The evaporation of surfactant-laden droplets: A comparison between contact line models

JOURNAL OF COLLOID AND INTERFACE SCIENCE

卷:579

Article

van Gaalen, R. T.¹  Diddens, C.^1,3  Wijshoff, H. M. A.^1,2  Kuerten, J. G. M.¹ 

[1] Eindhoven Univ Technol, Dept Mech Engn, POB 513, NL-5600 MB Eindhoven, Netherlands

[2] Canon Prod Printing Netherlands BV, POB 101, NL-5900 MA Venlo, Netherlands

[3] Univ Twente, Fac Sci & Technol TNW, POB 217, NL-7500 AE Enschede, Netherlands

关键词: Droplets;    Insoluble surfactants;    Evaporation;    Lubrication approximation;    Moving contact lines;   

DOI  :  10.1016/j.jcis.2020.06.099

来源: Elsevier

【 摘 要 】

Hypothesis: There are two different sharp-interface models for moving contact lines: slip models and precursor film models. While both models predict a mostly constant contact angle during the evaporation of pure droplets, it is expected that they behave differently when surfactants are present, because of the inherent dissimilarities in their respective interface definitions. Simulations: Both contact line models are numerically implemented using lubrication theory to analyze evaporating droplets. A convection-diffusion equation is implemented for insoluble surfactants. For pure droplets the models are compared with experiments performed by Nguyen et al. (2012). Findings: The two contact line models show results comparable to the experiments with pure droplets. If insoluble surfactants are present, the slip model increasingly shows pinning-like behavior as the initial surfactant concentration is increased. This 'quasi-pinning' is found to be consistent with experimental results in literature. The precursor film model, in contrast, shows no significant change when surfactants are added. This lack of change is a result of surfactant flowing from the droplet into the precursor film and vice versa. While suggesting potential solutions to this unphysical behavior, it is concluded that in the context of surfactants, slip models are preferable over precursor film models given the current state of the art. (C) 2020 The Author(s). Published by Elsevier Inc.

【 授权许可】

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