Critical conditions and breakup of non-squashed microconfined droplets: effects of fluid viscoelasticity

Cardinaels, Ruth; Moldenaers, Paula

doi:10.1007/s10404-010-0743-8

Cited by 20 publications

(14 citation statements)

References 44 publications

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“…The effect is larger in presence of a larger confinement ratio. In particular, in agreement with some recent experiments [31], we have found that the formation of multiple neckings, which is acknowledged as a distinctive feature of confined break-up [11,14], is also affected by the presence of viscoelasticity: it visibly changes as soon as the ratio of fluid relaxation time to droplet emulsion time (i.e. the Deborah number) becomes of the order of 1.…”

Section: Discussionsupporting

confidence: 92%

“…3-7. First, it is evident that viscoelasticity has a stabilizing effect on droplet break-up [16][17][18][19][20][21][22][23][24][25], with a larger effect in presence of a larger confinement ratio [31]. Second, the formation of multiple neckings -a distinctive feature of break-up of confined droplets -is also affected by the presence of viscoelasticity.…”

Section: Effects Of Droplet Viscoelasticity On Critical Capillarymentioning

confidence: 99%

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Deformation and breakup of viscoelastic droplets in confined shear flow

Gupta

Sbragaglia

2014

Phys. Rev. E

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The deformation and break-up of Newtonian/viscoelastic droplets are studied in confined shear flow. Our numerical approach is based on a combination of lattice-Boltzmann models (LBM) and finite difference schemes, the former used to model two immiscible fluids with variable viscous ratio, and the latter used to model the polymer dynamics. The kinetics of the polymers is introduced using constitutive equations for viscoelastic fluids with finitely extensible non-linear elastic dumbbells with Peterlin's closure (FENE-P).We quantify the droplet response by changing the polymer relaxation time τ P , the maximum extensibility L of the polymers, and the degree of confinement, i.e. the ratio of the droplet diameter to wall separation. In unconfined shear flow, the effects of droplet viscoelasticity on the critical Capillary number Ca cr for breakup are moderate in all cases studied. However, in confined conditions a different behaviour is observed: the critical Capillary number of a viscoelastic droplet increases or decreases, depending on the maximum elongation of the polymers, the latter affecting the extensional viscosity of the polymeric solution. Force balance is monitored in the numerical simulations to validate the physical picture.

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Section: Discussionsupporting

confidence: 92%

Section: Effects Of Droplet Viscoelasticity On Critical Capillarymentioning

confidence: 99%

Deformation and breakup of viscoelastic droplets in confined shear flow

Gupta

Sbragaglia

2014

Phys. Rev. E

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“…The two mechanisms can be distinguished because the equilibrium mechanism leads to binary droplet breakup with two daughter droplets whereas the transient mechanism via threads formation is characterized by multiple droplet breakup into smaller droplets. [20a,23] The dynamics of droplet breakup is further influenced by the presence of surfactants.…”

Section: Resultsmentioning

confidence: 99%

STED Analysis of Droplet Deformation during Emulsion Electrospinning

Kaltbeitzel

Friedemann

Turshatov

et al. 2017

Macromol. Chem. Phys.

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The shape and size distribution of polystyrene (PS) compartments formed during emulsion electrospinning in a poly(vinyl alcohol) fiber is investigated. Stimulated emission depletion microscopy is employed to image the compartments with subdiffraction (super) resolution. The size distribution of the emulsion droplets in the spinning solution emulsions is found to be the key factor for fiber and compartment morphology. By varying the emulsification method, it is demonstrated that fibers spun from miniemulsions are characterized by a homogeneous distribution of PS compartments with no indication for coalescence or breakup of PS droplets. Coarse emulsions are prone to develop fiber instabilities associated with large PS domains. The domains are irregularly distributed in the fiber. Above a critical size of domains, breakup of these domains in two daughter domains is observed. The size dependence of the emulsion droplet breakup is explained by fluid dynamics.

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“…For viscosity ratios below one, confinement suppresses breakup, whereas for viscosity ratios above one, breakup is promoted by confinement [Vananroye et al (2006)]. Furthermore, Cardinaels and Moldenaers (2011) studied the combined effect of confinement and viscoelasticity of one of the components. They found that droplet breakup in confined shear flow is also strongly dependent on the viscoelasticity of the components.…”

Section: Introductionmentioning

confidence: 99%

“…They found that droplet breakup in confined shear flow is also strongly dependent on the viscoelasticity of the components. More specifically, in confinement matrix viscoelasticity causes breakup at much lower critical Ca numbers as compared to that for droplets in a Newtonian matrix, whereas the viscoelastic effects in bulk conditions were limited [Cardinaels and Moldenaers (2011)]. …”

Section: Introductionmentioning

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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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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Critical conditions and breakup of non-squashed microconfined droplets: effects of fluid viscoelasticity

Cited by 20 publications

References 44 publications

Deformation and breakup of viscoelastic droplets in confined shear flow

Deformation and breakup of viscoelastic droplets in confined shear flow

STED Analysis of Droplet Deformation during Emulsion Electrospinning

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

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