Flow of wormlike micellar fluids around a sharp bend: Effects of branching and shear-banding

Yiran Zhang, Hadi Mohammadigoushki, Margaret Y. Hwang, and Susan J. Muller
Phys. Rev. Fluids 3, 093301 – Published 4 September 2018
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Abstract

The flow of wormlike micellar solutions around a 90° sharp microfluidic bend was studied using rheometry, flow visualization, and velocimetry. By carefully choosing the composition of the test solutions, all four combinations of linear or branched micelles and shear-banding or non-shear-banding solutions were accessed using four wormlike micellar solutions. The flow behavior of the solutions was examined in similar conditions of about 1 < Wi < 300 and 106<Re<102. When comparing the flow around the microbend of the two shear-banding solutions with the two non-shear-banding ones, the secondary flows showed distinct differences at about 10< Wi <100. Flow visualization showed that a steady lip vortex formed at the inner upstream corner of the microbend in the non-shear-banding solutions, while a lip (inner upstream corner) vortex and an outer corner vortex formed in the shear-banding solutions. On the other hand, when comparing the solutions with similar rheological characteristics but different micelle morphology (linear versus branched), no significant differences in the flow behavior were observed. These results suggest that shear-banding plays a central role in determining the secondary flow behavior around the microbend, while the effect of micelle morphology is minimal for wormlike micelle solutions. Additional particle tracking velocimetry measurements were carried out both upstream of and around the microbend. The resulting velocity profiles in the shear-banding solutions show marked disagreement with calculations based on the shear-rate-dependent apparent viscosity using the Carreau model. These results suggest that the shear-banding effect on the flow around the microbend could be correlated to the development of a “jetting” flow regime upstream of the bend, which could be a result of the nonmonotonic stress – shear rate relationship in shear-banding wormlike micellar solutions.

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  • Received 29 April 2018

DOI:https://doi.org/10.1103/PhysRevFluids.3.093301

©2018 American Physical Society

Physics Subject Headings (PhySH)

Fluid DynamicsPolymers & Soft Matter

Authors & Affiliations

Yiran Zhang1, Hadi Mohammadigoushki2, Margaret Y. Hwang1,*, and Susan J. Muller1,†

  • 1Department of Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, USA
  • 2Department of Chemical and Biomedical Engineering, FAMU-FSU College of Engineering, Tallahassee, Florida 32310, USA

  • *Current address: The Dow Chemical Company, Midland, Michigan 48686, USA.
  • Corresponding author: muller2@berkeley.edu

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Issue

Vol. 3, Iss. 9 — September 2018

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