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PMMH’s weekly seminar is held every Friday at 11 am (map)
Stéphane Perrard
Etienne Reyssat
Virgile Thiévenaz
PMMH
BARRE CASSAN
BAT A 1ER ETAGE CASE 18
7 QUAI SAINT BERNARD
75005 PARIS
France
Tel : (33) 1 40 79 45 22
Séminaire PMMH - Arthur Alexandre (EPFL)
Dispersion in heterogeneous media : how boundaries shape transport properties
Identifying transport properties of tracer particles in heterogeneous media at large time and length scales has applications in wide range of physical systems including microfluidics, hydrology, chemical engineering or soft matter. The effective diffusivity is a crucial input for problems of mixing, sorting, chemical delivery, as well as chemical reactions. Spatial variations of diffusion and advection can lead to drastic changes in the effective diffusion constant with respect to homogenous systems. Classic examples include Taylor dispersion in hydrodynamics, and the decrease of diffusivity due to the crowding effect produced by spatially-varying boundaries or the presence of an external periodic potential.
In particular, the effect of the confining geometry on the effective diffusivity has been widely studied, but the vast majority of existing theories focuses on perfectly reflecting boundaries. Using a general framework that incorporates surface-mediated diffusion, we show analytically that making surfaces or obstacles attractive can accelerate dispersion [1]. We notably show that this enhancement of diffusion can exist even when the surface diffusion constant is smaller than that in the bulk.
Our formalism can be generalized to encompass drifts or spatially-dependent diffusion tensor [2, 3]. Indeed, his spatial dependency results from hydrodynamic interactions between the tracer and the wall and are not negligible in the situation of strong confinement. In particular, we examine how the latter mechanism modifies the tracer displacement distribution by computing cumulants beyond the mean-squared displacement. Our results were confirmed by numerical simulations and experimental data.
References
[1] Alexandre, A., Mangeat, M., Guérin, T. & Dean, D. S. How stickiness can speed up diffusion in confined systems. Physical Review Letters 128, 210601 (2022).
[2] Alexandre, A., Gu´erin, T. & Dean, D. S. Generalized taylor dispersion for translationally invariant microfluidic systems. Physics of Fluids 33 (2021).
[3] Alexandre, A. et al. Non-gaussian diffusion near surfaces. Physical Review Letters 130, 077101 (2023).
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Seminars (4)
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Séminaire PMMH - Francesca Borghi Università degli Studi di Milano
Vendredi 20 juin de 11h00 à 12h00 - Salle réunion PMMH 1
REPROGRAMMABLE HARDWARE FOR DATA PROCESSING AT THE EDGE : A NEW COMPUTING PARADIGM BASED ON NEUROMORPHIC SYSTEMS
The brain's ability to perform efficient and fault-tolerant data processing is strongly related with its peculiar interconnected adaptive architecture, based on redundant neural circuits interacting at different scales. By emulating the brain's processing and learning mechanisms, computing technologies strive to (…) -
Séminaire PMMH - Francesca Borghi Università degli Studi di Milano
Vendredi 20 juin de 11h00 à 12h00 - Salle réunion PMMH 1
REPROGRAMMABLE HARDWARE FOR DATA PROCESSING AT THE EDGE : A NEW COMPUTING PARADIGM BASED ON NEUROMORPHIC SYSTEMS
The brain's ability to perform efficient and fault-tolerant data processing is strongly related with its peculiar interconnected adaptive architecture, based on redundant neural circuits interacting at different scales. By emulating the brain's processing and learning mechanisms, computing technologies strive to (…) -
Séminaire PMMH - Salvatore Federico (University of Calgary, Canada)
Vendredi 4 juillet de 11h00 à 12h00 - Salle réunion PMMH 1
Continuum Mechanics of Hydrated Fibre-Reinforced Soft Tissues
Biological tissues can be represented as bi-phasic continua, with a porous solid phase saturated by an interstitial fluid and reinforced by collagen fibers. This lecture will give an overview of the modelling techniques for fibre-reinforced porous composite materials with statistical orientation of the fibers. Both (…) -
Séminaire PMMH - Salvatore Federico (University of Calgary, Canada)
Vendredi 4 juillet de 11h00 à 12h00 - Salle réunion PMMH 1
Continuum Mechanics of Hydrated Fibre-Reinforced Soft Tissues
Biological tissues can be represented as bi-phasic continua, with a porous solid phase saturated by an interstitial fluid and reinforced by collagen fibers. This lecture will give an overview of the modelling techniques for fibre-reinforced porous composite materials with statistical orientation of the fibers. Both (…)
The audience is composed of people with rather heterogeneous backgrounds including specialists in solids, fluids, granular flows, statistical physics... so the idea is to keep your talk understandable by people not necessarily working in your field... The seminar time slot runs from 11am to noon so the best is to make the talk last around 45 minutes to leave some time for discussion.
- Séminaires ESPCI-ENS de biophysique
- Séminaires du Département de Physique de l’ENS
- Séminaires du Laboratoire d’Hydrodynamique de l’X
- Séminaire de Mécanique d’Orsay (page web FAST)
- Séminaire de Mécanique d’Orsay (page web LIMSI)
- Séminaire de Mécanique des Fluides de l’Institut Jean le Rond d’Alembert
- Séminaires du laboratoire MSC, Paris VII
- Séminaires Gulliver
Link to cofee seminar (internal, every Thursday)
