O presente trabalho realiza um estudo do desempenho aerodinâmico da turbina eólica de duas pás e 10 m de diâmetro da UAE Phase VI, testada pelo NREL no túnel de vento NASA Ames, através do uso de dinâmica dos fluidos computacional (CFD). Para tanto são apresentados conceitos fundamentais para análise da performance do aerogerador, a metodologia aplicada para a análise numérica e os resultados obtidos. O modelo geométrico da turbina foi inserido em ambiente computacional num domínio com as mesmas dimensões da seção de testes do túnel de vento. A esse domínio foi empregada uma malha de elementos tetraédricos. A modelagem numérica e as simulações foram efetuadas através do código comercial ANSYS FLUENT 13.0 e utilizaram as equações médias de Reynolds e modelos de turbulência k  SST e Spalart-Allmaras. A turbina simulada possui ângulo de giro (yaw) e de cone de 0°. Os casos simulados foram de turbina com ângulos de passo das pás de 0° e 3°, para velocidades de ar na entrada do domínio de 5 m/s, 7 m/s e 9 m/s. As simulações foram feitas em regime transiente utilizando o método de malha móvel. Dados provenientes da simulação numérica são comparados aos dados experimentais de empuxo, torque e potência, divulgados pelo laboratório. Os modelos de turbulência testados apresentaram boa concordância com os resultados experimentais de empuxo. O torque e a potência foram bem previstos para velocidades de entrada do domínio baixas, mas foram subdimensionados para velocidades mais altas. A separação da camada limite foi prevista por ambos os modelos. Na comparação com resultados obtidos com outros autores para o mesmo caso, o início de descolamento da camada limite se deu antes do previsto. A metodologia adotada nas simulações numéricas realizadas mostrou-se adequada e representativa nas análises desse estudo. / This study makes a CFD analysis of the aerodynamic performance of the NREL UAE Phase VI two-bladed wind turbine, which have been tested in the NASA Ames wind tunnel. Fundamental concepts on the evaluation of turbine performance, the applied methodology for the numerical analysis and the results are presented. A numerical model has been inserted in a computational environment that has the same dimensions as the real wind tunnel section, and a tetrahedral mesh has been created to fill this domain. Numerical modeling and the simulations have been performed using the ANSYS FLUENT 13.0 commercial code, making use of the RANS equations and the k  SST and Spalart-Allmaras turbulence models. The simulated turbine has 0 degrees of cone and yaw angle. Simulations were performed in unsteady state using the moving mesh technique. Results are compared to experimental data regarding to thrust, torque and power. The k  SST and Spalart-Allmaras turbulence models have shown good agreement with experimental values of thrust. Torque and power have been adequately predicted to lower free flow velocities, but have been underpredicted to higher velocities. Separation of the boundary layer has been adequately predicted by both models, but the beginning of the separation occurred earlier than expected in comparison with results of other authors to the same case. The methodology used in the numerical simulations proved to be adequate and representative in this study.

En dépit d’un développement opérationnel actuel seulement émergeant le long des côtes françaises, l’extraction de l’énergie cinétique des courants de marée par les hydroliennes apparaît, dès à présent, comme une solution prometteuse pour contribuer, localement, à la transition énergétique de territoires insulaires déconnectés du réseau électrique continental, ayant des besoins électriques limités, et situés dans des espaces naturels sensibles et/ou touristiques intégrant un patrimoine visuel à préserver. Ce travail de thèse se consacre à la modélisation numérique tridimensionnelle des impacts hydrodynamiques et sédimentaires d’hydroliennes d’axe horizontal déployées dans le site pilote d’implantation de fermes hydroliennes du Passage du Fromveur, au cœur du parc naturel marin d’Iroise, à la pointe Bretagne. Les simulations numériques se basent sur le modèle océanographique ROMS (« Regional Ocean Modelling System ») modifié pour intégrer un sous-modèle théorique de disque actuateur assimilant l’hydrolienne à un disque poreux opposant à l’écoulement une force équivalente à la poussée de la turbine. La méthode est validée avec des mesures effectuées en laboratoire dans le sillage d’un disque poreux de 10 cm de diamètre (D) immergé dans un courant permanent. Une résolution spatiale minimale égale à D/10 est nécessaire pour reproduire les observations. Après une étude de convergence numérique à échelle réelle, le modèle ROMS est appliqué, selon une approche gigogne de maillages imbriqués focalisée sur le Passage du Fromveur, pour examiner les interactions des sillages et les effets cumulés au sein d’un parc de huit turbines de 10 m de diamètre susceptible de satisfaire au besoin énergétique de l’île d’Ouessant. L’agencement des turbines suit les recommandations communément adoptées avec une disposition en quinconce et des espacements longitudinaux de 10D et latéraux de 5D. En condition de vive-eau moyenne, le désalignement du courant au pic de flot exacerbe les interactions entre sillages, réduisant la production énergétique du parc de près de 15 % par rapport à celle du pic de jusant. Ce déficit de production énergétique est limité à 2 % en ramenant l’espacement latéral des turbines à 3D. Les prédictions de ROMS sont enfin exploitées pour appréhender l’influence de cette dernière configuration de parc sur la dynamique sédimentaire locale. Les principaux effets attendus concernent (i) le dépôt de sédiments de plus de 2 mm de diamètre dans le sillage des dispositifs et (ii) la mise en mouvement de cailloutis de 5 cm de diamètre entre les sillages. / In spite of a present only emerging operational development along the coast of France, the extraction of the kinetic energy of tidal currents by turbines appears as a promising solution to contribute locally to the energetic transition of insulary territories that are not connected to the continental electricity grid, with limited power needs, and are located in protected and touristic natural areas with a visual heritage to preserve. This doctoral thesis was devoted to the three-dimensional numerical modelling of the hydrodynamic and sedimentary impacts induced by horizontal-axis turbines deployed within the pilot site of the Fromveur Strait, in the natural marine Iroise park, off western Brittany. Numerical simulations are performed with the oceanographic model ROMS (Regional Ocean Modelling System) modified to integrate a theoretical actuator-disk sub-model that assimilates the device to a porous disc opposing the flow with a force equal to the turbine’s thrust. This method was assessed against laboratory measurements within the wake of a porous disc with a diameter (D) of 0.1 m immersed in a permanent flow. A spatial resolution as small as D/10 was required to reproduce observations. After a numerical convergence study at full scale, ROMS was applied, using a nested grid approach targetted towards the Fromveur Strait, to examine wake interactions and cumulative effects within an array of height turbines of 10-m-diameter expected to fulfill the energy need of the island of Ushant. The array layout followed the commonly recommended staggered configuration with respective longitudinal and lateral spacings of 10D and 5D. During spring tidal conditions, the misalignment of the peak flood flow enhanced the wake interactions, reducing by about 15% the array power production in comparison with the peak ebb flow. This lack of power production capacity was lowered to 2% by reducing the lateral spacing to 3D. ROMS predictions were finally exploited to address the influence of this last array of turbines on the local sediment dynamics. Main effects were expected on (i) the deposition of sediments with diameter over 2 mm within the turbine wakes and (ii) the setting in motion of gravels with a diameter of 5 cm between the wakes.

Wind energy technologies are considered to be among the most promising types of renewable energy sources, which have since attracted broad considerations through recent years due to the soaring oil prices and the growing concerns over climate change and energy security. In Kuwait, rapid industrialisation, population growth and increasing water desalination are resulting in high energy demand growth, increasing the concern of oil diminishing as a main source of energy and the climate change caused by CO2 emissions from fossil fuel based energy. These demands and challenges compelled governments to embark on a diversification strategy to meet growing energy demand and support continued economic growth. Kuwait looked for alternative forms of energy by assessing potential renewable energy resources, including wind and sun. Kuwait is attempting to use and invest in renewable energy due to the fluctuating price of oil, diminishing reserves, the rapid increase in population, the high consumption of electricity and the environment protection. In this research, wind energy will be investigated as an attractive source of energy in Kuwait.

Research into advanced wind turbine design has shown that load alleviation strategies like bend-twist coupled blades and coned rotors could reduce costs. However these strategies are based on nonlinear aero-structural dynamics providing additional benefits to components beyond the blades. These innovations will require Multi-disciplinary Design Optimization (MDO) to realize the full benefits. This research expands the MDO capabilities of Horizontal Axis Wind Turbines. The early research explored the numerical stability properties of Blade Element Momentum (BEM) models. Then developed a provincial scale wind farm siting models to help engineers determine the optimal design parameters. The main focus of this research was to incorporate advanced analysis tools into an aero-elastic optimization framework. To adequately explore advanced designs with optimization, a new set of medium fidelity analysis tools is required. These tools need to resolve more of the physics than conventional tools like (BEM) models and linear beams, while being faster than high fidelity techniques like grid based computational fluid dynamics and shell and brick based finite element models. Nonlinear beam models based on Geometrically Exact Beam Theory (GEBT) and Variational Asymptotic Beam Section Analysis (VABS) can resolve the effects of flexible structures with anisotropic material properties. Lagrangian Vortex Dynamics (LVD) can resolve the aerodynamic effects of novel blade curvature. Initially this research focused on the structural optimization capabilities. First, it developed adjoint-based gradients for the coupled GEBT and VABS analysis. Second, it developed a composite lay-up parameterization scheme based on manufacturing processes. The most significant challenge was obtaining aero-elastic optimization solutions in the presence of erroneous gradients. The errors are due to poor convergence properties of conventional LVD. This thesis presents a new LVD formulation based on the Finite Element Method (FEM) that defines an objective convergence metric and analytic gradients. By adopting the same formulation used in structural models, this aerodynamic model can be solved simultaneously in aero-structural simulations. The FEM-based LVD model is affected by singularities, but there are strategies to overcome these problems. This research successfully demonstrates the FEM-based LVD model in aero-elastic design optimization. / Graduate / 0548 / pilot.mm@gmail.com

Αντικείμενο της εργασίας είναι η αεροδυναμική και αεροακουστική ανάλυση στροφείων ανεμοκινητήρων οριζοντίου άξονα (α-ο-α). Ο υπολογισμός του πεδίου ροής και των αεροδυναμικών συντελεστών του στροφείου ενός ανεμοκινητήρα επιτυγχάνεται κατά δύο τρόπους, με σκοπό την άμεση σύγκριση των αποτελεσμάτων με κριτήρια αφενός την ακρίβεια και αφετέρου την ευκολία ή πρακτικότητα που προσδιορίζεται κύρια σε όρους χρόνου υπολογισμού και διαθεσιμότητας υπολογιστικών πόρων. Οι δύο επιλεγμένοι τρόποι που διαφοροποιούνται στην φυσικο-μαθηματική μοντελοποίηση του προβλήματος ροής γύρω από το στροφείο του ανεμοκινητήρα, αποτελούν δύο δοκιμασμένες μεθοδολογίες ή τεχνικές ανάλυσης και σχεδιασμού περιστρεφόμενων στροφείων, τα οποία μπορούν να λειτουργούν ως κινητήριες μηχανές ή ως εργομηχανές, είναι η μέθοδος των επιφανειακών στοιχείων και η αριθμητική επίλυση των εξισώσεων Navier-Stokes. Για την αξιολόγηση των υπολογιστικών αποτελεσμάτων επιλέχθηκε ως στροφείο αναφοράς, ο πειραματικός ανεμοκινητήρας NREL phase II. Ο αλγόριθμος των επιφανειακών στοιχείων συμπλέχτηκε με ολοκληρωτικά σχήματα πρόλεξης και υπολογισμού του οριακού στρώματος με σκοπό να συμπεριληφθούν τα φαινόμενα συνεκτικότητας της ροής. Πραγματοποιήθηκε παραμετρική ανάλυση του δρομέα του ανεμοκινητήρα για διαφορετικές συνθήκες λειτουργίας του. Η σύγκριση των αποτελεσμάτων των συντελεστών πίεσης των περιστρεφόμενων πτερυγίων για τέσσερις θέσεις κατά το εκπέτασμα του πτερυγίου με τα πειραματικά δεδομένα δείχνει ικανοποιητική συμφωνία. Για την ανάλυση του πεδίου ροής που παράγεται γύρω από περιστρεφόμενους δρομείς α-ο-α χρησιμοποιήθηκε η μέθοδος της υπολογιστικής ρευστοδυναμικής (CFD). Πραγματοποιήθηκαν RANS προσομοιώσεις για διαφορετικές συνθήκες λειτουργίας του ανεμοκινητήρα και για τέσσερα διαφορετικά μοντέλα τύρβης. Το k-ω SST μοντέλο τύρβης έχει τις μικρότερες αποκλίσεις με τα πειραματικά αποτελέσματα. Η αεροακουστική ανάλυση του στροφείου ενός ανεμοκινητήρα επιτυγχάνεται με την επίλυση της ακουστικής εξίσωσης Ffowcs-Williams Hawkings, μέσω ενός υπολογιστικού κώδικα που αναπτύχθηκε γι’ αυτό το σκοπό. Από τα αποτελέσματα των προσομοιώσεων, φάνηκε στα ροδογράμματα κατευθυντικότητας του ήχου, τα επίπεδα της ακουστικής πίεσης να είναι υψηλότερα για θέσεις παρατηρητή ανάντη και κατάντη του ανεμοκινητήρα. / The aim of this study is to represent the aerodynamic and aeroacoustic analysis of horizontal axis wind turbine (ΗAWT) rotors. The calculation of the flow field and the aerodynamic coefficients over the wind turbine rotor are performed using two methodologies, the panel method and the numerical solution of Navier-Stokes equations. These two methodologies are differentiated in the mathematical modeling approach of the flow around the rotor and are utilized in the design and manufacturing phases of horizontal axis wind turbine rotors. Moreover, the results of these two methodologies are compared in terms of the accuracy and the computational time required. For the evaluation of the computational results the experimental wind turbine NREL phase II is chosen as the reference rotor. An invicid/viscous interaction algorithm is developed using integral boundary layer equations coupled with the low order panel method solution in order to account the viscous effects. A parametric analysis of the wind turbine rotor is conducted for different operating conditions. The comparison of the results of the pressure coefficients of the rotating blades for four spanwise positions along the blade with the experimental data shows satisfactory agreement. The analysis of the near and far flow field of HAWT is obtained via CFD by RANS simulations of four different turbulence models (Spalart-Allmaras, k-ε, k-ε RNG and k-ω SST). From the conducted study, it is confirmed the ability of analysis of a HAWT rotor flow field with the RANS equations and the good agreement of the computations with experimental data, when the k-ω SST turbulence model is used. The aeroacoustic analysis of the HAWT is based on the solution of the Ffowcs Williams-Hawkings (FW-H) equation via a computer code developed for this purpose. The radiation patterns of the calculated aeroacoustic noise show that high level amplitudes are calculated for upwind and downwind positions.

La raréfaction des ressources fossiles non renouvelables et le dérèglement climatique font de la question énergétique un enjeu d’envergure mondiale. L’exploitation de nouvelles sources d’énergie renouvelable devient alors un objectif de première importance. L’énergie produite à partir des courants marins suscite depuis quelques années un intérêt particulier. Le concept de turbine sous-marine, appelée hydrolienne, désigne le dispositif permettant de convertir l’énergie cinétique des courants marins en énergie électrique. Ce travail de recherche traite les problématiques que pose la conception des hydroliennes à axe horizontal. Il sera mis en évidence que le monde des hélices marines présente une piste intéressante pour l’étude du comportement hydrodynamique des hydroliennes. Certains concepteurs d’hydroliennes avancent que l’ajout d’un système de carénage est favorable pour améliorer le rendement hydrodynamique. L’étude du gain hydrodynamique à encombrement constant que pourrait procurer l’ajout d’un carénage a donc été choisie comme point de départ de ce travail de recherche. Pour répondre au besoin des industriels lié à une problématique de gain de masse, les matériaux composites présentent un atout considérable en raison de leurs excellents rapports «masse/résistance» et «masse/rigidité». Une réalisation d’un carénage en matériaux composites présentant le meilleur ratio «puissance/masse» a été obtenue. Un carénage d’hydrolienne est de par sa position particulièrement confronté à des chocs. Ceci peut s’avérer très délicat car la structure composite en question est soumise à des sollicitations sévères liées à l’environnement marin. L’impact sur un carénage d’hydrolienne a été traité en détail dans ce travail de recherche. / Against the backdrop of the increasing scarcity of non-renewable fossil resources and climate change, the energy problem has become a worldwide issue. Hence, the exploitation of new renewable energy sources becomes a worldwide goal of primary importance. The concept of the underwater turbine, called tidal current turbine, designates the device which allows the conversion of the kinetic energy produced by marine currents in electric energy. This research study examines the problems related to the design of horizontal axis tidal current turbines. The present study shows that the world of marine propellers, sometimes entirely left out by the designers of tidal current turbines, presents an interesting avenue of research with regard to the hydrodynamic behaviour of tidal current turbines. Certain designers of tidal current turbines use a duct and hold that the addition of the duct contributes to the improvement of the hydrodynamic performance. Therefore, the study of the hydrodynamic benefits of ducted turbine using a constant overall cross-section than the bare turbine was the starting point of the present research work. In order to meet the needs of the manufacturers of tidal current turbines, which is generally linked to a problem of mass gain, composite materials present a considerable asset on account of their excellent «mass/resistance» and «mass/rigidity» relations. A structural design of ducted tidal current turbines using composite materials has therefore been examined. Hence, the design of a composite duct which yields the best «power/mass» ratio has been proposed. The duct of the tidal current turbine is especially confronted by the impacts due to its particular position. The impact damage aspect has also been examined in detail in the present research study.

La technique d'intégration des systèmes éoliens verticaux (VAWT) au service des logements individuels, collectifs et tertiaires est une approche intéressante pour les acteurs de la maitrise d'énergie pour promouvoir une utilisation rationnelle de l'énergie. Le choix de l'implantation d'une éolienne en milieu urbain est déterminé par la hauteur des bâtiments, la vitesse du vent et l'intensité de turbulence du site. Les conditions de vents sévères à faible altitude sont favorables à une implantation de VAWT. Dans certaines villes, la hauteur moyenne des bâtiments est relativement faible et ceci fait qu'en ces lieux, les VAWTs sont appréciables par rapport aux HAWTs. La mécanique des fluides numériques (CFD) est mise en œuvre pour modéliser les écoulements d'air au travers d'éoliennes et des bâtiments. Un problème CFD modélisé avec un modèle de turbulence approprié donneront des résultats de simulations qui s'approcheront des réalités physiques et des résultats de l'expérimentation. Dans cette étude, les modèles standard k-" et SST k-! ont été utilisés. Après analyse des possibilités d'intégration d'une VAWT, la toiture reste la zone d'intégration la plus intéressante. En plus de l'étude aérodynamique, nous avons entamé une modélisation électrique de la chaîne de conversion de l'éolienne en utilisant le logiciel Matlab/Simulink. Le travail a été effectué dans le but de déterminer la puissance électrique susceptible d'être produite par l'éolienne. Pour finaliser cette étude, un modèle de couplage électrique de VAWTs avec un bâtiment considéré comme un modèle de charge est présenté. / The building integration of the vertical axis wind turbine (VAWT) to supply the individual, collective and tertiary residences consumption is an interesting approach that can help architects and the actors of the energy control to promote a rational use of renewable energy in the in homes. The choice of the location of the urban wind turbine type is determined by building height, wind speed and turbulence intensity of the site. The severe conditions of wind at low altitude are favorable for a VAWT installation. In some cities, the average buildings height is low, in these places, the VAWTs must be appreciable compared to the HAWTs. The modelling of the air flow through the wind turbine and the couple building-wind turbine involves the computation fluid dynamics (CFD). A problem modeled with a suitable turbulence model will give results that approach the physical reality and the experiment results. In this study, the standard k-" and SST k-! models were used. After analyzing the possibilities of VAWT integration, the roof is the most interesting integration area. In addition to CFD method, we have started to study the electrical model of the VAWT. The work was conducted to determine the electrical power generated by the wind turbine using Matlab/Simulink software. To complete the study, a VAWT model coupled with a building where the building is considered as a consumption model is presented.

Anthropogenic climate change is approaching predicted tipping points and there is an urgent need to de-carbonize energy systems on a global scale. Generation technologies that do not emit greenhouse gas need to be rapidly deployed, and energy grids need to be updated to accommodate an intermittent fluctuating supply. Rapidly advancing battery technology, cost reduction of solar and wind power and other emerging generation technologies are making the needed changes technically and economically feasible. Extracting energy from fast-flowing tidal currents using turbines akin to those used in wind farms, offers a reliable and predictable source of GHG free energy. The tidal power industry has established the technical feasibility of tidal turbines, and is presently up-scaling deployments from single isolated units to large tidal farms containing many turbines. However there remains significant economic uncertainty in financing such projects, partially due to uncertainty in predicting the long-term energy yield. Since energy yield is used in calculating the project revenue, it is of critical importance. Predicting yield for a prospective farm has not received sufficient attention in the tidal power literature. this task has been the primary motivation for this thesis work, which focuses on establishing and validating simulation-based procedures to predict flows through large tidal farms with many turbines, including the back effects of the turbines. This is a challenging problem because large tidal farms may alter tidal flows on large scales, and the slow-moving wake downstream of each rotor influences the inflow to other rotors, influencing their performance and loading. Additionally, tidal flow variation on diurnal and monthly timescales requires long-duration analysis to obtain meaningful statistics that can be used for forecasting. This thesis presents a hybrid simulation method that uses 2D coastal flow simulations to predict tidal flows over long durations, including the influence of turbines, combined with higher-resolution 3D simulations to predict how wakes and local bathymetry influence the power of each turbine in a tidal farm. The two simulation types are coupled using a method of bins to reduce the computational cost within reasonable limits. The method can be used to compute detailed 3D flow fields, power and loading on each turbine in the farm, energy yield and the impact of the farm on tidal amplitude and phase. The method is demonstrated to be computationally tractable with modest high-performance computing resources and therefore are of immediate value for informing turbine placement, comparing turbine farm-layout cases and forecasting yield, and may be implemented in future automated layout optimization algorithms. / Graduate