Fluids Seminar – November 20, 2019 – Professor Eric Climent

Preferential accumulation and vertical migration of phytoplankton cells in turbulence

Professor Eric Climent
Institut de Mécanique des Fluides de Toulouse (IMFT)

When: November 20, 2019 | 4 PM
Where: CEME 2202 | 6250 Applied Science Lane
 
 
Abstract:Many phytoplankton species are motile, propelling themselves through water with velocities ranging from 10 to 1000 microns per second. Daily, phytoplankton needs to migrate vertically from and towards the ocean surface for light and to find nutrients such as dissolved oxygen. To travel through the water column, they need to fight against gravity (by swimming) and fluid turbulence which can make their journey longer.

The spatial distribution of unicellular organisms in the Ocean is observed to be heterogeneous. This communication demonstrates that heterogeneity can be generated ex novo at the smallest scales of turbulent flows via an active coupling between motility and hydrodynamic shear, and stands in direct contrast with the aforementioned mechanism that considers phytoplankton cells to act as passive tracers. It is often observed that cells migrate across the water column as chains. The purpose of our study is to elaborate on this observation as a potential benefit to swim as a chain in turbulence.

We carried out numerical simulations of the coupled system of homogeneous isotropic turbulence and gyrotactic cell trajectories through Lagrangian tracking. Realistic flows are obtained by randomly forcing large-scale fluid motions and solving Navier-Stokes equations through direct numerical simulations for the resultant turbulent motion. This flow is seeded with hundreds of thousands of cells and statistical analysis is carried out to find out the physical mechanisms.

 

Biography: Eric Climent is a full professor at University of Toulouse, France, and the current head of the Fluid Mechanics Institute in Toulouse that counts about 200 researchers in the field of Fluid Mechanics. Eric graduated his Master degree in 1993 and PhD degree in 1996 from University of Toulouse. From 1998 to 2007, he was an Associate professor at University of Strasbourg and University of Toulouse. From 1999 to 2003, he spent about 1 year and a half at Brown University as a visiting professor. His main area of research is the multi-scale modelling and numerical simulation of dispersed phase flows (bubbles, droplets and rigid particles) with potentially additional effects as chemical reactions, magnetic forces, interface properties and biological interactions.