Effect of soluble surfactant on regime transitions at drop formation

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Abstract

Formation of surfactant-laden aqueous drops by liquid flow through a capillary is studied and compared with two reference pure liquids, water and low viscosity poly(dimethylsiloxane). Attention is paid to two transitions: (i) between regimes with and without satellite droplet formation and (ii) from dripping to jetting. It is shown that transition from dripping to jetting occurs at critical Weber number WeJ  = 1.2 ± 0.1 based on dynamic surface tension on the flow timescale. Critical Weber number for transition to the regime without satellite droplets depends noticeably on the liquid surface tension and therefore cannot be used as a single parameter characterising this transition. Flow rate at transition decreases with decrease of surface tension for pure liquids and solutions of surfactants with critical micelle concentration, CMC > 10 mM. For solutions of surfactants with CMC < 1 mM transition to the regime without satellite droplets occurs at flow rates either larger or smaller than that of pure solvent depending on concentration. Anomalously high transition flow rates are related to surfactant redistribution during the time between the primary and secondary pinch-off.
Original languageEnglish
Pages (from-to)1-7
JournalColloids and Surfaces A: Physicochemical and Engineering Aspects
Early online date17 Feb 2018
DOIs
Publication statusPublished - 20 May 2018

Keywords

  • Drop formation
  • Pinch-off
  • Flow rate
  • Dynamic surface tension
  • Critical micelle concentration
  • Satellite droplet
  • Dripping to jetting transition

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