Effect of contact line dynamics on the thermocapillary motion of a droplet on an inclined plate

Karapetsas, G and Sahu, K C and Matar, O K (2013) Effect of contact line dynamics on the thermocapillary motion of a droplet on an inclined plate. Langmuir, 29 (28). pp. 8892-8906. ISSN 0743-7463

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We study the two-dimensional dynamics of a droplet on an inclined, nonisothermal solid substrate. We use lubrication theory to obtain a single evolution equation for the interface, which accounts for gravity, capillarity, and thermo-capillarity, brought about by the dependence of the surface tension on temperature. The contact line motion is modeled using a relation that couples the contact line speed to the difference between the dynamic and equilibrium contact angles. The latter are allowed to vary dynamically during the droplet motion through the dependence of the liquid-gas, liquid-solid, and solid-gas surface tensions on the local contact line temperature, thereby altering the local substrate wettability at the two edges of the drop. This is an important feature of our model, which distinguishes it from previous work wherein the contact angle was kept constant. We use finite-elements for the discretization of all spatial derivatives and the implicit Euler method to advance the solution in time. A full parametric study is carried out in order to investigate the interplay between Marangoni stresses, induced by thermo-capillarity, gravity, and contact line dynamics in the presence of local wettability variations. Our results, which are generated for constant substrate temperature gradients, demonstrate that temperature-induced variations of the equilibrium contact angle give rise to complex dynamics. This includes enhanced spreading rates, nonmonotonic dependence of the contact line speed on the applied substrate temperature gradient, as well as "stick-slip" behavior. The mechanisms underlying this dynamics are elucidated herein

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IITH Creators:
IITH CreatorsORCiD
Item Type: Article
Uncontrolled Keywords: Contact-line dynamics; Evolution equations; Implicit Euler method; Non-monotonic dependence; Spatial derivatives; Substrate temperature; Temperature-induced; Wettability variation
Subjects: Chemical Engineering > Biochemical Engineering
Divisions: Department of Chemical Engineering
Depositing User: Team Library
Date Deposited: 28 Nov 2014 11:39
Last Modified: 05 Mar 2015 10:29
URI: http://raiith.iith.ac.in/id/eprint/1057
Publisher URL: http://dx.doi.org/10.1021/la4014027
OA policy: http://www.sherpa.ac.uk/romeo/issn/0743-7463/
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