Non-linear dynamics of semi-dilute polydisperse polymer solutions in microfluidics: effects of flow geometry |
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Authors: | Zhuo Li Xue-Feng Yuan Simon J Haward Jeffrey A Odell Stephen Yeates |
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Institution: | (1) Manchester Interdisciplinary Biocentre and School of Chemical Engineering and Analytical Science, University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK;(2) HH Wills Physics Laboratory, The University of Bristol, Tyndall Avenue, Bristol, BS8 1TL, UK;(3) School of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK; |
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Abstract: | The non-linear dynamics of a semi-dilute (c/c* = 15) polydisperse polyethylene oxide (PEO) solution in microfluidics are studied experimentally using benchmark contraction–expansion
flow geometries with three contraction–expansion ratios (4:1:4, 8:1:8 and 16:1:16) and two narrow channel lengths (L
c/D
h = 53 and 5.3, where L
c is the length of the narrow channel and D
h is its hydraulic diameter). Complex flows over a range of elasticity numbers (El), Weissenberg numbers (Wi) and Reynolds numbers (Re) are characterized using micro-particle image velocimetry (
\upmu\upmu-PIV) and pressure drop measurements. The evolution of vortex formation and dynamics has been visualized through a step-flow-rate
experiment. Various flow dynamics regimes have been quantified and are presented in a Wi–Re diagram. The experimental results reveal that the contraction ratio can result in qualitatively different vortex dynamics
of semi-dilute polymer solutions in microfluidics, whereas the length of the narrow channel merely affects the dynamics at
a quantitative level. A single elasticity number, if defined by the size of the narrow channel, is not sufficient to account
for the effects of contraction ratio on the non-linear vortex dynamics. |
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Keywords: | |
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