Post-Doc position Available now

Mixing at low Reynolds number in sheared particulate suspensions

in collaboration with Henri Lhuissier.

Labex

A post-doc position is immediately available. The goal is to measure experimentally the evolution of the concentration distribution of a fluorescent scalar in a sheared particulate suspension. More info here: Post_doc_LabexOffer

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Revealing the frictional transition in shear thickening suspensions

The sudden and severe increase in the viscosity of certain suspensions above an onset stress is one of the most spectacular phenomena observed in complex fluids.  This shear thickening, which has major implications for industry, is a long-standing puzzle in soft-matter physics.  Recently, a frictional transition was conjectured to cause this phenomenon. Using experimental concepts from granular physics, we provide direct evidences that such suspensions are frictionless under low confining pressure, which is key to understanding their shear thickening behavior. More from PNAS here (2017_PNAS_Clavaud)

silice

Taylor’s experiment in a periodically sheared particulate suspension

We revisit Taylor’s experiment investigating the evolution of a blob of dye in a periodically sheared suspension of non-Brownian particles. Above a critical strain amplitude, particulate suspensions are subject to phase transition where reversibility is lost and particles fail to return to their original positions. We investigate the effect of this transition on the dispersion of a blob of dye. Beyond the critical strain, the dispersion of the blob is found to increase significantly. The dispersion coefficient of the blob of dye is measured and compared to the self-diffusivity coefficient of the particles. More from Phys. Rev. Fluids here  [2016_souzy_prf].TaylorExp_Souzy.png

Origin of critical strain amplitude in periodically sheared suspensions

The role of solid-solid contacts on the transition between reversible and irreversible dynamics occurring in periodically sheared suspensions is investigated experimentally by modifying the particle roughness. Smoother particles lead to a larger critical strain amplitude. A geometrical model based on the assumption that colliding particles produce irreversibility is derived. The model, which considers a quasiparticle having a strain- and roughness-dependent effective volume, successfully reproduces the measured values of the critical strain amplitude as functions of the volume fraction and particle roughness. More from Phys. Rev. Fluids here [2016_phong_prf].wing.png