Surfactant-induced effects on turbulent swirling flows

Kartik Arora, Radhakrishna Sureshkumar, Matthew P. Scheiner, Justin L. Piper

Research output: Contribution to journalArticle

16 Scopus citations

Abstract

We employ digital particle imaging velocimetry (DPIV) to investigate the influence of a drag reducing cationic surfactant additive, cetyltrimethyl-ammonium chloride (CTAC), on turbulent swirling flows generated in a cylindrical vessel either by a rotating disk or a rotating disk fitted with vertical flat blades. The largest concentration of CTAC used in this study (0.05 ≤ C ≤ 0.5 mmol/1) is an order of magnitude smaller than those used in experimental investigations of surfactant induced drag reduction in turbulent pipe/channel flows. Even for such dilute systems, a number of dramatic and intriguing effects are observed. In the case of disk-driven flow, it is shown that the surfactant has a non-monotonic influence on turbulence intensity: both radial and axial root mean square velocity fluctuations first increase with increasing surfactant concentration C, reach a maximum and decrease upon further increase in C. Moreover, the maximum intensity is attained at a concentration that is practically independent of the angular frequency Ω of the disk. For the flow driven by bladed impeller, the introduction of the surfactant leads to flow reversal at the impeller plane for low concentrations. Enhancement in the radial and azimuthal mean velocities is also observed. For relatively larger concentrations (=0.5 mmol/1), a mean flow field that consists of multiple transient mixing pockets emerges as Ω exceeds a critical value. Plausible mechanisms are proposed to explain these observations.

Original languageEnglish (US)
Pages (from-to)25-34
Number of pages10
JournalRheologica Acta
Volume41
Issue number1
DOIs
StatePublished - Jan 1 2002
Externally publishedYes

Keywords

  • CTAC
  • Cationic surfactant
  • DPIV
  • Drag reduction
  • Rushton turbine
  • Stirred tank flow
  • Swirling flow
  • Viscoelastic

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics

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