A sequence of transcritical bifurcations in a suspension of gyrotactic microswimmers in vertical pipe
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Accepted version
Author(s)
Fung, Lloyd
Hwang, Yongyun
Type
Journal Article
Abstract
Kessler (Nature, vol. 313, 1985, pp. 218–220) first showed that plume-like structures spontaneously appear from both stationary and flowing suspensions of gyrotactic microswimmers in a vertical pipe. Recently, it has been shown that there exist multiple steady, axisymmetric and axially uniform solutions to such a system (Bees & Croze, Proc. R. Soc. A, vol. 466, 2010, pp. 2057–2077). In the present study, we generalise this finding by reporting that a countably infinite number of such solutions emerge as the Richardson number increases. Linear stability, weakly nonlinear and fully nonlinear analyses are performed, revealing that each of the solutions arises from the destabilisation of a uniform suspension. The countability of the solutions is due to the finite flow domain, while the transcritical nature of the bifurcation is because of the cylindrical geometry, which breaks the horizontal symmetry of the system. It is further shown that there exists a maximum threshold of achievable downward flow rate for each solution if the flow is to remain steady, as varying the pressure gradient can no longer increase the flow rate from the solution. All of the solutions found are unstable, except for the one arising at the lowest Richardson number, implying that they would play a role in the transient dynamics in the route from a uniform suspension to the fully developed gyrotactic pattern.
Date Issued
2020-11-01
Date Acceptance
2020-08-11
Citation
Journal of Fluid Mechanics, 2020, 902, pp.R2-1-R2-11
ISSN
0022-1120
Publisher
Cambridge University Press
Start Page
R2-1
End Page
R2-11
Journal / Book Title
Journal of Fluid Mechanics
Volume
902
Copyright Statement
© 2020 Cambridge University Press. This paper has been accepted for publication and will appear in a revised form, subsequent to peer-review and/or editorial input by Cambridge University Press.
Identifier
https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/sequence-of-transcritical-bifurcations-in-a-suspension-of-gyrotactic-microswimmers-in-vertical-pipe/E9D02870CD14AB742BAC68E4ED53D251
Subjects
physics.flu-dyn
physics.flu-dyn
physics.bio-ph
Fluids & Plasmas
01 Mathematical Sciences
09 Engineering
Publication Status
Published
Date Publish Online
2020-09-03