Particle dynamics: From microplastics in the ocean to red blood cells
| When |
Dec 13, 2022
from 11:00 to 12:00 |
|---|---|
| Where | Salle des thèses |
| Attendees |
Marie Poulain-Zarcos |
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During this seminar, I will mainly present the result of my PhD on the vertical dynamics of buoyant particles in anisotropic turbulence, whose direct application is the microplastic (1 µm<L<5mm) pollution in the ocean. I will also present my current post-doc on the characterization of sheared concentrated suspensions by ultrasound, which is a clinical application to estimate the rate of aggregation in blood and (in the much longer term) to allow pre-diagnosis.
Details on the dynamics of particles in turbulence:
Often less dense than seawater, microplastics are mixed under the surface due to a surface stirring induced by wind and waves. Thanks to an analysis of samples collected at sea, a model, taking into account the properties (density, size, and shape) of micro-plastics is first proposed to better predict their buoyancy. Then, laboratory experiments using an oscillating grid system have been used to reproduce the surface mixing induced by wind and waves. The transport of idealized plastics (spheres and disks) in this setup is investigated to identify the parameter which controls the coupling between the particles and the flow, the turbulent Schmidt number. We propose a value of it for microplastics for the first time.
Details on the ultrasonic characterization of dense sheared suspensions:
Over the past decade, it has been shown that dense (>8%) suspensions of spherical particles in single shear flow exhibit anisotropic microstructure along the flow direction due to particle roughness. We prove that ultrasound can measure this anisotropy. For deformable and anisotropic particles such as red blood cells, this microstructure is still poorly understood. Thanks to ultrasonic measurements coupled to numerical simulations, we show the first results on the microstructure of red blood cells in a simple shear flow.