Numerical modelling of micromixing in a T-mixer flow at low Reynolds numbers

International audienceHighlights  CFD simulations are performed to study micromixing in a laminar microfluidic flow.  Segregation indices are calculated using the Villermaux-Dushman protocol.  Micromixing is modelled directly with CFD and indirectly with a lamellar model.  The two solutions are compared in terms of computational cost and analysis times

Numerical modelling of micromixing in a T-mixer flow at low Reynolds numbers

International audienceHighlights  CFD simulations are performed to study micromixing in a laminar microfluidic flow.  Segregation indices are calculated using the Villermaux-Dushman protocol.  Micromixing is modelled directly with CFD and indirectly with a lamellar model.  The two solutions are compared in terms of computational cost and analysis times

Simulation of Micromixing in a T-mixer under Laminar Flow Conditions

The CFD simulation of fast reactions in laminar flows can be computationally challenging due to the lack of appropriate sub-grid micromixing models in this flow regime. In this work, simulations of micromixing via the implementation of the competitive-parallel Villermaux/Dushman reactions in a T-micromixer with square bends for Reynolds numbers in the range 60-300 are performed using both a conventional CFD approach and a novel lamellae-based model. In the first, both the hydrodynamics and the concentration fields of the reaction species are determined directly using a finite volume approach. In the second, the hydrodynamic field from the CFD calculations is coupled with a Lagrangian model that is used to perform the chemical reactions indirectly. Both sets of results are compared with previously published experimental data and show very good agreement. The lamellar model has the advantage of being much less computationally intensive than the conventional CFD approach, which requires extremely fine computational grids to resolve sharp concentration gradients. It is a promising solution to model fast chemical reactions in reactors with complex geometries in the laminar regime and for industrial applications

Contribution of pervaporation in eco design of processes

International audienceThe pervaporation, a membrane separation process, can be an excellent alternative to distillation. Though it is a relatively young technology, the attention of industries towards it increases every year mainly due to its low energy consumption and high separation performance. The aim of our work was to emphasize the new horizons of solvent dehydration technology and mark the contribution of pervaporation in process eco design. We have experimentally and theoretically studied the pervaporation applied to a dehydration of an aqueous mixture of three glycol ethers which are widely used in different chemical industries all over the world. The interest was mainly pointed towards the separation efficiency and energy consumption. The results were compared to those of distillation for the same mixture. The modeling of both processes was also performed in order to optimize operating conditions and increase the efficiency

A Validation of the Family Involvement Questionnaire-High School Version

The purpose of this study was to validate the Family Involvement Questionnaire (FIQ) for use in high school settings (9th-12th grade). After the FIQ was redesigned for use in the high school setting, 517 parents completed the questionnaire online. Internal consistency for the 40-item questionnaire was high (alpha = 0.93). A confirmatory factor analysis failed to substantiate the FIQ-HS to the elementary version from which it was adapted. However, an exploratory factor analysis yielded three factors consistent with the FIQ-E. Family demographics were compared to participants\u27 responses, and significant effects for students\u27 school and special education status were found

Health-related Sustainable Development Goals:Countdown on alcohol use, smoking prevalence, child overweight and suicide mortality

The Sustainable Development Goals (SDGs) are a set of goals that aspire to 'leave no one behind', adopted by all members of the United Nations and to be achieved by 2030. Now, four years after the SDGs entered into force, we examine the progress towards the health-related SDGs in the European region. In this region, least progress is made towards the targets set for alcohol consumption, smoking prevalence, child overweight, and suicide mortality. For each of these challenges we take stock of current policies, continuing challenges, and ways forward. Written from the perspective of European Public Health Association (EUPHA) we emphasize the potential contribution of civil society organizations in attaining the health-related SDGs

L'expérience de la Sologne dans les abris pour fraisiers

Characteristics of strawberry production in the Loir-et-Cher region. Use of plastic tunnels. Investment cost for one hectare of strawberry tunnels. / Caractéristiques de la production de fraise dans le Loir-et-Cher. Utilisation des tunnels plastiques. Coût d'investissement pour un hectare de tunnels de fraisier

Modélisation des dynamiques végétales et trajectoires des sociétés humaines en Europe pendant l'Holocène

Historically, paleo-environment and paleo-climate were studied through palynology, archaeology and ice-isotope study. Studies were often made on local sites and independently from each other. The European Pollen Database (EPD) allows us to study pollens recorded all over Europe. A new approach is used and consists of taxa dynamics modelling with a Bayesian statistics model. In this way, the influence of climate, human activities and taxa environment will be evaluated on the Holocene era. Climatic and soil data validate hypothesis made from bibliography researches in terms of taxa preferences. However, population density is lowly responsible for taxa extinction and rather allows stands/settlements conservation/sustainability/maintenance. Finally, agricultural intensification is favourable to open up of natural habitats and the colonization of pioneer and herbaceous species. But these practises have a negative effect on tree taxa. The lack of data regarding environmental DNA did not allow us to study it complementary with pollen data and this is still a rising prospect.Historiquement l’étude des paléo-environnements et des paléo-climats s’est faite à travers la palynologie, l’archéologie, l’anthracologie et l’étude des isotopes de glace. Ces études étaient souvent réalisées sur des sites localisés et indépendamment les unes des autres. La base de données européenne des pollens (EPD) permet aujourd’hui d’étudier les pollens enregistrés sur l’ensemble de l’Europe. Une nouvelle approche est également utilisée puisqu’elle consistera à modéliser les dynamiques végétales suivant un modèle probabiliste bayésien. Ainsi, l’influence du climat, des activités humaines et de l’environnement des taxons seront évalués sur l’ensemble de l’Holocène. Les données climatiques et pédologiques permettent principalement de valider des hypothèses issues de la bibliographie en termes d’écologie des taxons. En revanche la densité de population humaine est peu responsable d’extinction de taxon et permet au contraire majoritairement le maintien des populations végétales. Enfin, l’analyse des pollens confirme que l’intensification de l’agriculture, permettant l’ouverture des milieux, a majoritairement un effet favorable sur la colonisation des espèces pionnières et herbacées et un effet défavorable aux taxons arborés, alors sûrement abattus. Le manque de données n’a pas permis d’étudier les apports de l’ADN environnemental en complément des données polliniques, néanmoins cela reste une perspective prometteuse

Caractérisation chimique du micromélange par la réaction iodure-iodate : application aux milieux visqueux et aux suspensions liquide-solide

Not availableLe micromélange ou mélange à l'échelle moléculaire a une influence déterminante sur la qualité des produits, la sélectivité, le rendement de réactions d'importance industrielle comme certaines synthèses organiques, les réactions de polymérisation et de précipitation. Cette étude a pour but le développement d'une méthode chimique de caractérisation du micromélange: la réaction iodure-iodate. Nous avons tout d'abord considéré le protocole expérimental puis avons étudié dans l'eau, l'influence sur la qualité du micromélange des concentrations initiales des réactifs, de la vitesse d'agitation, de la position de l'injection, dans des réacteurs de 1, 20 et 100 litres. L’interprétation des résultats par le modèle d'incorporation a montré que les temps de micromélange obtenus sont, pour cette large gamme de conditions expérimentales, en très bon accord avec ceux prédits par la théorie de la turbulence. Enfin, nous avons étendu l'utilisation de ce test aux milieux visqueux et aux suspensions liquide-solide. Nous avons, en particulier, mis en évidence le ralentissement du micromélange au fur et à mesure que la viscosité augmente, ralentissement que nous pouvons décrire par un modèle IEM/incorporation. De plus, nous avons montré pour nos conditions d'étude (fraction massique de solide inferieure à 6% et diamètre de particule compris entre 20 et 1300 micromètres) que la présence de billes de verre ne modifie pas de manière significative la qualité du micromélang