Reference : UMR7641-NASNAA-011
Workplace : PALAISEAU
Date of publication : Wednesday, September 14, 2022
Scientific Responsible name : Aline Lefebvre-Lepot (junior CNRS researcher, CMAP) and Georges Gauthier (Assistant professor, FAST)
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 December 2022
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
Suspensions, composed of macroscopic particles immersed in a viscous fluid, are present in various fields, both industrial (waste treatment, concrete, transport of pastes or granules...), natural (silting, coastal dynamics, landslides, dispersion of pollutants...) or sanitary (wastewater treatment...). Although they are present in everyday life, the flow properties of these systems are still partly not understood. It is now well established that a better understanding of the behaviour of these systems requires their numerical simulation at the particle scale.
The objective of the project is to improve the understanding of the mechanisms behind concentration or blocking instabilities in the flow of rheo-thickening suspensions in confined geometries (e.g. flow in a small diameter tube) and then to compare them with the theoretical predictions of the rheological model developed by Wyart and Cates. In the framework of this project, the candidate will combine the numerical approach, which will give access to the details of the fluid/particle and particle/particle interactions, and the experimental approach, for the macroscopic study of the instability (threshold, growth rate, etc.) and the determination of the simulations to be performed.
- From a numerical point of view, the candidate will use the HPC simulation code developed by the CMAP team, coupling a fluid/particle finite element solver and a contact dynamics solver SCoPI. During the thesis, the candidate will have to complete the code in order to take into account the inertia of the particles and the unsteady term in the simulation of the fluid phase. The student will also have to develop tools for post-processing the data (numerical and experimental).
- The candidate will rely on two experimental devices of suspensions flows present in the FAST laboratory and will study the flow by analysis and image processing. The objective of these experiments is to obtain observables that can be compared with the results of numerical simulations.
- Thanks to these numerical and experimental tools, the candidate will study the influence of inertia on observables such as the tensor of deformations, stresses, the density of contacts and fraction of frictional and lubricated contacts.
The thesis will be carried out within the framework of the SISSI project (Simulations Instationnaires de Suspensions de Particles Solides Inertielles) at the interface between physics of macroscopic suspensions at low Reynolds number, mathematical modelling, numerical analysis and HPC programming. This project is supported by the Mission for Transversal and Interdisciplinary Initiatives of CNRS.
To achieve its objectives, the interdisciplinary SISSI project combines the expertise of two complementary teams: numerical analysis and software programming of the Centre of Applied Mathematics (CMAP) team and rheology and suspension flows of the Suspensions and Granular team of the FAST laboratory.
The thesis project will thus be carried out in interaction between two laboratories:
- CMAP (Ecole Polytechnique, Institut Polytechnique de Paris, Palaiseau) whose objective is the development and exploration of mathematics in relation to applications. Structured in 4 research poles and 10 teams, CMAP brings together 62 researchers and teacher-researchers, 13 engineers, technicians and administrative staff and approximately 150 doctoral students, post-docs, associate researchers and interns. The student will work in the "PDEs for physics" team of the "Numerical Analysis and Partial Differential Equations" division of the laboratory.
- The FAST (Paris-Saclay University, Orsay), whose subjects are related to hydrodynamics, transfers, mechanics and physics of dispersed media. Structured in 4 research themes, the FAST brings together 23 researchers and teacher-researchers, 7 engineers, technicians and administrative staff and approximately 15 doctoral students, post-docs, associate researchers and interns. The student will be part of the Granular and Suspension team of the laboratory.
The thesis will be supervised by A. Lefebvre-Lepot (CMAP) and G. Gauthier (FAST). The candidate will also be co-supervised by B. Darbois-Texier (FAST) and L. Gouarin (CMAP). He/she will be a member of both laboratories, whose geographical proximity will allow numerous exchanges. Bi-monthly meetings will be organised between the different partners.
The candidate should have a Master's degree in Physics or Mechanics of Continuous Media (Fluids or Solids) with a strong numerical orientation. Ideally, the person recruited should have a background in numerical simulation methods related to physical problems (granular media, suspensions or other...). A good knowledge of the Python language is desirable. Knowledge of C++ and/or experience in high performance computing would be an advantage.
Applications should include
- a curriculum vitae and contact details of persons who can give a reasoned opinion on the applicant
- a letter of motivation describing the applicant's interest in the research project
- Master's grades (M1, M2)
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