Steel has played an indispensable role in shaping our contemporary world  and will persist to play that role for the foreseeable future. However, the steel industry currently is responsible for 7% of the global CO2-emissions, primarily due to the conventional carbon-based reduction process of iron ore. Fossil-free steel manufacturing, such as hydrogen direct reduction,  could essentially make the  CO2-emissions from primary steel production obsolete. The product from hydrogen-based direct reduction of iron ore is H-DRI, which subsequently are molten in an EAF to produce crude steel. Due to H-DRI  being   a   novel   product,   its   thermophysical   properties   are   not   well documented,  which  are  essential  when  investigating  the  heating  and dissolution behavior.  When  feeding  H-DRI  to  an  EAF,  ferrobergs  may  form,  which  consist  of unmolten material that interrupts the continuous melting process. It is not established whether the heat transfer of the pellets or the heat transfer to the pellets is the leading cause of ferroberg-formation. Modelling the melting process in an EAF is considered near impossible, therefore a simplified heating model of H-DRI was required. In the present thesis, H-DRI pellets were examined with heating experiments in a lab-scale vertical tube furnace to 1500°C  while  the  surface- and center  temperatures  of  the  pellets were  measured.  The measured  surface  temperatures  were  applied  as  varying boundary  conditions  in COMSOL  Multiphysics  heat transfer simulations of  H-DRI  and H-HBI.  The  thermal conductivity  function  was  utilized  as  an  adjustable  parameter to  fit  the  theoretical center temperatures from the heat transfer simulations with the experimental center temperatures to acquire the temperature dependent effective heat conductivity and thermal diffusivity of H-DRI. By establishing an estimate correlation between the heat conductivity of H-DRI and H-HBI, the thermal conductivity and thermal diffusivity of H-HBI could also be obtained. The experiments together with the heat transfer simulations proved to be effective and yielded successful results of the effective heat conductivity and thermal diffusivity of H-DRI  and  H-HBI,  which  can  be  used  in  process  design,  future  models,  and simulations. Furthermore, it is unlikely that ferroberg-formation is caused by slow heat transfer of the H-DRI. It is more likely that it is due to slow heat transfer to the H-DRI. Therefore, the focus should be to increase the heat transfer to the H-DRI pellets while melting in an EAF to avoid ferrobergs. / Stål har haft en oumbärlig roll i att forma vår samtida värld och kommer att fortsätta att inneha  den  rollen  under  en  överskådlig  framtid.  Men  stålindustrin  ansvarar närvarande  för  7%  av  den  totala  globala  CO2-utsläppen,  främst  på  grund  av den konventionella kolbaserade reduktionsprocessen av järnmalm. Fossilfri ståltillverkning, som direktreduktion av järnmalm med vätgas, kan i princip göra CO2-utsläppen   från   primärståltillverkning föråldrat.   Produkten   från   vätgasbaserad direktreduktion  av järnmalm  är  H-DRI,  som  sedan  smälts  i  en  ljusbågsugn  för att producera  råstål. Eftersom  H-DRI  är  en  ny  produkt  så  är  dess  termofysiska egenskaper,  som  är väsentliga  när  man  undersöker  dess  uppvärmnings-  och smältbeteende, inte väl dokumenterat. Vid matning av H-DRI till en ljusbågsugn kan det bildas  ferroberg  som består  av  osmält  material  som  hindrar  den  kontinuerliga smältningsprocessen. Det är inte fastställt om det är värmeöverföringen i pelletsen eller värmeöverföringen  till pelletsen  som  är  den  främsta  orsaken  till  att  ferroberg bildas. Modellering  av  smältprocessen  i  en  ljusbågsugn  anses  nästintill  omöjlig, därför krävdes en förenklad uppvärmningsmodell av H-DRI. I detta examensarbete undersöktes H-DRI-pellets med uppvärmningsexperiment i en vertikal rörugn till 1500°C samtidigt som yt- och centrumtemperaturerna för pelletsen mättes. De uppmätta yttemperaturerna  användes  som  varierande  randvillkor  i  COMSOL Multiphysics värmeöverföringssimuleringar  av  H-DRI  och  H-HBI.  Den  termiska konduktiviteten användes som en justerbar parameter för att anpassa de teoretiska centrumtemperaturerna från värmeöverföringssimuleringarna med de experimentella centrumtemperaturerna  för  att  erhålla  den  temperaturberoende effektiva  termiska konduktiviteten och termiska diffusiviteten för H-DRI. Genom  att   fastställa   en uppskattad korrelation mellan värmeledningsförmågan för H-DRI och H-HBI, kunde även den termiska konduktiviteten och termiska diffusiviteten för H-HBI erhållas. Experimenten  tillsammans  med  värmeöverföringssimuleringarna  visade  sig  vara effektiva och gav framgångsrika resultat av den effektiva termiska konduktiviteten och termiska  diffusiviteten  hos H-DRI och H-HBI,  som  kan  användas  i  processdesign, framtida modeller och simuleringar. Det är osannolikt att ferrobergbildning orsakas av långsam värmeöverföring  i H-DRI, utan det är mer troligt att det beror  på långsam värmeöverföring till H-DRI. Därför bör fokus vara att öka värmeöverföringen till H-DRI pellets i en ljusbågsugn för att undvika ferrobergbildning.

We discuss a full-waveform based material profile reconstruction in two-dimensional heterogeneous semi-infinite domains. In particular, we try to image the spatial variation of shear moduli/wave velocities, directly in the time-domain, from scant surficial measurements of the domain's response to prescribed dynamic excitation. In addition, in one-dimensional media, we try to image the spatial variability of elastic and attenuation properties simultaneously. To deal with the semi-infinite extent of the physical domains, we introduce truncation boundaries, and adopt perfectly-matched-layers (PMLs) as the boundary wave absorbers. Within this framework we develop a new mixed displacement-stress (or stress memory) finite element formulation based on unsplit-field PMLs for transient scalar wave simulations in heterogeneous semi-infinite domains. We use, as is typically done, complex-coordinate stretching transformations in the frequency-domain, and recover the governing PDEs in the time-domain through the inverse Fourier transform. Upon spatial discretization, the resulting equations lead to a mixed semi-discrete form, where both displacements and stresses (or stress histories/memories) are treated as independent unknowns. We propose approximant pairs, which numerically, are shown to be stable. The resulting mixed finite element scheme is relatively simple and straightforward to implement, when compared against split-field PML techniques. It also bypasses the need for complicated time integration schemes that arise when recent displacement-based formulations are used. We report numerical results for 1D and 2D scalar wave propagation in semi-infinite domains truncated by PMLs. We also conduct parametric studies and report on the effect the various PML parameter choices have on the simulation error. To tackle the inversion, we adopt a PDE-constrained optimization approach, that formally leads to a classic KKT (Karush-Kuhn-Tucker) system comprising an initial-value state, a final-value adjoint, and a time-invariant control problem. We iteratively update the velocity profile by solving the KKT system via a reduced space approach. To narrow the feasibility space and alleviate the inherent solution multiplicity of the inverse problem, Tikhonov and Total Variation (TV) regularization schemes are used, endowed with a regularization factor continuation algorithm. We use a source frequency continuation scheme to make successive iterates remain within the basin of attraction of the global minimum. We also limit the total observation time to optimally account for the domain's heterogeneity during inversion iterations. We report on both one- and two-dimensional examples, including the Marmousi benchmark problem, that lead efficiently to the reconstruction of heterogeneous profiles involving both horizontal and inclined layers, as well as of inclusions within layered systems. / text

ABSTRACT Triticum sphaerococcum (AABBDD, 2n = 6x = 42) is a land race of wheat known from the Indian subcontinent. It has several favourable characters including short and strong culms, hemispherical grains with a shallow crease (that may increase the yield of white flour), higher protein content compared to bread wheat (T. aestivum), and resistance to drought, and yellow rust caused by Puccinia striiformis. However, an unfavourable characteristic of T. sphaerococcum is its lower yield compared to bread wheat. Being a land race, the sphaerococcum wheat is poorly studied. This study was undertaken to increase knowledge of the physiology and genetics of this land race and determine if it may be possible to separate the favourable characters of T. sphaerococcum from its unfavourable characters. Plant height in bread wheat is controlled by many genes. ‘Reduced Height’ (Rht) genes which differ in their response to externally applied gibberellic acid (GA3) are responsible for the short stature of modern bread wheat varieties. Therefore, GA3 was used to probe the relationship between the semidwarf sphaerococcum phenotype and the Rht gene. T. sphaerococcum variety Sp5 showed a unique “seedling response” to externally applied GA3 when compared with T. aestivum varieties harbouring Rht1, Rht2, Rht8, Rht12, Rht13 or Rht18 alleles. A mapping population of doubled haploids was generated through wide hybridisation of F1 (Sp5 x Otane) with Zea mays. A genome-wide scan of Sp5 and Otane (parents) using 348 microsatellite (SSR) markers showed that only 169 of these markers (49%) were polymorphic between the parents. A DArT profiling yielded 348 markers that were polymorphic between the parents. Microsatellite markers and DArT markers were used to create a genetic map. The mapping population was phenotyped and a quantitative trait loci (QTL) analysis was performed for component traits of the complex sphaerococcum trait including plant height, spike length, awn length, yield, grain shape and crease size. Results of the QTL analysis indicated that it may be difficult to separate the favourable characters of T. sphaerococcum from its unfavourable characters through mutation because the component traits of the complex sphaerococcum trait may be under pleiotropic control of the Sp gene. The hypothesis that T. sphaerococcum originated through a mutation in T. aestivum was tested through induced mutation using gamma rays. Mutants from sphaerococcum-type to aestivum-type were isolated and phenotyped. Sphaerococcum-type mutants also were isolated and characterised from mutated aestivum-type wheat suggesting a possible origin of T. sphaerococcum through a mutation in T. aestivum.

Silicon nitride is a bulk and a coating material exhibiting excellent mechanical properties. The understanding of the complex processes at the nanometre scale gained through experimental research will be enhanced by the existence of a computationally efficient and accurate model that is able to describe the mechanical properties of silicon nitride. Such a model has yet to be proposed. In this thesis we present a transferable reduced tight-binding (TB) model for the silicon nitride system. More precisely, this model consists of a reduced TB model for elemental silicon, a reduced TB model for elemental nitrogen, and a reduced TB model for silicon nitride. These models are developed within the framework of coarse-graining the electronic structure from density functional theory (DFT) to tight binding (TB) to bond-order potentials (BOPs), and can therefore be used in the future as the stepping stone to develop BOPs for the application in large scale simulations. The bond integrals employed in the reduced TB models are obtained directly from mixed-basis DFT projections of wave functions onto a minimal basis of atom-centred orbitals. This approach reduces the number of overall parameters to be fitted and provides models which are transferable through the different coarse-graining levels. We provide an example by using the same bond integrals in the reduced TB model for silicon and the preliminary bond-based BOP for silicon. DFT binding energies of ground state and metastable crystal structures are used as the benchmark to which the TB and BOP repulsive parameters are fitted. In addition to model development, we present an improved methodology when going from TB to reduced TB. By weighting all four σ TB bond integrals equally, we provide a new parameterisation (Eqs. (2.73) and (2.74)) and show that the quality of the silicon reduced TB model can be increased by choosing one of the reduced TB parameters to be distance invariant. The ingredients, the development methodology, and the quality of each of the four models are discussed in a separate chapter. The quality of the reduced TB models and BOP is demonstrated by comparing their predictions for the binding energies, heats of formation, elastic constants, and defect energies with DFT and experimental values.

Master of Science / Department of Agronomy / Ganga M. Hettiarachchi / Phosphorus (P) management in reduced tillage systems has been a great concern for farmers. Conclusive results for benefits of deep banding of P fertilizers for plant yield in reduced tillage system are still lacking. Knowledge of the dominant solid P species present in soil following application of P fertilizers and linking that to potential P availability would help us to design better P management practices. The objectives of this research were to understand the influence of placement (broadcast- vs. deep band-P or deep placed-P), fertilizer source (granular- versus liquid-P), and time on reaction products of P. Greenhouse and field based experiments were conducted to study P behavior in soils. Soil pH, resin extractable P, total P, and speciation of P were determined at different distances from the point of fertilizer application at 5 weeks (greenhouse and field) and 6 months (field) after P application (at rate 75 kg/ha) to a soil system that was under long-term reduced tillage. X-ray absorption near edge structure spectroscopy technique was used to speciate reaction products of fertilizer P in the soil. The reaction products of P formed upon addition of P fertilizers to soils were found to be influenced by soil pH, P placement methods, and P sources. Acidic pH (below~5.8) tended to favor formation of Fe-P and Al-P like forms whereas slightly acidic near neutral pH soils favored formation of Ca-P like forms. Scanning electron microscope with energy dispersive X-ray analysis of applied fertilizer granules at 5-wk showed enrichment of Al, Fe and Ca in granule- indicating these elements begin to react with applied P even before granules dissolve completely. The availability of an applied P fertilizer was found to be enhanced as a result of the deep banding as compared to the surface broadcasting or deep placed methods. Deep banded liquid MAP was found to be in more adsorbed P like forms and resulted greater resin extractable P both at 5 wk and 6 month after application. Deep banding of liquid MAP would most likely result both agronomically and environmentally efficient solution for no-till farmers.

<p>Combustion instability, a complex phenomenon observed in combustion chambers is due to the coupling between heat release and other unsteady flow processes. Combustion instability has long been a topic of interest to rocket scientists and has been extensively investigated experimentally and computationally. However, to date, there is no computational tool that can accurately predict the combustion instabilities in full-size combustors because of the amount of computational power required to perform a high-fidelity simulation of a multi-element chamber. Hence, the focus is shifted to reduced fidelity computational tools which may accurately predict the instability by using the information available from the high-fidelity simulations or experiments of single or few-element combustors. One way of developing reduced fidelity computational tools involves using a reduced fidelity solver together with the flame transfer functions that carry important information about the flame behavior from a high-fidelity simulation or experiment to a reduced fidelity simulation.</p> <p> </p> <p>To date, research has been focused mainly on premixed flames and using acoustic solvers together with the global flame transfer functions that were obtained by integrating over a region. However, in the case of rockets, the flame is non-premixed and distributed in space and time. Further, the mixing of propellants is impacted by the level of flow fluctuations and can lead to non-uniform mean properties and hence, there is a need for reduced fidelity solver that can capture the gas dynamics, nonlinearities and steep-fronted waves accurately. Nonlinear Euler equations have all the required capabilities and are at the bottom of the list in terms of the computational cost among the solvers that can solve for mean flow and allow multi-dimensional modeling of combustion instabilities. Hence, in the current work, nonlinear Euler solver together with the spatially distributed local flame transfer functions that capture the coupling between flame, acoustics, and hydrodynamics is explored.</p> <p> </p> <p>In this thesis, the approach to extract flame transfer functions from high-fidelity simulations and their integration with nonlinear Euler solver is presented. The dynamic mode decomposition (DMD) was used to extract spatially distributed flame transfer function (FTF) from high fidelity simulation of a single element non-premixed flame. Once extracted, the FTF was integrated with nonlinear Euler equations as a fluctuating source term of the energy equation. The time-averaged species destruction rates from the high-fidelity simulation were used as the mean source terms of the species equations. Following a variable gain approach, the local species destruction rates were modified to account for local cell constituents and maintain correct mean conditions at every time step of the nonlinear Euler simulation. The proposed reduced fidelity model was verified using a Rijke tube test case and to further assess the capabilities of the proposed model it was applied to a single element model rocket combustor, the Continuously Variable Resonance Combustor (CVRC), that exhibited self-excited combustion instabilities that are on the order of 10% of the mean pressure. The results showed that the proposed model could reproduce the unsteady behavior of the CVRC predicted by the high-fidelity simulation reasonably well. The effects of control parameters such as the number of modes included in the FTF, the number of sampling points used in the Fourier transform of the unsteady heat release, and mesh size are also studied. The reduced fidelity model could reproduce the limit cycle amplitude within a few percent of the mean pressure. The successful constraints on the model include good spatial resolution and FTF with all modes up to at least one dominant frequency higher than the frequencies of interest. Furthermore, the reduced fidelity model reproduced consistent mode shapes and linear growth rates that reasonably matched the experimental observations, although the apparent ability to match growth rates needs to be better understood. However, the presence of significant heat release near a pressure node of a higher harmonic mode was found to be an issue. This issue was rectified by expanding the pressure node of the higher frequency mode. Analysis of two-dimensional effects and coupling between the local pressure and heat release fluctuations showed that it may be necessary to use two dimensional spatially distributed local FTFs for accurate prediction of combustion instabilities in high energy devices such as rocket combustors. Hybrid RANS/LES-FTF simulation of the CVRC revealed that it might be necessary to use Flame Describing Function (FDF) to capture the growth of pressure fluctuations to limit cycle when Navier-Stokes solver is used.</p> <p> </p> <p>The main objectives of this thesis are:</p> <p>1. Extraction of spatially distributed local flame transfer function from the high fidelity simulation using dynamic mode decomposition and its integration with nonlinear Euler solver</p> <p>2. Verification of the proposed approach and its application to the Continuously Variable Resonance Combustor (CVRC).</p> <p>3. Sensitivity analysis of the reduced fidelity model to control parameters such as the number of modes included in the FTF, the number of sampling points used in the Fourier transform of the unsteady heat release, and mesh size.</p> <p> </p> <p>The goal of this thesis is to contribute towards a reduced fidelity computational tool which can accurately predict the combustion instabilities in practical systems using flame transfer functions, by providing a path way for reduced fidelity multi-element simulation, and by defining the limitations associated with using flame transfer functions and nonlinear Euler equations for non-premixed flames.</p> <p> </p><br>

Les architectures de calcul haute performance les plus récentes intègrent de plus en plus de nœuds de calcul qui contiennent eux-mêmes plus de cœurs. Les bus mémoires et les réseaux de communication sont soumis à un niveau d'utilisation critique. La programmation parallèle sur ces nouvelles machines nécessite de porter une attention particulière à ces problématiques pour l'écriture de nouveaux algorithmes. Nous analysons dans cette thèse un code de simulation de turbulences de plasma et proposons une refonte de la parallélisation de l'opérateur de gyromoyenne plus adapté en termes de distribution de données et bénéficiant d'un schéma de recouvrement calcul -- communication efficace. Les optimisations permettent un gain vis-à-vis des coûts de communication et de l’empreinte mémoire. Nous étudions également les possibilités d'évolution de ce code à travers la conception d'un prototype utilisant un modèle programmation par tâche et un schéma de communication asynchrone adapté. Cela permet d'atteindre un meilleur équilibrage de charge afin de maximiser le temps de calcul et de minimiser les communications entre processus. Un maillage réduit adaptatif en espace est proposé, diminuant le nombre de points sans pour autant perdre en précision, mais ajoutant de fait une couche supplémentaire de complexité. Ce prototype explore également une distribution de données différente ainsi qu'un maillage en géométrie complexe adapté aux nouvelles configurations des tokamaks. Les performances de différentes optimisations sont étudiées et comparées avec le code préexistant et un cas dimensionnant sur un grand nombre de cœurs est présenté. / Recent high performance computing architectures come with more and more cores on a greater number of computational nodes. Memory buses and communication networks are facing critical levels of use. Programming parallel codes for those architectures requires to put the emphasize on those matters while writing tailored algorithms. In this thesis, a plasma turbulence simulation code is analyzed and its parallelization is overhauled. The gyroaverage operator benefits from a new algorithm that is better suited with regard to its data distribution and that uses a computation -- communication overlapping scheme. Those optimizations lead to an improvement by reducing both execution times and memory footprint. We also study new designs for the code by developing a prototype based on task programming model and an asynchronous communication scheme. It allows us to reach a better load balancing and thus to achieve better execution times by minimizing communication overheads. A new reduced mesh is introduced, shrinking the overall mesh size while keeping the same numerical accuracy but at the expense of more complex operators. This prototype also uses a new data distribution and twists the mesh to adapt to the complex geometries of modern tokamak reactors. Performance of the different optimizations is studied and compared to that of the current code. A case scaling on a large number of cores is given.

Cette thèse porte sur le développement d’une approche pratique de modélisation/simulation des systèmes solaires combinés Photovoltaïques/Thermiques PV/T. Il s’agit d’une approche basée sur un modèle d’ordre réduit en représentation d’état (ORRE). En effet, les systèmes solaires thermiques, électriques et combinés intégrés aux bâtiments possèdent des spécificités permettant de s’affranchir des méthodes numériques classiques (mécanique des fluides numérique et thermique numérique). Ces méthodes sont réputées dans le domaine de l’aérodynamique, de l’aéraulique…etc. Par contre, dans le domaine du mix-énergétique tels que celui considéré dans ce mémoire, l’application directe de ce modèle peut conduire à des dépassements des capacités mémoire ou des temps de calcul exorbitants. Une alternative est de développer des méthodes adaptées au problème physique considéré, en traitant l’aspect multi-physique toute en restant dans une taille de données raisonnable et du temps de calcul réduit. La méthodologie de modélisation consiste à réduire les dimensions des équations qui régissent le problème. En se basant sur la symétrie du système, puis en découpant le système en zones de contrôle basées sur une valeur moyenne gouvernée par les nombres adimensionnels de Biot (Bi) et de Fourier (Fo). Les résultats obtenus en fonctionnement dynamique pourront nous fournir des paramètres de sorties, plus particulièrement, les rendements électrique, thermique et la puissance de circulation du fluide caloporteur. L’avantage de l’approche proposée réside dans la simplification du modèle résultant, qui est représenté par un seul système d’équations algébriques en représentation d’état regroupant tous les éléments physiques du système en fonctionnement dynamique (conditions aux limites variables dans le temps). Ce modèle regroupe la variable fondamentale qui est la température, et les deux types de contrôle et de conception. De plus, le modèle d’ORRE est intégrable dans le fonctionnement en temps réel des systèmes PV/T intégrés aux bâtiments (PV/T-Bât) afin d’accompagner leurs régulation et gestion des flux mise en jeu. Le modèle ainsi proposé a fait l’objet d’une validation où les résultats numériques ont été comparés aux résultats expérimentaux. En effet, quatre configurations ont été étudiées et évoquées dans une approche linéaire. Les résultats obtenus montrent une cohérence tolérable entre les résultats expérimentaux, et numériques. Cette cohérence a été évaluée en termes d’incertitude entre les résultats du modèle et le cas étudié expérimentalement. Le cas d’un système non-linéaire a été également abordé. En effet, rares sont les travaux qui ont été publiés mettant en valeur les phénomènes non-linéaires dans les systèmes complexes PV/T-Bât, Ainsi, on a développé avec la même stratégie, des modèles bilinéaires qui modélise le mieux possible le comportement thermique dans les systèmes PV/T-Bât. Une étude d’optimisation du système multi-physique en introduisant une étude paramétrique est menée en terme afin d’étudier la sensibilité des paramètres sur le rendement énergétique. Cependant, les études d’optimisation paramétriques restent limitées et insuffisantes à cause de la résolution mono-objectif du problème d’optimisation, alors que notre système manifeste un comportement combiné et multi-physique de nature contradictoire. Pour ce faire, une optimisation multi-objectifs est introduite avec trois fonctions objectif en employant l’algorithme génétique NSGA-II. L’originalité de notre méthode est d’employer l’algorithme en régime dynamique afin de choisir la conception du système la plus optimale. Les résultats trouvés peuvent contribuer à améliorer la conception des systèmes PV/T-Bât et l’optimisation de leur fonctionnement / This thesis consists to develop a simplified model approach for Photovoltaic / Thermal (PV / T) combined solar system based on state-space reduced order model. The building integrated solar systems are getting high attention in these last decencies, as well as the performance increasing which require high numerical methods to improve the design and reducing the costs. In one hand, the CFD methods are useful tool to predict the energy (mechanical and thermal) of combined PV/T systems, but it requires an expensive computing capacities and exorbitant calculation times, On the other hand, the PV/T systems can generate both the electrical and thermal flows, and requires an easily and performant optimization model. An alternative is to develop methods that are adapted to the physical problem under consideration, treating the multi-physics aspect while remaining in a reasonable data size and reduced computing time. The first part of the current thesis consists to develop a mathematical model which consists of reducing the dimensions of the governed equations. Based on the symmetry of the geometry, the system is subdivided into control areas which governed by the dimensionless Biot (Bi) and Fourier (Fo) numbers. The obtained results in dynamic mode can provide output key parameters, more particularly the electrical and thermal efficiencies and the dissipated hydrodynamic power. The advantage of this approach lies in the simplification of the resulting model, which is represented by a single state-space representation that groups all the physical elements of the system into dynamic mode, i.e. in continuous variation of the boundary condition. This model groups the fundamental variable, which is the temperature, and two type parameters, which are the control parameters and the design parameters. In addition, the reduced order model can be integrated into real-time operation of building-integrated PV / T (BIPV/T) systems in order to support their regulation and management of intervening flows. In order to validate the use of our model, it is necessary to test it for several cases of Building Integrated PV/T systems (BIPV/T). For this, four major configurations were studied and discussed in a linear approach; the found results show a good agreement with experimental works. A second level has been developed as part of our thesis work, which is the non-linearity in combined PV / T and BIPV/T systems; in particular, bilinear models have been developed with the same strategy which best models the thermal behavior in BIPV/T systems. The second issue, related to Multi-physics aspect. Furthermore, in order to evaluate the sensitivity of the parameters, a parametric optimization has been made with dimensionless numbers. However, parametric optimization studies remain limited and insufficient because of the single-objective resolution of the optimization problem, whereas our system manifests a mixed and multi-physics behavior with contradictory nature. To do this, a multi-objective optimization is introduced with three objective functions using the NSGA-II genetic algorithm. The originality of our method is to use the algorithm in dynamic mode in order to choose the design of the optimal system. The found results can contribute to the design of BIPV/T systems and optimize their operation

Concevoir une structure composite consiste à relever un défi de taille : alors qu'un ingénieur qui conçoit un produit mécanique à base de matériau métallique se concentre principalement sur le développement d'une forme qui garantira un comportement spécifique, l'ingénieur pour qui le problème de conception est celui d'un produit à base de matériaux composites doit trouver la meilleure combinaison forme - structure de matériau. Ainsi, il doit aussi concevoir simultanément un matériau et la topologie produit. La combinatoire s’avère être complexe et les espaces de solutions de très grande taille.Les outils de CAO et de simulation par éléments finis n'offrent pas au concepteur une approche permettant d'explorer les espaces de recherche de manière interactive et rapide. Le travail de thèse conduit à une nouvelle approche numérique permettant de manipuler chaque paramètre de conception caractérisant une structure composite, quelle que soit l’échelle à laquelle il est pertinent.Premièrement, le modèle de comportement paramétrique et réduit (Parametric and Reduced Behavior Model, PRBM) est un modèle dit séparé. Il permet :1- une approche multi-échelle : les paramètres mécaniques de la structure sont explicitement décrits comme issus de la qualité matérielle de chaque fibre, de la matrice, de chaque couche et de la topologie même du stratifié,2- une approche multi-physique: indépendamment le comportement mécanique de chaque couche et de chaque interface est traité pour donner lieu au comportement du stratifié. Des situations de comportements statiques et dynamiques sont étudiés. Dans le cas du comportement dynamique, le caractère visco-élastique est devenu un enjeu conceptuel.Deuxièmement, une méthode mixant dérivées non entières et usage de la méthode PGD a permis la réalisation du PRBM. Intégré dans un modèle de connaissance paramétrique (Parametric Knowledge Model, PKM) auprès de modèles de connaissances experts, il constitue la base d'une méthode interactive d’aide à la conception.Le PKM est traité par une méthode d'optimisation évolutionnaire. De ce fait, le concepteur peut explorer de façon interactive les espaces de conception. Pour qualifier nos modèles et notre PRBM, nous étudions 2 problèmes de conception de structures stratifiées. Les solutions déterminées sont qualifiées vis-à-vis de simulations par éléments finis ou selon une approche empirique. / The design process of laminated composites faces a major challenge: while an engineer designing a metallic based mechanical product is mainly focusing on the development of a shape that will guarantee a specific behavior, the engineer designing a composite based product must find the best combination of the shape-material structure. Therefore, he must simultaneously create a material and the product topology. The number of design solutions can be huge since the solution space is considerable.Standard CAE systems (CAD, Finite Element Simulation) do not provide an approach to explore these solution spaces efficiently and interactively. A new numerical procedure is proposed to allow engineers to handle each design parameter of a laminated composite structure, each at its relevant scale.First, the Parametric and Reduced Behavior Model (PRBM) is a separated model that enables reasoning based on1- A multiscale approach: the mechanical parameters of the structure are explicitly described as coming from the material quality of each fiber, the matrix, each layer and the topology of the laminate,2- A multiphysical approach: independently the mechanical behavior of each layer and each interface is processed, leading to the behavior of the laminate. Some situations of static and dynamic behavior are studied. In the case of dynamic behavior, the creeping becomes a conceptual issue.Secondly, a method mixing fractional derivatives and the Proper Generalized Decomposition (PGD) method allowed the creation of the PRBM. Integrated into a Parametric Knowledge Model (PKM) with other expert knowledge models, the PRBM makes the basis of an interactive method of design support.The PKM is processed by an evolutionary optimization method. As a result, the designer can interactively explore the design space. To qualify our models and our PRBM, we study two problems of design of laminated composite structures. The solutions determined are qualified versus finite element simulations or according to an empirical approach. / El diseño de una estructura compuesta es un desafío mayor, mientras que un ingeniero que diseña un producto mecánico con materiales metálicos se concentra principalmente en el desarrollo de una geometría que garantice un comportamiento específico, el ingeniero que diseña un producto con materiales compuestos debe encontrar la mejor combinación forma – estructura del material. De esta manera, el ingeniero debe diseñar simultáneamente el material y la topología del producto, razón por la que esta combinación se vislumbra compleja, puesto que los espacios de solución son gran tamaño.Las herramientas CAO y de simulación por elementos finitos no ofrecen al diseñador una metodología que permita explorar los espacios de solución de manera interactiva y rápida. Por lo tanto, este trabajo de tesis propone un nuevo enfoque numérico que permite manipular parámetros de diseño que caracterizan la estructura compuesta, cualquiera que sea la escala de pertinencia.Como primera medida, el modelo de comportamiento paramétrico y reducido (Parametric and Reduced Behavior Model, PRBM) es un modelo definido de manera separada que permite:1- Un enfoque multiescala: los parámetros mecánicos se presentan de manera explícita en términos de las propiedades de cada fibra, de la matriz, de cada capa y de la topología del mismo apilamiento.2- Un enfoque multifísico: el comportamiento mecánico de cada capa y cada interface se modela de manera independiente para dar lugar al comportamiento del apilamiento. Se estudian situaciones de casos de comportamiento estático y dinámico. En el caso dinámico en particular, se tiene en cuenta también la característica viscoelástica de las interfaces.Como segunda medida, un método que combina derivadas no enteras y el uso de la descomposición propia generalizada (PGD), permite la realización del PRBM. Este constituye la base de un método interactivo de ayuda al diseño, pues está integrado dentro de un modelo de conocimiento (PKM) que también incorpora mejores prácticas aprendidas por expertos.El PKM es utilizado por un método de optimización evolucionaria. De esta manera, el diseñador puede explorar de manera interactiva los espacios de solución. Para validar nuestros modelos y el PRBM, se estudian dos problemas de diseño de estructuras apiladas. Las soluciones obtenidas se comparan con respecto a simulaciones obtenidas por el método de los elementos finitos y con respecto a resultados experimentales.

Dans le domaine automobile, les modules électroniques de puissance des produits mécatroniques voient leur puissance sans cesse s'accroître, tout en étant confinés dans des volumes de plus en plus réduits. Au cours de leur fonctionnement, les composants semi-conducteurs et leur assemblage subissent ainsi des contraintes électro-thermo-mécaniques sévères, susceptibles d'entraîner leur destruction et de provoquer la défaillance du produit. L'étude de la fiabilité et le calcul de la durée de vie de tels produits dépendent des températures de jonction calculées au niveau des puces des composants de puissances. De surcroît, le contexte d'applications embarquées requiert de maîtriser, outre les paramètres électriques et mécaniques, les paramètres thermiques tels que les températures de jonctions et les puissances dissipées au niveau des composants, qu'il est nécessaire de réguler et contrôler en temps réel afin d'assurer le bon fonctionnement du produit. L'objectif de cette thèse est ainsi de proposer une méthode d'identification de modèles réduits dans le but d'estimer le comportement thermique des modules électroniques de puissance, en se fondant uniquement sur les données d'entrées et les résultats issus d'une simulation numérique d'un modèle détaillé du système étudié. Dans cette thèse, une nouvelle méthode d'identification, nommée « Kernel Identification Method », est développée. Cette méthode a été validée sur une application industrielle traitant d'un problème thermique couplé solide/fluide dont le comportement est essentiellement régi par de la convection forcée. Une étude exploratoire portant sur l'identification de problèmes non linéaires où la convection naturelle joue le rôle dominant est ensuite proposée. A cet effet, deux méthodes d’identification non-paramétrique sont proposées : (i) une première méthode basée sur l’extension de la méthode Kernel Identification Method ; et (ii) une deuxième méthode basée sur la variante dite « Unscented » du filtre de Kalman. / In automotive applications, the thermal dissipation of power electronics modules in mechatronic products is constantly increasing, whereas these products are confined in increasingly reduced volumes. During their operation, the semiconductor components and their environment are then submitted to severe electro-thermo-mechanical stresses that could cause their damage and lead to the product failure. The reliability and lifetime prevision of such products depend on the temperature junction located at the chip of power components. Furthermore, in order to ensure the safe operation of embedded applications, it is essential to perform a real-time control of thermal parameters such as the junction temperatures and power dissipated on the power components, in addition to the electrical and mechanical parameters. The objective of this thesis is to develop an identification method aimed at producing reduced thermal models to estimate the thermal behaviour of power electronic modules. Designed in a non-intrusive framework, this method post-processes the input data and the results produced by the numerical simulation of a detailed of the system under study. In this thesis, a new identification method, called "Kernel Identification Method" is developed. It has been validated on an industrial application dealing with a thermally coupled solid / fluid problem mainly governed by forced convection. An exploratory study of nonlinear problems identification where the natural convection plays the dominant role is then proposed. To this end, two identification methods of nonparametric nature are proposed: (i) a method based on the extension of the Kernel Identification Method; and (ii) a second method based on the "unscented" variant of the Kalman filter.