Flow of wormlike micellar solutions around microfluidic cylinders with high aspect ratio and low blockage ratio

• Simon J., Haward

• Naoyuki, Kitajima

• Kazumi, Toda-Peters

• Tsutomu, Takahashi

• Amy Q., Shen

抄録

We employ time-resolved flow velocimetry and birefringence imaging methods to study the flow of a well-characterized shear-banding wormlike micellar solution around a novel glass-fabricated microfluidic circular cylinder. In contrast with typical microfluidic cylinders, our geometry is characterized by a high aspect ratio alpha = H/W = 5 and a low blockage ratio beta = 2r/W = 0.1, where H and W are the channel height and width, and the cylinder radius r = 20 mum. The small cylinder radius allows access up to very high Weissenberg numbers 1.9 </= Wi = lambdaMU/r </= 3750 (where lambdaM is the Maxwell relaxation time) while inertial effects remain entirely negligible (Reynolds number, Re < 10-4). At low Wi values, the flow remains steady and symmetric and a birefringent region (indicating micellar alignment and tensile stress) develops downstream of the cylinder. Above a critical value Wic approximately 60 the flow transitions to a steady asymmetric state, characterized as a supercritical pitchfork bifurcation, in which the fluid takes a preferential path around one side of the cylinder. At a second critical value Wic2 approximately 130, the flow becomes time-dependent, with a characteristic frequency f0 approximately 1/lambdaM. This initial transition to time dependence has characteristics of a subcritical Hopf bifurcation. Power spectra of the measured fluctuations become complex as Wi is increased further, showing a gradual slowing down of the dynamics and emergence of harmonics. A final transition at very high Wic3 corresponds to the re-emergence of a single peak in the power spectrum but at much higher frequency. We discuss this in terms of possible flow-induced breakage of micelles into shorter species with a faster relaxation time.

source:https://creativecommons.org/licenses/by/3.0/

source:https://pubs.rsc.org/en/content/articlelanding/2019/sm/c8sm02099j#!divAbstract

収録刊行物

• Soft Matter

  Soft Matter 15 (9), 1927-1941, 2019-01-18

  Royal Society of Chemistry

キーワード

• Condensed Matter Physics
• General Chemistry

詳細情報

• CRID: 1050282814244446336
• NII論文ID: 120006652920
• ISSN: 1744683X
• ISSN: 17446848
• DOI: 10.1039/c8sm02099j
• Web Site: http://id.nii.ac.jp/1394/00000891/
• Web Site: http://pubs.rsc.org/en/content/articlepdf/2019/SM/C8SM02099J
• 本文言語コード: en
• 資料種別: journal article
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