Flow-driven collapse of lubricant-infused surfaces

Asmolov, Evgeny S.; Nizkaya, Tatiana V.; Vinogradova, Olga I.

doi:10.1017/jfm.2020.537

Cited by 16 publications

(10 citation statements)

References 44 publications

(68 reference statements)

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“…According to eqs 2 and 3 , slip length is predicted to be linearly proportional to the thickness of the air layer ( l air ) at a given viscosity ratio (μ l /μ air ). Since liquids with relatively lower surface tension can enter the microstructure of SHO surfaces more easily 20 and the meniscus/stability of the air pockets is dependent primarily on the surface tension 48 (or, in nondimensional terms, the capillary number 49 ) of the liquid, we make the assumption that the surface tension of a liquid has a positive relationship with l air . Therefore, the slip length is assumed to be linearly proportional to the so-called capillary length (λ c ) which is determined by mass density and surface tension as where γ is the surface tension of the liquid, ρ the mass density of the liquids, and g the gravitational acceleration.…”

Section: Resultsmentioning

confidence: 99%

Surface Tension and Viscosity Dependence of Slip Length over Irregularly Structured Superhydrophobic Surfaces

2022

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A comprehensive understanding of the slip phenomenon on liquid/solid interfaces is essential for multiple real-world applications of superhydrophobic materials, especially those involving drag reduction. In the current contribution, the so-called “slip-length” on an irregularly structured superhydrophobic surface was systematically evaluated, with respect to varying liquid surface tension and viscosity. The superhydrophobic polymer–nanoparticle composite (SPNC) material used exhibits a dual-scale surface roughness and was fabricated via coating a surface with a mixture of polydimethylsiloxane solution and functionalized silica particles. A cone-and-plate rheometric device was employed to quantify the slip length. To independently study the impact of surface tension and viscosity, three types of aqueous solutions were used: sodium dodecyl sulfate, ethanol, and polyethylene glycol. Our experimental results demonstrate that a decreasing surface tension results in a decreasing slip length when the fluid viscosity is held constant. Meanwhile, the slip length is shown to increase with increasing viscosity when the surface tension of the various liquids is matched to isolate effects. The study reveals a linear relationship between slip length and both capillary length and viscosity providing a reference to potentially predict the degree of achievable drag reduction for differing fluids on SPNC surfaces.

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Section: Resultsmentioning

confidence: 99%

Surface Tension and Viscosity Dependence of Slip Length over Irregularly Structured Superhydrophobic Surfaces

2022

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“…Under the effect of curvature, the motion direction of impinging droplets can be manipulated toward the center of the curvature. The findings help us acquire further understanding of the basic droplet impact process at the interface and offer a promising strategy to accurately control the droplet behavior, which shows great potential in microfluidics, , heat transfer, etc.…”

Section: Introductionmentioning

confidence: 90%

Directional Droplet Transport Mediated by Circular Groove Arrays. Part I: Experimental Findings

et al. 2020

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Directional transport of liquid droplets is crucial for various applications including water harvesting, anti-icing, and condensation heat transfer. Here, bouncing of water droplets with patterned superhydrophobic surfaces composed of circular equidistant grooves was studied. The directional transport of droplets toward the pole of the grooves was observed. The impact of the Weber number, initial polar distance r, and geometrical parameters of the surface on the directional droplet bouncing was experimentally explored. The nature of bouncing was switched when the Weber numbers exceeded We ≅ 20−25. The rebouncing height was slightly dependent on the initial polar coordinate of the impact point for a fixed We, whereas it grew for We > 20. The weak dependence of the droplet spreading time on the Weber number was close to the dependence predicted by the Hertz bouncing, thus evidencing the negligible influence of viscosity in the process. Change in the scaling exponent describing the dependence of the normalized spreading time on the Weber number was registered for We ≅ 25. The universal dependence of the offset distance ΔL of the droplets on the Weber number ΔL/D 0 ∼ We 1.5 was established. The normalized offset distance decreased with the normalized initial polar distance as ΔL/D 0 ∼ (r/S) −1 , where D 0 and S are the droplet diameter and groove width, respectively. This research may yield more insights into droplet bouncing on patterned surfaces and offer more options in directed droplet transportation.

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“…no slip at the upper wall and groovy structures at the lower wall), along with the perturbed Stokes equation and the Navier slip law, as the governing equations; this has led to a Fourier series solution yielding trigonometric dual series (with exact solutions at the limit of thin and thick channels), describing the complete physics of the slip. Several other analytical efforts have been made to address the flow of Newtonian fluids over SH surfaces, to which an interested reader can refer (Asmolov & Vinogradova 2012;Asmolov et al 2013a;Schönecker, Baier & Hardt 2014;Asmolov, Nizkaya & Vinogradova 2020).…”

Section: Introductionmentioning

confidence: 99%

“…Several other analytical efforts have been made to address the flow of Newtonian fluids over SH surfaces, to which an interested reader can refer (Asmolov & Vinogradova 2012; Asmolov et al. 2013 a ; Schönecker, Baier & Hardt 2014; Asmolov, Nizkaya & Vinogradova 2020).…”

Section: Introductionmentioning

confidence: 99%

Poiseuille flow of a Bingham fluid in a channel with a superhydrophobic groovy wall

Rahmani

Taghavi

2022

J. Fluid Mech.

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Plane Poiseuille flow of a Bingham fluid in a channel armed with a superhydrophobic (SH) lower wall is analysed via a semi-analytical model, accompanied by complementary direct numerical simulations (DNS). The SH surface represents a groovy structure with air trapped inside its cavities. Therefore, the fluid adjacent to the wall undergoes stick–slip conditions. The model is developed based on introducing infinitesimal wall-induced perturbations into the motion equations, followed by Fourier series expansions, and solving the resulting equations as a boundary value problem. The Navier slip law accounts for the slip at the liquid/air interface (assuming the Cassie state). The presented analysis is fairly comprehensive, covering the creeping and inertial regimes for thick channels (via the semi-analytical and DNS solutions). The main dimensionless numbers are the Reynolds ( $Re$ ), Bingham ( $Bi$ ) and slip ( $b$ ) numbers, as well as the groove periodicity length ( $\ell$ ) and the slip area fraction ( $\varphi$ ). By increasing $Bi$ , the perturbation and slip velocity fields grow. As $Re$ increases, the perturbation and slip velocity fields become asymmetric. For certain flow parameters, an unyielded plug zone may appear on the SH wall liquid/air interface, while its formation is accelerated by inertial effects. The results classify the regimes of creeping and inertial flows via predicting the onset of the unyielded plug zone formation at the SH wall.

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Flow-driven collapse of lubricant-infused surfaces

Abstract: Abstract

Cited by 16 publications

References 44 publications

Surface Tension and Viscosity Dependence of Slip Length over Irregularly Structured Superhydrophobic Surfaces

Surface Tension and Viscosity Dependence of Slip Length over Irregularly Structured Superhydrophobic Surfaces

Directional Droplet Transport Mediated by Circular Groove Arrays. Part I: Experimental Findings

Poiseuille flow of a Bingham fluid in a channel with a superhydrophobic groovy wall

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