Competing Marangoni and Rayleigh convection in evaporating binary droplets

Christian Diddens*, Yaxing Li, Detlef Lohse*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

For a small sessile or pendant droplet it is generally assumed that gravity does not play any role once the Bond number is small. This is even assumed for evaporating binary sessile or pendant droplets, in which convective flows can be driven due to selective evaporation of one component and the resulting concentration and thus surface tension differences at the air-liquid interface. However, recent studies have shown that in such droplets gravity indeed can play a role and that natural convection can be the dominant driving mechanism for the flow inside evaporating binary droplets (Edwards et al.Phys. Rev. Lett., vol. 121, 2018, 184501; Li et al.Phys. Rev. Lett., vol. 122, 2019, 114501). In this study, we derive and validate a quasi-stationary model for the flow inside evaporating binary sessile and pendant droplets, which successfully allows one to predict the prevalence and the intriguing interaction of Rayleigh and/or Marangoni convection on the basis of a phase diagram for the flow field expressed in terms of the Rayleigh and Marangoni numbers.

Original languageEnglish
Article numberA23
Number of pages26
JournalJournal of fluid mechanics
Volume914
Early online date5 Mar 2021
DOIs
Publication statusE-pub ahead of print/First online - 5 Mar 2021

Keywords

  • UT-Hybrid-D
  • drops
  • Marangoni convection
  • buoyancy-driven instability

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