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Evaporation of sessile droplets with moving contact lines - Pierre Colinet

TIPs, Université Libre de Bruxelles

This presentation will summarize some recent progresses in understanding the dynamics of partially or completely wetting sessile drops of volatile liquids, the contact line of which being free to advance by spreading or recede by evaporation. First, as moving contact lines are inherently associated with the well-known divergence of the viscous stress, some theoretical approaches enabling its relaxation are presented, in parallel with the corresponding resolution of the evaporation flux singularity [1,2]. Second, a recent asymptotic theory of evaporating sessile droplets is outlined, focusing on the possibility of reducing the overall dynamics to a simple coupled system of two ODE’s for the radius and volume [3].

Then, experimental results (mostly based on Mach-Zehnder interferometry) and interpreting theories are presented about : i) the values of apparent contact angles induced by evaporation, due to intense microflows occurring near the contact line [4] ; ii) the effect of buoyancy-induced convection in the gas phase, due to the vapor being heavier than air (here for a pendant droplet, see Ref. [5]) ; iii) the influence of the thermal Marangoni effect on the shape of thin droplets evaporating into air (see Ref. [6]) ; iv) the competition between spreading and evaporation of droplets deposited on structured substrates (square arrays of cylindrical pillars, see Ref. [7]).

Acknowledgements The author gratefully thanks co-authors of the presented work, namely A. Rednikov, S. Dehaeck, Y. Tsoumpas N. Savva, L. Mekhitarian, B. Sobac, and B. Haut. Financial support of ESA, BELSPO, and Fonds de la Recherche Scientifique – FNRS is also acknowledged.

[1] P. Colinet and A. Rednikov, EPJ – Special Topics, 2011, 197, 89–113.

[2] A. Rednikov and P. Colinet, Phys. Rev. E, 2013, 87, 010401(R).

[3] N. Savva, A. Rednikov and P. Colinet, J. Fluid Mech. 824, 574–623 (2017).

[4] Y. Tsoumpas, PhD thesis, 2014, Université Libre de Bruxelles, Bruxelles, Belgium.

[5] S. Dehaeck, A. Rednikov and P. Colinet, Langmuir, 2014, 30, 2002–2008.

[6] Y. Tsoumpas, S. Dehaeck, A. Rednikov and P. Colinet, Langmuir, 2015, 31,13334−13340.

[7] L. Mekhitarian, B. Sobac, S. Dehaeck, B. Haut and P. Colinet, Europhys. Lett. 120, 16001 (2017)


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