Abstract

Droplets of oil containing oleic acid were observed to spread, then recoil, on an aqueous solution of sodium hydroxide. Surfactant is produced at the interface during spreading, and for reagent concentrations of order O(1mM) spreading is observed to be much faster than in the absence of a chemical reaction [radius R(t)∝tα with 0.64<α<0.89]. After t∼10s, drops reach a maximum radius Rmax∼3-5 times the initial radius. Spreading is faster and Rmax is larger for higher concentrations of reagents. The drops are then observed to recoil (with apparent power-law behavior -0.34<α<-0.14), due to diffusion of surfactant away from the oil/water interface, with the rate of recoil being controlled by the NaOH concentration.

Original languageEnglish (US)
Article number038105
JournalPhysics of Fluids
Volume18
Issue number3
DOIs
StatePublished - Mar 2006

All Science Journal Classification (ASJC) codes

  • Computational Mechanics
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering
  • Fluid Flow and Transfer Processes

Keywords

  • Chemically reactive flow
  • Diffusion
  • Drops
  • Film flow
  • Liquid films
  • Oils
  • Sodium compounds
  • Surfactants
  • Two-phase flow
  • Water
  • Wetting

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