Breakup dynamics of capillary bridges on hydrophobic stripes

Hartmann, Maximilian; Fricke, Mathis; Weimar, Lukas; Gründing, Dirk; Marić, Tomislav; Bothe, Dieter; Hardt, Steffen

doi:10.1016/j.ijmultiphaseflow.2021.103582

Cited by 11 publications

(5 citation statements)

References 50 publications

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“…The simplest solution to add a bottom view camera and capture the contact areas from the bottom (Eddi et al 2013) and to record at very high frame rates. Plotting the contact line velocity against the dimensionless spreading radius (r/R) is another possible approach (Hartmann et al 2021). The advantage of the latter method is that it does not need a definition of zero time (see supplementary material).…”

Section: Spreading Of Viscoelastic and Viscous Newtonian Dropsmentioning

confidence: 99%

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Spreading of a viscoelastic drop on a solid substrate

Rostami,

Fricke,

Schubotz

et al. 2024

J. Fluid Mech.

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We study the spreading of Newtonian viscous (aqueous glycerin solution) and viscoelastic (aqueous polymer solution) drops on solid substrates with different wettabilities. For drops of the same zero-shear viscosity, we find in the early stages of spreading that viscoelastic drops (i) spread faster and (ii) their contact radius shows a different power law vs time than Newtonian drops. We argue that the effect of viscoelasticity is only observable for experimental time scales of the order of or larger than the internal relaxation time of the viscoelastic polymer solution. We attribute this behaviour to the shear thinning of the viscoelastic polymer solution. When approaching the contact line, the shear rate increases and the steady-state viscosity of the viscoelastic drop is lower than that of the Newtonian drop. We support our experimental findings with a simple (first-order) perturbation model that qualitatively agrees with our findings.

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Section: Spreading Of Viscoelastic and Viscous Newtonian Dropsmentioning

confidence: 99%

“…Plotting the contact line velocity against the dimensionless spreading radius () is another possible approach (Hartmann et al. 2021). The advantage of the latter method is that it does not need a definition of zero time (see supplementary material).…”

Section: Spreading Of Viscoelastic and Viscous Newtonian Dropsmentioning

confidence: 99%

Spreading of a viscoelastic drop on a solid substrate

Rostami,

Fricke,

Schubotz

et al. 2024

J. Fluid Mech.

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“…This has the potential for improving both PF and VOF ability to match the MD results. An alternative approach to prescribing larger friction in VOF simulations would be to use so-called staggered slip or negative slip (Hartmann et al 2021). Another effect, which was not considered in this work, is so-called disjoining pressure (Pismen & Pomeau 2000).…”

Section: Potential Modelling Directionsmentioning

confidence: 99%

Nanoscale sheared droplet: volume-of-fluid, phase-field and no-slip molecular dynamics

et al. 2022

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The motion of the three-phase contact line between two immiscible fluids and a solid surface arises in a variety of wetting phenomena and technological applications. One challenge in continuum theory is the effective representation of molecular motion close to the contact line. Here, we characterize the molecular processes of the moving contact line to assess the accuracy of two different continuum two-phase models. Specifically, molecular dynamics simulations of a two-dimensional droplet between two moving plates are used to create reference data for different capillary numbers and contact angles. We use a simple-point-charge/extended water model. This model provides a very small slip and a more realistic representation of the molecular physics than Lennard-Jones models. The Cahn–Hilliard phase-field model and the volume-of-fluid model are calibrated against the drop displacement from molecular dynamics reference data. It is shown that the calibrated continuum models can accurately capture droplet displacement and droplet break-up for different capillary numbers and contact angles. However, we also observe differences between continuum and atomistic simulations in describing the transient and unsteady droplet behaviour, in particular, close to dynamical wetting transitions. The molecular dynamics of the sheared droplet provide insight into the line friction experienced by the advancing and receding contact lines. The presented results will serve as a stepping stone towards developing accurate continuum models for nanoscale hydrodynamics.

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“…It can be advantageous to consider the spreading dynamics in phase space (see [18] for the phase space diagram of a breakup process). The idea is to express the timederivative of the base radius L as a function of the base radius itself.…”

Section: Spreading Dynamics In Phase Spacementioning

confidence: 99%

A geometry-based model for spreading drops applied to drops on a silicon wafer and a swellable polymer brush film

Fricke,

Fickel,

Hartmann

et al. 2020

Preprint

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We investigate the dynamics of spreading in a regime where the shape of the drop is close to a spherical cap. The latter simplification is applicable in the late (viscous) stage of spreading for highly viscous drops with a diameter below the capillary length. Moreover, it applies to the spreading of a drop on a swellable polymer brush, where the complex interaction with the substrate leads to a very slow spreading dynamics. The spherical cap geometry allows to derive a closed ordinary differential equation (ODE) for the spreading if the capillary number is a function of the contact angle as it is the case for empirical contact angle models. The latter approach has been introduced by de Gennes (Reviews of Modern Physics, 1985) for small contact angles. In the present work, we generalize the method to arbitrary contact angles. The method is applied to experimental data of spreading water-glycerol drops on a silicon wafer and spreading water drops on a PNIPAm coated silicon wafer. It is found that the ODE-model is able to describe the spreading kinetics in the case of partial wetting. Moreover, the model can predict the spreading dynamics of spherical cap-shaped droplets if the relationship between the contact angle and the capillary number is universal.

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Breakup dynamics of capillary bridges on hydrophobic stripes

Cited by 11 publications

References 50 publications

Spreading of a viscoelastic drop on a solid substrate

Spreading of a viscoelastic drop on a solid substrate

Nanoscale sheared droplet: volume-of-fluid, phase-field and no-slip molecular dynamics

A geometry-based model for spreading drops applied to drops on a silicon wafer and a swellable polymer brush film

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