Film drainage and interfacial instabilities in polymeric systems with diffuse interfaces

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

doi:10.1016/j.jcis.2005.08.062

Cited by 25 publications

(25 citation statements)

References 40 publications

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“…Therefore, the net cell contact area (the shaded area in Figure 3B) shows a maximum value as capillary number increases. It is noteworthy that dimple formation has been simulated in liquid droplets (Zinchenko and Davis, 2002), and observed in experiments (Horn et al, 2006;Zdravkov et al, 2006). Thus, it may represent a characteristic of deformable particles.…”

Section: Resultsmentioning

confidence: 87%

Shear modulation of intercellular contact area between two deformable cells colliding under flow

Jadhav

Chan

Κωνσταντόπουλος

et al. 2007

Journal of Biomechanics

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Shear rate has been shown to critically affect the kinetics and receptor specificity of cell-cell interactions. In this study, the collision process between two modeled cells interacting in a linear shear flow is numerically investigated. The two identical biological or artificial cells are modeled as deformable capsules composed of an elastic membrane. The cell deformation and trajectories are computed using the Immersed Boundary Method for shear rates of 100-400 s −1 . As the two cells collide under hydrodynamic shear, large local cell deformations develop. The effective contact area between the two cells is modulated by the shear rate, and reaches a maximum value at intermediate levels of shear. At relatively low shear rate, the contact area is an enclosed region. As the shear rate increases, dimples form on the membrane surface, and the contact region becomes annular. The nonmonotonic increase of the contact area with the increase of shear rate from computational results implies that there is a maximum effective receptor-ligand binding area for cell adhesion. This finding suggests the existence of possible hydrodynamic mechanism that could be used to interpret the observed maximum leukocyte aggregation in shear flow. The critical shear rate for maximum intercellular contact area is shown to vary with cell properties such as radius and membrane elastic modulus.

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Section: Resultsmentioning

confidence: 87%

Shear modulation of intercellular contact area between two deformable cells colliding under flow

Jadhav

Chan

Κωνσταντόπουλος

et al. 2007

Journal of Biomechanics

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“…Here, a so called coalescence bridge between the drops is built (Chen et al, 2004;Radoev et al, 1983;Scheludko et al, 1965;Vrij, 1966). From this 'hole' in the film the coalescence front extends rapidly across the contact area driven by the interfacial tension and coalescence of the two droplets occurs (Aarts et al, 2005;Zdravkov et al, 2006). According to these phases of the coalescence process, the crucial influencing factors are the contact time of the droplets, the drainage time of the film, the critical film thickness and the time of confluence.…”

Section: Introductionmentioning

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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“…Although our results are somewhat scattered, trends are clear. In an attempt to interpret them, two effects are considered that might help their explanation: (1) for partially immiscible blends, coalescence is drastically increased (Zdravkov et al 2006), which leads to large drops after a step-down in shear rate, (2) on the other hand, confinement of flows can cause phenomena like droplet ordering, string formation, etc. (Migler 2001;Pathak et al 2002;Pathak and Migler 2003;Tufano et al 2008a;Vananroye et al 2006).…”

Section: Pb In Pdmsmentioning

confidence: 99%

“…However, the thread-like structures can also survive for long periods of time, depending on the local degree of confinement (Son et al 2003). As an example, for the 10% PB/PDMS blend, it is known that partial miscibility is present between the phases that enhances the coalescence process dramatically (Zdravkov et al 2006); larger droplets are formed quicker, strengthening the confinement. (see Fig.…”

Section: Pb In Pdmsmentioning

confidence: 99%

Study of morphological hysteresis in partially immiscible polymers

et al. 2008

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The morphology evolution of two systems of partially immiscible polymers, differing in miscibility, is investigated by means of rheological experiments and optical microscopy. For each system, two concentrations, 10% and 20%, are used. For immiscible systems, a hysteresis zone, defined by coalescence and breakup, exists where the average drop radius is not a unique function of the shear rate. We investigate whether the findings also apply to partially immiscible polymers. The average radii at different shear rates, measured with rheology, are compared to model predictions. The hysteresis zone, if present, is indeed affected by the polymeric system, the concentration and the flow history applied. Coalescence evolution is measured for three different step-downs in shear rate. For both 10% systems, the resulting average radii show a rather high scattering and do not match the theoretical predictions. For the 20% concentrations, the average experimental drop sizes seem independent of the magnitude of the step-down, at least during a certain period of time. Thereafter, it experiences a sudden, in the time scale of the experiments unbounded, increase in size that is more pronounced for the higher step-downs. Deviations of the experimental data from theoretical predictions are attributed to the partially immiscible character of the systems, yielding enhanced coalescence which, in turn, can induce confinement effects.

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Film drainage and interfacial instabilities in polymeric systems with diffuse interfaces

Cited by 25 publications

References 40 publications

Shear modulation of intercellular contact area between two deformable cells colliding under flow

Shear modulation of intercellular contact area between two deformable cells colliding under flow

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

Study of morphological hysteresis in partially immiscible polymers

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