Signature of elastic turbulence of viscoelastic fluid flow in a single pore throat

Eseosa M. Ekanem, Steffen Berg, Shauvik De, Ali Fadili, Tom Bultreys, Maja Rücker, Jeffrey Southwick, John Crawshaw, and Paul F. Luckham
Phys. Rev. E 101, 042605 – Published 23 April 2020
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Abstract

When a viscoelastic fluid, such as an aqueous polymer solution, flows through a porous medium, the fluid undergoes a repetitive expansion and contraction as it passes from one pore to the next. Above a critical flow rate, the interaction between the viscoelastic nature of the polymer and the pore configuration results in spatial and temporal flow instabilities reminiscent of turbulentlike behavior, even though the Reynolds number Re1. To investigate whether this is caused by many repeated pore body–pore throat sequences, or simply a consequence of the converging (diverging) nature present in a single pore throat, we performed experiments using anionic hydrolyzed polyacrylamide (HPAM) in a microfluidic flow geometry representing a single pore throat. This allows the viscoelastic fluid to be characterized at increasing flow rates using microparticle image velocimetry in combination with pressure drop measurements. The key finding is that the effect, popularly known as “elastic turbulence,” occurs already in a single pore throat geometry. The critical Deborah number at which the transition in rheological flow behavior from pseudoplastic (shear thinning) to dilatant (shear thickening) strongly depends on the ionic strength, the type of cation in the anionic HPAM solution, and the nature of pore configuration. The transition towards the elastic turbulence regime was found to directly correlate with an increase in normal stresses. The topology parameter, Qf, computed from the velocity distribution, suggests that the “shear thickening” regime, where much of the elastic turbulence occurs in a single pore throat, is a consequence of viscoelastic normal stresses that cause a complex flow field. This flow field consists of extensional, shear, and rotational features around the constriction, as well as upstream and downstream of the constriction. Furthermore, this elastic turbulence regime, has high-pressure fluctuations, with a power-law decay exponent of up to |−2.1| which is higher than the Kolmogorov value for turbulence of |−5/3|.

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  • Received 28 September 2019
  • Accepted 23 March 2020

DOI:https://doi.org/10.1103/PhysRevE.101.042605

©2020 American Physical Society

Physics Subject Headings (PhySH)

Fluid DynamicsPolymers & Soft Matter

Authors & Affiliations

Eseosa M. Ekanem1, Steffen Berg1,3,2, Shauvik De4, Ali Fadili3, Tom Bultreys2,5, Maja Rücker1, Jeffrey Southwick3, John Crawshaw1, and Paul F. Luckham1,*

  • 1Department of Chemical Engineering, Imperial College London SW7 2AZ, United Kingdom
  • 2Department of Earth Science and Engineering, Imperial College London SW7 2AZ, United Kingdom
  • 3Shell Global Solutions International B.V, 1031HW Amsterdam, The Netherlands
  • 4Shell India Markets Private Limited, Karnataka 562149, Bangalore, India
  • 5PProGRess UGCT, Department of Geology, Ghent University, 9000 Gent, Belgium

  • *Corresponding author: p.luckham01@imperial.ac.uk

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Vol. 101, Iss. 4 — April 2020

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