Tidal power, or the use of tides for electricity production, exists in many forms including tidal barrages, which exploit tidal head differentials, and turbines placed directly in regions with large tidal current velocities. The latter is actively being investigated in many countries around the world as a means of providing renewable and wholly predictable electricity (cf. wind, solar and wave power). The expansion of the in-stream tidal industry is hindered however by several factors including: turbine durability, deployment and maintenance costs, and the lack of abundant locations which meet the necessary current velocities for turbine start-up and economic power production. A new novel type of augmentation device, entitled the ‘Tidal Acceleration Structure’ or TAS (Canadian patent pending 2644792), has been proposed as a solution to the limited number of coastal regions which exhibit fast tidal currents. In preliminary investigations, the TAS, a simple Venturi section consisting of walls extending from the seafloor to above the high water mark in an hourglass shape, was found as able to more than double current velocities entering the device. The results indicated a significant advantage over other current channeling technologies and thus the need for more in-depth investigations. The main objective of the present study was to optimise the design of the TAS and to predict the power that a turbine placed within it could extract from flow. To do this, two principal methods were employed. Firstly, a 1:50 scale model of the TAS was tested and its shape optimised in a 1.5 m wide flume. Secondly, a 3D numerical model (ANSYS Fluent) was used for comparison with the experimental results. During the tests, a TAS configuration was found that could accelerate upstream velocities by a factor of 2.12. In separate tests, turbines were simulated using Actuator Disc Theory and porous plates. The TAS-plate combination was found to be able to extract up to 4.2 times more power from flow than the stand-alone plate, demonstrating that the TAS could provide turbines with a significant advantage in slower currents. Though further research is needed, including the testing of a larger TAS model in conjunction with a small in-stream turbine, the results of this thesis clearly demonstrate the potential of the TAS concept to unlock vast new areas for tidal energy development.

This work is focused on oxide scale failure and characteristics created in high temperature – supercritical processes. The presence of high temperature corrosion in supercritical processes is minimalised by selection of the right material. For this work was selected material X10CrMoVNb9-1, where formulas of present oxidation scales are Fe2O3, Fe3O4 and FeCr2O4. Each oxidation scale has its own mechanical properties thus it is important to notice scale arrangement, thickness and geometry. Oxide scale mechanical properties, scale failure mechanisms and oxidation scale growth is evaluated in this work. Tension and pressure oxide scale failure are determined by critical values, which are mentioned in this work. Thanks to these values there was possibility to verify the authenticity of the finite element model. Oxidation scales created in heat exchangers are badly accessible thus it is difficult to observe them or remove them mechanically. Tube finite element model with oxidation scales was created in this work. There are simulations of scales on selected steel in supercritical conditions (pressure 24 MPa, temperature 500 °C). Simulation and analytic results are compared. Failure operative conditions are searched for scale FeCr2O4 until its compleate delamination and separation from metal. Aim of this work is to create an oxidation scale model with a possibility of futher use.

Wind propulsion is a traditional way to propel ships over the oceans. In the recent development towards more sustainable shipping, sailing is considered in the industry again with high momentum. For a modern merchant ship, the aerodynamic forces generated on the particular rigging are unusual. Tailored research and experiments are required to understand their influence on the ship’s sailing behaviour. This work concerns the aerodynamic interactions on a model-sized car carrier with four 360° rotatable, symmetric, rigid wings aligned along the centreline on deck. Differential pressures on the wings are measured to capture the generated normal forces. In a comprehensive post-processing, data recorded in systematic experiments at two apparent wind angles were evaluated. A comparison for the different wing positions on board the model shows stronger interactions in upwind sailing conditions than when reaching. The two-dimensional data prove a significant influence of the hull in the normal force profiles over the wing span. The results of this work indicate that the aerodynamic conditions while sailing have to be attentively considered for efficient wing trimming. / Under en lång tid användes främst vindkraft för framdrivningen av fartyg. Det är först på senare år att seglingskonceptet har fått ett nytt uppsving inom marinindustrin med tanke på dess hållbarhet. För fraktfartyg är de aerodynamiska krafterna vid segling ovanliga. Därför behövs särskild forskning och experimentella metoder för att förstå hur de påverkar fartygens seglingsbeteende. I detta arbete undersöks aerodynamiska interaktioner på en modell av ett biltransportfartyg med fyra symmetriska, 360° roterbara vingsegel på däck längs midskeppslinjen. I systematiska experiment på två kurser mot vinden mättes differenstryck över vingprofilen för att undersöka de genererade normalkrafterna. En jämförelse av data från de fyra olika vingpositionerna och båda kurserna mot vinden visar att de aerodynamiska interaktionerna är starkare på kryss än vid halvvind. De upmätta profilerna av tvådimensionella normalkraftkoefficienter över vingspannet visar på betydande aerodynamiska interaktioner med fartygets skrov. Resultaten av detta arbete visar hur viktigt det är med en grundlig undersökning av strömningsförhållandena för en effektiv segeltrim.

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Borehole heat exchangers are widely used in heat pumps of residential buildings and industrialsystems. It is known as one of the most energy ecient technologies which provides heatingand cooling by using sustainable geothermal energy. The life time of borehole heat exchangerslasts more than 50 years which is longer than combustion boilers. Therefore, designing abore eld with accurate sizing is important for its future applications. Due to the large volumeof the ground, the transient heat transfer process of the bore eld lasts for a long time span. Because of this, only a few of the heat transfer models for borehole ground heat exchangersare validated by experiments. Besides, experimental validation in a real scale borehole can bedicult because of the uncertainty of the composition and thermal properties of the ground. A solution to faster experimental validation is to scale down the size of the borehole andground. This report presents the construction process of a lab-scale model simulating a 4x4 bore eldof 300 m depth vertical boreholes. The process of experimental construction is describedin detail, including ground set up, conductivity test, construction of hydraulic system anddata acquisition system. The pressure drop of hydraulics system is around 2.8 bar under the a flow rate of 200 ml/min and corresponding pump speed is around 2900 to 3100 rpm. The property of the sand has been investigated through a series of conductivity tests, which shows an average thermal conductivity of 1.75 W / (m • K) and average thermal diffusivity of 8.14x10-7 m2/s. Numerical simulation (via COMSOL) is carried out for preliminary validation. Comparison of experimental and simulation results shows discrepancies and one possible reason can be: the actual heat injection rate in experiment is lower than simulation due to heat losses of hydraulic system; uncertainty of ground (saturated sand) conductivity and thermal diffusivity. / Borrhålsvärmeväxlare används ofta i värmepumpar i bostadshus och industrisystem. Det är känt som en av de mest energieffektiva teknikerna som tillhandahåller värme och kyla genom att använda hållbar geotermisk energi. Livslängden för borrhålsvärmeväxlare varar mer än 50 år vilket är längre än förbränningspannor. Därför är det viktigt att utforma ett borrfalt med exakt dimensionering för dess framtida tillämpningar. På grund av den stora markvolymen varar den transienta värmeöverforingsprocessen i borrfältet under lång tid. På grund av detta är endast ett fåtal av värmeöverföringsmodellerna för borrhålsjordvärmeväxlare validerade genom experiment. Dessutom kan experimentell validering i ett borrhål i verklig skala vara svårt på grund av osäkerheten i markens sammansättning och termiska egenskaper. En lösning för snabbare experimentell validering är att skala ner storleken på borrhålet och marken. Denna rapport presenterar konstruktionsprocessen av en modell i labbskala som simulerar ett 4x4-borrfält med 300 m djupa vertikala borrhål. Processen for experimentell konstruktion beskrivs i detalj, inklusive markuppställning, konduktivitetstest, konstruktion av hydraulsystem och datainsamlingssystem. Tryckfallet for hydrauliksystemet är cirka 2,8 bar under en flödeshastighet pa 200 ml/min och motsvarande pumphastighet är runt 2900 till 3100 rpm. Sandens egenskaper har undersökts genom en serie konduktivitetstester, som visar en genomsnittlig värmeledningsformåga pa 1,75 W/(m • K) och en genomsnittlig termisk dffusivitet på 8.14x10 -7 m2/s.  Numerisk simulering (via COMSOL) utförs för preliminär validering. Jämförelse av experimentella och simuleringsresultat visar avvikelser och en möjlig orsak kan vara: den faktiska värmeinsprutningshastigheten i experimentet är lägre än simulering på grund av värmeförluster i hydraulsystemet; osäkerhet i markens (mättad sand) konduktivitet och termisk diffusivitet.

Reduced-order models are frequently used in the simulation of complex flows to overcome the high computational cost of direct numerical simulations, especially for three-dimensional nonlinear problems. Proper orthogonal decomposition, as one of the most commonly used tools to generate reduced-order models, has been utilized in many engineering and scientific applications. Its original promise of computationally efficient, yet accurate approximation of coherent structures in high Reynolds number turbulent flows, however, still remains to be fulfilled. To balance the low computational cost required by reduced-order modeling and the complexity of the targeted flows, appropriate closure modeling strategies need to be employed. In this dissertation, we put forth two new closure models for the proper orthogonal decomposition reduced-order modeling of structurally dominated turbulent flows: the dynamic subgrid-scale model and the variational multiscale model. These models, which are considered state-of-the-art in large eddy simulation, are carefully derived and numerically investigated. Since modern closure models for turbulent flows generally have non-polynomial nonlinearities, their efficient numerical discretization within a proper orthogonal decomposition framework is challenging. This dissertation proposes a two-level method for an efficient and accurate numerical discretization of general nonlinear proper orthogonal decomposition closure models. This method computes the nonlinear terms of the reduced-order model on a coarse mesh. Compared with a brute force computational approach in which the nonlinear terms are evaluated on the fine mesh at each time step, the two-level method attains the same level of accuracy while dramatically reducing the computational cost. We numerically illustrate these improvements in the two-level method by using it in three settings: the one-dimensional Burgers equation with a small diffusion parameter, a two-dimensional flow past a cylinder at Reynolds number Re = 200, and a three-dimensional flow past a cylinder at Reynolds number Re = 1000. With the help of the two-level algorithm, the new nonlinear proper orthogonal decomposition closure models (i.e., the dynamic subgrid-scale model and the variational multiscale model), together with the mixing length and the Smagorinsky closure models, are tested in the numerical simulation of a three-dimensional turbulent flow past a cylinder at Re = 1000. Five criteria are used to judge the performance of the proper orthogonal decomposition reduced-order models: the kinetic energy spectrum, the mean velocity, the Reynolds stresses, the root mean square values of the velocity fluctuations, and the time evolution of the proper orthogonal decomposition basis coefficients. All the numerical results are benchmarked against a direct numerical simulation. Based on these numerical results, we conclude that the dynamic subgrid-scale and the variational multiscale models are the most accurate. We present a rigorous numerical analysis for the discretization of the new models. As a first step, we derive an error estimate for the time discretization of the Smagorinsky proper orthogonal decomposition reduced-order model for the Burgers equation with a small diffusion parameter. The theoretical analysis is numerically verified by two tests on problems displaying shock-like phenomena. We then present a thorough numerical analysis for the finite element discretization of the variational multiscale proper orthogonal decomposition reduced-order model for convection-dominated convection-diffusion-reaction equations. Numerical tests show the increased numerical accuracy over the standard reduced-order model and illustrate the theoretical convergence rates. We also discuss the use of the new reduced-order models in realistic applications such as airflow simulation in energy efficient building design and control problems as well as numerical simulation of large-scale ocean motions in climate modeling. Several research directions that we plan to pursue in the future are outlined. / Ph. D.

Esta dissertação de mestrado tem como objetivo fundamental a apresentação de análises e comparações, que visam fazer parte do processo de aprimoramento constante do método numérico de simulação de unidades flutuantes produtoras de petróleo, chamado TPN Tanque de Provas Numérico. Para tanto, foram executados ensaios com modelo em escala reduzida, cujos resultados foram comparados com o modelo numérico do TPN. A unidade padrão utilizada nos ensaios foi a plataforma semi-submersível ITTC-SR192, escala 1:105, ensaios estes realizados no tanque de provas do IPT Instituto de Pesquisas Tecnológicas do Estado de São Paulo. Por meio de comparação com os resultados dos ensaios, foram verificadas as habilidades do TPN em reproduzir os movimentos do casco, a tração no topo das linhas de produção e o amortecimento induzido pelas mesmas. Importante destacar que os parâmetros verificados tiveram a finalidade adicional de confrontar os resultados numérico-experimentais com foco na investigação da influência das linhas de produção na própria dinâmica do sistema flutuante. Tendo em vista esse objetivo complementar, todos os ensaios foram realizados com e sem a presença de linhas de produção, no texto referenciadas apenas por risers, modeladas como um grupo de estruturas bastante flexíveis e de grande diâmetro, a fim de prover um aumento significativo no amortecimento do sistema. Sendo assim, o comportamento dinâmico dos casos com e sem risers foram comparados buscando observar as diferenças nos movimentos do sistema em ondas e correnteza. Além disso, utilizando o método recomendado pela API, referência [3] , doravante denominado apenas por método Near and Far, a tração de topo de um dos risers foi simulada numericamente com a imposição de movimentos obtidos nos experimentos, dando assim meios para comparação dos critérios de projeto, considerando a influência das linhas conectadas nas plataformas de petróleo. / This research aims to present analysis and comparisons, intended to make part of the constant improvement of the oil platform analysis software, called Numerical Offshore Tank (Tanque de Provas Numérico - TPN). For this purpose, small-scale model tests were performed, and the results compared with the numerical model in TPN. The standard unit used in these model tests was the semisubmersible ITTC-SR192, at scale 1:105, and the tests were performed at IPT (State of São Paulo Institute for Technological Research) towing tank. By means of the model tests results comparisons, the ability of the TPN in reproduce the hull motions, the risers top tensions and damping induced by these lines was evaluated. Importantly, these parameters were verified with the further purpose of comparing the numerical and the experimental results, focusing on the influence of the production lines in the dynamics of the floating system. Taking into account this additional objective, all the model tests were performed with and without production lines, i.e. risers, modeled as a group of highly flexible and large diameter structures, in order to provide a significant increment in the damping of the system. Thus, the dynamic behaviors of the cases with and without risers were compared, giving means to observe motion differences in waves and current. Moreover, using the method recommend by API, reference [3], hereinafter called Near and Far, the top tension of one riser was numerically simulated with the imposition of the motions obtained in the experiments, giving means to compare the riser design criteria, considering the influence of lines attached to the oil platforms.

O estudo do fenômeno de vibrações induzidas pela emissão de vórtices, ou VIV, em risers é um tópico de grande relevância para a engenharia oceânica. Nos últimos anos, diversos resultados vêm sendo apresentados, numéricos e/ou experimentais, buscando o entendimento dos fundamentos deste fenômeno de interação fluido-estrutural, no entanto, sem um entendimento conclusivo e abrangente. Neste contexto, risers também estão sujeitos à ação de correntezas oceânicas e, consequentemente, ao fenômeno de VIV. Neste sentido, o presente estudo traz resultados de uma abordagem experimental para o entendimento do fenômeno de VIV em risers lançados em catenária, configuração que representa grande parte das geometrias adotadas em lançamentos atuais. No entanto, a realização de experimentos com risers em tanque de provas pressupõe a utilização de modelos reduzidos, o que, por si só, representa um grande desafio de pesquisa. Para tanto, desenvolveu-se uma metodologia para a modelagem de risers em escala reduzida, com foco na similaridade entre parâmetros importantes que garantam um comportamento dinâmico equivalente àquele em escala real. Foram, então, realizados experimentos de VIV com catenárias concebidas e construídas com base nesta metodologia, posteriormente ensaiadas em tanque de reboque. Para análise dos resultados, foram utilizadas técnicas como a decomposição modal, que possibilitou a comparação desses com alguns resultados da literatura, mostrando que o fenômeno de VIV na catenária se processa de maneira bastante semelhante ao identificado nos cilindros flexíveis. Além disso, a extensa base de dados experimentais apresentada e discutida nesta tese contribui para futura validação de diversos modelos matemáticos e códigos numéricos de predição do VIV em catenárias, descrevendo com detalhes inúmeros comportamentos imersos neste problema importante de engenharia. / The study of Vortex-induced vibrations in risers is a topic of great relevance in the context of ocean engineering. In recent years, several numerical and experimental results have been presented, addressing the understanding of the fundamentals of this fluid-structure interaction phenomenon, however without a conclusive and comprehensive understanding. In this context, risers are exposed to the action of ocean currents and consequently to the phenomenon of VIV. In this sense, the present study provides results of an experimental approach to understanding the VIV phenomenon on risers launched in catenary configuration, which represents much of the geometries adopted today. However, performing risers experiments in towing-tanks presupposes the use of small-scale models, which represents a major research challenge. Therefore, a methodology for modeling reduced scale risers was developed. The focus of this methodology was on the similarity between certain important parameters that guarantee an equivalent full-scale dynamic behavior. VIV experiments were then performed in the towing tank, with the designed and constructed catenary, based on this methodology. Techniques such as modal decomposition were used for the analysis of the results. This allows the comparison of the results with classical literature paradigms showing that VIV response in the catenary is close to results obtained with flexible cylinders. Furthermore, the large experimental database presented and discussed in the study may contribute to future validation of several mathematical models and numerical codes of VIV prediction in catenary risers, describing in detail several immersed behaviors in this important engineering problem.

Ce travail de thèse s'inscrit dans la thématique de la pollution particulaire de l'air intérieur et concerne plus particulièrement les phénomènes de remise en suspension liés à l'impact, au niveau du sol, des pas d'une personne qui marche sur un plancher chargé en particules. La première partie présente un état de l'art des connaissances de la pollution particulaire. Les différents paramètres expérimentaux qui influencent la remise en suspension des particules ainsi que les coefficients utilisés pour la quantification du phénomène sont recensés. Les différentes perturbations mécaniques et aérodynamiques générées lors de l'impact d'un pied avec le sol pendant la marche d'une personne sont présentées et comparées. Nous terminons la première partie par une présentation des différents modèles de remise en suspension des particules émanant d'une surface. La seconde partie est consacrée à la présentation de la maquette qui a été mise au point au laboratoire LaSIE à La Rochelle afin d'étudier le dépôt et la remise en suspension des particules par un simulateur mécanique du pas humain depuis un sol chargé en particules. Cette étude a permis de classer les différents types de surfaces utilisées dans le bâtiment en fonction de leurs émissions en particules après l'impact mécanique d'un solide. La troisième partie du travail consiste à mesurer les vitesses de l'écoulement de l'air généré par un simulateur mécanique automatisé du pas humain en différents emplacements. Les mesures de la vitesse ont été effectuées par trois types de méthodes largement utilisées dans le domaine de la mécanique des fluides : deux méthodes de Vélocimétrie Laser (Vélocimétrie par Image des particules et Vélocimétrie Laser Doppler), mais également une méthode d’Anémométrie à Fil Chaud. Ces mesures nous ont permis de trouver la zone de forte vitesse qui correspond à la zone où nous avons une remise en suspension importante. Nous avons également étudié l'influence de l'état de la surface sur les vitesses de l'écoulement générées à proximité du sol suite au mouvement du simulateur mécanique. Ces mesures ont mis en évidence que l'influence de la rugosité de la surface sur la vitesse de l'écoulement généré par le pas est marginale. Finalement, nous avons étudié analytiquement le détachement des particules en utilisant un modèle basé sur le bilan des moments de forces. Des perspectives à la fois sur l'amélioration des deux maquettes mises en place au LaSIE et à l'ERM, ainsi que le développement d'un code numérique pour simuler le pas humain sont présentées et argumentées en conclusion. / This thesis work is part of indoor air particle pollution theme and more particularly the phenomenon of walking-induced particle resuspension. The first part presents a state of the art knowledge of particulate pollution. The different experimental parameters that influence the particles resuspension, as well as the coefficients used for the phenomenon quantification, are identified. The various mechanical and aerodynamic disturbances generated during person walking are presented and compared. We end the first part with a presentation of the different particles resuspension models. The second part is dedicated to present the experiment made on a small scale model developed at the LaSIE laboratory in La Rochelle to study particles deposition and resuspension by amechanical simulator of the human step from a particle-laden soil. This study classified the different types of surfaces used in the building according to their particulate emissions after the mechanical simulator impact. The third part of the work consists of measuring the airflow velocities generated by an automated mechanical simulator of the human footstep at different locations. The velocity measurements have been done in the Royal Military Academy at Brussels (RMA) by three types of methods widely used in the field of fluid mechanics : two methods of Laser Velocimetry (Particle Image Velocimetry and Laser Doppler Velocimetry), but also a method of Wire Anemometry. These measurements allowed us to find the high-speed zone that corresponds to the area where we have a significant resuspension. We also studied the influence the surface roughness on the flow velocities generated near the ground following the movement of the mechanical simulator. We have shown that the influence of the surface roughness on the speed of the flow generated by the pitch is marginal. Finally, we analytically studied the detachment of particles using a model based on the momentum balance. Perspectives on both the improvement of the two models set up in LaSIE and the RMA, as well as the development of a numerical code to simulate the human step, are presented and argued in conclusion.

Noise has become a main nuisance in urban areas to the point that according to the World Health Organization 40% of the European population is exposed to excessive noise levels, mainly due to ground transportation. There is therefore a need to find new ways to mitigate noise in urban areas. In this work, a possible device to achieve this goal is studied: a low-height noise barrier. It consists of a barrier typically less than one meter high placed close to a source, designed to decrease the noise level for nearby pedestrians and cyclists. This type of device is studied both numerically and experimentally. Tramway noise barriers are especially studied since the noise sources are in this case very close to the ground and can therefore be attenuated efficiently. The shape and the surface treatment of the barrier are optimized using a gradient-based method coupled to a 2D boundary element method (BEM). The optimization variables are the node coordinates of a control mesh and the parameters describing the surface impedance. Sensitivities are calculated efficiently using the adjoint state approach. Numerical results show that the shapes generated by the optimization algorithm tend to be quite irregular but provide a significant improvement of more than 5 dB(A) compared to simpler shapes. Utilizing an absorbing treatment on the source side of the barrier is shown to be efficient as well. This second point has been con firmed by scale model measurements. In addition, a full scale low height noise barrier prototype has been built and tested in situ close to a tramway track in Grenoble. Measurements show that the device provides more than 10 dB(A) of attenuation for a close receiver located at the typical height of human ears. These results therefore seem to con rm the applicability of such protections to efficiently decrease noise exposure in urban areas.