Loading…

Effect of blockage ratio on flow of a viscoelastic wormlike micellar solution past a cylinder in a microchannel

We present experiments on the flow of a viscoelastic wormlike micellar solution around cylinders (radius R ) confined in straight microchannels (width W ). Thirteen flow geometries are tested where the blockage ratio is varied over a wide range 0.055 ≤ B R = 2 R / W ≤ 0.63. Experiments are performed...

Full description

Saved in:
Bibliographic Details
Published in:Soft matter 2022-11, Vol.18 (46), p.8856-8866
Main Authors: Hopkins, Cameron C, Shen, Amy Q, Haward, Simon J
Format: Article
Language:English
Subjects:
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:We present experiments on the flow of a viscoelastic wormlike micellar solution around cylinders (radius R ) confined in straight microchannels (width W ). Thirteen flow geometries are tested where the blockage ratio is varied over a wide range 0.055 ≤ B R = 2 R / W ≤ 0.63. Experiments are performed at negligible Reynolds number, and for Weissenberg numbers Wi = λU / R up to 1000, where U is the average flow speed and λ is the relaxation time of the fluid. Micro-particle image velocimetry is used to characterise the flow state at each B R and Wi . In all of the geometries, a first critical Weissenberg number marks a transition from symmetric flow to an asymmetric but time-steady flow state, while a second higher critical Weissenberg number marks the onset of time-dependent flows. However, we report a clear shift in behaviour over a narrow intermediate range of 0.33 B R 0.41. Channels with B R ≤ 0.33 fall in a 'low' B R regime, with instabilities that originate from the downstream stagnation point, while those with B R ≥ 0.44 fall in a 'high' BR regime, with instabilities developing at the upstream stagnation point. Behaviour within the newly-identified intermediate B R regime is complex due to the competing influence of the two stagnation points. We summarise all our results in a flow state diagram covering Wi - B R parameter space, clearly defining the different regimes of blockage ratio for the first time. Our results contribute to the understanding of the complexities of viscoelastic flow in this benchmark geometry. We present experiments on the flow of a viscoelastic fluid past a cylinder in a microchannel. Different elastic flow instabilities are examined and summarised in a flow state diagram covering Weissenberg number - blockage ratio parameter space.
ISSN:1744-683X
1744-6848
1744-6848
DOI:10.1039/d2sm01162j