Numerical prediction of the film thickening due to surfactants in the Landau–Levich problem

Campana, Diego Martin; Ubal, Sebastian; Giavedoni, Maria Delia; Saita, Fernando A.

doi:10.1063/1.3341019

Cited by 22 publications

(30 citation statements)

References 14 publications

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“…In a previous paper, 8 we showed that the thickening factors larger than one detected when the coating liquid contains a soluble surfactant are mainly associated with changes in both the interfacial shape and the pressure distribution in the dynamic meniscus and not with the nonzero values detected in the tangential component of the surface stress.…”

Section: Resultsmentioning

confidence: 96%

“…In fact, if the concentration of solute is not fixed, its value will continuously diminish due to the convective transport of surfactant towards the film region and no steady state will be achieved. Equation (8) also establishes that far away from x ¼ 0 (in the thin film region), the free surface is parallel to the solid surface.…”

Section: A Governing Equations and Boundary Conditionsmentioning

confidence: 94%

“…(1)-(8) can be found in Ref. 8. Therefore, in this Section, we will discuss the tests carried out to establish the appropriateness of the domain extension as well as the number of the elements and their distribution in the computational grid.…”

Section: B Solution Methodsmentioning

confidence: 99%

“…The experiments of Krechetnikov and Homsy 7 (K&H) were conducted at a parameter range where the adsorption of surfactant from the bulk to the interface is fast enough to compensate the dilution produced by the stretching of the free surface and, consequently, Marangoni stresses are not likely to be responsible for the observed film thickening. In an attempt to disclose the underlying mechanisms involved in the thickening process under the operating conditions assumed by K&H, we carried out a numerical analysis 8 to mimic their experiments; the study is based on the hydrodynamic modeling of the surfactant effect and shows predictions of the thickening factor (i.e., the ratio between the thickness of the contaminated system and the LandauLevich 1 for a uniformly distributed surfactant) in very good agreement with the experimental ones. The numerical solutions show that the elastic effects of the surfactant reduce the interfacial curvature all along the dynamic meniscus; thus, the pressure gradient (i.e.…”

mentioning

confidence: 87%

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A deeper insight into the dip coating process in the presence of insoluble surfactants: A numerical analysis

Campana¹,

Ubal²,

Giavedoni³

et al. 2011

Physics of Fluids

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A numerical investigation is carried out to study the effects of an insoluble surfactant on the dip coating of a flat substrate. Predictions of both the film thickness and the concentration of surfactant in the film as a function of the capillary number compare well with the solutions of a simpler asymptotic model based on the lubrication approximation. Streamline patterns confirm the existence of a stagnation point located in the bulk phase in the region of the dynamic meniscus—a conjecture postulated forty years ago. The evolution of the flow patterns and the interfacial variables shows how the classical result of Landau and Levich is recovered as the coating speed is augmented. Finally, we show that the effect of inertia forces cannot be neglected when the viscosity of the coating liquid is low.

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Section: Resultsmentioning

confidence: 96%

Section: A Governing Equations and Boundary Conditionsmentioning

confidence: 94%

Section: B Solution Methodsmentioning

confidence: 99%

mentioning

confidence: 87%

See 2 more Smart Citations

A deeper insight into the dip coating process in the presence of insoluble surfactants: A numerical analysis

Campana¹,

Ubal²,

Giavedoni³

et al. 2011

Physics of Fluids

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“…in LLD configuration) defined as as a function of the control parameter Λ. Comparison to equation (29) shows that the thickening factor α Fr (resp. α LLD ) is simply the ratio between the film thickness predicted by our model and the one predicted by the Frankel (resp.…”

Section: A Comparison Of Linearized and Nonlinearized Equations Of Statementioning

confidence: 99%

Surfactant-induced rigidity of interfaces: a unified approach to free and dip-coated films

et al. 2015

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The behavior of thin liquid films is known to be strongly affected by the presence of surfactants at the interfaces. The detailed mechanism by which the latter enhance film stability is still a matter of debate, in particular concerning the influence of surface elastic effects on the hydrodynamic boundary condition at the liquid/air interfaces. In the present work, "twin" hydrodynamic models neglecting surfactant transport to the interfaces are proposed to describe the coating of films onto a solid plate (LandauLevich-Derjaguin configuration) as well as soap film pulling (Frankel configuration). Experimental data on the entrained film thickness in both configurations can be fitted very well using a single value of the surface elasticity, which is in good agreement with independent measurements by mean of surface expansion experiments in a Langmuir through. The analysis shows how and when the soap films or dip coating experiments may be used to precisely and sensitively measure the surface elasticity of surfactant solutions.

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Slot coating flows of non‐colloidal particle suspensions

2016

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Slot coating is used in the manufacturing of functional films, which rely on specific particle microstructure to achieve the desired performance. Final structure on the coated film is strongly dependent on the suspension flow during the deposition of the coating liquid and on the subsequent drying process. Fundamental understanding on how particles are distributed in the coated layer enables optimization of the process and quality of the produced films. The complex coating flow leads to shear‐induced particle migration and non‐uniform particle distribution. We study slot coating flow of non‐colloidal suspensions by solving the mass and momentum conservation equations coupled with a particle transport equation using the Galerkin/Finite element method. The results show that particle distribution in the coating bead and in the coated layer is non‐uniform and is strongly dependent on the imposed flow rate (wet thickness). © 2016 American Institute of Chemical Engineers AIChE J, 63: 1122–1131, 2017

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Numerical prediction of the film thickening due to surfactants in the Landau–Levich problem

Cited by 22 publications

References 14 publications

A deeper insight into the dip coating process in the presence of insoluble surfactants: A numerical analysis

A deeper insight into the dip coating process in the presence of insoluble surfactants: A numerical analysis

Surfactant-induced rigidity of interfaces: a unified approach to free and dip-coated films

Slot coating flows of non‐colloidal particle suspensions

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