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

Bruyn, Pieter De; Cardinaels, Ruth; Moldenaers, Paula

doi:10.1016/j.jcis.2013.07.058

Cited by 29 publications

(19 citation statements)

References 45 publications

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“…These sequences are similar to Fig. 2 of De Bruyn et al (2013), except that in Fig. 3 the viscosity ratio is 2.6 instead of 0.1.…”

Section: B Critical Initial Offset For Coalescencesupporting

confidence: 60%

“…11 for viscosity ratio 0.1 and 2.6. For offsets below the lower critical offset boundary, reversing trajectories occur, which have been attributed to the presence of reversing streamlines at the front and rear of confined droplet pairs [De Bruyn et al (2013)]. It can be seen that the shape of the trajectories is different for the different viscosity ratios.…”

Section: Effects Of Viscosity Ratiomentioning

confidence: 99%

“…Thus, confinement can clearly promote droplet coalescence. De Bruyn et al (2013) further explored the effects of geometrical confinement on the coalescence of droplet pairs by varying the initial offset between the droplet centers in the velocity gradient direction. For droplet pairs with a droplet-to-matrix viscosity ratio of 0.1, a new phenomenon of reversing trajectories for droplets with low initial offsets was demonstrated.…”

Section: Introductionmentioning

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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“…These sequences are similar to Fig. 2 of De Bruyn et al (2013), except that in Fig. 3 the viscosity ratio is 2.6 instead of 0.1.…”

Section: B Critical Initial Offset For Coalescencesupporting

confidence: 60%

Section: Effects Of Viscosity Ratiomentioning

confidence: 99%

Section: Introductionmentioning

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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“…8, have not yet been reported in the literature. However, the effect of geometrical confinement on the coalescence efficiency of droplet pairs in shear flow has been experimentally investigated by De Bruyn et al 41 These authors report an increase of the highest initial offset in the velocity gradient direction between the droplets leading to coalescence and hence an increase in the coalescence efficiency with confinement. Their results are thus in qualitative agreement with the aggregation diagram presented in Fig.…”

Section: B a Simplified Characterization Of Aggregate Formationmentioning

confidence: 99%

Lubrication analysis of interacting rigid cylindrical particles in confined shear flow

Cardinaels

Stone

2015

Physics of Fluids

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Lubrication analysis is used to determine analytical expressions for the elements of the resistance matrix describing the interaction of two rigid cylindrical particles in two-dimensional shear flow in a symmetrically confined channel geometry. The developed model is valid for non-Brownian particles in a low-Reynolds-number flow between two sliding plates with thin gaps between the two particles and also between the particles and the walls. Using this analytical model, a comprehensive overview of the dynamics of interacting cylindrical particles in shear flow is presented. With only hydrodynamic interactions, rigid particles undergo a reversible interaction with no cross-streamline migration, irrespective of the confinement value. However, the interaction time of the particle pair substantially increases with confinement, and at the same time, the minimum distance between the particle surfaces during the interaction substantially decreases with confinement. By combining our purely hydrodynamic model with a simple on/off non-hydrodynamic attractive particle interaction force, the effects of confinement on particle aggregation are qualitatively mapped out in an aggregation diagram. The latter shows that the range of initial relative particle positions for which aggregation occurs is increased substantially due to geometrical confinement. The interacting particle pair exhibits tangential and normal lubrication forces on the sliding plates, which will contribute to the rheology of confined suspensions in shear flow. Due to the combined effects of the confining walls and the particle interaction, the particle velocities and resulting forces both tangential and perpendicular to the walls exhibit a non-monotonic evolution as a function of the orientation angle of the particle pair. However, by incorporating appropriate scalings of the forces, velocities, and doublet orientation angle with the minimum free fraction of the gap height and the plate speed, master curves for the forces versus orientation angle can be constructed.

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“…Coalescence has been intensively studied both theoretically and experimentally (for polymer blends and low‐molecular weight emulsions) . Only some of related references are given, we are not able to mention all articles concerning coalescence.…”

Section: Introductionmentioning

confidence: 99%

Flow‐Induced Coalescence Involving Attractive Interparticle Forces

Jůza

Fortelný

2019

Macromolecular Symposia

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Coalescence is one of mechanisms of increasing average size of droplets dispersed in a matrix. Extensional‐flow‐induced coalescence where the motion can be described using two coordinates, distance and angle, and shear‐flow‐coalescence described in three dimensions have been studied. Unlike approaches in most of our previous papers where trajectories are solved as dependence of distance on angle or of distance and polar angle on azimuth, parallel integration of all spatial coordinates with respect to time is employed here, which allowed also more correct solution of coalescence including attractive forces. In contrast to previous studies, where interdroplet interaction is neglected till their close approach, this paper is based on the switch between equations describing hydrodynamic interactions between droplets at their moderate distance and equations for matrix drainage between close droplets. The results have been compared for zero and finite critical distance with and without considering van der Waals forces. For droplets keeping spherical shape during coalescence, non‐zero critical distance plays qualitatively the same role as attractive forces in calculation of collision. On the other hand, the critical distance cannot be omitted in models considering droplets flattening where the motion equations diverge for zero intersurface distance.

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

Cited by 29 publications

References 45 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

Lubrication analysis of interacting rigid cylindrical particles in confined shear flow

Flow‐Induced Coalescence Involving Attractive Interparticle Forces

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