Olivier Millet

Analytic Calculation of Capillary Bridge Properties Deduced as an Inverse Problem from Experimental Data

In this work, we propose an original resolution of Young–Laplace equation for capillary doublets from an inverse problem. We establish a simple explicit criterion based on the observation of the contact point, the wetting angle and the gorge radius, to classify in an exhaustive way the nature of the surface of revolution. The true shape of the admissible static bridges surface is described by parametric equations; this way of expressing the profile is practical and well efficient for calculating the binding forces, areas and volumes. Moreover, we prove that the inter-particle force may be evaluated on any section of the capillary bridge and constitutes a specific invariant.

Determination of the macroscopic chloride diffusivity in cementitious by porous materials coupling periodic homogenization of Nernst-Planck equation with experimental protocol

In this paper, we propose a macroscopic migration model for cementitious porous media obtained from periodic homogenization technique. The dimensional analysis of Nernst-Planck equation leads to dimensionless numbers characterizing the problem. According to the order of magnitude of the dimensionless numbers, the homogenization of Nernst-Planck equation leads at the leading order to a macroscopic model where several rates can be coupled or not. For a large applied electrical field accelerating the transfer of ionic species, we obtain a macroscopic model only involving migration. A simple experimental procedure of measurement of the homogenized chlorides diffusivity is then proposed for cement-based materials.

Modeling the Chlorides Transport in Cementitious Materials By Periodic Homogenization

In this work, we develop a macroscopic model for diffusion–migration of ionic species in saturated porous media, based on periodic homogenization. The prior application is chloride transport in cementitious materials. The dimensional analysis of Nernst–Planck equation lets appear dimensionless numbers characterizing the ionic transfer in porous media. Using experimental data, these dimensionless numbers are linked to the perturbation parameter

Modelling moisture transport for a predominant water vapour diffusion in a partially saturated porous media

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Analytical and experimental analysis of an asymptotic thin-walled beam model

. For a weak-imposed electrical field, or in natural diffusion, the asymptotic expansion of Nernst–Planck equation leads to a macroscopic model coupling diffusion and migration at the same order. The expression of the homogenized diffusion coefficient only involves the geometrical properties of the material microstructure. Then, parametric simulations are performed to compute the chloride diffusion coefficient through different complexity of the elementary cell to go on as close as possible to experimental diffusion coefficient of the two cement pastes tested.

Theoretical and experimental study of pendular regime in unsaturated granular media

A continuous media approach for the calculation of the stresses in an ensiled granular media which improves on the Janssen theory has been developed. This approach also allows us to represent qualitatively as well as quantitatively the stress saturation phenomenon in granular silos. It is based on three-dimensional equilibrium equations, coupled with a slip condition and a Mohr–Coulomb criterion at the silo walls. Predictions obtained using the proposed model are in close agreement with the classical approaches for non-cohesive materials. The effect of the cohesion and the friction walls on the stored materials was also investigated.

Application of the periodic homogenization technique to ionic transfer in cementitious materials: Case of chloride in concrete

The aim of this paper is to establish by periodic homogenisation a macroscopic model for moisture transport in porous media for predominant water vapour diffusion, taking into account evaporation/condensation phenomena. The dimensional analysis of the continuity equations of moisture transport (and the associated boundary conditions) written at the pore scale lets appear dimensional numbers characterising the transfer phenomenon. The asymptotic expansion of these equations leads to a macroscopic homogenised equation governing the moisture transport. Moreover, we obtain an accurate definition of the homogenised diffusion tensor of moisture involving the geometry of the microstructure and known transport properties of the material. As an example, the diffusion of water vapour in a layered porous medium is considered and the homogenised diffusion tensor of water vapour is calculated. L’objectif de ce papier est d’établir par homogénéisation périodique un modèle macroscopique du transport d’humidité dans les milieux poreux pour une diffusion prédominante de vapeur d’eau, en prenant en compte le phénomène d’évaporation/condensation. L’analyse dimensionnelle des équations de transport d’humidité (et des conditions aux limites associées) écrites à l’échelle locale fait apparaître des nombres sans dimension caractérisant le phénomène de tranfert. Le développement asymptotique des équations conduit à une équation macroscopique homogénéisée de transport d’humidité. De plus, on obtient une définition précise du tenseur de diffusion homogénéisé tenant compte de la géometrie de la microstructure et des propriétés de transport connues du matériau. Le tenseur de diffusion homogénéisé de vapeur d’eau dans un milieu poreux stratifié est calculé analytiquement comme exemple illustratif.

Exact calculation of axisymmetric capillary bridge properties between two unequal-sized spherical particles

ABSTRACT This article presents the application of DKMQ24 shell element for twist of thin-walled beams. This element passed the patch tests for membrane, bending and shear problems and gave fine results for plate and shell problems analysis without shear locking. Thin-walled cantilever beams are analyzed using this element. DKMQ24 gives good results for cantilever beams with open cross-section for a very few number of element. Moreover, the comparison of the results obtained with Vlassov analytical solution enables to evaluate the accuracy of the twist rigidity, Jd, which depends on an empirical coefficient in Vlassov theory.