Soutenance de Thomas Basset
| When |
Jun 26, 2023
from 02:00 to 04:00 |
|---|---|
| Where | Amphi Physique Chimie |
| Contact Name | Thomas Basset |
| Attendees |
Thomas Basset |
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Describing a flow as a set of fluid particle trajectories is a necessary approach to understand its Lagrangian dynamics but also to characterise the dispersion of particles it generates, omnipresent in natural environments (pollutants in the ocean or the atmosphere) or industrial environments (chemical reactors). The recent development of optical particle tracking methods allows to study experimentally this question for different types of particles and/or flows. In this thesis, we limit ourselves to tracers (fluid particles) and to two types of turbulent flow.
A first part focuses on a large database of experimental trajectories in homogeneous isotropic turbulence. A complete Lagrangian study is carried out to obtain a fine characterisation of turbulence in velocity and acceleration for a wide range of Reynolds numbers. A modelling of pair dispersion is also proposed, with new elements for its understanding in the framework of the ballistic cascade phenomenology.
A second part is devoted to the Lagrangian experimental study of a turbulent jet. The influence of an inhomogeneous nozzle seeding is described quantitatively. This approach, which reveals the original phenomenon of effective compressibility, allows a new understanding of entrainment and turbulent diffusion. A Lagrangian analysis of this inhomogeneous flow is also performed. A new stationarisation method is successfully applied to compensate the flow inhomogeneity and provide a large-scale characterisation in velocity and acceleration.