Universality in dynamic wetting dominated by contact-line friction

Carlson, Andreas; Bellani, Gabriele; Amberg, Gustav

doi:10.1103/physreve.85.045302

Cited by 79 publications

(79 citation statements)

References 19 publications

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“…Most recently, Carlson and co-workers considered the influence of surface wettability and liquid viscosity on dynamic wetting by introducing additional energy dissipation terms, such as contact line friction due to molecular process, viscous dissipation in the liquid, and a diffusive dissipation [39][40][41]. However, these contributions are hard to be directly integrated into the derivation of the power law of inertial wetting.…”

Section: A Inertial Wettingmentioning

confidence: 98%

Effects of surface wettability and liquid viscosity on the dynamic wetting of individual drops

Chen

Bonaccurso

2014

Phys. Rev. E

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In this paper, we experimentally investigated the dynamic spreading of liquid drops on solid surfaces. Drop of glycerol water mixtures and pure water that have comparable surface tensions (62.3-72.8 mN/m) but different viscosities (1.0-60.1 cP) were used. The size of the drops was 0.5-1.2 mm. Solid surfaces with different lyophilic and lyophobic coatings (equilibrium contact angle θ(eq) of 0°-112°) were used to study the effect of surface wettability. We show that surface wettability and liquid viscosity influence wetting dynamics and affect either the coefficient or the exponent of the power law that describes the growth of the wetting radius. In the early inertial wetting regime, the coefficient of the wetting power law increases with surface wettability but decreases with liquid viscosity. In contrast, the exponent of the power law does only depend on surface wettability as also reported in literature. It was further found that surface wettability does not affect the duration of inertial wetting, whereas the viscosity of the liquid does. For low viscosity liquids, the duration of inertial wetting corresponds to the time of capillary wave propagation, which can be determined by Lamb's drop oscillation model for inviscid liquids. For relatively high viscosity liquids, the inertial wetting time increases with liquid viscosity, which may due to the viscous damping of the surface capillary waves. Furthermore, we observed a viscous wetting regime only on surfaces with an equilibrium contact angle θ(eq) smaller than a critical angle θ(c) depending on viscosity. A scaling analysis based on Navier-Stokes equations is presented at the end, and the predicted θ(c) matches with experimental observations without any additional fitting parameters.

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Section: A Inertial Wettingmentioning

confidence: 98%

Effects of surface wettability and liquid viscosity on the dynamic wetting of individual drops

Chen

Bonaccurso

2014

Phys. Rev. E

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“…Much less is known about the early stages of spreading after a spherical drop is brought into contact with a solid at negligible speed. In contrast to Tanner's law, this dynamics is very fast [8][9][10][11][12]: capillary energy suddenly becomes available when the drop touches the solid, and this energy is concentrated into a singular point of contact. It has remained unclear whether or not the wetting conditions can influence such rapid inertial flows [13][14][15].…”

mentioning

confidence: 92%

“…2 and 4 are very close, the Reynolds numbers defined as Re = ρr(dr/dt)/η are very different: it is order unity in MD, and order 100 in experiments. This suggests that the MD could be influenced by viscous effects, and it would be interesting to further investigate spreading for highly viscous liquids [12,21]. Another key difference is the importance of thermal fluctuations at molecular scales.…”

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confidence: 99%

Initial spreading of low-viscosity drops on partially wetting surfaces

et al. 2012

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Liquid drops start spreading directly after coming into contact with a partially wetting substrate. Although this phenomenon involves a three-phase contact line, the spreading motion is very fast. We study the initial spreading dynamics of low-viscosity drops using two complementary methods: molecular dynamics simulations and high-speed imaging. We access previously unexplored length and time scales and provide a detailed picture on how the initial contact between the liquid drop and the solid is established. Both methods unambiguously point toward a spreading regime that is independent of wettability, with the contact radius growing as the square root of time.

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“…7 It is worth mentioning the effect of the relaxation coefficient Γ in Eq. (4) 17,19 they suggested for the microscopic contact angle (cos θ e cos θ )/sin θ ∼ Ca. In the present study, the wall has no defects and the fluids have no polar interactions; hence, the relaxation time constant is small and Γ is large.…”

Section: A Effect Of the System Sizementioning

confidence: 98%

“…The microscopic contact angle has been investigated theoretically 11 and by means of molecular dynamics (MD) simulation [12][13][14][15][16] and continuum mechanics; [16][17][18][19] however, the effect of the length scales involved in the contact angle measurement and the difference between the microscopic and apparent contact angles have not been explored. When it comes to the apparent contact angle, there have also been theoretical studies [20][21][22][23] and computational studies, 17,24,25 but there has been no attempt to investigate the universal behavior of the apparent contact angle claimed in the experimental studies.…”

Section: Introductionmentioning

confidence: 99%

Apparent and microscopic dynamic contact angles in confined flows

Omori

Kajishima

2017

Physics of Fluids

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An abundance of empirical correlations between a dynamic contact angle and a capillary number representing a translational velocity of a contact line have been provided for the last decades. The experimentally obtained dynamic contact angles are inevitably apparent contact angles but often undistinguished from microscopic contact angles formed right on the wall. As Bonn et al. [“Wetting and spreading,” Rev. Mod. Phys. 81, 739–805 (2009)] pointed out, however, most of the experimental studies simply report values of angles recorded at some length scale which is quantitatively unknown. It is therefore hard to evaluate or judge the physical validity and the generality of the empirical correlations. The present study is an attempt to clear this clutter regarding the dynamic contact angle by measuring both the apparent and the microscopic dynamic contact angles from the identical data sets in a well-controlled manner, by means of numerical simulation. The numerical method was constructed so that it reproduced the fine details of the flow with a moving contact line predicted by molecular dynamics simulations [T. Qian, X. Wang, and P. Sheng, “Molecular hydrodynamics of the moving contact line in two-phase immiscible flows,” Commun. Comput. Phys. 1, 1–52 (2006)]. We show that the microscopic contact angle as a function of the capillary number has the same form as Blake’s molecular-kinetic model [T. Blake and J. Haynes, “Kinetics of liquid/liquid displacement,” J. Colloid Interface Sci. 30, 421–423 (1969)], regardless of the way the flow is driven, the channel width, the mechanical properties of the receding fluid, and the value of the equilibrium contact angle under the conditions where the Reynolds and capillary numbers are small. We have also found that the apparent contact angle obtained by the arc-fitting of the interface behaves surprisingly universally as claimed in experimental studies in the literature [e.g., X. Li et al., “An experimental study on dynamic pore wettability,” Chem. Eng. Sci. 104, 988–997 (2013)], although the angle deviates significantly from the microscopic contact angle. It leads to a practically important point that it suffices to measure arc-fitted contact angles to make formulae to predict flow rates in capillary tubes.

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Universality in dynamic wetting dominated by contact-line friction

Cited by 79 publications

References 19 publications

Effects of surface wettability and liquid viscosity on the dynamic wetting of individual drops

Effects of surface wettability and liquid viscosity on the dynamic wetting of individual drops

Initial spreading of low-viscosity drops on partially wetting surfaces

Apparent and microscopic dynamic contact angles in confined flows

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