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Towards a relevant dispersion model for urban areas
No full textInternational audienceFlammable and toxic gas dispersion is a key issue when designing the potential consequences of industrial accident. While resulting distances for land use planning are important, models used nowadays are quite simple. It should be reminded that several levels of approach could be used for the cloud dispersion modelling. The simplest is Gaussian models based on dispersion coefficients fitted using experimental data. Integral models enable the user to model this phenomenon quite more precisely using a simplified 1D solution of fluid flow equation in the vicinity of the release, then, for larger distances, those models used a Gaussian like approach. For those two families of model, obstacles are represented using a global ground roughness. For configurations with distributed non-regular obstacles, 3D models, as CFD or LPDM, suit better. Those models enable taking into account the different obstacles with their real characteristics and their distribution on the ground. Using those models let the user able to capture specific phenomena as for example turbulence induced by the obstacles and resulting mixture and canyon effect that can reduce dispersion. While those 3D models are more and more required regarding the importance of consequence area, two main issues remain. First, very few data are available for validating those codes in an urban like configuration. Most of large-scale experimental campaigns were achieved in free filed configuration or with regularly distributed obstacles, configuration that is relevant for Gaussian or integral validation but not for pointing out the interest and specificity of 3D models. Data available in urban like area are based on small scale wind tunnel experiments with the obvious scale effect limitation. Furthermore, since few experiments were achieved in such a configuration, some physical phenomena as the interaction between atmospheric boundary layer (ABL) and large obstacles were not studied in detail. Then, after a description of this state of the art, this paper presents an experimental campaign that aims to provide reference experimental measurement in urban like area at large scale. This campaign will also offer the opportunity in studying some specific phenomena concerning the interaction of ABL with an urban geometry
Numerical modeling of salt and gypsum rocks dissolution : from micro-scale to industrial scale
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High time resolution measurement of the OM to OC ratio in PM1 and PM2.5
No full textInternational audienceMeasurements of carbonaceous aerosols are of vital importance for air quality monitoring and quantifiable measurements of climate change. Because they are extremely diverse, their direct impact on air quality, visibility, cloud nucleation and cloud optical properties, the planetary radiation balance, and public health varies greatly with composition. This impact remains highly uncertain due to their complex chemical and microphysical properties. We present here a highly time-resolved online measurement of carbonaceous aerosol species in Paris, France..
Assessing the flammability of liquid mixtures by predictive approach as a complement to experimental measurements
No full textInternational audienceAssessing the flammability of liquid mixtures by predictive approach as a complement to experimental measurementsThe flammability of organic mixtures can be dramatically changed upon concentrations and can reveal, in some cases, more flammable than its components taken as pure liquids. For this reason, estimating the flammability of mixtures represents a great challenge with high importance in industrial safety. In that context, efforts were engaged in the development and use of predictive methods to estimate the flash point of liquid mixtures for practical industrial applications as a complement to the classical experimental approach. Different predictive approaches are proposed according to the level of information available on the investigated mixture (in terms of properties of pure compounds) based on mixing rules and/or QSPR (Quantitative Structure-Property Relationship) models. Different case studies are proposed to illustrate how they can complement experimental tests. These case studies highlight the precautions to be considered for their accurate use (e.g. choice of the model), their limits notably for specific types of flammable mixtures (like halogenated substances) and their complementarity with the information provided by experimental measurements to improve industrial safety issues
Stronger together ? Influence of the agglomeration on nanopowders explosion
No full textInternational audienceAmong the factors influencing dust explosion, the particle size distribution (PSD) is both one of the most important and the most complex to consider. For instance, it is commonly accepted that the explosion sensitivity increases when the particle size decreases. Such an assertion may be questionable for nano-objects which easily agglomerate. However, agglomerates can be broken during the dispersion process. Correlating the explosion parameters to the actual PSD of a dust cloud at the moment of the ignition becomes then essential. Powders were characterized before and during their dispersion using in situ laser particle size measurement and a fast mobility particle sizer. The turbulence was determined by particle image velocimetry. The explosion severity and sensitivity of nanocellulose was determined under various operating conditions and for wet and dried powders. The impact of the turbulence on the flame kernel growth was highlighted using a flame propagation tube. It appears that the ignition sensitivity of nanocellulose depends on the PSD and on water activity whereas its explosion severity is less modified by the presence of agglomerates in the raw powder
Ecodesign tool for pyrotechny
No full textInternational audienceEcodesign is widely integrated in the development of new products in a lot of industries. It concerns the conception but also the industrialization. Regarding ammunition, their environmental impact throughout all their life cycle has begun to be taken into account through eco-design methodology. Many software and tools have been proposed. They result from need of specific industry like automobile or organism, like ADEME for example. Even if the methodologies are quite similar, databases never include many chemical substances, except wide used polymers. For energetic materials or system these different tools are not convenient. Itʼs impossible to implement data base with explosives or pyrotechnic compositions. Even if their production process can be described, their environmental impact canʼt be assayed. For these reasons, ammunitionʼs life cycle analysis canʼt be performed. Actors of the pyrotechny joined together into a committee of the GTPS to elaborate a guide of eco-design, simple in use and adapted to the specific area of energetic materials. This tool completes the whole life cycle of the ammunition from energetic material production to system dismantling. It includes different criteria like regulation compliance (REACh, ROHs,…), environmental impact (human, aquatic, atmosphere), resources decreasing, recycling. Fictive ammunition with three levels of design were proposed to validate the pertinence and sensitivity of the chosen criteria. The presentation of results has been design to identify the environmental impact of the different part of the life cycle and validate the choice of conception in term of material and process
Qualité de l’air extérieur et santé environnementale des jeunes enfants : représentations et pratiques parentales
No full textInternational audienceL’influence de la mauvaise qualité de l’air (QA) extérieur sur la santé des enfants (Rancière & al., 2017 ; Bowatte & al., 2017), le développement cognitif (Sunyer & al., 2017) et le développement socio-affectif (Margolis & al., 2016 ; Yorifuji & al., 2017) semble attestée dans plusieurs travaux. Des dispositions récentes, prises pour limiter les épisodes de pollution et améliorer la qualité de l’air extérieur en France, rendent le public en partie acteur de l’évolution de la qualité de l’air extérieur à laquelle il est exposé et contribuent, par ailleurs, à façonner les normes de « santé environnementale ». A notre connaissance, aucune étude n’examine la représentation de la qualité de l’air extérieur qu’ont les parents et les pratiques (éducatives et de santé) qui y sont liées à l’égard de leurs jeunes enfants. Ainsi, le projet AIRES6 s’inscrit dans une visée i) exploratoire concernant les représentations et pratiques parentales en matière de qualité de l’air extérieur et santé environnementale à destination des jeunes enfants et ii) opérationnelle consistant à produire des réflexions théoriques et méthodologiques préliminaires et à réfléchir aux conséquences socio-éthiques d’un projet de recherche portant sur les liens entre vulnérabilités, qualité de l’air extérieur et santé environnementale des jeunes enfants
