Viscoelastic flow in an obstructed microchannel at high Weissenberg number

Kevin P. Nolan, Akshat Agarwal, Shenghui Lei, Robin Adam Shields

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)

Abstract

Detailed measurements of the flow instability of dilute shear-thinning viscoelastic aqueous solutions, with relatively low zero-shear viscosities, in an obstructed microchannel flow are reported. We examine the flow behaviour resulting from a 100 mu m post placed in the channel centreline over a range of Reynolds numbers (5 <Re <300) and Weissenberg numbers (20 <Wi <10(3)). Micro-particle image velocimetry measurements show the onset of an upstream instability within a Reynolds number range and at a critical elasticity number corresponding to polymer concentrations above 25 ppm of long-chain polyacrylamide. The instability results in significant local fluctuations in the flow field approaching 30 % of the mean velocity. The magnitude of the local viscosity ratio in the region upstream of the post is proposed as a driving mechanism for the instability which resembles a buckling flow. Additionally, the classical instability owing to separation and vortex formation downstream of the post in Newtonian flow is suppressed and a very long stable wake is observed extending over 10 post-diameters downstream.

Original languageEnglish
Article number101
JournalMicrofluidics and Nanofluidics
Volume20
Issue number7
Early online date27 Jun 2016
DOIs
Publication statusPublished - Jul 2016

Keywords

  • HEAT-TRANSFER
  • ELASTIC TURBULENCE
  • CIRCULAR-CYLINDER
  • MOLECULAR-WEIGHT
  • CHANNEL FLOW
  • INSTABILITIES
  • FLUIDS
  • POWER

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