Gyrotactic suppression and emergence of chaotic trajectories of swimming particles in three-dimensional flows

Richardson, S.I. H., Baggaley, A.W. and Hill, N.A. (2018) Gyrotactic suppression and emergence of chaotic trajectories of swimming particles in three-dimensional flows. Physical Review Fluids, 3(2), 023102. (doi: 10.1103/PhysRevFluids.3.023102)

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We study the effects of imposed {three-dimensional flows} on the trajectories and mixing of gyrotactic swimming micro-organisms, and identify new phenomena not seen in flows restricted to two dimensions. Through numerical simulation of Taylor--Green and ABC flows, we explore the role that the flow and the cell shape play in determining the long-term configuration of the cells' trajectories, which often take the form of multiple sinuous and helical `plume-like' structures, even in the chaotic ABC flow. This gyrotactic suppression of Lagrangian chaos persists even in the presence of random noise. Analytical solutions for a number of cases reveal the how plumes form and the nature of the competition between torques acting on individual cells. \note{Furthermore, studies of Lyapunov exponents reveal that as the ratio of cell swimming speed relative to the flow speed increases from zero, the initial chaotic trajectories are first suppressed and then give way to a second unexpected window of chaotic trajectories at speeds greater than unity, before suppression of chaos at high relative swimming speeds.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Hill, Professor Nicholas and Richardson, Scott Ian
Authors: Richardson, S.I. H., Baggaley, A.W., and Hill, N.A.
College/School:College of Science and Engineering > School of Mathematics and Statistics > Mathematics
Journal Name:Physical Review Fluids
Publisher:American Physical Society
ISSN (Online):2469-990X
Published Online:23 February 2018
Copyright Holders:Copyright © 2018 American Physical Society
First Published:First published in Physical Review Fluids 3(2): 023102
Publisher Policy:Reproduced in accordance with the publisher copyright policy

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