Coalescence of two equal-sized deformable drops in an axisymmetric flow

Yoon, Yosang; Baldessari, Fabio; Ceniceros, Héctor D.; Leal, L. Gary

doi:10.1063/1.2772900

Cited by 105 publications

(131 citation statements)

References 44 publications

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“…They found that the drainage time increases and the critical capillary number decreases with increasing viscosity ratio. These observations were later confirmed by means of numerical simulations [Yoon et al (2007)]. Moreover, the effect of initial offset between the droplets in the velocity gradient direction was investigated.…”

Section: Introductionsupporting

confidence: 53%

“…It must be noted that according to this simple scaling the range of angles leading to a flat film is not that sensitive to changes in the Ca number and the viscosity ratio. However, simulations performed by Yoon et al (2007) showed that there are cases, depending on initial offset, viscosity ratio, and Ca number for which the film is always parabolic or parabolic for a considerable amount of time at high angles. Hence, it can be concluded that for a more accurate determination of the transition from a parabolic to a flat film, simulations of the full problem are necessary.…”

Section: Appendix: Film Shapementioning

confidence: 99%

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The effects of geometrical confinement and viscosity ratio on the coalescence of droplet pairs in shear flow

Bruyn

Chen

Moldenaers

et al. 2014

Journal of Rheology

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SynopsisThe effects of geometrical confinement and viscosity ratio on droplet coalescence in shear flow are experimentally investigated by means of a counter rotating parallel plate device, equipped with a microscope. The ratio of droplet diameter to gap spacing is varied between 0.03 and 0.33 to study both bulk and confined conditions. Three grades of a Newtonian droplet material are combined with a Newtonian matrix, resulting in three different viscosity ratios, namely, 0.1, 1.1, and 2.6. The effects of confinement are qualitatively similar for all three viscosity ratios. For each system, confinement decreases the coalescence angle and renders coalescence possible up to higher capillary numbers and initial offsets. Moreover, for all three viscosity ratios, confinement induces a lower initial offset boundary below which the approaching droplets reverse flow direction without coalescence. However, there are quantitative differences between the systems. With increasing viscosity ratio, the critical capillary number and critical upper and lower offset boundaries decrease. Since the decrease of the upper offset boundary is more predominant, the coalescence efficiency decreases with viscosity ratio. The droplet trajectories of interacting droplets are affected by both the viscosity ratio and geometrical confinement, which clearly has implications on the coalescence behavior. V C 2014 The Society of Rheology.

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Section: Introductionsupporting

confidence: 53%

Section: Appendix: Film Shapementioning

confidence: 99%

The effects of geometrical confinement and viscosity ratio on the coalescence of droplet pairs in shear flow

Bruyn

Chen

Moldenaers

et al. 2014

Journal of Rheology

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“…Key characteristics of thin films such as dimple formation [9][10][11] , wimple excitation 12 and dynamic force measurements [4][5][6][7] have been predicted with good quantitative agreement. However, a recent drop coalescence study using a microfluidic cell revealed "a counter-intuitive phenomenon: coalescence occurs during the separation phase and not during the impact" and "there is no model that describes this phenomenon" 13 .…”

mentioning

confidence: 84%

Dynamic deformations and forces in soft matter

2009

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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: 96%

“…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. 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: 96%

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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Coalescence of two equal-sized deformable drops in an axisymmetric flow

Cited by 105 publications

References 44 publications

The effects of geometrical confinement and viscosity ratio on the coalescence of droplet pairs in shear flow

The effects of geometrical confinement and viscosity ratio on the coalescence of droplet pairs in shear flow

Dynamic deformations and forces in soft matter

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

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