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Quasi-static secondary flow regions formed by microfluidic contraction flows of wormlike micellar solutions
Cited 7 time in
Web of Science
Cited 8 time in Scopus
- Authors
- Issue Date
- 2021-09
- Publisher
- American Institute of Physics
- Citation
- Physics of Fluids, Vol.33 No.9, p. 093112
- Abstract
- This study investigates the effects of yield stress (tau(0)) and shear banding on the fluidic behaviors of cetyltrimethylammonium bromide/sodium salicylate wormlike micellar solutions flowing through a microfluidic planar contraction (8:1) geometry. Test solutions with different surfactant concentrations (C-d = 75, 87.5, and 100 mM) at a fixed molar ratio of salt to surfactant (R = 0.32) were characterized by shear and extensional rheometry. While the lower concentrated test solution (C-d = 75 mM) with low tau(0) (& AP; 0.02 Pa) and no shear banding showed a Newtonian-like flow behavior for Mach number, Ma < 1, the flow with corner vortices was formed when Ma exceeds unity. For higher C-d (87.5 and 100 mM), new fluidic phenomena are documented: (i) even at a low volumetric flow rate (Q), the fluid velocity at upstream corners was slower than that of Newtonian-like flows and (ii) at higher Q, the secondary flow with a quasi-static condition was formed at Ma well lower than unity. Micro-particle image velocimetry showed the lower shear rates at upstream corners, which can be understood by the effects of contraction entry, shear thinning, and high yield stress. The quasi-static secondary flow region was not induced by generation of elastic shock waves; instead the shear banding was found to be the underlying mechanism for the separation of the region from the main flow. In addition, the length of secondary flow regions showed a close correlation with the Deborah number, which was calculated using the extensional relaxation time.
- ISSN
- 1070-6631
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