LMA - Laboratoire de Mécanique et d’Acoustique

Marie Poulain Zarcos

Post-Doctorante, IMI

Key words : experimental techniques – particles dynamics – suspensions – micro-structure – turbulence – homogeneous and stratified fluid

Research Interests

- Vertical distribution of buoyant particles in anisotropic turbulence : laboratory modelling of the plastic pollution in the ocean

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  • Characterization of oscillating grid turbulence in homogeneous and two-layer fluid (PIV measurements)
  • Characterization of the suspension and measurements of depth concentration profile (2D measurements and PTV-4D measurements)
  • Modelling of the vertical distribution of buoyant particles (advection-diffusion equation)

- Micro-structure in sheared concentrated suspensions : laboratory modelling of red blood cells (more details below)

  • Characterization of opaque suspensions using both optical and ultrasound techniques (pair correlation function and structure factor)

Key words : experimental techniques – particles dynamics – suspensions – micro-structure – turbulence – homogeneous and stratified fluid

My Scientific Publications

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Transfer of technology

Plasticount (open-source tool to calculate corrected concentrations of plastic in the ocean, from sea surface measurements) : https://sourceforge.net/projects/pl...

Current research topic : Ultrasound for probing the micro-structure in sheared concentrated suspensions

Host institution : LMA & IUSTI
Supervisor : Emilie FRANCESCHINI (CR, LMA)
Co-supervisor : Laurence BERGOUGNOUX (MdC, IUSTI)
Funding : 2020 fellowship Institut de Mécanique et Ingéniérie (IMI)

Complex fluids are ubiquitous in nature and in industry : biological fluids (blood, mucus), erosion sludge or industrial pastes. From a theoretical point of view, the characterization of these media is confronted firstly to the huge variety of particle size and shape that compose them, and secondly to the coupling between the macroscopic and microscopic scales : the flow is controlled by the spatial distribution of the particles (i.e. the micro-structure of the suspension), but the macroscopic flow back-acts and modifies this micro-structure. From an experimental point of view, it is crucial to develop tools to investigate the micro-structure of concentrated suspensions. The use of optical methods is limited to diluted suspensions or transparent concentrated suspensions (by using an iso-index technique) that are not representative of natural or industrial conditions.

Our goal is to develop an ultrasonic tool for measuring the micro-structure of concentrated suspensions of particles in a shear flow. The principle is based on the experimental measurement of the structure factor, which is related to the Fourier transform of the pair correlation function. More precisely, the aim of my post doc fellow is to carry out ultrasonic and optical measurements on concentrated suspensions sheared in the same Couette flow device, using the optics (with refractive index matching) as a reference measurement. The ultrasound/optical confrontation will allow the validation of the ultrasound tool to characterize the micro-structure of concentrated suspensions, and will make it possible to consider in the future the characterization of the micro-structure of opaque suspensions with deformable particles (red blood cells), for which the rheology is still poorly understood.

Key words : Concentrated suspension – shear flow – ultrasounds – refractive index matching – micro-structure