Contact angles for perfectly wetting pure liquids evaporating into air: Between de Gennes-type and other classical models

Rednikov, Alexei; Colinet, Pierre

doi:10.1103/physrevfluids.5.114007

Cited by 4 publications

(3 citation statements)

References 41 publications

(153 reference statements)

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“…e.g. Morris (2014), Rednikov & Colinet (2020) and references therein). However, as the evaporation-flux singularity at the contact line here turns out to be removed due to the local water depletion and the rectification of the evaporation flux j (cf.…”

Section: Discussionmentioning

confidence: 99%

Water–propylene glycol sessile droplet shapes and migration: Marangoni mixing and separation of scales

et al. 2022

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New light is shed on morphological features of water–propylene glycol sessile droplets evaporating into ambient air at not too high relative humidity. Such droplets adopt a Marangoni-contracted shape even on perfectly wetting substrates, an effect well known since Cira et al. (Nature, 519, 2015). We here highlight a strong separation of scales normally occurring for such droplets. Namely, there is a narrow high-curvature zone localized at the foot of the droplet, where the apparent contact angle is formed, while the core of the droplet merely adheres to the classical (capillary–gravity) static shape. Experimentally, we rely upon interferometry to discern such fine key details. We detect a maximum of the droplet slope profile in the foot region, which amounts to the apparent contact angle. Theoretically, a local description of the foot region is devised. We indicate a crucial role of convective mixing by the solutal Marangoni flow, here accounted for by the Taylor dispersion, which proves to underlie the separation of scales and ensure self-consistency of the local model. Migration of such droplets in a humidity gradient is also approached within the same experimental and theoretical framework. It is considered that the resulting back–front asymmetry of the apparent contact angles drives the motion similarly to a wettability gradient, although the drag (‘Cox–Voinov’) factor is here found to be different. The predictions, comparing well with the measurements (our own and from the literature), are based on rigorous models, isothermal and as reduced as possible, without any fitting parameters or microphysics effects.

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Section: Discussionmentioning

confidence: 99%

Water–propylene glycol sessile droplet shapes and migration: Marangoni mixing and separation of scales

et al. 2022

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“…Two-dimensional and axissymmetric stationary problems were studied in [23] in the case of capillary numbers being small. Theoretical results of the study of apparent contact angles in a problem of an evaporating liquid placed on a solid substrate are presented in [26]. In [27], a moving contact line problem for two-phase incompressible flows was investigated based on the kinematic approach using an evolution equation for the contact angle in terms of the transporting velocity field; this approach and other common models including the gradients of surface tension and mass transfer across the fluid-fluid interface were analyzed.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of Thermocapillary Convection with Evaporation Induced by Boundary Heating

Goncharova,

Bekezhanova

2024

FDMP

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The dynamics of a bilayer system filling a rectangular cuvette subjected to external heating is studied. The influence of two types of thermal exposure on the flow pattern and on the dynamic contact angle is analyzed. In particular, the cases of local heating from below and distributed thermal load from the lateral walls are considered. The simulation is carried out within the frame of a two-sided evaporative convection model based on the Boussinesq approximation. A benzine-air system is considered as reference system. The variation in time of the contact angle is described for both heating modes. Under lateral heating, near-wall boundary layers emerge together with strong convection, whereas the local thermal load from the lower wall results in the formation of multicellular motion in the entire volume of the fluids and the appearance of transition regimes followed by a steady-state mode. The results of the present study can aid the design of equipment for thermal coating or drying and the development of methods for the formation of patterns with required structure and morphology.

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“…Evaporation of liquid droplets is an everyday life phenomenon that includes surprisingly complex problems of basic science. − A phenomenon which kept long interest of scientists is that single-component droplets on completely wetting substrates do not spread continuously but exhibit pseudostable apparent contact angles θ app . − …”

Section: Introductionmentioning

confidence: 99%

Evaporation Dynamics of Sessile Droplets: The Intricate Coupling of Capillary, Evaporation, and Marangoni Flow

Yang

Doi

et al. 2022

Langmuir

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A single-component droplet placed on a completely wetting substrate shows a pseudostable apparent contact angle (θ app ) during evaporation. We propose a simple theory to explain the phenomenon accounting for the liquid evaporation and the internal flow induced by the capillary and Marangoni effects. The theory predicts that when evaporation starts, the contact angle approaches to θ app in a short time τ s , remains constant for most of the time of evaporation, and finally increases rapidly when the droplet size becomes very small. This explains the behavior observed for alkane droplets. Analytical expressions are given for the apparent contact angle θ app and the relaxation time τ s , which predict how they change when the evaporation rate, droplet size, and other experimental parameters such as thermal conductivity of the substrate are changed.

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Contact angles for perfectly wetting pure liquids evaporating into air: Between de Gennes-type and other classical models

Cited by 4 publications

References 41 publications

Water–propylene glycol sessile droplet shapes and migration: Marangoni mixing and separation of scales

Water–propylene glycol sessile droplet shapes and migration: Marangoni mixing and separation of scales

Numerical Simulation of Thermocapillary Convection with Evaporation Induced by Boundary Heating

Evaporation Dynamics of Sessile Droplets: The Intricate Coupling of Capillary, Evaporation, and Marangoni Flow

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