drop size distribution is only possible with restrictions when varying for example the power input or material and process conditions. Consequently, excessive and expensive experimental investigations are still necessary at different scales for process development. For instance, the design of extraction columns still requires pilot plants using high amounts of the original physical system. To diminish the number of influencing...

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“…1 illustrates the head-on collision and subsequent coalescence of two Newtonian drops in a Newtonian matrix. The draining film develops a "dimple" in the middle [61] and the rupture occurs toward the outside of the film, trapping some matrix fluid inside.…”

mentioning

confidence: 99%

An Energetic Variational Formulation with Phase Field Methods for Interfacial Dynamics of Complex Fluids: Advantages and Challenges

Feng

Shen

et al.

Modeling of Soft Matter

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Abstract. The use of a phase field to describe interfacial phenomena has a long and fruitful tradition. There are two key ingredients to the method: the transformation of Lagrangian description of geometric motions to Eulerian description framework, and the employment of the energetic variational procedure to derive the coupled systems. Several groups have used this theoretical framework to approximate Navier-Stokes systems for two-phase flows. Recently, we have adapted the method to simulate interfacial dynamics in blends of microstructured complex fluids. This review has two objectives. The first is to give a more or less self-contained exposition of the method. We will briefly review the literature, present the governing equations and discuss a numerical scheme based on different numerical schemes, such as spectral methods. The second objective is to elucidate the subtleties of the model that need to be handled properly for certain applications. These points, rarely discussed in the literature, are essential for a realistic representation of the physics and a successful numerical implementation. The advantages and limitations of the method will be illustrated by numerical examples. We hope that this review will encourage readers whose applications may potentially benefit from a similar approach to explore it further.

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Film drainage between two captive drops: PEO–water in silicon oil

Cited by 29 publications

References 26 publications

Diffuse-interface simulations of drop coalescence and retraction in viscoelastic fluids

Diffuse-interface simulations of drop coalescence and retraction in viscoelastic fluids

Influence of drop size and superimposed mass transfer on coalescence in liquid/liquid dispersions – Test cell design for single drop investigations

An Energetic Variational Formulation with Phase Field Methods for Interfacial Dynamics of Complex Fluids: Advantages and Challenges

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