Дисертації з теми "Réduction de modèle (ROM)"
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Dubot, Claire. "Modélisation CFD thermohydraulique des générateurs de vapeur et application de techniques de réduction de modèle." Electronic Thesis or Diss., La Rochelle, 2022. http://www.theses.fr/2022LAROS029.
Повний текст джерелаNAVAL GROUP has been carrying out a R&D approach for the modeling and simulation of heat exchangers. This led to the thermal-hydraulic calculation code SIMEC-CFD based on the analogy between the tube bundle and a porous medium. In this work, the steam generator is studied. It is proposed here to use the mixture model where the drift velocity is reformulated as a function of slip in order to implement a model from the literature suitable to flows in tube bundles. SIMEC-CFD is defined mainly by correlations or empirical models. To compensate for the lack of data in the literature, this thesis evaluates the use of model reduction techniques based on POD (Proper Orthogonal Decomposition) in order to supply more precise elements to SIMEC-CFD. These are thus used to calculate the flow and for the inside-tube heat exchange coefficient by a intrusive reduced order model obtained by Galerkin projection on the POD basis and to define the outside-tube two-phase friction pressure loss by the interpolation of reduced solutions Bi-CITSGM. Finally, in the near future, the aim is to expand the system simulation of the secondary loop using SIMEC-CFD. However, these CFD simulations being costly in computation time and in resources, the non-intrusive model reduction by interpolation of the parametric coefficients of the whole heat exchanger is implemented
Mosquera, Meza Rolando. "Interpolation sur les variétés grassmanniennes et applications à la réduction de modèles en mécanique." Thesis, La Rochelle, 2018. http://www.theses.fr/2018LAROS008/document.
Повний текст джерелаThis dissertation deals with interpolation on Grassmann manifolds and its applications to reduced order methods in mechanics and more generally for systems of evolution partial differential systems. After a description of the POD method, we introduce the theoretical tools of grassmannian geometry which will be used in the rest of the thesis. This chapter gives this dissertation a mathematical rigor in the performed algorithms, their validity domain, the error estimate with respect to the grassmannian distance on one hand and also a self-contained character to the manuscript. The interpolation on Grassmann manifolds method introduced by David Amsallem and Charbel Farhat is afterward presented. This method is the starting point of the interpolation methods that we will develop in this thesis. The method of Amsallem-Farhat consists in chosing a reference interpolation point, mapping forward all interpolation points on the tangent space of this reference point via the geodesic logarithm, performing a classical interpolation on this tangent space and mapping backward the interpolated point to the Grassmann manifold by the geodesic exponential function. We carry out the influence of the reference point on the quality of the results through numerical simulations. In our first work, we present a grassmannian version of the well-known Inverse Distance Weighting (IDW) algorithm. In this method, the interpolation on a point can be considered as the barycenter of the interpolation points where the used weights are inversely proportional to the distance between the considered point and the given interpolation points. In our method, denoted by IDW-G, the geodesic distance on the Grassmann manifold replaces the euclidean distance in the standard framework of euclidean spaces. The advantage of our algorithm that we show the convergence undersome general assumptions, does not require a reference point unlike the method of Amsallem-Farhat. Moreover, to carry out this, we finally proposed a direct method, thanks to the notion of generalized barycenter instead of an earlier iterative method. However, our IDW-G algorithm depends on the choice of the used weighting coefficients. The second work deals with an optimal choice of the weighting coefficients, which take into account of the spatial autocorrelation of all interpolation points. Thus, each weighting coefficient depends of all interpolation points an not only on the distance between the considered point and the interpolation point. It is a grassmannian version of the Kriging method, widely used in Geographic Information System (GIS). Our grassmannian Kriging method require also the choice of a reference point. In our last work, we develop a grassmannian version of Neville's method which allow the computation of the Lagrange interpolation polynomial in a recursive way via the linear interpolation of two points. The generalization of this algorithm to grassmannian manifolds is based on the extension of interpolation of two points (geodesic/straightline) that we can do explicitly. This algorithm does not require the choice of a reference point, it is easy to implement and very quick. Furthermore, the obtained numerical results are notable and better than all the algorithms described in this dissertation
Dumon, Antoine. "Réduction dimensionnelle de type PGD pour la résolution des écoulements incompressibles." Phd thesis, Université de La Rochelle, 2011. http://tel.archives-ouvertes.fr/tel-00644565.
Повний текст джерелаSaleh, Marwan. "Étude mathématique et numérique des méthodes de réduction dimensionnelle de type POD et PGD." Thesis, La Rochelle, 2015. http://www.theses.fr/2015LAROS004/document.
Повний текст джерелаThis thesis is formed of four chapters. The first one presents the mathematical notions and tools used in this thesis and gives a description of the main results obtained within. The second chapter presents our generalization of a result obtained by Rousselet-Chenais in 1990 which describes the sensitivity of eigensubspaces for self-adjoint compact operators. Rousselet-Chenais were limited to sensitivity for specific subspaces of dimension 1, we have extended their result to higher dimensions. We applied our results to the Proper Orthogonal Decomposition (POD) in the case of parametric, temporal and spatial variations (Gappy- POD). The third chapter discusses the optical flow estimate with quadratic or linear energies at infinity. Mathematical results of convergence are shown for the method Progressive Generalized Decomposition (PGD) in the case of quadratic energies. Our proof is based on the decomposition of Brézis-lieb via the convergence almost everywhere of the PGD sequence gradients. A detailed numerical study is made on different types of images : on the passive scalar transport equations, whose displacement fields are solutions of the Navier-Stokes equations. These equations present a challenge for optical flow estimates because of the presence of low gradient regions in the image. We applied our method to the MRI image sequences to estimate the movement of the abdominal organs. PGD presented a superiority in both computing time level (even in 2D) and accuracy representation of the estimated motion. The local diffusion of standard methods (Horn Schunck, for example) limits the convergence rate, in contrast to the PGD which is a more global approach by construction. The last chapter deals with the application of PGD method in the case of variational elliptic equations whose energy present all challenges to classical variational methods : lack of convexity, lack of coercivity and lack of boundedness. We prove convergence results for the weak topology, the PGD sequences converge (when they are well defined) to two extremal solutions on the Nehari manifold. Several mathematical questions about PGD remain open in this chapter. These questions are part of our research perspectives
Tissot, Gilles. "Réduction de modèle et contrôle d'écoulements." Thesis, Poitiers, 2014. http://www.theses.fr/2014POIT2284/document.
Повний текст джерелаControl of turbulent flows is still today a challenge in aerodynamics. Indeed, the presence of a high number of active degrees of freedom and of a complex dynamics leads to the need of strong modelling efforts for an efficient control design. During this PhD, various directions have been followed in order to develop reduced-order models of flows in realistic situations and to use it for control. First, dynamic mode decomposition (DMD), and some of its variants, have been exploited as reduced basis for extracting at best the dynamical behaviour of the flow. Thereafter, we were interested in 4D-variational data assimilation which combines inhomogeneous informations coming from a dynamical model, observations and an a priori knowledge of the system. POD and DMD reduced-order models of a turbulent cylinder wake flow have been successfully derived using data assimilation of PIV measurements. Finally, we considered flow control in a fluid-structure interaction context. After showing that the immersed body motion can be represented as an additional constraint in the reduced-order model, we stabilized a cylinder wake flow by vertical oscillations
Vuong, Thi Thanh Thuy. "Réduction de modèle de crash automobile : application en optimisation." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEC025.
Повний текст джерелаThe numerical simulation is more and more applied in the industry in order to reduce the physical tests costs. A crash simulation (pre-processing, processing and post-processing) takes about one or two days. Renault uses the optimization, so numerous crash simulations, to size cars. To cut back the total cost of a whole crash simulations, the aim of this thesis is to propose a or some Reduced-Order Model (ROM) methods that can be applied in a parametric space. The suggested methods in this thesis are nonintrusive and neither the solver nor the model should not be modified . The first tested method is the Proper Orthogonal Decomposition. This method allows reducing the behavior of a crash simulation and understanding the crash properties but not interpolating in a parametric space. The second method, ReCUR, is a variant of the classical decomposition CUR. It will be demonstrated as a general form of the non-intrusive methods. It allows overcoming two important limits of actual ROM methods : size of the model and the interpolation
Ventura, Jérôme. "Réduction de modèle en convection forcée par des méthodes d'identification." Phd thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2010. http://www.theses.fr/2010ESMA0013.
Повний текст джерелаMost engineering processes dealing with aerothermics involve numerical simulations (CFD) which need to take transient phenomena into account to be realistic. Low order models and responses surfaces offer the engineer an alternative to the high costs associated with CFD processes, providing him with surrogates for the outputs of his interest. This work is devoted to extend the Modal Identification Method (MIM) in the field of fluid dynamics. MIM is a low order modelling techniques, based on the minimization of the discrepancy between a usually large reference model, and a low order model. It solves an optimization problem whose variables are the low order model parameters. Low order models are built for several kinds of turbulent flows. The circular cylinder in a crossflow provides us with several test cases. We cope with steady flows or unsteady ones, be them in forced convection or isothermal cases. Those models are able to produce outputs as different as velocity and temperature fields, heat fluxes. . . The compressible flow around a wing profile is also considered to investigate the sampling effect. Those models give quick approximates of the pressure distribution or the force coefficients
Gstalter, Étienne. "Réduction d’ordre de modèle de crash automobile pour l’optimisation masse / prestations." Thesis, Compiègne, 2020. http://www.theses.fr/2020COMP2576.
Повний текст джерелаThis thesis is a part of a global research work dedicated to reduced-order modelling applications in the Renault engineering direction. It's research topic has been improved in the IRT System)('s project on Reduced Order Model and Multi-disciplinary Optimization. Some previous thesis can help understand the context. ([Vuong], [Charrier]). The main industrial application of the research theme is the focus on a body structure, in a crash loading. Some research works on acoustic, combustion and aerodynamic are currently ongoing. This thesis is both a contribution to the generic ReCUR method, and its application to a car body structure optimization for crash loadings. Engineering teams at Renault uses optimization to obtain the best crash simulation, with a numerical optimization software, based on designs of experiments. It requires a lot of crash simulation because each simulation is considered as unique, with only one response for each parameter. Only Inputs and Outputs are known. The ReCUR method consider that each simulation is a huge mine that needs our attention. We hope that we can decrease the number of crash simulation required to compute a model, by using much more data for each simulation
Pinto, Marinho Nuno. "Réduction d'un modèle de système électrique pour des études technico-économiques." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLC051/document.
Повний текст джерелаThe simulation of complex processes in large scale power systems needs the reduction of the problem. How to reduce the spatial complexity of a large scale power network while minimizing information loss? To answer this question we have divided this work in three main steps: 1) network buses aggregation; 2) modelling of the clusters' links; 3) defining the equivalent branches maximum exchange capacity.The bus aggregations in a cluster implies that it will be treated as a coppper-plate by the market model. Therefore, the most frequent network congestions must be identified ideally placed at the clusters frontiers. After the reduction, the same power flow repartition must be found in both reduced and complete model. To do that, a methodology to define a PTDF matrix was developed. For economic purpose studies, the branches maximum capacity is a key parameter, to define this value, a methodology is proposed that estimates the equivalent transmission capacities using historical system operating set points.These approaches were applied to the European transmission network and allowed to define a reduced model that minimises the information loss
Oulefki, Abdelhakim. "Réduction de modèles thermiques par amalgame modal." Phd thesis, Ecole Nationale des Ponts et Chaussées, 1993. http://tel.archives-ouvertes.fr/tel-00523620.
Повний текст джерелаPonsignon, Jean-Charles. "Réduction fuchsienne et modèles stellaires." Thesis, Reims, 2013. http://www.theses.fr/2013REIMS046/document.
Повний текст джерелаThe object of this thesis is the study of a non linear differential equation stemming from a stellar model. After reduction and unknowns changes and variables, we achieve to an analytic second member in each of the problem variables and well chosen functions. Then we show that the solutions can be described in a space of absolute convergent series. This theorem of existence will be used as an elementary brick to a nearby method of Fuchsian reduction. The objective was to obtain a development which elicits arbitrary various constants inherent to this type of equations
Hachette, Rémy. "Réduction de modèle thermique par identification : utilisation pour des conditions aux limites variables, couplage à un modèle détaillé." Aix-Marseille 1, 1995. http://www.theses.fr/1995AIX11048.
Повний текст джерелаNguyen, Tien Minh. "Dynamique non linéaire des systèmes mécaniques couplés: réduction de modèle et identification." Phd thesis, Ecole des Ponts ParisTech, 2007. http://pastel.archives-ouvertes.fr/pastel-00002994.
Повний текст джерелаAssaf, Ali. "Réduction de modèle, observation et commande prédictive d'une station d'épuration d'eaux usées." Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0282/document.
Повний текст джерелаWastewater treatment processes are large scale, non linear systems, submitted to important disturbances of influent flow rate and load. Model predictive control (MPC) widely used industrial technique for advanced multivariable control, has been applied to the Benchmark Simulation Model 1 (BSM1) simulation benchmark of wastewater treatment process. An open loop identification method has been developed to determine a linear model for a set of input-output measurements of the process. All the step responses have been obtained in open loop from step variations of the manipulated inputs and measured disturbances around their steady state values. The non-linearities of the model are taken into account by variable parameters. The step responses coefficient obtained make it possible to determine by optimization the corresponding transfer functions. That functions are classified by five mathematical models, such as : first order, first order with integrator, inverse response, second order and second order with zero. The numerical values of coefficients of each model selected were calculated using a least squares criterion. Model predictive control (MPC) uses the resulting model as an internal model to control the process. Dynamic matrix control DMC and quadratic dynamic matrix control QDMC predictive control strategies, in the absence and presence of feedforward compensation, have been tested. Two measured disturbances have been used for feedforward control, the influent flow rate and ammonium concentration
Lombard, Jean-Pierre. "Contribution à la réduction des modèles éléments finis par synthèse modale." Phd thesis, Université de Franche-Comté, 1999. http://tel.archives-ouvertes.fr/tel-00351693.
Повний текст джерелаUne nouvelle technique de synthèse modale est proposée: elle permet l'obtention de modèles réduits exempts de coordonnées de jonction. Ses performances sont comparées vis-à-vis des méthodes de sous-structuration classiques lors de la réduction de modèles de structures automobiles. Un modèle sous-structuré d'une caisse nue de véhicule de 450 000 ddl, présentant une forte connectivité, est condensé à 2000 ddl par cette méthode.
L'usage de transformations de coordonnées physiques avec la prise en compte des chargements appliqués est généralisé à l'ensemble des méthodes de réduction.
La robustesse des modèles réduits paramétrés est traitée ainsi que les techniques d'adaptation, par réductions multiplies, des données issues du modèle aux observations mesurées sur la structure dans des objectifs de recalage de modèle et d'optimisation de comportement.
Beyrouthy, Joëlle. "Réduction dimensionnelle d'un modèle viscoélastique en grandes déformations : Analyse théorique et simulation numérique." Paris 6, 2008. http://www.theses.fr/2008PA066113.
Повний текст джерелаMissoffe, Alexia. "Réduction d'ordre de modèle d'un phénomène d'amortissement non-linéaire dans le cadre des microsystèmes." Phd thesis, Ecole Centrale Paris, 2010. http://tel.archives-ouvertes.fr/tel-00552076.
Повний текст джерелаMansouri, Mohamed. "Etude mécano-fiabiliste et réduction du modèle des problèmes vibro-acoustiques à paramètres aléatoires." Phd thesis, INSA de Rouen, 2013. http://tel.archives-ouvertes.fr/tel-00845562.
Повний текст джерелаMacherey, Arthur. "Approximation et réduction de modèle pour les équations aux dérivées partielles avec interprétation probabiliste." Thesis, Ecole centrale de Nantes, 2021. http://www.theses.fr/2021ECDN0026.
Повний текст джерелаIn this thesis, we are interested in the numerical solution of models governed by partial differential equations that admit a probabilistic interpretation. In a first part, we consider partial differential equations in high dimension. Based on a probabilistic interpretation of the solution which allows to obtain pointwise evaluations of the solution using Monte-Carlo methods, we propose an algorithm combining an adaptive interpolation method and a variance reduction method to approximate the global solution. In a second part, we focus on reduced basis methods for parametric partial differential equations. We propose two greedy algorithms based on a probabilistic interpretation of the error. We also propose a discrete optimization algorithm probably approximately correct in relative precision which allows us, for these two greedy algorithms, to judiciously select a snapshot to add to the reduced basis based on the probabilistic representation of the approximation error
Berger, Julien. "Contribution à la modélisation hygrothermique des bâtiments : application des méthodes de réduction de modèle." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENA028/document.
Повний текст джерелаExcessive levels of moisture in buildings may damage the construction quality. Moisture also has an effect on indoor air quality and thermal comfort of the occupants. Thus moisture is a possible source of disorders in buildings. It is therefore important to continue developing numerical models to simulate the global hygrothermal behaviour of buildings. To achieve this aim, it is necessary to solve non-linear problems, with high space and time scales, with fine discretisation and sometimes parametric. This mathematical problems are complex to solve. Thus model reduction techniques and efficient ways of numerical simulation are worth investigations. Two techniques were assessed : the Proper Orthogonal Decomposition (POD) and the Proper Generalised Decomposition (PGD). They were first applied on non-liner coupled heat and mass transfers in porous materials. Both were compared and evaluated carrying about the reduction of the cost of resolution and the precision of the solution computed. Following this analysis, the PGD was selected for our next investigations. Due to it representation, the PGD method has several interesting features, already reviewed in literature.Thus, chapter 3 proposed to illustrate this advantages on different issues of modelling buildings hygrothermal behaviours. We focused on the reduction of the complexity of multi-dimensional problems, on the globalisation of local problems and on building PGD parametric solution or meta-model. Several academic case study were considered to illustrate these points. We analysed non-linear heat and mass transfers in porous materials and multizone air building transfers. In last part, we elaborated a PGD reduced order model to perform whole building energy simulation. Two different models were built. The first one associates a PGD model for envelope problem and a large original model for multizone problem. This work was done during a collaboration with the LST laboratory, at PUCPR University, Curitiba, Brazil. The main interest was the benefits of using their validated and admitted model Domus for solving multizone problem. Two case study were analysed. The first one analyse a parametric problem for the study of the retrofitting a building in function of the vapour permeability of the insulating material. The second one focused on the whole building energy simulation of a two-zone building with 2-dimension transfers in the wall assembly. A second global PGD reduced order model was elaborated, with a higher reduction of the numerical complexity of the problem. This model associates a PGD model for solving envelope problem and a PGD parametric solution for the multizone problem. The performance of this model was analysed investigating the numerical gain and the precision of the solution computed. In conclusion, the relevance of reduction model techniques for performing whole building energy simulation was revealed. The PGD method contributes to a new approach for solving this problems
Sammut, Sébastien. "Compensation rénale après réduction du parenchyme néphronique in utero dans un modèle fœtal ovin." Paris 6, 2013. http://www.theses.fr/2013PA066174.
Повний текст джерелаIn humans, in response to unilateral (1/2Nx) or subtotal (5/6Nx) nephrectomy, the contralateral kidney ensures filtration for the missing kidney; tubular and glomerular hypertrophy develop, the kidney weight and renal size increase. As glomerular number is determined at birth, no additional nephrons may be formed and the overload filtration results in structural lesions. Few studies in fetuses suggest that the renal response to renal mass reduction can begin in utero. Experimental data are rare and restricted for the 1/2Nx model only, performed at the end of nephrogenesis or ex utero. In our work, we studied the morphological, functional and molecular effects for both groups (1/2Nx and 5/6Nx) in the ovine fetus. In both models, the renal mass and glomerular number increased, but the response was strikingly different. In the 5/6Nx group, two lobes were formed at the incision sites of the kidney displaying a “butterfly-like” remodelling and glomerular number markedly increased. To improve renal regeneration in the 5/6Nx model, we studied the possibility of transplanting stem cells; in vitro, our first experiments have allowed to isolate and characterize ovine stem cells from amniotic fluid. In conclusion, our study highlighted unsuspected renal compensation capacity in the fetus during the period-specific nephrogenesis; additional work will enable us to determine if renal compensation can be further improved by an exogenous contribution of stem cells
Madelaine, Béatrice. "Détermination d'un modèle dynamique pertinent pour la commande : de la réduction à la construction." Toulouse, ENSAE, 1998. http://www.theses.fr/1998ESAE0011.
Повний текст джерелаDespret, Pierre. "Simulation numérique de la solidification avec réduction de modèle PGD appliquée à la fonderie." Thesis, Compiègne, 2015. http://www.theses.fr/2015COMP2226/document.
Повний текст джерелаThe PhD Thesis was carried out in a metallurgy and numerical simulation environment. The main topic was to model solidification, thought heat equation formulation and reduced order model PGD resolution. Montupet, specialized in aluminium alloys foundry hold and financed the project, the Université de Technologie de Compiègne did the acadernic supervising. The PGD method "Proper General Decomposition" is a hot topic based on variable separation. We proposed, regarding the non-linear materials, a space-time discretization of material matrix. With a temperature formulation, without latent heat, gains are high. With latent heat, gains fall drastically. We proposed the hypothesis that temperature could be an inadapted formulation. We decided to use the enthalpy formulation. This formulation offers good perspectives but needs more developments. During the thesis, five months were spent in the USA to get a better caracterisation of the solid fraction, particularly its variation in function of the cooling rate. Under reservation, the samples show a modification of solid fraction curves and particularly a change of solidification interval in function of cooling rate
Vitse, Matthieu. "Réduction de modèle pour l'analyse paramétrique de l'endommagement dans les structures en béton armé." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLN055/document.
Повний текст джерелаThis thesis is dedicated to the development of an algorithm for the resolution of nonlinear problems for which there is a variability on some of the model parameters or on the loading conditions, which are only described by their intervals of variation. This study is part of the SINAPS@ project, which aims at evaluating the uncertainties in civil engineering structures and to quantify their influence on the global mechanical response of a structure to a seismic hazard. Unlike statistical or probabilistic approaches, we rely here on a deterministic approach. However, in order to reduce the computation cost of such problems, a PGD-based reduced-order modeling approach is implemented, for which the uncertain parameters are considered as additional variables of the problem. This method was implemented into the LATIN algorithm, which uses an iterative approach to solve the nonlinear aspect of the equations of the mechanical problem. This work present the extension of the classical time-space LATIN—PGD algorithm to parametric problems for which the parameters are considered as additional variables in the definition of the quantities of interest, as well as the application of such method to a damage model with unilateral effect, highlighting a variability on both material parameters and the loading amplitude. The feasibility of such coupling is illustrated on numerical examples for reinforced concrete structures subjected to different types of cyclic loading conditions (tension—compression, bending)
Portier, François. "Réduction de la dimension en régression." Phd thesis, Université Rennes 1, 2013. http://tel.archives-ouvertes.fr/tel-00871049.
Повний текст джерелаBoucinha, Luca. "Réduction de modèle a priori par séparation de variables espace-temps : Application en dynamique transitoire." Thesis, Lyon, INSA, 2013. http://www.theses.fr/2013ISAL0118/document.
Повний текст джерелаNumerical simulation of physical phenomena has become an indispensable part of the mechanical engineer's toolbox. Robust and flexible tools, based on classical approximation methods, are now commonly used in industry. However, these tools require lots of computational resources to solve complex problems. Even if such resources are more and more affordable thanks to the remarkable progress in computer industry, it is now necessary to propose innovative approximation methods in order to better exploit the impressive amount of computational resources that are todays available. Reduced order modeling techniques are presented as ideal candidates to address this issue. Among these, methods based on the construction of low rank separated approximations have been shown to be very efficient to approach solutions of a wide variety of problems, reducing computational costs by several orders of magnitude. Nonetheless, efficiency of these methods significantly depends on the considered problem. In this manuscript, we propose to evaluate interest of space-time separated representations to approach solutions of academical transient dynamic problems. We first define the best space-time separated approximation (with respect to a minimization problem) of a given solution of a transient problem. The construction of this approximation being based on the hypothesis that the problem's solution is known (a posteriori method), the following of the manuscript is dedicated to the construction of such an approximation without any other knowledge on the reference solution than the operators of the space-time problem from which it is solution (a priori method). We then introduce a generic formalism, based on the tensor product structure of the operators of the space-time problem, in a multi-field framework. Next, this formalism is used to develop a generic solver that builds a separated approximation of a transient problem's solution, with the help of the Proper Generalized Decomposition (PGD). A state of art of existing algorithms is done, and efficiency of classical definitions of PGD to approach solutions of several academical transient dynamic problems is evaluated. Numerical results highlight the lack of optimality of the more robust PGD. Therefore, a new PGD definition, recently introduced in literature, is applied to solution of an elastodynamic problem in a multi-field framework. This new definition is based on minimization of an ideal residual norm and allows to find a very good approximation of the best approximation of a given rank, without having to calculate more space-time modes than needed
Safatly, Elias. "Méthode multiéchelle et réduction de modèle pour la propagation d'incertitudes localisées dans les modèles stochastiques." Phd thesis, Université de Nantes, 2012. http://tel.archives-ouvertes.fr/tel-00798526.
Повний текст джерелаDuquesne, Marie. "Résolution et réduction d'un modèle non-linéaire de stockage d'énergie par adsorption sur des zéolithes." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2013. http://tel.archives-ouvertes.fr/tel-00821894.
Повний текст джерелаBatou, A. "Dynamique des structures déformables et des solides rigides - Quantification des incertitudes et réduction de modèle." Habilitation à diriger des recherches, Université Paris-Est, 2014. http://tel.archives-ouvertes.fr/tel-01010584.
Повний текст джерелаSafatly, Elias Emile. "Méthode multiéchelle et réduction de modèle pour la propagation d'incertitudes localisées dans les modèles stochastiques." Nantes, 2012. http://archive.bu.univ-nantes.fr/pollux/show.action?id=cc8428f5-edf4-4ce1-96c9-42d69e43459a.
Повний текст джерелаIn many physical problems, an uncertain model can be represented as a set of stochastic partial differential equations. We are here interested in problems with many sources of uncertainty with a localized character in space. In the context of functional approaches for uncertainty propagation, these problems present two major difficulties. The first one is that their solutions are multi-scale, which requires model reduction methods and appropriate computational strategies. The second difficulty is associated with the representation of functions of many parameters in order to take into account many sources of uncertainty. To overcome these difficulties, we first propose a multi-scale domain decomposition method that exploits the localized side of uncertainties. An iterative algorithm is proposed, which entails the alternated resolution of global and local problems, the latter being defined on patches containing localized variabilities. Tensor approximation methods are then used to deal with high dimensional functional representations. Multi-scale separation improves the conditioning of local and global problems and also the convergence of the tensor approximation methods which is related to the spectral content of functions to be decomposed. Finally, for the handling of localized geometrical variability, specific methods based on fictitious domain approaches are introduced
Dollinger, Nicolas. "Méthodologie de réduction de modèles thermiques nodaux avec écoulement de fluide par la théorie des réseaux : application à la réduction d'un modèle de moteur thermique." Poitiers, 2005. http://www.theses.fr/2005POIT2269.
Повний текст джерелаDue to increasing environmental concern, the automotive industry needs a better control of consumption and pollutants emission. A predictive study of these requires complex physical models that have high computation times. So this research work aims at elaborating a simplified model of thermal engine behavior during temperature increase phases. A reduction methodology of nodal thermal models is adaptated to systems including variable and non-symmetric elements (fluid flow). Starting from heat transfer model of the engine (1700 nodes) we obtain a reduced model (10 nodes) giving the dynamics at the system interfaces with low computation times. To produce a both simple and harmonically rich reduced model, we use nodal models structures called “arborescent” corresponding to a form of Padé approximation. The termination of these structures in cases where the initial model changes (variable fluid flow) is a necessary progress to consider such a complex model as an internal thermal engine
Barbagallo, Alexandre. "Réduction de modèle et contrôle en boucle fermée d'écoulements de type oscillateur et amplificateur de bruit." Phd thesis, Ecole Polytechnique X, 2011. http://pastel.archives-ouvertes.fr/pastel-00654930.
Повний текст джерелаCorus, Mathieu. "Amélioration de méthodes de modification structurale par utilisation de techniques d'expansion et de réduction de modèle." Phd thesis, Ecole Centrale Paris, 2003. http://tel.archives-ouvertes.fr/tel-00011298.
Повний текст джерелаLes concepts fondamentaux utilisés dans cette thèse sont ensuite présentés. Les relations de la dynamique des structures pour les problèmes discrets sont rappelées, ainsi que les principes de la synthèse modale, de la sous-structuration dynamique et de la réduction de modèle, tout comme la notion de modes d'interface. Les formulations classiques des méthodes de modification structurale sont ensuite détaillées pour en illustrer les limitations et les restrictions.
Une formulation originale permettant de prendre en compte les incompatibilités entre les mesures et les DDL de l'interface structure/modification et de régulariser la construction d'un modèle de comportement couplé est alors proposée. Cette première contribution de la thèse repose sur l'utilisation des techniques d'expansion de données et de réduction de modèle. Des indicateurs sont également construits pour estimer la cohérence de la prédiction réalisée. Les évolutions sont appliquées au cas d'un démonstrateur numériques et les résultats sont comparés avec les prédictions réalisées par les méthodes classiques. La méthodologie associée à cette nouvelle formulation est alors largement exposée.
L'influence des différents facteurs intervenant dans la construction du modèle couplé et la qualité de la prédiction est ensuite analysée en détail. Cette analyse permet de dresser une liste non exhaustive des précautions à prendre lors de la mise en œuvre de la méthode proposée, depuis la réalisation pratique de l'analyse modale expérimentale jusqu'à l'interprétation des premiers résultats.
Enfin, plusieurs applications sont présentées. Une première structure académique démontre la faisabilité de la méthode. Une deuxième étude, réalisée sur un cas industriel, illustre les gains de temps potentiels en comparant la prédiction avec les résultats d'une étude basée sur un modèle EF recalé de la structure. La troisième étude illustre l'application de la méthode dans un cas type. L'analyse modale de la structure cible permet de comprendre le problème, une modification est conçue, réalisée et mise en place. La prédiction est ensuite comparée aux résultats de l'analyse modale de la structure modifiée. Enfin, la dernière application montre les limites de la méthodologie. L'étude multi-objectifs sur une large bande de fréquences d'une structure industrielle permet de faire une ouverture vers la suite des travaux et montre la nature des difficultés à surmonter.
Guillet, Jérôme. "Etude et réduction d'ordre de modèles linéraires structurés : application à la dynamique du véhicule." Phd thesis, Université de Haute Alsace - Mulhouse, 2011. http://tel.archives-ouvertes.fr/tel-00807199.
Повний текст джерелаBa, Alassane. "Croissance économique et réduction de la pauvreté : modèle de prévision adapté à l'évaluation de politiques économiques, cas du modèle de Cadre Budgétaire à Moyen Terme." Nantes, 2009. http://www.theses.fr/2009NANT4023.
Повний текст джерелаPoverty has become a major concern in the international context of globalization. Poor countries like Mali, whose economy is subject to the vagaries of the international environment and impacts of climate, face the challenge to ensure a harmonious economic and social development. The condition of this success through accelerated growth, a significant reduction of poverty and human development. If Mali is an average growth of 5% since 1994, however, the reduction of poverty was very low. Development policies are confronted with challenges to the quality, targeting and evaluation. The quality of macroeconomic policies and the optimal allocation of resources towards priority sectors for development are essential to arrive at the triangle of development: growth, reduction of poverty and human development. To facilitate this interaction, we choose whether to develop a budgetary model of framework in the medium term (CBMT) which is a tool for decision support and a tool for dialogue and arbitration to ensure the articulation between the macroeconomic framework, budget and development stratégies. The model structure consists of a real sector, a sector of public finances (including the state budget, budgets and sectoral performance indicators), a monetary sector and a module poverty analysis. Model CBMT is by its structure a model quasi-accountant with equations of behavior. It is intended to improve the assessment of economic and fiscal policies by strengthening the quality of budget decisions and managing for results
Joannin, Colas. "Réduction de modèle par sous-structuration et modes non-linéaires : Application à la dynamique des roues aubagées." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEC014/document.
Повний текст джерелаMistuning of bladed disks has been a key topic of research for the aeronautics industry. To get accreditation for their engines, manufacturers must comply with evermore stringent requirements, and thus constantly seek for better simulation tools. Even though the phenomenon is well understood nowadays for linear systems, nonlinearities are still seldom taken into account when dealing with the mistuning of industrial structures, partly due to the lack of a dedicated method to tackle such a complex problematic. The main objective of this work is to develop a novel method allowing to compute efficiently the forced response of a mistuned bladed disk, while taking into account the impact of nonlinearities on the vibrations at a macroscopic scale. The method derived relies on a substructuring approach, and uses the concept of nonlinear complex modes to capture the nonlinearities in the reduction basis of each substructure. In the frequency domain, the substructures take the form of nonlinear superelements, which once assembled lead to the reduced-order model of the mistuned bladed disk. The resulting mathematical system is then solved by means of iterative solvers. This new method is tested and validated on different systems subjected to dry friction nonlinearities, from basic phenomenological models to large-scale finite element models of industrial structures. On lumped-parameter models, the performance of this method allows to investigate the statistical impact of mistuning in the presence of nonlinearities, by performing thousands of simulations. The results suggest that the behaviour of the nonlinear model can be significantly different from that of the linear one, hence the importance to carry out such investigations. The capabilities of the method have also been confirmed on large-scale models, by performing several forced response computations on a nonlinear and mistuned finite element model, at a reasonable cost
Thomas, Sébastien. "La fragmentation moléculaire : modèle statistique et réduction par plasma de l’acétone avec identification en ligne des produits." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS559.
Повний текст джерелаMolecular fragmentation is a promising technique for the treatment of polluted gaseous effluents. This work deals with the theoretical and experimental study of the reduction of VOC chemical pollutants by fragmentation. We have transformed an atomic nucleus and cluster fragmentation model, redesign at CSNSM, into a model that treats any type of molecules (SMF moldel). The efforts have been focused on accelerating the computation of the weights with multivariate incomplete Beta functions (factor 30 on speed), on the interfacing with the Gaussian ab-initio software, on the generalization of the molecular formalism as well as on molecular rearrangements. To account for the characteristics of our experimental setup (reactivity between fragmentation and detection) the results were processed by a 0-D chemical kinetics model. Predictions on acetone fragmentation were then compared to our experimental results obtained using an innovative device. Acetone degradation was carried out in a homogeneous plasma reactor, developed at LPGP, to guarantee the uniformity of the reaction conditions. To measure the large number of discharge by-products, we used a new detection method developed at LCP: compact FT-ICR mass spectrometers producing in situ real-time measurements. This new experimental device has been successfully implemented. It allowed the fine study of the acetone excitation - de-excitation - oxidation mechanisms and the validation of the theoretical predictions
Hammadi, Youssef. "Réduction d'un modèle 0D instationnaire et non-linéaire de thermique habitacle pour l’optimisation énergétique des véhicules automobiles." Thesis, Université Paris sciences et lettres, 2020. http://www.theses.fr/2020UPSLM027.
Повний текст джерелаThe use of automotive air conditioning leads to a fuel overconsumption. To reduce this overconsumption, we can either work upstream on the technical definitions of the cabin and the HVAC system or optimize control strategies. In both cases, it is essential to build a cabin thermal model that well balances accuracy and complexity. This is the topic of this PhD thesis driven by Renault Group. First, a model reduction methodology is used to build a 0D model starting from a 3D finite element cabin thermal model. This 0D model is based on mass and energy balances on the different cabin walls and air zones. It consists of a nonlinear differential algebraic equations system which can be reinterpreted as a Bond Graph. In addition, the 0D model is based on a weak coupling between the thermal equations and the fluid mechanics ones resulting from CFD calculations (internal airflow and external aerodynamics). Secondly, we apply a machine learning method to the data generated by the 0D model in order to build a reduced 0D model. A design of experiment is considered at this stage. Due to the nonlinearity of the heat exchanges, we have developed an approach which is inspired by the Gappy POD and EIM methods. We use a multiphysics reduced basis that takes several contributions into account (temperatures, enthalpies, heat fluxes and humidities). The resulting reduced model is a hybrid model that couples some of the original physical equations to an artificial neural network. The reduction methodology has been validated on Renault vehicles. The reduced order models have been integrated into a vehicle system-level energetic simulation platform (GREEN) which models different thermics (engine, transmission, cooling system, battery, HVAC, refrigerant circuit, underhood) in order to perform thermal management studies which are of particular importance for electric and hybrid vehicles. The reduced order models have been validated on several scenarios (temperature control for thermal comfort, driving cycles, HVAC coupling) and have achieved CPU gains of up to 99% with average errors of 0.5 °C on temperatures and 0.6% on relative humidities
Bergmann, Michel. "Optimisation aérodynamique par réduction de modèle POD et contrôle optimal : application au sillage laminaire d'un cylindre circulaire." Vandoeuvre-les-Nancy, INPL, 2004. http://www.theses.fr/2004INPL120N.
Повний текст джерелаThis thesis focus on the circular cylinder drag minimization by rotary oscillations in a laminar flow. The originality of this approach is to couple optimal control and Reduced Ordre Model based on POD. Preliminary works concemed the parametric study of the influence of the control parameters on the drag force. We also found necessary to lInprove the dynamlcal representatlveness of the reduced order model by adding artificial viscosity and shift modes. Then, various control strategies have been developed. Firstly, a generalized POD basis, which accounts for the dynamics of the forced flow, will be used throughout the optimisation process. Secondly, an adaptative resolution method is performed. Two different algorithms are then used to determine when a actualization of the POD basis is necessary. Both control methods allows us to reduce and minimize the drag coefficient at much lower costs than the optimal control method applied to the Navier-Stokes equations
Videcoq, Etienne. "Problèmes inverses en diffusion thermique instationnaire : résolution par représentation d'état et apport de la réduction de modèle." Poitiers, 1999. http://www.theses.fr/1999POIT2355.
Повний текст джерелаTeghbit, Saliha. "Contribution à la modélisation floue, minimisation de l'écart modèle-système par réduction du contour du graphe flou." Valenciennes, 1995. https://ged.uphf.fr/nuxeo/site/esupversions/5142ac51-a8ff-4d6b-8979-acb9641b3abc.
Повний текст джерелаNasri, Mohamed Aziz. "Réduction dimensionnelle pour la simulation de la fatigue des métaux." Thesis, Paris, ENSAM, 2017. http://www.theses.fr/2017ENAM0016/document.
Повний текст джерелаIn order to take account of fatigue cracks initiation and growth, it is necessary to know the history of the various mechanical quantities in fatigue initiation site. This requires knowledge of the stabilized cyclic mechanical states. From a numerical approach, numerical simulation of polycrystalline aggregates with conventional resolution methods are only carried out for a few cycles. This work presents the development of accelerated numerical methods to reduce the computation time of the Finite Element method in the case of numerical simulation of polycrystalline aggregates under cyclic loading. The first idea is to keep a constant stiffness matrix during overall simulation in order to get just one single factorization to carry out. An algorithm has been proposed in this sense with an incremental and non incremental resolution. The second proposal is based on the use of a model reduction method coupled with the finite element method to solve space/time problem. The PGD has been selected. This method allows to decouple spatial and time coordinates and the displacement fields are computed for a certain number of modes. Two possibilities have been proposed to implement the PGD method in the context of plasticity. The third proposal is to use an a priori adaptative approach based on the use of APR strategy to solve a reduced order model in terms of number of degrees of freedom. An incremental adaptive strategie has been proposed in order to master the quality of the reduced-basis for a certain time steps. Four possibilities of using the APR method have been proposed. The applicability and the performance of the different methods have been first analyzed on a conventional three-dimensional elastoplastic problem with a spherical defect, then on the scale of the microstructure with numerical simulation of polycrystalline aggregates under cyclic elasto-visco-plastic loading. The analyzes have shown that the macroscopic and mesoscopic mechanical responses of the model reduction methods are very close to the incremental method. The simulation time has been reduced by the different methods. The time gains are more significant by increasing the size of the meshes and the non-linearity of the problem. Nevertheless, the idea of keeping a constant stiffness matrix with the incremental method has enabled more CPU time saving at the microstructural scale
Gati, Yousra. "Analyse mathématique et simulations numériques d'un modèle de fluides complexes." Phd thesis, Ecole des Ponts ParisTech, 2004. http://pastel.archives-ouvertes.fr/pastel-00000883.
Повний текст джерелаUghetto, Pascal. "A la recherche d'un nouveau modèle d'emploi : dynamique des changements structurels et institutionnels affectant le travail et l'emploi." Paris 9, 1998. https://portail.bu.dauphine.fr/fileviewer/index.php?doc=1998PA090011.
Повний текст джерелаThe microeconomic transformations of work and employment since the eighties do not seem to have yield any obvious result on the macroeconomic situation of employment (especially in France). This work has sought to identify the reason of such a situation and the conditions through which the rela, tion between work in a microeconomic level and employment in a macroeconomic one could be im, proved. It has suggested it could be done by studying the dynamics of structural and institutional change of work. After having examined present theories, it argues that the issue for such a dynamics is the stabilization of a new employment pattern likely to concur to the development of a new growth dynamics. Whereas the present pattern (toyotaism), by focusing on the suppression of overcosts, is contributing to the development of a vicious circle of growth, the question is raised of how beneficient a pattern could be which would be established on the service relation and the reduction of working time. This pattern compels to seek new internal and external economies in a very original manner, which, in turn, justifies to engage expenditure (to invest in human resources and to remunerate these by the reduction of their working time) which are likely to yield positive macroeconomic effects. The state intervention is required to promote this new employment pattern. It must build institutions sus, taining this pattern and the new growth regime
Balima, Olivier Florent. "Réduction du modèle non linéaire par identification modale : application en thermique et comparaison avec la méthode POD-Galerkin." Poitiers, 2006. http://www.theses.fr/2006POIT2355.
Повний текст джерелаThese numerical works deal with model reduction. The aim is to build a reduced order model that uses low CPU time to compute, compared to the original detailed model of reference
Audoux, Yohann. "Développement d’une nouvelle méthode de réduction de modèle basée sur les hypersurfaces NURBS (Non-Uniform Rational B-Splines)." Thesis, Paris, ENSAM, 2019. http://www.theses.fr/2019ENAM0016/document.
Повний текст джерелаDespite undeniable progress achieved in computer sciences over the last decades, some problems remain intractable either by their numerical complexity (optimisation problems, …) or because they are subject to specific constraints such as real-time processing (virtual and augmented reality, …). In this context, metamodeling techniques can minimise the computational effort to realize complex multi-field and/or multi-scale simulations. The metamodeling process consists of setting up a metamodel that needs less resources to be evaluated than the complex one that is extracted from by guaranteeing, meanwhile, a minimal accuracy. Current methods generally require either the user’s expertise or arbitrary choices. Moreover, they are often tailored for a specific application, but they can be hardly transposed to other fields. Thus, even if it is not the best, our approach aims at obtaining a metamodel that remains a good one for whatever problem at hand. The developed strategy relies on NURBS hypersurfaces and stands out from existing ones by avoiding the use of empiric criteria to set its parameters. To do so, a metaheuristic (a genetic algorithm) able to deal with optimisation problems defined over a variable number of optimisation variables sets automatically all the hypersurface parameters so that the complexity is not transferred to the user
Bertin, Michaël. "Propagation des incertitudes dans un modèle réduit de propagation des infrasons." Thesis, Cachan, Ecole normale supérieure, 2014. http://www.theses.fr/2014DENS0020/document.
Повний текст джерелаThe perturbation of a system can give rise to wave propagation. A classical approach to understand this phenomenon is to look for natural modes of vibration of the medium. Mathematically, finding these modes requires to seek the eigenvalues and eigenfunctions of the propagation operator. However, from a numerical point of view, the operation can be costly because the matrices can be of very large size. Furthermore, in most applications, uncertainties are inevitably associated with our model. The question then arises as to whether we should allocate significant computational resources for simulation while the accuracy of the result is not guaranteed. We propose in this thesis an approach that allows both a better understanding of the influence of uncertainties on the propagation and a significant decrease of computational costs for infrasound propagation in the atmosphere. The main idea is that all modes do not have the same importance and only a few of them is often sufficient to account for the phenomenon without a significant loss of accuracy. These modes appear to be those which are most sensitive to atmospheric disturbances. Specifically, a sensitivity analysis is used to identify the most influential structures of the atmosphere, the associated groups of modes and their associated parts of the infrasound signal. These groups of modes can be specifically targeted in a spectrum calculation with the projection of the operator onto Krylov subspaces, that allows a significant decrease of the computational cost. This method of model reduction can be applied in a statistical framework as well and estimations of the expectation and the variance of the results are carried out without a significant loss of accuracy and still with a low cost
Otaño, Aramendi Nerea. "Réduction du coût de calcul pour la simulation du comportement mécanique de câbles." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLC061.
Повний текст джерелаThe work presented in this dissertation is focused on the simulation of the mechanical behaviour of lift's wire ropes. The aim of the work is to elaborate a method to simulate the mechanical behaviour of such wire ropes with low computational cost and sufficient accuracy.First of all, several methods to model or simulate wire ropes have been compared and their weak and strong points have been highlighted. Analytical and finite element methods have been compared with experimental tests. It was concluded that analytical methods considered in this work have a lower computational cost than finite element methods, but the results obtained using them are not accurate enough to simulate lift wire ropes. Therefore, finite element methods have been considered as the most appropriate to simulate these wire ropes. However, their computational cost is high so some methods to reduce it must be applied.In order to reduce the computational time, three type of methods have been considered: homogenization, metamodeling and model order reduction. Model order reduction technique was chosen as the most adequate method and it was implemented in the wire rope finite element simulation program Multifil. Accurate results have been obtained, however the computational cost needed by initial simulations to get the snapshots used to define a reduce basis was too high for long wire ropes. To solve this problem, a sectionwise reduction method was proposed and implemented. This formulation takes advantage of the periodic structure of wire ropes: the reduced basis is identified only on a reference elementary section and used for all repetitive sections of a multi-section wire rope. The computational cost induced by the multiplication of matrices in order to transform the linear system of the initial problem into the linear system of the reduced problem was shown to remain too high, particularly in the context of the solving of a non-linear problem, to allow the global computational time to be significantly decreased using the proposed techniques. To overcome this difficulty, an additional technique, namely the so-called Discrete Empirical Interpolation Method (DEIM) was successfully implemented and tested, allowing a time reduction factor of 4 to be obtained
Park, Jie-Won. "Réduction des oxydes d'azote émis lors de la combustion du gaz naturel, par des composés organiques oxygènes." Paris 6, 2005. http://www.theses.fr/2005PA066103.
Повний текст джерелаCourtier, Vivien. "Réduction de modèle et simplification de l'intégration de loi de comportement pour la prévision de la durée de vie." Phd thesis, Ecole Polytechnique X, 2013. http://pastel.archives-ouvertes.fr/pastel-00854149.
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