Contact-angle-hysteresis effects on a drop sitting on an incline plane

Ravazzoli, Pablo D.; Cuellar, Ingrith; González, Antonio Bueno; Diez, Javier A.

doi:10.1103/physreve.99.043105

“…Here, is the radius describing the position of the contact line, is the azimuthal angle, is the contact angle. After integration, one obtains: in which, is a geometric factor, whose precise value depends on the shape of the drop 35 . Equation ( 4 ) is often referred as the Furmidge-Kawasaki equation 24 , 36 , 37 .…”

Section: Resultsmentioning

confidence: 99%

Kinetic drop friction

Li

¹

,

Bodziony

²

,

Yin

³

et al. 2023

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Liquid drops sliding on tilted surfaces is an everyday phenomenon and is important for many industrial applications. Still, it is impossible to predict the drop’s sliding velocity. To make a step forward in quantitative understanding, we measured the velocity $$(U)$$ ( U ) , contact width $$(w)$$ ( w ) , contact length $$(L)$$ ( L ) , advancing $$({\theta }_{{{{{{\rm{a}}}}}}})$$ ( θ a ) , and receding contact angle $$({\theta }_{{{{{{\rm{r}}}}}}})$$ ( θ r ) of liquid drops sliding down inclined flat surfaces made of different materials. We find the friction force acting on sliding drops of polar and non-polar liquids with viscosities ($${\eta }$$ η ) ranging from 10−3 to 1 $${{{{{\rm{Pa}}}}}}\cdot {{{{{\rm{s}}}}}}$$ Pa ⋅ s can empirically be described by $${F}_{{{{{{\rm{f}}}}}}}(U)={F}_{0}+\beta w\eta U$$ F f ( U ) = F 0 + β w η U for a velocity range up to 0.7 ms−1. The dimensionless friction coefficient $$(\beta )$$ ( β ) defined here varies from 20 to 200. It is a material parameter, specific for a liquid/surface combination. While static wetting is fully described by $${\theta }_{{{{{{\rm{a}}}}}}}$$ θ a and $${\theta }_{{{{{{\rm{r}}}}}}}$$ θ r , for dynamic wetting the friction coefficient is additionally necessary.

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“…Consequently, the space between the resulting drops also differs. It should be mentioned that the inclination angle, α, needs to be small enough so that the formed drops remain static and do not slide over the substrate leading to drop coalescence [10].…”

Section: Resultsmentioning

confidence: 99%

Gravity Effects in the Retraction of Liquid Filaments Resting on an Inclined Plane

Ravazzoli¹,

González²,

Diez³

2022

AnAFA

0

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We study the retraction of liquid filaments resting on inclined solid substrates under partially wetting condition. This one causes each extreme of the filament to retract and form a region of mass accumulation (head) that subsequently develops a neck at its rear part. This neck then breaks up into a separate drop, while the rest of the filament restarts the sequence. In the horizontal case, this process is symmetric and leads to a regular arrangement of evenly spaced drops. When the substrate is inclined, gravity acts differently at each end, thus modifying the distance retracted by each end, the retraction speed and the final distance between drops, which also ceases to be uniform. We find that in the case of the inclined plane, the maximum distance retracted by the end that recedes against (in favor of) gravity decreases(increases) with respect to the horizontal case. This effect turns out to be a useful mechanism for the self–positioning of the resulting drops at the end of the process. Our experimental results, such as end positions, thickness profiles in the longitudinal section, etc., are contrasted with numerical simulations of the Navier–Stokes equations, obtaining a good agreement. This is achieved by using in the contact line the boundary condition known as Cox–Voinov–Blake (CVB)relationship, which includes both the effects of macroscopic hydrodynamics as well as molecular dynamics.

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“…Hysteresis of contact angles can be recorded in different configurations [3,4]. The most technically simple configuration is the configuration in which the study of static and dynamic behavior of the drop is carried out on the inclined plane [5][6][7]. The study of hysteresis on the inclined plane can be carried out at the constant drop volume.…”

Section: Introductionmentioning

confidence: 99%

Hysteresis Phenomena in a Liquid Sessile Drop on a Stretchable Inclined Elastic Substrate

Dekhtyar,

Dubinov

2023

SV

0

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The authors studied states of liquid sessile drops on a stretchable inclined elastic substrate to find out peculiarities of the contact angles hysteresis by digital optical microscopes. The drop elongation and contact angles were recorded on the stages of the band stretching and contraction. An anomalous behavior of the drop was found on the first step of the contraction during which the measured drop parameters remained unchanged. Finally, a new hydrophysical effect was found. It is hysteresis of the drop states, on the background of which the contact angle hysteresis exists.

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Contact-angle-hysteresis effects on a drop sitting on an incline plane

Cited by 6 publications

References 31 publications

Kinetic drop friction

Kinetic drop friction

Gravity Effects in the Retraction of Liquid Filaments Resting on an Inclined Plane

Hysteresis Phenomena in a Liquid Sessile Drop on a Stretchable Inclined Elastic Substrate

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