We study the dynamics and the statistics of dilute suspensions of gyrotactic swimmers, a model for many aquatic motile microorganisms. By means of extensive numerical simulations of the Navier-Stokes equations at different Reynolds numbers, we investigate preferential sampling and small-scale clustering as a function of the swimming (stability and speed) and shape parameters, considering in particular the limits of spherical and rod-like particles. While spherical swimmers preferentially sample local downwelling flow, for elongated swimmers we observe a transition from downwelling to upwelling regions at sufficiently high swimming speed. The spatial distribution of both spherical and elongated swimmers is found to be fractal at small scales in a wide range of swimming parameters. The direct comparison between the different shapes shows that spherical swimmers are more clusterized at small stability and speed numbers, while for large values of the parameters elongated cells concentrate more. The relevance of our results for phytoplankton swimming in the ocean is briefly discussed.

Borgnino, M., Boffetta, G., De Lillo, F., Cencini, M. (2018). Gyrotactic swimmers in turbulence: shape effects and role of the large-scale flow. JOURNAL OF FLUID MECHANICS, 856, 1-11 [10.1017/jfm.2018.767].

Gyrotactic swimmers in turbulence: shape effects and role of the large-scale flow

Borgnino, M
;
2018

Abstract

We study the dynamics and the statistics of dilute suspensions of gyrotactic swimmers, a model for many aquatic motile microorganisms. By means of extensive numerical simulations of the Navier-Stokes equations at different Reynolds numbers, we investigate preferential sampling and small-scale clustering as a function of the swimming (stability and speed) and shape parameters, considering in particular the limits of spherical and rod-like particles. While spherical swimmers preferentially sample local downwelling flow, for elongated swimmers we observe a transition from downwelling to upwelling regions at sufficiently high swimming speed. The spatial distribution of both spherical and elongated swimmers is found to be fractal at small scales in a wide range of swimming parameters. The direct comparison between the different shapes shows that spherical swimmers are more clusterized at small stability and speed numbers, while for large values of the parameters elongated cells concentrate more. The relevance of our results for phytoplankton swimming in the ocean is briefly discussed.
Articolo in rivista - Articolo scientifico
microorganism dynamics; nonlinear dynamical systems; turbulent flows;
English
2018
856
1
11
R1
reserved
Borgnino, M., Boffetta, G., De Lillo, F., Cencini, M. (2018). Gyrotactic swimmers in turbulence: shape effects and role of the large-scale flow. JOURNAL OF FLUID MECHANICS, 856, 1-11 [10.1017/jfm.2018.767].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/440943
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