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Accueil > Groupes de Recherche > Particules, Sprays et Combustion > Transferts, écoulements et suspensions biologiques > Collective dynamics of active swimmers

Collective dynamics of active swimmers

27 mai 2013

Academic involved : Eric Climent, Olivier Praud, Pascal Fede, Franck Plouraboué

Collaborators : M. Durham Oxford Univ, R. Stocker MIT - USA, X. Druart, INRA Tours, P. Degond, Imperial College, London UK, X. Descombes, INRIA, Sophia-Antipolis.

This topic is interested in active micro-swimmers.

First, we are interested in phytoplankton which is responsible for nearly half of the world’s production of oxygen and comprise
the base of the marine food web. The spatial
distribution of these unicellular organisms is
observed to be heterogeneous at nearly all scales.
We have shown that two simple ingredients, both ubiquitous in the ocean, are sufficient to generate striking small-scale
heterogeneity in the distribution of motile phytoplankton : asymmetric cell morphology and hydrodynamic shear.
By seeding a turbulent flow field generated by
Direct Numerical Simulation with Lagrangian gyro-tactic cells, we are able to explore the parameter space inhabited by marine
phytoplankton (white trajectory in the figure).
Individuals might be able to actively determine their tendency to accumulate by controlling their morphology and swimming
speed.

Furthermore we are interested in the collective dynamic which governs sperm motility. This research is funded by project MOTIMO (http://perso.math.univ-toulouse.fr/…) directed par Pr Pierre Degond de IMT (UMR CNRS 5219).

We are working on the numerical modeling and the experimental analysis of sperm collective motility, called massal motility by fertility biologist. The aim of this project is to provide some objective scoring of ovine semen.

From the experimental side we observe the collective motion of whirlpools resulting from the microscope phase-contrast observation of fresh semen. We also analyze the rheology of various sperm components (plasma, mucus, pure semen). We are interested in understanding the origin of whirlpools, and identifying the main mechanisms which couples the spermatozoan swim.

From the numerical side, we try to develop new methods for the description of complex deformable active particle resulting from assembling spherical and/or elliptic beads (Cf figure) as well as to take into account their interactions within a Newtonian fluid resulting in self-organized collective states.

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