Calculation of the flame size from burning liquid pools

The calculation of the consequences associated with a pool fire consists in a stepwise procedure where a number of parameters must be characterized, which depend on the geometrical size and shape of the flame. A number of calculation models exists in the literature, characterized by different levels of accuracy and complexity. In the present work we will focus on the characterization of the geometrical configuration of the flame generated from a pool fire: some of the most commonly adopted models will be shortly recalled, and compared against experimental data taken from the literature. It is expected that this would provide useful information about the range of applicability and the level of accuracy of these models. Also, it will help improve the quality of the results, and reduce the time required for carrying out important applications such as consequence assessment and risk analysis, where a large number of calculations must be run

Recent patents on in-plane permeability measurement of LCM composite reinforcements

International audienceOptimization of Liquid Composite Molding (LCM) processes using Darcy flow numerical simulation requires inputting accurate reinforcement permeability data. Historically introduced by its author to describe infiltration phenomenon, permeability coming from Darcy's law is usually used in LCM processes as a rheological parameter in order to predict the macroscopic resin motion during the filling stage. Resulting from the flow through a complex fibrous architecture, its measurement is very sensitive to the test conditions due to the high filaments flexibility and meso-structure heterogeneity. Reinforcements are currently anisotropic fibrous media and their in-plane permeability measurement requires specific facilities. Measurements can be performed in transient or steady state conditions, and in one-, two-or three-dimensional configurations. This paper describes the different existing experimental configurations, identification procedures and instrumentation techniques. Advantages and drawbacks of each method are discussed, in the particular case of 2D transient measurements, which are the most representative of Resin Transfer Molding process. Two recent patents using different instrumentation techniques are detailed. They are focused on the simultaneous identification of the in-plane principal permeability values in an anisotropic fibrous reinforcement. Some perspectives are suggested to improve the repeatability of such measurement results

Review of 62 risk analysis methodologies of industrial plants: review

International audienceFor about 10 years, many methodologies have been developed to undertake a risk analysis on an industrial plant. In this paper, 62 methodologies have been identified, these are separated into three different phases (identification, evaluation and hierarchisation). In order to understand their running, it seems necessary to examine the input data, methods used, obtained output data and to rank them in several classes. First, all the input data are grouped together into seven classes (plan or diagram, process and reaction, products, probability and frequency, policy, environment, text, and historical knowledge). Then, the methods are ranked in six classes based on the combination of four usual criteria (qualitative, quantitative, deterministic and probabilistic). And finally, the output data are classified into four classes (management, list, probabilistic and Merarchisation). This classification permits the appraisal of risk analysis methodologies. With the intention of understanding the running of these methodologies, the connections between the three defined previously criteria (determinist, probabilistic and determinist and probabilistic) are brought to the fore. Then the paper deals with the application fields and the main limitations of these methodologies. So the hierarchisation phase is discussed and the type of scale used. This paper highlights the difficulties in taking into account all risks for an industrial plant and suggests that there is not only one general method to deal with the problems of industrial risks

TRANSPORT MARITIME DE PRODUITS CHIMIQUES LIQUIDES ET FLOTTANTS (ETUDE EXPERIMENTALE DU REJET ACCIDENTEL SOUS-MARIN SUITE A UN NAUFRAGE)

Le transport par voie maritime s est développé très rapidement durant la dernière décennie. Il constitue la solution idéale pour déplacer à faibles coûts d importantes quantités de marchandises sur de longues distances. L accroissement de ces échanges entraine inévitablement une augmentation de la fréquentation des routes maritimes, de la densité du trafic et donc du risque d accident et de naufrage.Les quantités impliquées lors d un accident étant importantes, un rejet sous-marin de produit chimique issu d une épave peut provoquer de graves conséquences environnementales et humaines. Or, les mécanismes physico-chimiques apparaissant lors du transfert du produit à la surface sont encore mal compris. Ces mécanismes dépendent de nombreux paramètres dont les propriétés physico-chimiques intrinsèques au produit et celles propres à l environnement de l accident.Ce travail de recherche, réalisé en collaboration entre l Ecole des Mines d Alès et le Cedre, s inscrit dans l amélioration de la compréhension du comportement d un rejet de produit chimique liquide, flottant et soluble issu d une épave. Cette étude expérimentale a été réalisée selon 3 points :- La phénoménologie du rejet à la brèche dont l objectif est de quantifier le débit et les modes de rejet,- Le comportement hydrodynamique du produit libéré et son évolution lors de la remontée dans la colonne d eau,- Le transfert de matière du produit lors de sa solubilisation dans la colonne d eau.Pour chaque point, les résultats obtenus sont comparés à ceux prédits par les corrélations disponibles dans la littérature afin de proposer une modélisation globale des conséquences adaptée à la gestion des pollutions marines.Maritime transport quickly increases during the last decade. It is the cheapest way to transport large quantities of goods over long distances. The growth of this trade necessarily leads to an increase in the traffic density and therefore the risk of accident and sinking increases as well.The large amount of chemicals involved in an accident may threaten the environment and human health in case of shipwreck with underwater chemical release. Unfortunately the physicochemical mechanisms occurring during the transfer of a chemical to the sea surface are still poorly understood. Those mechanisms depend on various parameters such as the physicochemical properties of the chemicals and the specific properties of the accident surroundings. This research was conducted in collaboration with the Ecole des Mines d'Alès and Cedre in a global approach to understand the behaviour of liquid, floating and soluble chemicals released after a shipwreck. This experimental study has been carried out according to 3 main points:- The phenomenology of a release at the breach. The objectives are to quantify the flow rate and the release pattern,- The hydrodynamic behaviour of the released chemicals and their fate in the water column,- The mass transfer of the chemical during its solubilization in the water column.For each point, the results are compared to those predicted by correlations in the literature in order to propose a global model of consequences that is adapted to the marine pollution management.ST ETIENNE-ENS des Mines (422182304) / SudocSudocFranceF

Stratégies de modélisation des conséquences d'une dispersion atmosphérique de gaz toxique ou inflammable en situation d'urgence au regard de l'incertitude sur les données d'entrée.

En cas d accident impliquant des produits chimiques, il peut être fait appel à des experts pour évaluer les effets générés par cet accident. Ces experts fournissent des distances d effets à l aide de modélisations informatiques et sont confrontés à une difficulté majeure : peu d éléments à leur disposition pour caractériser la situation.L objectif de cette thèse est de proposer une méthodologie permettant de prendre en compte les incertitudes relatives aux données d entrée dans les modélisations effectuées en situation d urgence tout en restituant de manière explicite cette incertitude au gestionnaire de la situation d urgence.Une première phase a consisté à évaluer, pour une situation à même de générer un nuage toxique ou explosible, la dispersion des résultats des modélisations. Il a été établi une hiérarchisation des variables d entrée en fonction de leur influence sur le résultat final. Cette phase a été réalisée au moyen d une analyse de sensibilité dont la stratégie a été spécifiquement développée.Une seconde phase a eu pour but d établir une méthodologie d estimation des distances d effets en situation d urgence en tenant compte du niveau d incertitude des variables d entrée. Une méthodologie de classification opérationnelle des données d entrée a été réalisée. Elle s appuie sur deux critères : la sensibilité du modèle au paramètre d entrée et l incertitude sur sa valeur (imprécision ou variabilité). Sur cette base, une nouvelle manière d utiliser ces variables a été proposée. Enfin, différentes façons de restituer de manière opérationnelle les résultats des modélisations ont été proposées.During accidents involving chemicals, experts can be asked to assess the effects generated. These experts provide distance effects using computer modeling and are faced with a major difficulty: little (or no) information available in order to assess the situation.The objective of this thesis is to suggest a methodology able to take into account uncertainties in the input data for the modeling carried out in emergency situations and to return explicitly these uncertainties to the manager of the crisis.A first step was to evaluate, for a given situation generating a toxic or flammable cloud, the dispersion of modeling results. A ranking of the input variables according to their influence on the final result was established. This phase was carried out on the basis of a sensitivity analysis with a specifically developed strategy.A second phase aimed to establish a methodology for estimating distance effects (in crisis situations), which takes into account the level of uncertainty in the input variables. A methodology for the classification of input operational data was carried out. This methodology is based on two criteria: the sensitivity of the model to the input parameter and the uncertainty about its value (imprecision or variability). On this basis, a new way of using these variables was suggested. Finally, several methods aimed to restore explicitly the results of this modeling were suggested.ST ETIENNE-ENS des Mines (422182304) / SudocSudocFranceF

Le traitement de l'incertitude en gestion de crise : mise en place d'une veille stratégique du territoire

National audienceThe catastrophic events of these last years such as the catastrophe of AZF in 2001 or the various terrorist attacks made evolve the concept of risk by integrating dimensions of crisis and threat. The damages which result from this do not limit to a delimited zone but impact the whole society. The crisis organizations are destabilized by the unusual feature of these situations. The managers must anticipate these situations as soon as possible; react efficiently and in a fast way in order to avoid the consequences of the crisis. However, the decision makers need a fast, clear and structured expertise allowing reducing uncertainties related to the situation. The objective of this project is to present, after a state of the art on the crises, a methodology of decision-making aid to help the Prefects through a potential of crisis usable in vigilance and during the emergency phase.Les évènements catastrophiques de ces dernières années tels que la catastrophe d'AZF en 2001 ou les différents attentats terroristes ont fait évoluer le concept de risque en lui intégrant les dimensions de crise et de menace. Les dommages qui en découlent ne se limitent pas à une zone délimitée mais impactent la société dans son ensemble. Les organisations gestionnaires des crises sont déstabilisées en raison du caractère inhabituel de ces situations. Les gestionnaires se doivent d'anticiper au plus tôt ces situations, de réagir efficacement et de manière rapide afin d'éviter une crise. Or, les décideurs ont besoin d'une expertise rapide, claire et structurée permettant de réduire les incertitudes liées à la situation. L'objectif de ce projet est de présenter, après un état de l'art sur les situations de crise, une méthodologie d'aide à la décision permettant d'apporter de la lisibilité aux préfets à travers l'établissement d'un potentiel de crise utilisable en veille et pendant la phase d'urgence

Elastic properties of short fibres reinforced polymers in the vicinity of a weld line

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Modelling the hysteretic wale-wise stretching behaviour of technical plain knits

International audienceThis paper investigates the effect of friction on the stretching behaviour of plain-knits in the wale-wise direction. The capstan method was carried out to measure the yarn-to-yarn coefficient of kinetic friction between perpendicular yarns. The coefficient of kinetic friction between E-glass yarns and basalt yarns is similar and exhibits significant normal load sensitivity. However only E-glass yarns exhibit sensitivity to the sliding velocity. The yarn-to-yarn friction was then introduced in an existing semi-analytical model to simulate the wale-wise stretching of plain knits. This model was used to perform a sensitivity study, which has shown that friction significantly affects the knit behaviour both before and after jamming. The enhanced model proved to be able to properly describe the hysteretic behaviour of plain knits in the wale-wise direction. This allows concluding that friction at the loops crossing point is the main mechanism that controls the hysteretic behaviour of plain-knits, even if other mechanisms should be accounted for to perfectly describe the actual behaviour of the knit. (C) 2014 Elsevier Masson SAS. All rights reserved

Elastic properties of short fibres reinforced polymers in the vicinity of a weld line

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A Two-Temperature Model Based on Fin-Approximation for Transient Longitudinal Heat Transfer in Unidirectional Composite

International audienceThe reliability of a two-temperature model is assessed in the case of longitudinal heat transfer in unidirectional composites. One interest is that it makes it possible to apply separate boundary conditions or source terms on the fibre and the matrix (emissivity for example), without necessitating an explicit description of the fibre and matrix domains. For the sake of simplicity, the model under study is based on a fin-approximation in both fibre and matrix, which implies a high interfacial thermal resistance. The range of validity of this assumption is investigated by comparing the model to an axisymmetric one-temperature model, using non-dimension variables and Dirichlet boundary conditions. It turns out that this range of validity is strongly dependent on the parameters