Milieux Divisés et Fluides Complexes
Les activités de cet axe traitent de l’écoulement, de la mécanique et de la caractérisation optique des milieux divisés et des fluides complexes, allant des nanoparticules et aérosols jusqu’aux suspensions et milieux granulaires, en passant par les systèmes biologiques ou biomimétiques. Ces matériaux, constitués d’une phase solide dispersée et d’un fluide interstitiel, sont omniprésents dans l’industrie, les phénomènes naturels ou la biologie. Nous les abordons sur la base d’expérimentations contrôlées, souvent couplées à des approches théoriques et/ou numériques.
Les activités de l’axe se regroupent autour de 4 grandes thématiques :
Cette thématique porte sur la diffusion de la lumière par des milieux particulaires de taille nano- ou micrométrique (…)
Cette thématique porte sur comportement statique et dynamique des milieux granulaires secs et des poudres (…)
Cette thématique porte sur les mélanges fluide/grain, les suspensions denses, les granulaires immergés (…)
Cette thématique porte sur des questions de biomécanique des plantes et de couplages fluide/structure (…)
Ouardia AIT OUCHEGGOU, Alice BILLON, Bruno ETCHEVERRY, Adrien GANS, Quentin GAUBERT, Cédric MONTET, Mariam OUATTARA, Valentin PAUME, Saif SHAIKH, Scott STREDNAK
Nahed-Sihem BOUNOUA, Baptiste DARBOIS-TEXIER, Nicolas LEVERNIER, Coraline LLORENS, Sandip MANDAL, Hugo PERRIN, Aloïs de RIVAS, Jeongeun RYU, Franco TAPIA
In this paper, we show using discrete numerical simulations that the cohesiveness during flow is not only controlled by the interparticle adhesion, but also by the stiffness and inelasticity of the grains. For the same adhesion, stiffer and less dissipative grains yield a less cohesive flow, i.e., higher “flowability.” This combined effect can be embedded in a single dimensionless number—a result that enriches our understanding of powder rheology.
Mandal et al PNAS – Published 2 April 2020
Using index matching and particle tracking, we measure the three-dimensional velocity field in an isotropic porous medium composed of randomly packed solid spheres. Our results confirm the chaotic nature of advection within three-dimensional porous media and, by providing the laws of dispersion and stretching, opens the way to a complete description of mixing in porous media.
Souzy et al J. Fluid Mech. – Published 23 March 2020
In this paper, we present a new device called the Darcytron, allowing pressure-imposed rheological measurements on dense suspensions made of very small particles, like shear-thickening suspensions. Our results on a model shear-thickening suspensions of micrometric silica beads provide direct evidence of a transition between a frictionless and a frictional state as the particle pressure is increased, providing support to the recent frictional transition scenario for shear thickening.
Clavaud et al J. Rheology – Published 5 March 2020
The next LIP conference will be held on August 22-28th, 2020 in the Institute of Physics, Warsaw, Poland. Main topics: interactions between laser beams and particles, encompassing the following fundamental topics : particle characterization methods, near-field, far-field and time-resolved scattering, plasmonics and other resonances, complex shaped particles and aggregates, multiple scattering and random media, mechanical effects of light, laser beams description (contributions acoustical and quantum beams are also welcomed) and application domains: two-and multiphase-flow characterization, aerosol science and atmospheric environment, plasma and soft matter physics, biomedical optical engineering, remote sensing…
Conveners: D. Jakubczyk, M. Kolwas, F. Onofri, G. Gouesbet
We studied experimentally the discharge of a vertical silo filled by spherical glass beads and assisted by injection of air from the top at a constant flow rate. Using a two-phase continuum model with a frictional rheology to describe particle-particle interactions, we reveal the role played by the air-pressure gradient at the orifice and proposed a simple analytical model to predicts the mass flow rate of a granular media discharged from a silo with injection of gas.
Zhou et al Phys. Rev. Fluids – Published 18 December 2019
Macroscopic granular materials and colloids are usually studied by different communities. But what happens if particles in a granular heap are so small that their thermal agitation becomes comparable to their weight? In this paper, we study such ‘Brownian granular flows’ using a microfluidic setup and show that thermal agitation can completely erase the flow threshold, a first step to bridge the gap between the physics of granular matter and colloids.
Bérut et al Phys. Rev. Lett. – Published 12 December 2019
In this paper, we use pressure-imposed rheometry to study the influence of surface roughness on the rheology of immersed and dry frictional spheres in the dense regime. We show that the quasistatic value of the effective friction coefficient is not significantly affected by particle roughness while the critical volume fraction at jamming decreases with increasing roughness. Collapse of rheological data is obtained by rescaling the volume fraction by the maximum volume fraction.
Tapia et al Phys. Rev. Fluids – Published 17 October 2019
Hysteresis is a major feature of the solid-liquid transition in granular materials but its origin is still debated. To study this phenomenon, we monitor the avalanche dynamics of non-Brownian suspensions in slowly rotating drums. By using microsilica particles whose interparticle friction coefficient can be turned off, we show that microscopic friction, conversely to inertia, is key to triggering hysteresis in granular suspensions.
In this paper, we study the plant gravitropic response to transient inclinations at the organ scale and the associated motion of statoliths at the cellular level. Our results reveal the existence of a memory process in the signalling pathway, independent of statolith dynamics. By combining this memory process with statolith motion, we build a mathematical model that unifies the different laws found in the literature and that predicts the early bending response of shoots to arbitrary gravi-stimulations.
Chauvet et al J Exp Bot 70,1955–1967 (2019) – Published 27 March 2019
Adding solid particles to a liquid, which increases the effective viscosity, can paradoxically shorten the breakup length of a liquid capillary jet accelerated by gravity. This apparent contradiction is rationalized by considering finite-size effects occurring at the scale of a few particles. A model is presented which captures the breakup length of suspension jets for a broad range of conditions.
Château et al Phys. Rev. Fluid 4, 012001(R) – Published 10 January 2019
Des offres de stages, thèses et post-doctorats sont régulièrement proposés par les membres de l’axe. N’hésitez pas à nous contacter !