Collective and convective effects compete in patterns of dissolving surface droplets

Abstract

Detlef (2016) Collective and convective effects compete in patterns of dissolving surface droplets. Soft Matter, 12 (26 Northumbria University has developed Northumbria Research Link (NRL) to enable users to access the University's research output. Copyright © and moral rights for items on NRL are retained by the individual author(s) and/or other copyright owners. Single copies of full items can be reproduced, displayed or performed, and given to third parties in any format or medium for personal research or study, educational, or not-for-profit purposes without prior permission or charge, provided the authors, title and full bibliographic details are given, as well as a hyperlink and/or URL to the original metadata page. The content must not be changed in any way. Full items must not be sold commercially in any format or medium without formal permission of the copyright holder. The full policy is available online: http://nrl.northumbria.ac.uk/policies.html This document may differ from the final, published version of the research and has been made available online in accordance with publisher policies. To read and/or cite from the published version of the research, please visit the publisher's website (a subscription may be required.) This is an Accepted Manuscript, which has been through the Royal Society of Chemistry peer review process and has been accepted for publication.Accepted Manuscripts are published online shortly after acceptance, before technical editing, formatting and proof reading. Using this free service, authors can make their results available to the community, in citable form, before we publish the edited article. We will replace this Accepted Manuscript with the edited and formatted Advance Article as soon as it is available.You can find more information about Accepted Manuscripts in the Information for Authors. The effect of neighboring droplets on the dissolution of a sessile droplet, i.e. collective effects, are investigated both experimentally and numerically. On the experimental side small 20 n approximately mono-disperse surface droplets arranged in an ordered pattern were dissolved and their size evolution is studied optically. The droplet dissolution time was studied for various droplet patterns. On the numerical side, Lattice-Boltzmann simulations were performed. Both simulations and experiments show that the dissolution time of a droplet placed in the center of a pattern can increase with as much as 60% as compared to a single, isolated droplet, due to the shielding effect of the neighboring droplets. However, the experiments also show that neighboring droplets enhance the buoyancy driven convective flow of the bulk, increasing the mass exchange and counteracting collective effects. We show that this enhanced convection can reduce the dissolution time of droplets at the edges of the pattern to values below that of a single, isolated droplet.

Diffusion dominated evaporation in multicomponent lattice Boltzmann simulations

“…Therefore, it is not surprising that a number of groups has simulated evaporating fluids using the LBM recently. Ledesma-Aguilar et al [22,23] present a diffusion based evaporation method based on the free energy multiphase lattice Boltzmann method and demonstrate quantitative agreement with several benchmark cases as well as qualitative agreement with the experimental data of evaporating droplet arrays. Jansen et al [24] study the evaporation of droplets on a chemically patterned substrate and qualitatively compare the simulation results with experimental data.…”

Natural convection above circular disks of evaporating liquids

“…Consequently, from Eqs. (23) and (20), our analysis yields the following law for the evaporation flux: where a 1 and a 2 are two constant numbers. By inspection of Eq.…”

“…From the point of view of the governing equations, the evaporation of a liquid is similar to the dissolution of a liquid into another. Recent attention has been devoted to the sessile drop dissolution [21,22,23] and bubble growth in supersaturated solutions [24] with a combination of experimental, numerical and theoretical investigations. These studies show that natural convection is also observed above dissolving drops.…”

Convection-dominated dissolution for single and multiple immersed sessile droplets

“…the effect of the neighbouring droplets). When there are multiple droplets, one expects that the presence of the neighbouring droplets leads to shielding effects, as are indeed seen in Carrier et al (2016), Laghezza et al (2016), Bao et al (2018) and Wray, Duffy & Wilson (2019). As a result, the lifetime for multiple droplets becomes longer than that for a single droplet.…”

“…These authors have constructed the theoretical framework to account for such purely diffusive shielding effects; but, for collective effects affected by convection, many questions remain open. Laghezza et al (2016) have experimentally studied collective droplet dissolution in the regime in which convection is relevant. They report that, remarkably, the neighbouring droplets can enhance the mass flux because of enhanced buoyancydriven convective flow in the bulk, but the detailed fluid dynamics of the process remains to be elucidated.…”