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A squirmer across Reynolds numbers

Chisholm, Nicholas G. and Legendre, Dominique and Lauga, Eric and Khair, Aditya S. A squirmer across Reynolds numbers. (2016) Journal of Fluid Mechanics, 796. 233-256. ISSN 0022-1120

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Official URL: https://doi.org/10.1017/jfm.2016.239

Abstract

The self-propulsion of a spherical squirmer – a model swimming organism that achieves locomotion via steady tangential movement of its surface – is quantified across the transition from viscously to inertially dominated flow. Specifically, the flow around a squirmer is computed for Reynolds numbers (Re) between 0.01 and 1000 by numerical solution of the Navier–Stokes equations. A squirmer with a fixed swimming stroke and fixed swimming direction is considered. We find that fluid inertia leads to profound differences in the locomotion of pusher (propelled from the rear) versus puller (propelled from the front) squirmers. Specifically, pushers have a swimming speed that increases monotonically with Re, and efficient convection of vorticity past their surface leads to steady axisymmetric flow that remains stable up to at least Re = 1000. In contrast, pullers have a swimming speed that is non-monotonic with Re. Moreover, they trap vorticity within their wake, which leads to flow instabilities that cause a decrease in the time-averaged swimming speed at large Re. The power expenditure and swimming efficiency are also computed. We show that pushers are more efficient at large Re, mainly because the flow around them can remain stable to much greater Re than is the case for pullers. Interestingly, if unstable axisymmetric flows at large Re are considered, pullers are more efficient due to the development of a Hill’s vortex-like wake structure

Item Type:Article
Additional Information:Thanks to Cambridge University Press editor. The original PDF of the article can be found at https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/squirmer-across-reynolds-numbers/D94B6D2BBD1DFE2B41525794128BBEF3
HAL Id:hal-01792474
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Other partners > Carnegie Mellon University - CMU (USA)
Université de Toulouse > Institut National Polytechnique de Toulouse - INPT (FRANCE)
Other partners > University of Cambridge (UNITED KINGDOM)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UPS (FRANCE)
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Deposited By: Dominique LEGENDRE
Deposited On:15 May 2018 13:01

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