Este trabalho contextualiza o problema da análise estrutural bidimensional de risers verticais ou lançados em catenária livre, fazendo uma breve descrição das etapas para a modelagem dessas estruturas. O problema que este trabalho se propõe a resolver é o da análise dinâmica não linear destas estruturas, no domínio do tempo, apresentando uma formulação que seja capaz de representar de forma adequada as etapas de modelagem destes sistemas. A modelagem foi dividida em duas etapas. A primeira delas é referente à fase de lançamento do riser, com o objetivo de determinar a configuração deformada de equilíbrio, assim como os esforços solicitantes internos decorrentes dessa configuração deformada. Ressalta-se que para os casos de risers em catenária livre, considera-se também o contato unilateral da estrutura com o solo marinho. A segunda etapa é a modelagem da fase de operação da estrutura, por meio de um modelo dinâmico bidimensional. Em ambas as etapas, a formulação apresentada considera os efeitos de acoplamento fluidoestrutura. No caso dos risers em catenária, considera-se também o efeito da interação solo-estrutura. Todo o desenvolvimento das equações foi realizado utilizando-se o método dos elementos finitos MEF. A formulação desenvolvida contempla dois elementos finitos, um de treliça e outro de barra, utilizando-se um sistema de coordenadas corrotacionais. A utilização deste sistema de coordenadas possibilitou a adoção de teorias estruturais de pequenas deformações, para a análise de problemas que envolvem grandes deslocamentos e rotações finitas. Além da formulação do problema, também foi apresentado o projeto da ferramenta computacional RiserSys, que é específica para o estudo de risers nas configurações reta (vertical) e em catenária livre. Muito embora não seja o objetivo deste trabalho a implementação computacional do código nesta ferramenta e o estudo de casos referentes a fenômenos de dinâmica não linear nessas estruturas, nas considerações finais, propõe-se, como trabalhos futuros, a utilização desta formulação para o estudo da compressão dinâmica e a instabilidade paramétrica. / This work addresses the problem of the bidimensional analysis of risers, either straight or free hanging, giving a brief description of the modeling steps of these structures. The problem that it is meant to be solved is the nonlinear dynamic analysis in the time domain of these structures, presenting a formulation capable of correctly modeling the steps of the analysis of the system. The modeling was divided into two steps. The first one is referred to the riser installation, in which the objective was to find the deformed configuration of equilibrium and its internal forces. For the free hanging risers, the unilateral contact with the seabed is taken into account. The second step of the modeling is the phase of operation, using a bidimensional dynamic model. Both steps of the modeling consider the fluid-structure coupling phenomenon. For the free hanging risers, the soil-structure interaction is taken into account. All the analyses were performed using the finite element method FEM. Two finite elements were formulated 2D truss and 2D Bernoulli Euler beam both using a co-rotational coordinate system. The co-rotational coordinate system allowed the use of small-strain theory to develop these finite elements to study problems that involve large displacements. Besides the problem formulation, the project of a computational code, named RiserSys, was described. RiserSys is a dedicated computational tool to analyze straight and free hanging risers. Although the objective of this work is not the computational implementation and the analysis of cases studies, in the concluding chapter it is proposed, as future work, the use of the formulation presented herewith to analyze non-linear dynamic phenomena that may take place in these systems, such as dynamic compression and parametric instability.

Na última década foram descobertas jazidas de petróleo e gás em águas profundas ao longo da costa sudeste do Brasil, o que tem levado à reavaliação de conceitos e técnicas até então utilizados para sua exploração em pequenas profundidades. Parâmetros que anteriormente eram supostamente não críticos passaram a ser relevantes no dimensionamento estrutural dos risers. Efetivamente, a descoberta de novas jazidas na Bacia de Santos incentivou o desenvolvimento de pesquisas nesta área, no Brasil e no mundo. Os depósitos de petróleo e gás encontrados abaixo da camada de sal (daí serem referidas por pré-sal) ocorrem em áreas com lâmina dágua de mais de 2.000 metros, requerendo novas tecnologias para viabilizar sua extração. Os risers de produção nada mais são do que tubulações que levam petróleo e gás do fundo do oceano para a superfície. Nas suas diversas configurações geométricas (vertical, em catenária, lazy wave, entre outros), são elementos estruturais extremamente esbeltos, que devem suportar carregamentos dinâmicos oriundos da correnteza marítima em grande profundidade, ondas de superfície, escoamento interno e deslocamentos impostos, atendendo a exigentes critérios de projeto. O riser vertical será o foco deste trabalho, no qual se pretende utilizar modelos matemáticos com poucos graus de liberdade, denominados modelos de ordem reduzida (MOR), mas com adequada capacidade de representação qualitativa e quantitativa da resposta estrutural, fazendo uso de modos não lineares como funções de projeção, dentro do método de Galerkin não linear. Os modos não lineares, intensivamente estudados no Grupo de Pesquisa Dinâmica, Estabilidade e Controle de Sistemas Estruturais da Escola Politécnica da USP, por conterem intrinsecamente informações de harmônicos de ordem superior, são capazes de, em menor número do que os modos lineares utilizados no método da superposição modal clássico, descreverem acuradamente a resposta do sistema não linear. Serão utilizados procedimentos baseados tanto no método das variedades invariantes, quanto no método das múltiplas escalas, em modelos analíticos. Para a redução de graus de liberdade, será utilizado o método de projeção que se baseia na imposição da igualdade entre os trabalhos virtuais dos modelos de alta e baixa hierarquia (MOR), de sorte que o sistema sob carregamento dinâmico possa ser estudado em espaço de fase de baixa dimensão. A presente pesquisa, além dos desafios acadêmicos inerentes ao tema, apresenta evidente relevância econômica e estratégica para o País. / In the last decade, deposits of oil and gas under deep waters were discovered along the Brazilian Southeast coast, which led to reassessment of concepts and techniques previously used for their exploitation under shallow waters. Parameters that were not previously considered to be critical became relevant in the structural design of the risers. Indeed, the discovery of new deposits in the so-called Santos Basin encouraged the development of research in this area in Brazil and worldwide. The oil and gas deposits found in the pre-salt layer occur in waters deeper than 2,000 meters, requiring new technologies to facilitate their extraction. The risers of production are nothing more than pipes that carry oil and gas from the ocean to the surface. In its various geometric configurations (vertical, catenary, lazy waves, etc.), they are extremely slender structural elements, which must withstand dynamic loads from deep currents, surface waves, internal flow and imposed motions, observing the strict design criteria regarding ultimate and service limit states. The vertical riser will be the focus of this work, which uses mathematical models with few degrees of freedom, known as reduced-order models (ROM), but with adequate capacity to represent the structural response both qualitatively and quantitatively, using non-linear modes as projection functions within the non-linear Galerkin method. The non-linear modes were intensively studied in the research group \"Dynamics, Stability and Control of Structural Systems\" at the Escola Politécnica of USP. Because they contain information of higher-order harmonics, they are able to accurately describe the response of the nonlinear system, using a smaller number of modes than the linear modes used in the classical modal superposition method. Procedures based on the method of invariant manifold and the method of multiple scales alike will be applied to analytical continuum models (with infinite number of degrees of freedom). For the reduction of degrees of freedom, a method based on the identification of the virtual works in both the high-hierarchy and the ROM will be used, so that the system under dynamic loading can be studied in a low-dimension phase space. 13 This research, in addition to academic challenges inherent to the subject has obvious economic and strategic importance for the country.

O trabalho tem como objetivo realizar um estudo experimental na bancada do Laboratório Multipropósito de Escoamento Multifásico com o intuito de estudar o fenômeno de intermitência severa em um sistema pipeline-riser com os fluidos água e ar. A intermitência severa pode ocorrer em sistemas pipeline-riser onde o pipeline é descendente seguido de um riser vertical, além de ser necessário a presença de baixas vazões de fluidos. Esse fenômeno é caracterizado por ser cíclico em que há acúmulo de líquido na base do riser e por acabar causando perdas na produção de petróleo e gás devido a grandes flutuações de pressão e vazão que podem durar horas a depender do comprimento do sistema. Os picos de pressão e vazão também podem causar o desligamento do sistema de separação na plataforma. O estudo se dividiu em várias etapas onde inicialmente foram definidos os procedimentos experimentais a serem utilizados. A calibração de placas de orifício foi necessária para o controle de vazão mássica de gás. Os resultados experimentais foram divididos em casos estáveis e instáveis onde a instabilidade é caracterizada pela presença de ciclos de pressão que podem ser observados em históricos de pressão na base do riser. Mapas de estabilidade foram criados e a região instável obtida experimentalmente foi comparada com a curva de estabilidade obtida pelo uso da teoria de estabilidade linear. Os históricos de pressão na base do riser para os casos instáveis obtidos foram comparados com dois modelos numéricos. A variação da pressão no separador foi usada para verificar a mitigação da intermitência severa e/ou da condição instável obtida no sistema para alguns casos instáveis. / The objective of this work is to do an experimental study of the severe slugging phenomenon in the pipeline-riser system of the Multipurpose Multiphase Flow Laboratory by using the fluids air and water. Severe slugging may occur for low flow rates in pipeline-riser systems where a downward pipeline is followed by a vertical riser. In this phenomenon there is liquid accumulation at the bottom of the riser resulting in production losses due to the great fluctuations of pressure and flow rate during its cycles which may last for hours depending on the length of the system. The high pressure values can also cause shutdown of the platform separation system. The first stage of this study was to define the experimental procedure to be adopted. It was necessary to perform a calibration of the orifice plates in order to have a precise control of the gas mass flow rate. The experimental results were divided in stable and unstable cases. The instability is defined by the presence of pressure oscillations at the bottom of the riser. Stability maps were created to compare the stabiliy curve obtained by the stability linear theory with the experimental results. The experimental pressure oscillations were compared with two numerical models. The pressure variation at the separator was studied to verify the mitigation effects during unstable and/or severe slugging conditions.

A produção de petróleo em ambiente marítimo é feita através de plataformas, em geral flutuantes, conectadas aos reservatórios através de dutos, os chamados risers, responsáveis pelo transporte de petróleo bruto, gás ou água. Do ponto de vista estrutural, estes risers podem ser rígidos ou flexíveis, porém, independente do tipo empregado, com o aumento da profundidade, aumentam-se os esforços de tração sobre essas estruturas. Em águas profundas, essa desvantagem pode ser diminuída com a utilização de configurações mais complexas, dentre as quais se destaca a riser tower, que é foco do presente estudo. Este sistema é composto por vários dutos unidos ao longo de um tubo vertical único, sustentado por uma bóia de subsuperfície. Um grande atrativo desta configuração é a redução da fadiga devido às ondas, uma vez que a bóia e parte significativa dos risers rígidos verticais não sofrem efeitos relevantes das ondas de superfície. No entanto, dois problemas de interação fluido-estrutural persistem: um associado ao fenômeno de VIV Vibração Induzida pela Emissão de Vórtices no riser vertical e outro relativo ao VIM - Movimento Induzido pela Emissão de Vórtices na bóia. Devido ao fato da correnteza ser quase permanente, bem como das altas frequências passíveis de excitação, tem-se um número de ciclos de tensão bastante elevado, associados à flexão, o que pode ser importante no estudo de fadiga do material que compõe as referidas estruturas. De maneira mais completa, no que compete à fenomenologia das interações fluidoestruturais mencionadas, o presente trabalho propõe-se a estudar numérica e analiticamente a dinâmica transversal e longitudinal do conjunto formado pelo riser rígido e pela bóia de subsuperfície, particularmente focado nos efeitos da dinâmica sobre a vida útil do riser vertical. / The offshore oil production is performed with platforms, floating in most cases, which are connected to the well through pipes. These pipes are called risers and are responsible for the transport of crude oil, gas and water from seabed to the platform and vice-versa. From the structural standpoint, these risers can be rigid or flexible. However, independently of the type, the topside tension of these structures increases with the water depth. In deep water this disadvantage can be reduced by using more complex configurations, for example the riser tower, which is the focus of the current study. The riser tower is a system composed by pipes bundled around a central steel tube supported by a subsurface buoyancy tank. This configuration is attractive due to the reduction on waves fatigue since the buoy and most of the vertical risers length is not impacted by the effects of the surface waves. Nevertheless, two issues from the fluid-structural interaction still persist: one related to the VIV phenomena vortex-induced vibration on the vertical riser and the other associated to the VIM vortex induced motion on the buoyancy tank. Considering the almost permanent nature of the offshore currents associated to the high frequencies that can be excited, during the operational life, the riser is subjected to a large amount of stress cycles which are important for the evaluation of the structural integrity in terms of fatigue. In a more complete sense, considering the phenomenology of the fluid-structure interactions, the purpose of the present work is studying numerical and analytically the inline and cross-flow dynamics of the riser tower system especially focused on the impact of the dynamics on the vertical riser operational life.

La combustion en boucle chimique (CLC) est un procédé du type oxy-combustion où des particules sont utilisées pour fournir de l'oxygène à la combustion. Des études sont nécessaires pour l'extrapolation et l'optimisation du procédé CLC, fonction des propriétés des particules du groupe B et de la technologie CFB. Les études hydrodynamiques ont été faites dans un riser de 18 m de hauteur. Des profils axiaus de pression, ainsi que les profils radiaux de flux et de quantité de mouvement ont été obtenus. Trois types de particules ont été utilisées ayant un diamètre de Sauter entre 250 et 300 μm et une densité entre 2600 et 3300 kg/ m3. Un impact de la sphéricité des particules sur la perte de charge a été révélé. Dans des conditions identiques, les billes de verre génèrent des pertes de charge d'environ 50% inférieures à celles du sable. Dans la zone d'écoulement développée, la présence du régime cœur-anneau a été détectée. Un modèle hydrodynamique 1D du riser qui est à la fois fondé sur des données expérimentales et sur les équations gaz-solide Euler-Euler, a été développé. Une nouvelle corrélation pour la force de traînée moyennée sur la section est proposée. Une nouvelle corrélation des conditions limite dans la partie inférieure du riser a aussi été établie. Le modèle 1D final est en mesure de prédire la perte de charge du riser pour différentes conditions opératoires et en tenant compte des propriétés des particules, comme la densité, la taille et la forme. Une étude sur la pertinence de l'utilisation du logiciel Barracuda CPFD® pour simuler des particules du groupe B en régime de transport a été réalisée. Il a été montré que le code sous-estime la perte de charge pour le sable / Chemical Looping Combustion (CLC) is an oxy-combustion like process where particles are used to supply oxygen to combustion. Further work is still needed for extrapolation and optimization of the CLC process, concerning properties of Group B particles and CFB technology. Hydrodynamic tests were made on a 18 m tall riser. Axial pressure profiles as well as radial flux profiles and radial momentum quantity profiles were obtained. Three types of Group B particles were used with Sauter mean diameters between 250 and 300 μm and densities between 2600 and 3300 kg/m²s. An important impact of particle sphericity on riser pressure drop has been revealed. At identical conditions, glass beads present about half the pressure drop generated by sand. In the developed region of the riser, the core-annulus regime has been found. A 1D model of the riser, based on experimental results and on the Euler-Euler gas-solid equations, has been developed. Moreover, a new cross section averaged drag force correlation is presented. A new boundary condition on the bottom of the riser has been investigated. The final 1D model is capable of predicted riser pressure drop from the operating conditions and it takes into account particle properties such as density, size and shape. A study on the adequacy of the use of the commercial CFD code Barracuda to simulate risers with Group B particles was made. It was shown that the code under estimates pressure drop along the riser for sand simulations

The principal objective of this investigation is to develop a nonlinear continuum based finite element formulation to examine dynamic response of flexible riser structures with large displacement and large rotation. Updated Lagrangian incremental approach together with the 2nd Piola-Kirchhoff stress tensor and the Green-Lagrange strain tensor is employed to derive the nonlinear finite element formulation. The 2nd Piola-Kirchhoff stress and the Green-Lagrange strain tensors are energy conjugates. These two Lagrangian tensors are not affected by rigid body rotations. Thus, they are used to describe the equilibrium equation of the body independent of rigid rotations. While the current configuration in Updated Lagrangian incremental approach is unknown, the resulting equation becomes strongly nonlinear and has to be modified to a linearized form. The main contribution of this work is to obtain a modified linearization method during development of incremental Updated Lagrangian formulation for large displacement and large rotation analysis of riser structures. For this purpose, the Green-Lagrange strain and the 2nd Piola-Kirchhoff stress tensors are decomposed into two second-order six termed functions of through-thethickness parameters. This decomposition makes it possible to explicitly account for the nonlinearities in the direction along the riser thickness, as well. It is noted that using this linearization scheme avoids inaccuracies normally associated with other linearization schemes. The effects of buoyancy force, riser-seabed interaction as well as steady-state current loading are considered in the finite element solution for riser structure response. An efficient riser problem fluid-solid interaction Algorithm is also developed to maintain the quality of the mesh in the vicinity of the riser surface during riser and fluid mesh movements. To avoid distortions in the fluid mesh two different approaches are proposed to modify fluid mesh movement governing elasticity equation matrices values; 1) taking the element volume into account 2) taking both element volume and distance between riser centre and element centre into account. The formulation has been implemented in a nonlinear finite element code and the results are compared with those obtained from other schemes reported in the literature.

Apresenta-se um modelo matemático que avalia numericamente a estabilidade do estado estacionário para escoamentos água-ar em sistemas pipeline-riser de geometria variável. Uma análise a partir da teoria de estabilidade linear é aplicada a um modelo matemático adequado ao escoamento água-ar no sistema pipeline-riser. O modelo considera equações de continuidade para a fase líquida e para a fase gasosa, admite-se escoamento unidimensional e em condição isotérmica. O líquido é considerado incompressível enquanto que a fase gasosa é considerada um gás ideal. Admite-se uma equação de momento simplificada para mistura onde despreza-se a inércia (NPW - Modelo No Pressure Wave) e o padrão de escoamento local é definido com base nas condições do escoamento e na inclinação local. Assim, a intermitência severa é controlada principalmente pela gravidade no riser e pela compressibilidade do gás no pipeline. Tanto a correlação de fluxo de deriva quanto o cálculo da queda de pressão por atrito, adotados como lei de fechamento do modelo, são determinados em função do padrão de escoamento. Injeção de gás e válvula de choke são consideradas, respectivamente, na base e no topo do riser. O modelo é aplicado à sistemas pipeline-riser com escoamento água-ar citados na literatura. Os resultados da análise de estabilidade linear numérica são comparados aos resultados experimentais e numéricos apresentando uma excelente concordância. / A mathematical model that numerically evaluates the stability of the stationary state for hilly terrain air-water flows systems is presented. Numerical linear stability analysis is performed to a suitable mathematical model for the two-phase flows in a pipeline-riser system. The mathematical model considers the continuity equations for the liquid and gas phases, one-dimensional flow and isothermal conditions. The liquid is assumed incompressible while the gas phase is considered as an ideal gas. A simplified momentum equation for the mixture, neglecting inertia (NPW - No pressure wave model) is considered and the local flow pattern is defined based on the flow conditions and the local inclination. In this way, severe slugging is controlled mainly by gravity in the riser and compressibility in the pipeline. The void fraction and friction pressure drop, utilized as closure laws, are determined based on the local flow pattern. Gas injection at the bottom of the riser and a choke valve at the top are considered. The model is applied to air-water pipeline-riser systems reported in the literature. Numerical linear stability analysis results are compared with experimental and numerical results reported in the literature with excellent agreement.

Esta dissertação estuda o controle multivariável de uma plataforma \"offshore\" típica. Com esse propósito, um modelo dinâmico rigoroso do processo não-linear foi desenvolvido e usado para representar o processo real nas simulações das estratégias de controle propostas. Baseado no modelo rigoroso e usando métodos de identificação, foram desenvolvidos modelos lineares aproximados para representar o processo no controlador preditivo (MPC). O sistema de controle foi projetado visando manter as variáveis controladas em valores adequados e reduzir o efeito de golfadas severas nos equipamentos à jusante da plataforma. Foram testados dois controladores preditivos: o MPC convencional que opera com \"setpoints\" fixos para as variáveis controladas e o controlador preditivo que opera com zonas para as variáveis controladas. Os resultados da simulação mostram que o controlador preditivo com controle por zonas é capaz de ter uma performance bem melhor que o controlador preditivo convencional, com uma significativa redução na amplitude das oscilações causadas pelas golfadas na vazão de petróleo na saída da plataforma. / This dissertation studies the multivariable control of a typical offshore platform. For this purpose, a rigorous nonlinear dynamic model of the process system is developed and used to represent the true process in the simulation of the proposed control strategies. Based on this rigorous model, approximate linear models are obtained through identification methods in order to represent the platform process in the Model Predictive Control (MPC). The control system was designed aimed at keeping all the controlled variables at adequate values and to reduce the effect of severe riser slugging on the downstream systems. Two model predictive controllers are tested: the conventional MPC with fixed set-points to the controlled outputs and the MPC with zone control of the outputs. The simulation results show that the controller based on the output zone control has a better performance than the conventional MPC with a significant reduction on the amplitude of the oscillation of oil flow at the outlet of the platform process.

Each of the studies conducted herein is related to best management practices for stormwater pollutant removal. This thesis is divided into two chapters. Chapter One details the development and functionality of a novel stormwater detention pond outlet, the solid state skimmer. The device is a perforated riser having no moving parts that is capable of draining detention ponds primarily from the topmost orifices. We found that such a device is capable of reducing effluent turbidity and sediment concentrations compared to a traditional riser outlet. Chapter Two describes a water quality monitoring study performed to show that a pervious concrete detention system can remove stormwater pollutants from parking lot runoff. The stormwater flowed across asphalt paving before infiltrating into the pervious concrete and an aggregate sub-base below. We sampled the runoff before it entered the pervious and after it passed through the detention system and found significant decreases in several pollutants.

Many particulate processes are preferably implemented in circulating fluidized beds (CFB) over traditional low-velocity fluidization to take advantage of the many benefits of circulating systems. Fluid catalytic cracking (FCC) is one of the most successfully applied processes in CFB technology, with more than 350 FCC units in operation worldwide. Despite its extensive use, an understanding of the complex behaviour of these units is incomplete.<p> A theoretical and experimental evaluation of the fluidization behaviour was conducted in the CFB riser, standpipe, and stripper. Initially, an extension of the existing CFB in the Fluidization Laboratory of Saskatchewan was designed. The experimental program conducted in this study included an examination of the solids flow behaviour in the riser, interstitial gas velocity in the downcomer, and stripping efficiency measurements. The hydrodynamic behaviour of the stripper was modeled using Multiphase Flow with Interphase eXchanges (MFIX) CFD code.<p> The solids flow behaviour in the bottom zone of a high-density riser was investigated by measuring the local upwards and downwards solids flux. Solids circulation rates between 125 and 243 kg/(m2⋅s) were evaluated at a constant riser superficial gas velocity of 5.3 m/s. The effect of the riser superficial gas velocity of the local upflow at the riser centerline was also conducted at a solids circulation rate of 187 kg/(m2⋅s). The results show that there is little variation in the local net solids flux at radial locations between 0.00 ¡Ü r/R ¡Ü 0.87. The results indicate that a sharp regime change from a typical parabolic solids flux profile to this more radially uniform solids flux profile occurs at a gas velocity between 4.8 and 4.9 m/s.<p> To quantify stripping efficiency, the underflow of an injected tracer into the standpipe must be known. Quantification of the underflow into the standpipe requires knowledge of two main variables: the interstitial gas velocity and the tracer gas concentration profiles in the standpipe. Stripping efficiency was determined for stripper solids circulation rates of 44, 60, and 74 kg/(m2⋅s) and gas velocities of 0.1, 0.2, and 0.3 m/s. For most conditions studied, the interstitial gas velocity profile was found to be flat for both fluidized and packed bed flow. The stripping efficiency was found to be sensitive to the operating conditions. The highest efficiency is attained at low solids circulation rates and high stripping gas velocities.<p> In the numeric study, stripper hydrodynamics were examined for similar operating conditions as those used in the experimental program. Due to an improved radial distribution of gas and decreasing bubble rise velocity, mass transfer is deemed most intense as bubbles crest above the baffles into the interspace between disc and donut baffles. Stripping efficiency is thought to improve with increasing gas velocity due to an increased bubbling frequency. Stripping efficiency is thought to decrease with increasing solids circulation rates due to a lower emulsion-cloud gas interchange coefficient and a decreased residence time of the emulsion in the stripper.