An experimental and numerical investigation of the dynamics of microconfined droplets in systems with one viscoelastic phase

Cardinaels, Ruth; Afkhami, Shahriar; Renardy, Yuriko; Moldenaers, Paula

doi:10.1016/j.jnnfm.2010.10.005

Cited by 22 publications

(20 citation statements)

References 53 publications

(121 reference statements)

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“…As a consequence of the symmetry, the streamlines coming from the left and right show the same behavior. Similar large recirculation zones at the front and rear of a droplet were already reported from 3D numerical simulations of the flow field around a single highly confined droplet [46]. This large recirculation zone, present in confined conditions, causes the offset to decrease during approach of the droplets, as can be seen in Fig.…”

Section: δX/2r (-)supporting

confidence: 83%

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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Section: δX/2r (-)supporting

confidence: 83%

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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“…From numerical simulations for droplets that have attained a steady state shape in a subcritical shear flow, it is known that the viscoelastic stresses in and around the droplet increase with confinement whereas their location remains approximately the same. [33] For an unbounded viscoelastic droplet close to breakup, Verhulst et al [38] have shown that during elongation of the droplet, the viscoelastic stresses in the droplet shift from the droplet tips toward the thinning center of the droplet, thereby stabilizing it against necking. This is schematically depicted in Figure 6a.…”

Section: Comparison Of the Effects Of Component And Interfacial Rheologymentioning

confidence: 99%

“…Although theoretical and numerical studies of droplet dynamics that take into account one of the aforementioned complexities are readily available (see for instance [20,[28][29][30][31][32] and references therein), a limited amount of numerical studies consider their combined effects. [25,26,33,34] Concerning droplet breakup, no results are available in this respect, neither from experimental nor from numerical studies.…”

Section: Introductionmentioning

confidence: 99%

Breakup Criteria for Confined Droplets: Effects of Compatibilization and Component Viscoelasticity

Cardinaels

Vananroye

Puyvelde

et al. 2011

Macro Materials & Eng

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The breakup of confined droplets was studied systematically for systems with either interfacial or component viscoelasticity. The former was obtained by adding a compatibilizer, the latter by using a viscoelastic fluid as the droplet or as the matrix phase. The critical capillary numbers of Newtonian and compatibilized droplets showed a similar increase with increasing confinement ratio. However, a decrease in breakup length was observed in the compatibilized case, caused by the viscoelastic interface. Viscoelastic droplets experienced more stabilization by confinement compared to Newtonian droplets. Matrix viscoelasticity, on the other hand, induced a destabilization with a minimum in critical capillary number as a function of confinement ratio, resulting from a complex interplay of viscoelastic stresses. magnified image

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“…Verhulst et al and Cardinaels et al considered fully three‐dimensional shear‐driven droplets in which either the droplet or the surrounding fluid is viscoelastic. The Oldroyd‐B model is employed in the present study to facilitate a direct comparison with the results of the work of Verhulst et al and Cardinaels et al The spherical droplet of radius R is at the center of the computational domain. Opposite velocities, ie, V and − V , are enforced on the two walls located at z = 0 and z = H to obtain the shear rate

\overset{γ}{true} = 2 V false/ H

.…”

Section: Validationmentioning

confidence: 99%

“…Periodic boundary conditions are imposed in the x (spanwise) and y (streamwise) directions and no‐slip conditions at the two walls. Following the works of Verhulst et al and Cardinaels et al, the nondimensional parameters are defined as follows. The Reynolds number

R e = ρ_{1} \overset{γ}{true} R^{2} false/ μ_{1}

, the capillary number

C a = R \overset{γ}{true} μ_{1} false/ σ

, the Weissenberg number

W i = λ \overset{γ}{true}

, the viscosity ratio k μ = μ 2 / μ 1 , the density ratio k ρ = ρ 2 / ρ 1 , and the confinement ratio χ = 2 R / H .…”

Section: Validationmentioning

confidence: 99%

Computational modeling of multiphase viscoelastic and elastoviscoplastic flows

Izbassarov

Rosti

Ardekani

et al. 2018

Numerical Methods in Fluids

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Summary In this paper, a three‐dimensional numerical solver is developed for suspensions of rigid and soft particles and droplets in viscoelastic and elastoviscoplastic (EVP) fluids. The presented algorithm is designed to allow for the first time three‐dimensional simulations of inertial and turbulent EVP fluids with a large number particles and droplets. This is achieved by combining fast and highly scalable methods such as an FFT‐based pressure solver, with the evolution equation for non‐Newtonian (including EVP) stresses. In this flexible computational framework, the fluid can be modeled by either Oldroyd‐B, neo‐Hookean, FENE‐P, or Saramito EVP models, and the additional equations for the non‐Newtonian stresses are fully coupled with the flow. The rigid particles are discretized on a moving Lagrangian grid, whereas the flow equations are solved on a fixed Eulerian grid. The solid particles are represented by an immersed boundary method with a computationally efficient direct forcing method, allowing simulations of a large numbers of particles. The immersed boundary force is computed at the particle surface and then included in the momentum equations as a body force. The droplets and soft particles on the other hand are simulated in a fully Eulerian framework, the former with a level‐set method to capture the moving interface and the latter with an indicator function. The solver is first validated for various benchmark single‐phase and two‐phase EVP flow problems through comparison with data from the literature. Finally, we present new results on the dynamics of a buoyancy‐driven drop in an EVP fluid.

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An experimental and numerical investigation of the dynamics of microconfined droplets in systems with one viscoelastic phase

Cited by 22 publications

References 53 publications

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

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

Breakup Criteria for Confined Droplets: Effects of Compatibilization and Component Viscoelasticity

Computational modeling of multiphase viscoelastic and elastoviscoplastic flows

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