Ce travail porte sur la mise en œuvre de simulations sur des pales de machines tournantes. Une première partie de la thèse porte sur l’amélioration des performances du couplage fluide-structure. Des nouveaux algorithmes sont présentés. Une nouvelle méthode de déformation de maillage est évaluée. Les développements sont validés à partir de plusieurs cas tests. La deuxième partie porte sur l’application des avancées à des machines tournantes. Une première validation est faite sur une hydrolienne. La vibration d’une pale au passage du mat est étudiée. Enfin, des résultats sur une hydrolienne industrielle sont exposés. / A methodology to simulate blades of turbines is developed. A first part is dedicated to improving the performance of the fluid-structure coupling. New algorithms are presented. A new mesh morphing solution is shown. Developments are validated on many test cases. A second part is dedicated to applying the developments on turbines. A first validation is made on a water turbine. The vibration of a blade interacting with a mast is studied. Finally, some results of an industrial water turbine are shown.

The modern engineering design process includes computer software packages that require approximations to be made when representing geometries. These approximations lead to inherent discrepancies between the design geometry of a part or assembly and the corresponding manufactured geometry. Further approximations are made during the analysis portion of the design process. Manufacturing defects can also occur, which increase the discrepancies between the design and manufactured geometry. These approximations combined with manufacturing defects lead to discrepancies which, for high precision parts, such as jet engine compressor blades, can affect the modal analysis results. In order to account for the manufacturing defects during analysis, mesh morphing is used to morph a structural finite element analysis mesh to match the geometry of compressor blades with simulated manufacturing defects. The mesh morphing process is improved by providing a novel method to convert heteromorphic shape matching within Sculptor to homeomorphic shape matching. This novel method is automated using Java and the NX API. The heteromorphic to homeomorphic conversion method is determined to be valid due to its post-mesh morphing maximum deviations being on the same order as the post-mesh morphing maximum deviations of the ideal homeomorphic case. The usefulness of the automated heteromorphic to homeomorphic conversion method is demonstrated by simulating manufacturing defects on the pressure surface of a compressor blade model, morphing a structural finite element analysis mesh to match the geometry of compressor blades with simulated manufacturing defects, performing a modal analysis, and making observations on the effect of the simulated manufacturing defects on the modal characteristics of the compressor blade.

No description available.

The use of CAD models and CFD analysis has become an essential part of fluid flow design. To reduce the time spent determining a design, optimization frameworks have been implemented to automate the process. Mesh morphing has been implemented within these frameworks to further reduce the time needed. While optimization methods have been developed to optimize a fluid flow path, the optimum design needs to be recreated in a CAD model. A method has been developed which eliminates the need to recreate the optimal results in CAD. This is accomplished by using mesh morphing, CAD and CFD together in an optimization framework. The method developed has been implemented with a significant time savings over the use of a traditional meshing optimization framework.

Finite Element (FE) head models are very convenient tools forthe study of Traumatic Brain Injuries (TBIs) but lack significantanatomical details for the investigation of morphology or age-dependantinjury mechanisms. In this context, the use of deformable registrationalgorithms for the generation of personalized head models is veryconsistent for the development of improved protection systems likehelmets. This thesis presents the performances of the registrationpipeline Demons combined to the Difformable Registration via AttributesMatching and Mutual-SaliencyWeighting (DRAMMS) for the generationof FE head models. Twelve subject-specific models are formed bymorphing the baseline mesh with the displacement fields resultingfrom the registration methods. The obtained models are assessedand compared through the evaluation of elements’ quality by analysisof the distortion index distribution. The Dice similarity coefficientis also calculated to estimate the personalization accuracy of theapplied pipeline. The Demons+DRAMMS registration pipeline showssatisfactory personalization accuracy for cranial mask and internalbrain structures. No significant degradation of mesh quality dueto the morphing process or specific subject morphology is observed.The present work corroborates previous study regarding the use ofDemons+DRAMMS registration pipeline for generating subject-specifichead models and validates the performances of the registration methodsand the repeatability of the morphing process for this purpose.

It has been known for decades that fatigue crack propagation in elastic-plastic media is very sensitive to load history since the nonlinear behavior of the material can have a great influence on propagation rates. However, the raw computation of millions of fatigue cycles with nonlinear material behavior on tridimensional structures would lead to prohibitive calculation times. In this respect, we propose a global model reduction strategy, mixing both the a posteriori and a priori approaches in order to drastically decrease the computational cost of these types of problems. First, the small scale yielding hypothesis is assumed, and an a posteriori model reduction of the plastic behavior of the cracked structure is performed. This reduced model provides incrementally the plastic state in the vicinity of the crack front, from which the instantaneous crack growth rate is inferred. Then an additional a priori model reduction technique is used to accelerate even more the time to solution of the whole problem. This a priori approach consists in building incrementally and without any previous calculations a reduced basis specific to the considered test-case, by extracting information from the evolving displacement field of the structure. Then the displacement solutions of the updated crack geometries are sought as linear combinations of those few basis vectors. The numerical method chosen for this work is the finite element method. Hence, during the propagation the spatial discretization of the model has to be updated to be consistent with the evolving crack front. For this purpose, a specific mesh morphing technique is used, that enables to discretize the evolving model geometry with meshes of the same topology. This morphing method appears to be a key component of the model reduction strategy. Finally, the whole strategy introduced above is embedded inside an adaptive approach, in order to ensure the quality of the results with respect to a given accuracy. The accuracy and the efficiency of this global strategy have been shown through several examples; either in bidimensional and tridimensional cases for model crack propagation, including the industrial example of a helicopter structure.

Due to legislative reasons and environmental concerns the automotive and transport sector are shifting their focus from traditional internal combustion engine (ICE) vehicles to development of battery electric vehicles (BEVs). This brings new challanges to design of cooling systems where axial fans are one of the key components. Axial fans are usually designed with regards to a certain operating condition and outside this region the efficiency of the fan drops drastically. Due to difficulty in specifying the exact operational parameters when placed in a car, post-design optimization may be necessary to ensure maximized performance. This thesis focuses on fan blade shape optimization through mesh morphing using the surrogate based optimization algorithm called Efficient Global Optimization (EGO). The target fans was a 9 bladed prototype fan by Johnson Electric with uneven blade spacing. The optimization uses steady state Reynolds-averaged Navier-Stokes (RANS) simulations to evaluate the fan designs and a Bezier curve parametrization in order to change the fan blade shape together with mesh morphing. The simulation setup was evaluated before peceding with the optimization, and showed good agreement close to intended operational conditions. Differences in turbulence modeling treatments were also evaluated in order to have a satisfactory agreement with measurement data. The EGO algorithm manages to provide fan designs with higher total-to-static efficiency at several different operational conditions. Evaluation of the optimized fan designs was limited to comparison with the provided measurement data and corrensponding simulations. Acoustic evaluation of selected fan designs is also attemped, but further work is required in order for the study to result in a quantitative comparison. / På grund av lagstiftning och miljöpåverkan har bil- och transportindustrin börjat skifta fokus från traditionella förbränningsfordon till utveckling av batteridrivna elbilar. Med detta medföljer nya utmaningar kring kylsystemsdesign där axiella fläktar är en av huvudkomponenterna hos systemet. Axiella fläktar är vanligtvis designade kring ett specifikt drifttillstånd och utanför detta har fläkten avsevärt lägre verkningsgrad. På grund av svårigheter att specificera detta drifttillstånd med hög precision, speciellt när fläkten monteras i en bil, kan efterdesigns-optimering vara nödvändigt för att uppnå maximal prestanda. Denna avhandling fokuserar på form-optimering av fläkt via mesh morphing med hjälp av den surrogat-baserade optimeringsalgoritmen Efficient Global Optimization (EGO). Fläkten som optimerades var en prototypfläkt designad av Johnson Electric med 9 fläktblad och icke-symmetriska mellanrum mellan bladen. I optimeringsprocessen användes icke-tidsberoende Reynolds-averaged Navier-Stokes (RANS) simuleringar för att utvärdera fläktdesignerna och parametrisering med hjälp av Bezier kurvor och mesh morphing för att ändra fläktbladen. Simulerings-uppställningen utvärderades innan optimeringen och bra överensstämning nära avsett driftstillstånd kunde påvisas. Skillnader i turbulens-modelering utvärderades även för att få en tillfredställande överensstämning med mätdata. EGO-algoritmen klarar att förse fläktdesigner med högre total-till-statisk verkningsgrad vid flera olika driftstillstånd. Utvärdering av fläktdesignerna var dock begränsad till jämförelse med mätdata och motsvarande simuleringsdata. En akustik utvärdering av utvalda fläkt-designer försöktes, men mer arbete krävs för att studien ska erhålla en kvantitativ jämförelse.

Il est connu depuis des décennies que la propagation des fissures de fatigue dans les matériaux élastoplastiques est très sensible à l’histoire du chargement car le comportement non-linéaire du matériau peut avoir une grande influence sur les vitesses de propagation. Cependant, le calcul brut de millions de cycles de fatigue avec des comportements matériaux non-linéaires sur des structures tridimensionnelles réalistes conduirait à des temps de calcul prohibitifs. Ainsi, nous proposons de coupler deux approches de réduction de modèle a priori et a posteriori, afin de diminuer considérablement le coût de calcul de ce type de problèmes. Tout d’abord, considérant l’hypothèse de plasticité confinée, une stratégie de réduction de modèle a posteriori du comportement plastique de la structure fissurée est proposée. Le modèle réduit ainsi obtenu fournit incrémentalement l’état plastique autour du front de fissure, duquel est déduite la vitesse instantanée de la fissure. De plus, une seconde approche de réduction de modèle, a priori cette fois, est aussi mise en place afin d’accélérer encore plus les temps de résolution du problème global. Cette approche a priori consiste à construire incrémentalement —et sans calculs préalables— une base réduite spécifique à chaque cas-test, en extrayant de l’information des champs de déplacement de la structure au cours du temps et pendant la propagation éventuelle de la fissure. Ainsi, les champs de déplacement solutions de la géométrie fissurée réactualisée sont vus comme une combinaison linéaire de cette base réduite de vecteurs. La méthode numérique considérée ici est la méthode des éléments finis. De fait, pendant la propagation de la fissure, la discrétisation spatiale du modèle doit être réactualisée afin d’être conforme avec le front de la fissure. Dans ce but, une technique spécifique de déformation de maillage est utilisée, et permet de discrétiser la géométrie variable du modèle avec des maillages de même topologie. Cette technique de déformation de maillage apparaît comme une étape clé de la stratégie de réduction de modèle. Finalement, une approche adaptative est construite autour de cette stratégie. Elle permet de garantir la qualité des résultats obtenus par rapport à un critère de précision donné. La précision et l’efficacité de cette stratégie globale sont démontrées à travers de nombreux exemples bidimensionnels et tridimensionnels dans le cadre de propagation de fissure en model, de même que pour un exemple industriel d’une pièce fissurée d’hélicoptère. / It has been known for decades that fatigue crack propagation in elastic-plastic media is very sensitive to load history since the nonlinear behavior of the material can have a great influence on propagation rates. However, the raw computation of millions of fatigue cycles with nonlinear material behavior on tridimensional structures would lead to prohibitive calculation times. In this respect, we propose a global model reduction strategy, mixing both the a posteriori and a priori approaches in order to drastically decrease the computational cost of these types of problems. First, the small scale yielding hypothesis is assumed, and an a posteriori model reduction of the plastic behavior of the cracked structure is performed. This reduced model provides incrementally the plastic state in the vicinity of the crack front, from which the instantaneous crack growth rate is inferred. Then an additional a priori model reduction technique is used to accelerate even more the time to solution of the whole problem. This a priori approach consists in building incrementally and without any previous calculations a reduced basis specific to the considered test-case, by extracting information from the evolving displacement field of the structure. Then the displacement solutions of the updated crack geometries are sought as linear combinations of those few basis vectors. The numerical method chosen for this work is the finite element method. Hence, during the propagation the spatial discretization of the model has to be updated to be consistent with the evolving crack front. For this purpose, a specific mesh morphing technique is used, that enables to discretize the evolving model geometry with meshes of the same topology. This morphing method appears to be a key component of the model reduction strategy. Finally, the whole strategy introduced above is embedded inside an adaptive approach, in order to ensure the quality of the results with respect to a given accuracy. The accuracy and the efficiency of this global strategy have been shown through several examples; either in bidimensional and tridimensional cases for model crack propagation, including the industrial example of a helicopter structure.

In der vorliegenden Arbeit wird die Entwicklung eines effizienten Verfahrens zur parametrischen Finite Elemente Simulation von Mikrosystemen und zum Export dieser Modelle in Elektronik- und Systemsimulationswerkzeuge vorgestellt. Parametrische FE-Modelle beschreiben den Einfluss von geometrischen Abmessungen, Schwankungen von Materialeigenschaften und veränderten Umgebungsbedingungen auf das Funktionsverhalten von Sensoren und Aktuatoren. Parametrische FE-Modelle werden für die Auswahl geeigneter Formelemente und deren Dimensionierung während des Entwurfsprozesses in der Mikrosystemtechnik benötigt. Weiterhin ermöglichen parametrische Modelle Sensitivitätsanalysen zur Bewertung des Einflusses von Toleranzen und Prozessschwankungen auf die Qualität von Fertigungsprozessen. In Gegensatz zu üblichen Sample- und Fitverfahren wird in dieser Arbeit eine Methode entwickelt, welche die Taylorkoeffizienten höherer Ordnung zur Beschreibung des Einflusses von Designparametern direkt aus der Finite-Elemente- Formulierung, durch Ableitungen der Systemmatrizen, ermittelt. Durch Ordnungsreduktionsverfahren werden die parametrischen FE-Modelle in verschiedene Beschreibungssprachen für einen nachfolgenden Elektronik- und Schaltungsentwurf überführt. Dadurch wird es möglich, neben dem Sensor- und Aktuatorentwurf auch das Zusammenwirken von Mikrosystemen mit elektronischen Schaltungen in einer einheitlichen Simulationsumgebung zu analysieren und zu optimieren. / The thesis deals with advanced parametric modeling technologies based on differentiation of the finite element equations which account for parameter variations in a single FE run. The key idea of the new approach is to compute not only the governing system matrices of the FE problem but also high order partial derivatives with regard to design parameters by means of automatic differentiation. As result, Taylor vectors of the system’s response can be expanded in the vicinity of the initial position capturing dimensions and physical parameter. A novel approaches for the parametric MEMS simulation have been investigated for mechanical, electrostatic and fluidic domains in order to improve the computational efficiency. Objective of reduced order modeling is to construct a simplified model which approximates the original system with reasonable accuracy for system level design of MEMS. The modal superposition technique is most suitable for system with flexible mechanical components because the deformation state of any flexible system can be accurately described by a linear combination of its lowest eigenvectors. The developed simulation approach using parametric FE analyses to extract basis functions have been applied for parametric reduced order modeling. The successful implementation of a derivatives based technique for parameterization of macromodel by the example of microbeam and for exporting this macromodel into MATLAB/Similink to simulate dynamical behavior has been reported.

In der vorliegenden Arbeit wird die Entwicklung eines effizienten Verfahrens zur parametrischen Finite Elemente Simulation von Mikrosystemen und zum Export dieser Modelle in Elektronik- und Systemsimulationswerkzeuge vorgestellt. Parametrische FE-Modelle beschreiben den Einfluss von geometrischen Abmessungen, Schwankungen von Materialeigenschaften und veränderten Umgebungsbedingungen auf das Funktionsverhalten von Sensoren und Aktuatoren. Parametrische FE-Modelle werden für die Auswahl geeigneter Formelemente und deren Dimensionierung während des Entwurfsprozesses in der Mikrosystemtechnik benötigt. Weiterhin ermöglichen parametrische Modelle Sensitivitätsanalysen zur Bewertung des Einflusses von Toleranzen und Prozessschwankungen auf die Qualität von Fertigungsprozessen. In Gegensatz zu üblichen Sample- und Fitverfahren wird in dieser Arbeit eine Methode entwickelt, welche die Taylorkoeffizienten höherer Ordnung zur Beschreibung des Einflusses von Designparametern direkt aus der Finite-Elemente- Formulierung, durch Ableitungen der Systemmatrizen, ermittelt. Durch Ordnungsreduktionsverfahren werden die parametrischen FE-Modelle in verschiedene Beschreibungssprachen für einen nachfolgenden Elektronik- und Schaltungsentwurf überführt. Dadurch wird es möglich, neben dem Sensor- und Aktuatorentwurf auch das Zusammenwirken von Mikrosystemen mit elektronischen Schaltungen in einer einheitlichen Simulationsumgebung zu analysieren und zu optimieren. / The thesis deals with advanced parametric modeling technologies based on differentiation of the finite element equations which account for parameter variations in a single FE run. The key idea of the new approach is to compute not only the governing system matrices of the FE problem but also high order partial derivatives with regard to design parameters by means of automatic differentiation. As result, Taylor vectors of the system’s response can be expanded in the vicinity of the initial position capturing dimensions and physical parameter. A novel approaches for the parametric MEMS simulation have been investigated for mechanical, electrostatic and fluidic domains in order to improve the computational efficiency. Objective of reduced order modeling is to construct a simplified model which approximates the original system with reasonable accuracy for system level design of MEMS. The modal superposition technique is most suitable for system with flexible mechanical components because the deformation state of any flexible system can be accurately described by a linear combination of its lowest eigenvectors. The developed simulation approach using parametric FE analyses to extract basis functions have been applied for parametric reduced order modeling. The successful implementation of a derivatives based technique for parameterization of macromodel by the example of microbeam and for exporting this macromodel into MATLAB/Similink to simulate dynamical behavior has been reported.