Numerical analysis of anisotropic wetting of chemically striped surfaces

Sui, Xin; He, Liang; Wang, Zhenqing; Akbarzadeh, A.H.

doi:10.1039/c8ra06626d

Cited by 12 publications

(8 citation statements)

References 40 publications

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“…The free energy of the system G is expressed as where A lv is the contact area of the liquid, γ lv is the liquid–vapor interfacial tension, and θ is the contact angle. This free energy G is normalized by γ lv to achieve the equilibrium droplet shape . The contact angle is defined by Young’s equation , where γ lv is the liquid–vapor interfacial tension, γ sv is the solid–vapor interfacial tension, and γ sl is the solid–liquid interfacial tension.…”

Section: Methodsmentioning

confidence: 99%

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1D Roughness Driven Depinning of Self-Assembly of Liquid Droplets

2019

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The conventional hexagonal, uniform breath figure pattern formed over smooth substrates and substrates with constraints of the order of 50 μm is distorted when the underlying constraints are down to 1 μm. This paper explores this phenomenon further and concludes that, in addition to topology-based arguments presented by other authors previously, it is necessary to invoke the depinning effects of the three-phase contact line in order to explain the same. The influence of surface constraints on the self-assembly of liquid droplets is investigated. A semiquantitative explanation for large-scale pattern formation consisting of small-scale closely arranged droplets inside the large-scale distorted ring of droplets is presented in this paper. The scale at which the influence of constraints becomes dominant is also determined in this study. It is seen that the underlying roughness has a larger impact than the nature of polymer on pore size. Comparative studies of pore patterns formed on smooth and constrained substrates are reported. The simulated energy-minimized shapes of the droplets on smooth and constrained substrates are obtained using Surface Evolver.

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Section: Methodsmentioning

confidence: 99%

“…This free energy G is normalized by γ lv to achieve the equilibrium droplet shape. 30 The contact angle is defined by Young's equation 31,32 cos ( )…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

1D Roughness Driven Depinning of Self-Assembly of Liquid Droplets

2019

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“…It has been found that the increase of surface roughness increases the hydrophobicity of the fibrous structure [22]. The surface energy minimization approach has been successful in the prediction and computation of the shape of droplets on different textures [23][24][25][26][27][28]. Tafreshi et al [29] experimentally and numerically studied the wetting of ferrofluid droplets on fibrous mats.…”

Section: Introductionmentioning

confidence: 99%

Pore-Scale Simulation of the Interaction between a Single Water Droplet and a Hydrophobic Wire Mesh Screen in Diesel

Elsayed

Kirsch

Krull

et al. 2021

Fluids

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Recently, the trend towards sustainable energy production and pollution control has motivated the increased consumption of ultra-low-sulfur diesel (ULSD) or bio-fuels. Such fuels have relatively low surface tension with water and therefore, the separation of water from fuel has become a challenging problem. The separation process relies on using porous structures for the collection and removal of water droplets. Hence, understanding the interaction between water droplets and the separators is vital. The simplest geometry of a separator is the wire mesh screen, which is used in many modern water–diesel separators. Thus, it is considered here for systematic study. In this work, pore-scale computational fluid dynamics (CFD) simulations were performed using OpenFOAM® (an open-source C++ toolbox for fluid dynamics simulations) coupled with a new accurate scheme for the computation of the surface tension force. First, two validation test cases were performed and compared to experimental observations in corresponding bubble-point tests. Second, in order to describe the interaction between water droplets and wire mesh screens, the simulations were performed with different parameters: mean diesel velocity, open area ratio, fiber radii, Young–Laplace contact angle, and the droplet radius. New correlations were obtained which describe the average reduction of open surface area (clogging), the pressure drop, and retention criteria.

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“…In the present study the focus lies on chemically patterned striped surfaces which are wetted by water droplets with radii of the order of magnitude of the stripe width. For such kind of systems, static wetting behavior has been studied by using energy minimization techniques [5][6][7], lattice Boltzmann simulations [8,9] and experiments [10]. Also inertia-driven spreading [9] and the splitting [11][12][13] of impinging droplets on such kind of surfaces has been investigated in some detail.…”

Section: Introductionmentioning

confidence: 99%

Breakup Dynamics of Capillary Bridges on Hydrophobic Stripes

Hartmann,

Fricke,

Weimar

et al. 2019

Preprint

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The breakup dynamics of a capillary bridge on a hydrophobic stripe between two hydrophilic stripes is studied experimentally and numerically. The capillary bridge is formed from an evaporating water droplet wetting three neighboring stripes of a chemically patterned surface. The simulations are based on the Volume-of-Fluid (VOF) method implemented in Free Surface 3D (FS3D). In order to construct physically realistic initial data for the VOF simulation, Surface Evolver is employed to calculate an initial configuration consistent with experiments. Numerical instabilities at the contact line are reduced by a novel adaptation of the Navier-slip boundary condition. By considering the breakup process in phase space, the breakup dynamics can be evaluated without the uncertainty in determining the precise breakup time. It is found that within an intermediate inviscid regime, the breakup dynamics follows a t 2/3 -scaling, indicating that the breakup process is dominated by the balance of inertial and capillary forces. For smaller bridge widths, the breakup velocity reaches a plateau, which is due to viscous forces becoming more important. In the final stage of breakup, the capillary bridge forms a liquid thread that breaks up consistent with the Rayleigh-Plateau instability. The critical wavelength is identical to the distance between the tips of two liquid cones between which the thread is arranged. The existence of satellite droplets in a regular pattern indicates that the primary breakup process is followed by self-similar secondary breakups.

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Numerical analysis of anisotropic wetting of chemically striped surfaces

Cited by 12 publications

References 40 publications

1D Roughness Driven Depinning of Self-Assembly of Liquid Droplets

1D Roughness Driven Depinning of Self-Assembly of Liquid Droplets

Pore-Scale Simulation of the Interaction between a Single Water Droplet and a Hydrophobic Wire Mesh Screen in Diesel

Breakup Dynamics of Capillary Bridges on Hydrophobic Stripes

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