Flow instabilities due to the interfacial formation of surfactant-fatty acid material in a Hele-Shaw cell

Zahra Niroobakhsh, Matthew Litman, Andrew Belmonte

Research output: Contribution to journalArticle

10 Scopus citations

Abstract

We present an experimental study of pattern formation during the penetration of an aqueous surfactant solution into a liquid fatty acid in a Hele-Shaw cell. When a solution of the cationic surfactant cetylpyridinium chloride is injected into oleic acid, a wide variety of fingering patterns are observed as a function of surfactant concentration and flow rate, which are strikingly different than the classic Saffman-Taylor (ST) instability. We observe evidence of interfacial material forming between the two liquids, causing these instabilities. Moreover, the number of fingers decreases with increasing flow rate Q, while the average finger width increases with Q, both trends opposite to the ST case. Bulk rheology on related mixtures indicates a gel-like state. Comparison of experiments using other oils indicates the importance of pH and the carboxylic head group in the formation of the surfactant-fatty acid material.

Original languageEnglish (US)
Article number053102
JournalPhysical Review E
Volume96
Issue number5
DOIs
StatePublished - Nov 6 2017

All Science Journal Classification (ASJC) codes

  • Statistical and Nonlinear Physics
  • Statistics and Probability
  • Condensed Matter Physics

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