Sylvain Girard

Sylvain Girard
Phimeca Engineering SA · Fiabilité et robustesse

PhD

About

36
Publications
6,014
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150
Citations

Publications

Publications (36)
Preprint
Full-text available
Advanced computer experiments enable to understand and optimise a model. However, using these methods require skills in programming and a deep understanding of their underlying theory. Persalys is an open-source software, based on OpenTURNS methods, which guides the user in the analysis and makes computer experiments accessible to non-programmers....
Article
Full-text available
Modelica models represent static or dynamic systems. Their outputs can be scalar (numbers) or time-dependent (time series). Most advanced mathematical methods for the analysis of numerical models cannot cope with functional outputs. This paper aims at showing an efficient method to reduce a time-dependent output to a few numbers. The Principal comp...
Article
Full-text available
Decision of emergency response to releases of hazardous material in the atmosphere increasingly rely on numerical simulations. This paper presents two contributions for accounting for the uncertainty inherent to those simulations. We first focused on one way of modelling these uncertainties, namely by applying stochastic perturbations to the inputs...
Presentation
Full-text available
- Our Approach : 1. Explore data, 2. Map complex structure, possibly with help of a digital twin and 3. Set up a monitoring and forecast system - Our stance to artificial intelligence aims at reliable generalisation, high interpretability and compatibility with small samples. - The output a 10+ years of R&D is now available to your industry.
Presentation
Full-text available
Decision of emergency response to releases of hazardous material in the atmosphere increasingly rely on numerical simulations. This paper presents two contributions for accounting for the uncertainty inherent to those simulations. We first focused on one way of modelling these uncertainties, namely by applying stochastic perturbations to the inputs...
Presentation
Full-text available
Case study: infer the health of a motor-pump system from flow rate time series using statistical learning (Python). A physical model (Modelica) allows for deeper insights on degradation root causes.
Conference Paper
Full-text available
Most advanced mathematical methods for the analysis of numerical model cannot cope with functional outputs of dynamic Modelica models. Principal component analy- sis is a well established method for dimension reduction, and can be used to tackle this issue. It relies however on a linear hypothesis that limits its applicability. We illus- trate on a...
Conference Paper
Full-text available
A 0D/1D system model is a mathematical of the dynamic behaviour and interactions between the parts of a complex system. Modelica is a language for programming such models using differential equations. By leveraging the object oriented paradigm, it enables to reuse model components, collected in library of modules. Difficult industrial risk manageme...
Thesis
Full-text available
The mathematical modeling of physical phenomena is massively used in the industry in three purposes: analyze the functioning of systems, anticipate evolutions of their state, and obtain information which are inaccessible through observation. Computer experiments are methods for the methodical exploration of the output of a model according to a desi...
Presentation
Full-text available
Portfolio of case studies involving numerical simulation and statistical learning.
Article
ADMS-Urban is a non-linear, static, urban air quality model, with high-dimensional outputs. A simulation of NO2 and PM10 concentrations every hour during a full year and over an entire city can take dozens of days of computations, which greatly limits the range of methods that can be applied to the model, especially for uncertainty quantification....
Technical Report
Full-text available
The functional mock-up interface (FMI) standard specifies a format for multipurpose, easy to build and reusable data interfaces to numerical models. A functional mock-up unit (FMU) is a black box defined by the FMI standard, akin to the wrappers familiar to the OpenTURNS' community. The purpose of the otfmi Python module is to promote the use of t...
Technical Report
Full-text available
The functional mock-up interface (FMI) standard specifies a format for multipurpose, easy to build and reusable data interfaces to numerical models. A functional mock-up unit (FMU) is a black box defined by the FMI standard, akin to the wrappers familiar to the OpenTURNS' community. The purpose of the otfmi Python module is to promote the use of...
Article
Full-text available
Modeling studies on the atmospheric diffusion and deposition of the radiocesium associated with the Fukushima Dai-ichi Nuclear Power Plant accident is reviewed here, with a focus on a research collaboration between l'Institut de Radioprotection et de Sûreté Nucléaire (IRSN) - the French institute in charge of evaluating the consequences of nuclear...
Presentation
Full-text available
Combiner modélisation physique et apprentissage statistique renouvelle le pronostic de fatigue des installations en mer, depuis la conception à la prolongation d’exploitation, en passant par la surveillance en ligne. Technique clef : Identifier des représentations de faible dimension pertinentes des modèles et données sélectionnés
Presentation
Full-text available
Short overview of the application of robust engineering to health monitoring of offshore industrial installations.
Article
Simulations of the atmospheric dispersion of radionuclides involve large uncertainties originating from the limited knowledge of meteorological input data, composition, amount and timing of emissions, and some model parameters. The estimation of these uncertainties is an essential complement to modeling for decision making in case of an accidental...
Poster
Full-text available
Sensitivity analysis is a first step toward estimating uncertainties in atmospheric dispersion models used to estimate the consequences of a nuclear accident.
Article
Numerical models used to forecast the atmospheric dispersion of radionuclides following nuclear accidents are subject to substantial uncertainties. Input data, such as meteorological forecasts or source term estimations, as well as poorly known model parameters contribute for a large part to this uncertainty. A sensitivity analysis with the method...
Chapter
The wide range level response during a power transient is dependent on the clogging state of the steam generators and the numerical model presented in Chap. 4 can simulate this phenomenon satisfactorily. In Chap. 3, we saw that visual inspection and eddy current testing are rare and provide a partial information about the clogging state. In the sam...
Chapter
Simulating the effect of clogging requires a detailed representation of the two-phase flow in the riser. This rules out simple models based on energy balance and global approximations such as log mean temperature difference or number of transfer unit. Computational multi-fluid dynamics is becoming increasingly powerful but for now it is still confi...
Chapter
Any deterministic process can be represented by a mathematical function, a model, mapping a set of input values to an output. Sensitivity analysis is the study of how variations of its inputs affect the output of a model. This generic principle covers a set of techniques of disparate aims and complexity. Local sensitivity analysis focuses on the re...
Chapter
The main hurdle to clogging diagnosis lies in the difficulty to access the inside of steam generators and the absence of internal sensors. These issues are addressed in different manners by diagnosis methods that are used for routine monitoring or occasional assessment of a steam generators “health”. Monitoring devices can be inserted through the u...
Chapter
Visual inspection only provides information about the clogging of the uppermost plate. Eddy current testing informs about the vertical repartition of clogging but is of limited accuracy. Both methods cannot be used frequently enough for the optimisation of the maintenance strategy. They can be complemented by steady state wide range level monitorin...
Chapter
Principal component analysis can be used as a dimension reduction method by discarding the components whose variance is below a given threshold. Projecting the model output on the low dimensional subspace thus determined preserves its most salient features. However, this only uses the information carried by the output data. As the physical model li...
Chapter
In pressurised water reactors power plants, water is vaporised by the heat extracted from the nuclear reaction by heat exchangers, the steam generators. Iron oxide particles produced by the corrosion of the secondary piping get deposited in the steam generators. They gradually obstruct the flow holes of plates inside the steam generators, thus impe...
Chapter
A new clogging diagnosis method was designed using the results of the statistical analysis presented in the previous chapter. The measured responses during RGL 4 tests are projected onto the first principal components of a sample of simulations, denoted \(s_{1}\). Then, this information is used in conjunction with the simulation sample to predict a...
Book
Clogging of steam generators in nuclear power plants is a highly sensitive issue in terms of performance and safety and this book proposes a completely novel methodology for diagnosing this phenomenon. It demonstrates real-life industrial applications of this approach to French steam generators and applies the approach to operational data gathered...
Article
Nuclear steam generators are subject to clogging of their internal parts which causes safety issues. Diagnosis methodologies are needed to optimize maintenance operations. Clogging alters the dynamic behaviour of steam generators and particularly the response of the wide range level (WRL – a pressure measurement) to power transients. A numerical mo...
Article
Steam generators are massive heat exchangers feeding the turbines of pressurised water nuclear power plants. Internal parts of steam generators foul up with iron oxides which gradually close some holes aimed for the passing of the fluid. This phenomenon called clogging causes safety issues and means to assess it are needed to optimise the maintenan...
Thesis
Full-text available
Les générateurs de vapeur sont d’imposants échangeurs de chaleur qui alimentent les turbines des centrales nucléaires à eau pressurisée. Au cours de leur exploitation, des dépôts d’oxydes s’y accumulent et obstruent progressivement des trous prévus pour le passage du fluide. Ce phénomène, appelé colmatage, pose des problèmes de sûreté. Une méthode...
Article
Full-text available
Tube support plate clogging of steam generators affects their operating and requires frequent maintenance operations. A diagnosis method based on dynamic behaviour analysis is under development at EDF to provide means of optimisation of maintenance strategies. Previous work showed that the dynamic response to a power transient of the wide range lev...
Poster
Full-text available
Sensitivity analysis of a steam generator model dynamic output

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Projects

Projects (8)
Project
Les « Rencontres chercheurs et ingénieurs » de Phimeca visent à stimuler la créativité des chercheurs et des ingénieurs pour la résolution de problèmes mettant en jeu la simulation numérique et l’analyse de données, et à encourager les transferts de savoirs et de technologies entre communautés scientifiques.
Project
Study the uncertainties of atmospheric dispersion models, applied to the Fukushima accident or synthetical accidents in Europe.