Este trabalho visa a determinação numérico-experimental de propriedades hidrodinâmicos em um cilindro de seção circular parcialmente submerso. A solução numérica do problema foi desenvolvida através do método dos painéis, o qual foi programado no pacote MATLAB®, sendo que o modelo do cilindro é excitado segundo os parâmetros de onda registrados a partir do ensaio de arrasto do cilindro, possibilitando a determinação da massa adicional e amortecimento hidrodinâmico. O desenvolvimento experimental foi efetivado através de ensaios em tanque de testes, com o uso de um carro de arrasto, tendo sido utilizado um sistema PIV (Particle Imagem Velocimetry) para mapear a não ocorrência da formação de vórtices na superfície submersa do cilindro. O cilindro foi fixado na base do carro, através de uma haste, na posição vertical, permanecendo parcialmente submerso nos ensaios de movimento oscilatório, com frequência e deslocamento longitudinal definidos. Nos ensaios, o conjunto de sensores no sistema detectou as variáveis de aceleração e carregamento na haste de sustentação do cilindro, deslocamento do carro e altura de onda, este último, realizado por dois wave probes simetricamente distanciados da posição inicial do cilindro. Os ensaios possibilitaram a obtenção da massa adicional e dos parâmetros necessários à solução numérica. O desenvolvimento da solução numérica hidrodinâmica via simulação em programa comercial foi realizado no pacote ANSYS® AQWATM, onde o cilindro foi modelado parcialmente submerso, sendo excitado pela frequência e velocidade de onda, os quais foram obtidos nos ensaios experimentais. Os resultados numéricos da programação e da simulação mostraram boa correspondência com os resultados experimentais. / This study involves the experimental and numerical determination of the hydrodynamic properties of a partially submerged cylinder with circular cross section. The numerical solution to the problem was developed using the panel method, which was programmed in the MATLAB® package, and the cylinder model was excited according to the wave parameters recorded during the cylinder drag test, enabling the determination of added mass and hydrodynamic damping. The experimental part of this study involved using a drag car in a test tank, with a PIV (Particle Image Velocimetry) system to map the non-occurrence of vortex formation on the submerged surface of the cylinder. The cylinder was attached vertically to the bottom of the car base by a rod, remaining partially submerged in the oscillatory motion tests, with defined frequency and longitudinal displacement. In the tests, the system’s sensor array detected the variables of acceleration and loading on the cylinder support rod, the car’s displacement and wave height, the latter measured by two wave probes placed at symmetrical distances from the cylinder’s initial position. The experimental tests made it possible to determine the added mass and the parameters required for the numerical solution. The development of the numerical solution of the hydrodynamic problem via simulation with commercial software was performed using the ANSYS® AQWATM package, in which the modeled cylinder was partially submerged and was excited by the wave frequency and velocity that were determined in the experimental tests. The numerical results of the programming and simulation showed a good correspondence with the experimental results.

The aerodynamic behavior of wind tunnels with porous, flexible walls formed from tensioned Kevlar has been characterized and new measurement techniques in such wind tunnels explored. The objective is to bring the aerodynamic capabilities of so-called Kevlar-wall test sections in-line with those of traditional solid-wall test sections. The primary facility used for this purpose is the 1.85-m by 1.85-m Stability Wind Tunnel at Virginia Tech, and supporting data is provided by the 2-m by 2-m Low Speed Wind Tunnel at the Japanese Aerospace Exploration Agency, both of which employ Kevlar-wall test sections that can be replaced by solid-wall test sections. The behavior of Kevlar fabric, both aerodynamically and mechanically, is first investigated to provide a foundation for calculations involving wall interference correction and determination of the boundary conditions at the Kevlar wall. Building upon previous advancements in wall interference corrections for Kevlar-wall test sections, panel method codes are then employed to simulate the wind tunnel flow in the presence of porous, flexible Kevlar walls. An existing two-dimensional panel method is refined by examining the dependency of correction performance on key test section modeling assumptions, and a novel three-dimensional method is presented. Validation of the interference corrections, and thus validation of the Kevlar-wall aerodynamic performance, is accomplished by comparing aerodynamic coefficients between back-to-back tests of models carried out in the solid- and Kevlar-wall test sections. Analysis of the test results identified the existence of three new mechanisms by which Kevlar walls cause wall-interference. Additionally, novel measurements of the boundary conditions are made during the Kevlar-wall tests to characterize the flow at the boundary. Specifically, digital image correlation is used to measure the global deformation of the Kevlar walls under wind loading. Such data, when used in conjunction with knowledge of the pre-tension in the Kevlar wall and the material properties of the Kevlar, yields the pressure loading experienced by the wall. The pressure loading problem constitutes an inverse problem, and significant effort is made towards overcoming the ill-posedness of the problem to yield accurate wall pressure distributions, as well as lift measurements from the walls. Taken as a whole, this document offers a comprehensive view of the aerodynamic performance of Kevlar-wall test sections. / Ph. D. / Traditional wind tunnels, which measure the aerodynamic behavior of vehicles and components relevant to the aerospace industry, enclose some test object with solid walls and accelerate flow around the object. A new configuration has been developed which uses instead flexible, porous walls which are formed from tensioned Kevlar fabric. The original advantage of this configuration lies in its ability to produce high fidelity measurements of the acoustic signature of a model in a stream of air. This new configuration also has been emerging as tool for making the traditional measurements of aerodynamic behavior noted above. However, special considerations have to be made for the so-called Kevlar-wall test section because of the flexibility and porosity of the walls. This study focuses on understanding and exploiting Kevlar-wall wind tunnels with the hope to bring the aerodynamic measurement capabilities of Kevlar-wall test sections in-line with those of traditional solidwall test sections. The primary facility used for this purpose is the Stability Wind Tunnel at Virginia Tech, and supporting data is provided by the Low Speed Wind Tunnel at the Japanese Aerospace Exploration Agency, both of which employ Kevlar-wall test sections that can be replaced by solid-wall test sections. The behavior of Kevlar fabric, both aerodynamically and mechanically, is first investigated to provide a foundation for calculations of the effect of the Kevlar’s porosity and flexibility on the flow around a model in the test section. Building upon previous advancements in this area, computer simulations are then employed to predict the wind tunnel flow in the presence of porous, flexible Kevlar walls. An existing two-dimensional simulation is refined by examining the dependency of the simulation on key modeling assumptions, and a novel three-dimensional method is presented. Validation of the simulations’ effectiveness in providing accurate corrections for the Kevlar porosity and flexibility is accomplished by comparing measurements between back-to-back tests of models carried out in the solid- and Kevlar-wall test sections. Additionally, novel measurements of the deflection and pressure distributions over the Kevlar walls are made during the Kevlar-wall tests. Specifically, a three-dimensional camera imaging system is used to measure the deformation of the Kevlar walls under wind loading. Such data, when used in conjunction with knowledge of the pre-tension in the Kevlar wall, yields the pressure loading experienced by the wall. Taken as a whole, this document offers a comprehensive view of the aerodynamic performance of Kevlar-wall test sections.

L'éolienne Darrieus connaît un intérêt accru ces dernières années parce qu'elle représente une solution alternative potentielle de production d'électricité dans les milieux urbains. En particulier,une éolienne de forte solidité peut être choisie car certaines de ses propriétés peuvent être avantageuses pour son implantation proche de zones habitées. A l'inverse, certaines difficultés aérodynamiques émergent. Ce type d'éolienne fonctionne à de faibles vitesses réduites pour lesquelles le décrochage dynamique a un rôle très significatif. L'objectif de ce travail de thèse consiste à compléter la connaissance du phénomène de décrochage dynamique sur une éolienne à axe vertical afin d'améliorer les modèles numériques de prédiction existants. Cette étude s'appuie sur une analyse combinée de résultats numériques et expérimentaux. Les simulations numériques sont produites avec une méthode des panneaux bidimensionnelle instationnaire. Les effets de la viscosité sont introduits par des corrections utilisant notamment un modèle semi-empirique de décrochage dynamique. Le travail expérimental s'est concentrée sur la dynamique tourbillonnaire à proximité immédiate du rotor résultante du décrochage dynamique. Le montage se compose d'une éolienne à pale droite placée dans une soufflerie. Des mesures instationnaires de la répartition de pression pariétale le long de la corde et des mesures de champ de vitesse par vélocimétrie par images de particules ont été accomplies. Les résultats révèlent la manière dont les caractéristiques du décrochage dynamique sont conditionnées par la vitesse réduite. Le retard au décrochage, l'intensité de l'effet du tourbillon de décrochage dynamique et sa convection ont été quantifiés. Enfin, un examen critique de l'applicabilité du modèle de Leishman-Beddoes pour simuler efficacement les effets du décrochage dynamique a été réalisé. / The Darrieus wind turbine has entered a period of renewed interest over the last years because it may stand for an alternative solution to produce electricity in urban areas. In particular, high solidity wind turbine can be chosen to take benefit from some of its key properties for use near populated city areas. Conversely, some aerodynamic problems arise. This type of wind turbine operates at low tip speed ratio for which dynamic stall has a very significant role. The goal of this work is to provide valuable data to complement the knowledge of the dynamic stall phenomenon that occurs on a vertical axis wind turbine in order to improve existing numerical models. This study relies on a combined analysis of numerical and experimental results. The numerical simulations are based on a bidimensional unsteady vortex panel method. Effects of viscosity are introduced by adding corrections computed with a semi-empirical dynamic stall model. The experimental work focuses on the dynamics of the shed vortices existing in the vicinity of the rotor as a result of dynamic stall. The set-up consists of a straight-bladed wind turbine tested in a wind tunnel. Unsteady pressure distribution measurements along the chord and velocity fields measurements by particle image velocimetry were carried out. Results indicate how the characteristics of dynamic stall are conditioned by the tip speed ratio. Stall inception delay, magnitude of the dynamic stall vortex effects and its convection velocity were evaluated. Blade/Vortex interaction was analyzed through the observation of the vortical system downstream of the rotor. In addition, a critical review of the suitability of the Leishman-Beddoes model to effectively simulate the effects of dynamic stall was accomplished.

This thesis presents an aerodynamic shape optimization methodology for rotor blades of horizontal axis wind turbines. Genetic Algorithm and Blade Element Momentum Theory are implemented in order to find maximum power production at a specific wind speed, rotor speed and rotor diameter. The potential flow solver, XFOIL, provides viscous aerodynamic data of the airfoils. Optimization variables are selected as the sectional chord length, the sectional twist and the blade profiles at root, mid and tip regions of the blade. The blade sections are defined by the NACA four digit airfoil series or arbitrary airfoil profiles defined by a Bezier curve. Firstly, validation studies are performed with the airfoils and the wind turbines having experimental data. Then, optimization studies are performed on the existing wind turbines. Finally, design optimization applications are carried out for a 1 MWwind turbine.

L’objectif de ce travail porte sur le développement d’un modèle d’interaction fluide-structure adapté à la dynamique des éoliennes de grandes tailles avec des pales flexibles qui se déforment de manière significative sous l’effet de la pression exercée par le vent. Le modèle développé est basé sur une approche efficace d’IFS partitionnée pour un fluide incompressible et non visqueux en interaction avec une structure flexible soumise a des grandes transformations. Il permet de fournir une meilleure estimation de la charge aérodynamique et de la réponse dynamique associée du système (pales, mat, attachements, câbles) avec un temps de calcul raisonnable et pour des simulations sur des longues périodes. Pour la modélisation structurale, un élément fini de type solide 3D est développé pour l’étude dynamique des pales d’éolienne soumises à des grands déplacements et des grandes rotations. Une amélioration du comportement en flexion est proposée par l’introduction des degrés de liberté en rotation et l’enrichissement du champ de déplacements afin de décrire plus précisément la flexibilité des pales. Cet élément solide est apte de capter des modes de hautes fréquences qui peuvent s’avérer néfastes pour la stabilité du calcul. Deux techniques sont donc proposées pour les contrôler : la régularisation de la matrice masse et le développement des schémas d’intégration robustes de conservation et de dissipation d’énergie. Les chargements aérodynamiques sont modélisés en utilisant la Panel Method. Il s’agit d’une méthode aux frontières, relativement rapide par rapport à la CFD mais suffisamment précise pour calculer la distribution de la pression exercée sur la pale. Les modèles fluide et structure interagissent via un algorithme de couplage partitionné itératif dans lequel des considérations particulières sont prises en compte dans le contexte des grandes transformations. Dans un effort visant à instaurer un indicateur de fatigue dans la méthodologie proposée, des câbles précontraints sont introduits reliant le mat de l’éolienne au support. Une nouvelle formulation complémentaire en termes de contraintes est ainsi développée pour l’analyse dynamique des câbles 3D en comportement élasto-visco-plastique. Chaque méthode proposée a été d’abord validée sur des cas tests pertinents. Par la suite, des simulations numériques d’éoliennes avec des pales flexibles sont effectuées en vue d’affiner la compréhension de leur comportement dynamique et l’intérêt que la flexibilité des pales peut apporter à leur fonctionnement. / In this work, a numerical model of fluid-structure interaction is developed for dynamic analysis of giant wind turbines with flexible blades that can deflect significantly under wind loading. The model is based on an efficient partitioned FSI approach for incompressible and inviscid flow interacting with a flexible structure undergoing large transformations. It seeks to provide the best estimate of true design aerodynamic load and the associated dynamic response of such system (blades, tower, attachments, cables). To model the structure, we developed a 3D solid element to analyze geometrically nonlinear statics and dynamics of wind turbine blades undergoing large displacements and rotations. The 3D solid bending behavior is improved by introducing rotational degrees of freedom and enriching the approximation of displacement field in order to describe the flexibility of the blades more accurately. This solid iscapable of representing high frequencies modes which should be taken under control. Thus, we proposed a regularized form of the mass matrix and robust time-stepping schemes based on energy conservation and dissipation. Aerodynamic loads are modeled by using the 3D Vortex Panel Method. Such boundary method is relatively fast to calculate pressure distribution compared to CFD and provides enough precision. The aerodynamic and structural parts interact with each other via a partitioned coupling scheme with iterative procedure where special considerations are taken into account for large overall motion. In an effort to introduce a fatigue indicator within the proposed framework, pre-stressed cables are added to the wind turbine, connecting the tower to the support and providing more stability. Therefore, a novel complementary force-based finite element formulation is constructed for dynamic analysis of elasto-viscoplastic cables. Each of theproposed methods is first validated with differents estexamples.Then,several numerical simulations of full-scale wind turbines are performed in order to better understand its dynamic behavior and to eventually optimize its operation.

This thesis addresses the development of a weakly non-linear Higher Order Time Domain Rankine Panel Method (TDRPM) for the linear and weakly non-linear seakeeping analysis of floating offshore structures, including wave-current interaction effects. A higher order boundary elements method is adopted based on the body geometry description using Non-uniform Rational B-splines (NURBS) formulation, which can be generated by many standard Computed Aided Design (CAD) softwares widely available, and the several computed quantities (velocity potential, free surface elevation and others) are described using a B-spline formulation of arbitrary degree. The problem is formulated considering wave-current-body interactions up to second order effects, these ones considering the terms obtained by interaction of zero/first order quantities. In order to provide numerical stability, the Initial Boundary Value Problem (IBVP) is formulated in terms of the velocity potential and the local acceleration potential, the later used to predict the hydrodynamic pressure accurately. The zeroth order problem is solved using the double-body linearization instead of the Neumman-Kelvin one in order to allow bluff bodies simulation, leading to very complex expressions regarding the m-terms computation. The method adopts the Rankine sources as Green\'s function, which are integrated using Gauss quadrature in the entire domain, but for the self-influence terms that are integrated using a desingularized procedure. The numerical method is verified initially considering simplified geometries (sphere and circular cylinder) for both, first and second-order computations, with and without current effects. The derivatives of the velocity potential are verified by comparing the numerical m-terms to the analytical solutions for a hemisphere under uniform flow. The mean and double frequency drift forces are computed for fixed and floating structures and the quantities involved in these computations (wave runup, velocity field) are also compared to literature results, including the free floating response of a sphere under current effects. Two practical cases are also studied, namely the wave-induced second order responses of a semi-submersible platform and the wavedrift-damping effect evaluated through the equilibrium angle of a turret moored FPSO. For the former, some specific model tests were designed and conducted in a wave-basin. / Essa tese aborda o desenvolvimento de um método de Rankine de ordem alta no domínio do tempo (TDRPM) para o estudo de problemas lineares e fracamente não lineares, incluindo o efeito de corrente, envolvendo sistemas flutuantes. O método de ordem alta desenvolvido considera a geometria do corpo como descrita pelo padrão Non-uniform Rational Basis Spline (NURBS), que está disponível em diverso0s softwares de Computed Aided Design (CAD) disponíveis, sendo as diversas funções (potencial de velocidades, elevação da superfície-livre e outros) descritos usando B-splines de grau arbitrário. O problema é formulado considerando interações onda-corrente-estrutura para efeitos de até segunda ordem, os de ordem superior sendo calculados considerando as interações somente dos termos de ordem inferior. Para garantir a estabilidade numérica, o problema de contorno com valor inicial é formulado0 com relação ao potencial de velocidade e de parcela local do potencial de acelerações, este para garantir cálculos precisos da pressão dinâmica. O problema de ordem zero é resolvido usando a linearização de corpo-duplo ao invés da linearização de Neumman-Kelvin para permitir a análise de corpos rombudos, o que requer o cálculo de termos-m de grande complexidade. O método adota fontes de Rankine como funções de Green, que são integradas através de quadratura de Gauss-Legendre no domínio todo, exceto com relação aos termos de auto-influência que adotasm um procedimento de dessingularização. O método numérico é inicialmente verificado considerando corpos de geometria simplificada (esfera e cilindro), considerando efeitos de primeira e segunda ordens, com e sem corrente. As derivadas do potencial de velocidade são verificadas comparando os termos-m obtidos numericamente com soluções analíticas disponíveis para a esfera em fluído infinito. As forças de deriva média e dupla-frequência são calculadas para estruturas fixas e flutuantes, sendo as funções calculadas (elevação da superfície, campo de velocidade) comparadas com resultados disponíveis na literatura, incluindo o movimento da esfera flutuante sob a ação de corrente e ondas. São também estudados dois casos de aplicação prática, a resposta de segunda ordem de uma plataforma semi-submersível e o efeito de wave-drift damping para o ângulo de equilíbrio de uma plataforma FPSO ancorada através de sistema turred. No caso da semi-submersível, os ensaios foram projetados e realizados em tanque de provas.

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.

This thesis addresses the development of a weakly non-linear Higher Order Time Domain Rankine Panel Method (TDRPM) for the linear and weakly non-linear seakeeping analysis of floating offshore structures, including wave-current interaction effects. A higher order boundary elements method is adopted based on the body geometry description using Non-uniform Rational B-splines (NURBS) formulation, which can be generated by many standard Computed Aided Design (CAD) softwares widely available, and the several computed quantities (velocity potential, free surface elevation and others) are described using a B-spline formulation of arbitrary degree. The problem is formulated considering wave-current-body interactions up to second order effects, these ones considering the terms obtained by interaction of zero/first order quantities. In order to provide numerical stability, the Initial Boundary Value Problem (IBVP) is formulated in terms of the velocity potential and the local acceleration potential, the later used to predict the hydrodynamic pressure accurately. The zeroth order problem is solved using the double-body linearization instead of the Neumman-Kelvin one in order to allow bluff bodies simulation, leading to very complex expressions regarding the m-terms computation. The method adopts the Rankine sources as Green\'s function, which are integrated using Gauss quadrature in the entire domain, but for the self-influence terms that are integrated using a desingularized procedure. The numerical method is verified initially considering simplified geometries (sphere and circular cylinder) for both, first and second-order computations, with and without current effects. The derivatives of the velocity potential are verified by comparing the numerical m-terms to the analytical solutions for a hemisphere under uniform flow. The mean and double frequency drift forces are computed for fixed and floating structures and the quantities involved in these computations (wave runup, velocity field) are also compared to literature results, including the free floating response of a sphere under current effects. Two practical cases are also studied, namely the wave-induced second order responses of a semi-submersible platform and the wavedrift-damping effect evaluated through the equilibrium angle of a turret moored FPSO. For the former, some specific model tests were designed and conducted in a wave-basin. / Essa tese aborda o desenvolvimento de um método de Rankine de ordem alta no domínio do tempo (TDRPM) para o estudo de problemas lineares e fracamente não lineares, incluindo o efeito de corrente, envolvendo sistemas flutuantes. O método de ordem alta desenvolvido considera a geometria do corpo como descrita pelo padrão Non-uniform Rational Basis Spline (NURBS), que está disponível em diverso0s softwares de Computed Aided Design (CAD) disponíveis, sendo as diversas funções (potencial de velocidades, elevação da superfície-livre e outros) descritos usando B-splines de grau arbitrário. O problema é formulado considerando interações onda-corrente-estrutura para efeitos de até segunda ordem, os de ordem superior sendo calculados considerando as interações somente dos termos de ordem inferior. Para garantir a estabilidade numérica, o problema de contorno com valor inicial é formulado0 com relação ao potencial de velocidade e de parcela local do potencial de acelerações, este para garantir cálculos precisos da pressão dinâmica. O problema de ordem zero é resolvido usando a linearização de corpo-duplo ao invés da linearização de Neumman-Kelvin para permitir a análise de corpos rombudos, o que requer o cálculo de termos-m de grande complexidade. O método adota fontes de Rankine como funções de Green, que são integradas através de quadratura de Gauss-Legendre no domínio todo, exceto com relação aos termos de auto-influência que adotasm um procedimento de dessingularização. O método numérico é inicialmente verificado considerando corpos de geometria simplificada (esfera e cilindro), considerando efeitos de primeira e segunda ordens, com e sem corrente. As derivadas do potencial de velocidade são verificadas comparando os termos-m obtidos numericamente com soluções analíticas disponíveis para a esfera em fluído infinito. As forças de deriva média e dupla-frequência são calculadas para estruturas fixas e flutuantes, sendo as funções calculadas (elevação da superfície, campo de velocidade) comparadas com resultados disponíveis na literatura, incluindo o movimento da esfera flutuante sob a ação de corrente e ondas. São também estudados dois casos de aplicação prática, a resposta de segunda ordem de uma plataforma semi-submersível e o efeito de wave-drift damping para o ângulo de equilíbrio de uma plataforma FPSO ancorada através de sistema turred. No caso da semi-submersível, os ensaios foram projetados e realizados em tanque de provas.

This thesis deals with computing the pressure distribution around a swimming slender fish and the thrust generated by its flapping motion. The body of the fish is modeled as a missile like slender body to which a tail is attached that is modeled as a swept wing. The tail is attached to the tip of the slender body and maintains its slope with it. The motion for the swimming fish is prescribed. The fluid flow is modeled as an unsteady potential flow problem with the flow around the slender body modeled as flow over an array of cylinders of varying radii and the flow over the swept wing modeled using the vortex panel method. The pressure distribution is computed using the unsteady Bernoulli equation. The overall thrust & drag for different parameters are studied and compared