Unsteady feeding and optimal strokes of model ciliates

Abstract : The flow field created by swimming micro-organisms not only enables their locomotion but also leads to advective transport of nutrients. In this paper we address analytically and computationally the link between unsteady feeding and unsteady swimming on a model micro-organism, the spherical squirmer, actuating the fluid in a time-periodic manner. We start by performing asymptotic calculations at low Peclet number (Pe) on the advection-diffusion problem for the nutrients. We show that the mean rate of feeding as well as its fluctuations in time depend only on the swimming modes of the squirmer up to order Pe(3/2), even when no swimming occurs on average, while the influence of non-swimming modes comes in only at order Pe(2). We also show that generically we expect a phase delay between feeding and swimming of 1/8th of a period. Numerical computations for illustrative strokes at finite P e confirm quantitatively our analytical results linking swimming and feeding. We finally derive, and use, an adjoint-based optimization algorithm to determine the optimal unsteady strokes maximizing feeding rate for a fixed energy budget. The overall optimal feeder is always the optimal steady swimmer. Within the set of time-periodic strokes, the optimal feeding strokes are found to be equivalent to those optimizing periodic swimming for all values of the Peclet number, and correspond to a regularization of the overall steady optimal.
Type de document :
Article dans une revue
Journal of Fluid Mechanics, Cambridge University Press (CUP), 2013, 715, pp.1-31. 〈10.1017/jfm.2012.484〉
Liste complète des métadonnées

Littérature citée [29 références]  Voir  Masquer  Télécharger

https://hal-polytechnique.archives-ouvertes.fr/hal-00996495
Contributeur : Denis Roura <>
Soumis le : mardi 3 juin 2014 - 21:17:09
Dernière modification le : jeudi 12 avril 2018 - 01:48:57
Document(s) archivé(s) le : mercredi 3 septembre 2014 - 10:55:18

Fichier

S0022112012004843a.pdf
Fichiers éditeurs autorisés sur une archive ouverte

Identifiants

Collections

Citation

Sebastien Michelin, Eric Lauga. Unsteady feeding and optimal strokes of model ciliates. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2013, 715, pp.1-31. 〈10.1017/jfm.2012.484〉. 〈hal-00996495〉

Partager

Métriques

Consultations de la notice

179

Téléchargements de fichiers

63