Description du sujet de thèse

Over the past fifteen years, it has been established that there are close links between microstructure in a suspension under flow, rheology and particle characteristics (interaction between particles, particle shape). These links have made it possible, in simple cases, to propose a general framework for describing the complex rheological properties of concentrated non-Brownian suspensions. For example, we understand how direct contact interactions between particles, and in particular friction, influence rheological properties, and we know the microstructure created by simple shear flow in a suspension of frictional spheres.
In more complex cases, where particles may not be perfectly rigid, or may have an anisotropic shape or undergo adhesive interactions, the rheology is somewhat less well known and the microstructure has never been studied.
Filling this gap is the subject of the proposed PhD thesis. In addition, the characterisation of microstructure and rheology and the understanding of the links between them will be directly applied to the study of red blood cell suspensions. Certain blood diseases, such as sickle cell anaemia, cause defects in the aggregability and deformability of red blood cells. As part of the ANR HEMO project, we are working with biologists and acousticians to develop a tool based on acoustic backscatter for the early diagnosis of sickle cell diseases. Analysis of the acoustic backscatter signal gives access to the spatial arrangement of red blood cells. Before this can be done, it is necessary to understand, by studying model particle suspensions, how adhesion between particles and their rigidity affect the microstructure of a suspension.
The experiments will consist in investigating the 3D-microstructure and rheology of transparent suspensions (matching of refractive index of particles and liquid) of particles whose shape, rigidity and adhesion properties will be varied. The suspensions will be subjected to shear in a Couette cell equipped with an optical device (laser sheet + camera) that will provide measurements of the position and velocity of the particles in order to deduce the pair distribution function and the velocity field.

Contexte de travail

The work will include a significant experimental component, even though the device has already been developed and tested. In addition, the PhD student will have to process the images acquired using algorithms that have already been successfully tested, but which will need to be improved and adapted to the different types of Images collected.
The PhD student will be co-supervised by Frédéric Blanc and will interact with the entire INPHYNI Suspension Rheology team, which is developing experiments and numerical simulations in the field of the rheology of non-Brownian suspensions.

Le poste se situe dans un secteur relevant de la protection du potentiel scientifique et technique (PPST), et nécessite donc, conformément à la réglementation, que votre arrivée soit autorisée par l'autorité compétente du MESR.