La végétation arborée sur les digues ou les barrages en remblai est un facteur de fragilité pouvant favoriser l'apparition de mécanismes de détérioration par érosion. Définir la structure géométrique des systèmes racinaires ainsi que la nature des sols dans lesquels ils croissent, à partir de méthodes géophysiques non destructives, est nécessaire afin d'appréhender les conséquences de leur développement sur la sécurité d'un ouvrage hydraulique. Des expériences en laboratoire ont d'abord permis de déterminer les propriétés acoustiques et électriques intrinsèques d'échantillons racinaires menant à l'identification de signatures indispensables à la discrimination de l'anomalie liée à la racine sur le terrain. Le montage de supports expérimentaux adaptés nous a conduits à progressivement étudier des paramètres d'influences en conditions contrôlées. Des essais en conditions semi-contrôlées sur un dispositif d'arbres plantés dans un sol homogène ont permis d'évaluer la pertinence des différentes méthodologies d'acquisition, tels que l'utilisation de la polarisation provoquée en tomographie de résistivité complexe ou encore la géométrie des capteurs pour la tomographie acoustique. Des traitements innovants tels que l'analyse en ondelettes sont associés afin d'exploiter la richesse des enregistrements. Les résultats obtenus ont été validés par le relevé des positions réelles des racines. Enfin, des campagnes d'auscultation sur un ouvrage réel ont été réalisées et ont permis de mettre en évidence une variabilité spatiale du corps de digue associée à la présence d'arbres. Une méthodologie adaptée au diagnostic géophysique de la végétation sur les ouvrages a été mise en place. / Woody vegetation from earth dikes or dams is a fragility factor which can promote mechanisms of degradation such as erosion. An accurate assessment of root system structure, from geophysical non-destructive methods, of root position into the embankment (depth, extension), and a good knowledge of soil conditions are critical in order to anticipate the consequences of vegetation development for the hydraulic structure’s safety. Laboratory experiments allowed determining intrinsic acoustical and electrical root properties leading to identify relevant signatures and discriminate anomalies related to roots in the field. The establishment of adapted experimental devices led us progressively to assess different parameters (roots mass, water content. . . ) under controlled conditions. Experiments in semi-controlled conditions with trees planted into a homogenous soil, were conducted to assess the relevance of different methodologies, such as the use of temporal induced polarization in complex resistivity tomography or the geometry of sensors for acoustical tomography. Innovative data processing such as wavelet analysis were used to valorize the rich database. The results were validated by the determination of actual root position.Finally, field investigations into an embankment have been performed to highlight a spatial variability of dike structures associated with trees presence. A methodology adapted to the geophysical diagnostic of vegetation roots in embankments was developed.

The durability of concrete is of major concern in all types of concrete structures where the combined effect of exposure conditions and the type and quality of the concrete material usually determines the rate of degradation. Furthermore, there are synergy effects between different deterioration mechanisms, which means that the combined rate of degradation is higher than the sum of the individual rates of each mechanism. Therefore, to accurately predict the residual service life of existing structures or when designing new structures, it is essential to consider all these aspects. This means that various chemical and physical processes, as well as how these interact, must be taken into account in models aiming to be used for service life predictions. This thesis presents the first part of a research project with the aim to investigate common deterioration mechanisms of concrete in hydraulic structures, and to improve the knowledge how these and other related phenomena can be described using mathematical models. The objective is also to study how different mechanisms interact and to find suitable approaches to account for these interactions in the models. To this end, a literature survey on commonly detected damage in hydraulic structures is presented. In addition, it also addresses in what types of and where in hydraulic structures the various damage types are usually observed. The mathematical models presented in this part of the project are focused on long-term water absorption in air-entrained concrete as well as on freezing of partially saturated air-entrained concrete. Both models are based on a multiphase description of concrete and poromechanics to describe the coupled hygro-thermo-mechanical behaviour. The thesis also presents some of the basic concepts of multiphase modelling of porous media, including discretization of the models using the finite element method (FEM). Furthermore, it covers the simplifications that are usually introduced in the general macroscopic balance equations for mass, energy and linear momentum when modelling cement-based materials. To verify the developed models and to show their capabilities, simulation results are compared with experimental data, in situ measurements and other simulations from the literature. The results indicate that both models perform well and can be used to predict long-term moisture conditions in hydraulic structures as well as freezing-induced strains in partially saturated air-entrained concrete, respectively. Even though no interactions with other deterioration mechanisms are included in the models, the development and use of these have given insights to which parameters that are important to consider in such extensions. Furthermore, based on the insights gained, the complexity of describing the full interactions between several mechanisms in mathematical models is also discussed. It is concluded that models aiming to be used for service life predictions of hydraulic structures in day-to-day engineering work need to be simplified. However, the type of advanced models presented in this thesis can serve as a basis to study which aspects and parameters that are essential to consider in simplified prediction models. / Beständigheten hos betong är av avgörande betydelse i alla typer av betongkonstruktioner där den kombinerade effekten av exponeringsförhållanden samt typ och kvalitet på betongmaterialet vanligtvis avgör nedbrytningshastigheten. Dessutom finns synergieffekter mellan olika nedbrytningsmekanismer som innebär att den kombinerade nedbrytningshastigheten är större än summan av de enskilda nedbrytningshastigheterna. För att noggrant kunna prediktera den återstående livislängden hos befintliga konstruktioner eller vid design av nya konstruktioner är det därför viktigt att ta hänsyn till samtliga av dessa aspekter. Detta innebär att olika kemiska och fysikaliska processer, samt hur dessa interagerar med varandra, måste tas i beaktande i modeller som avses användas för livslängdsbedömningar. Den här licentiatuppsatsen presenterar den första delen av ett forskningsprojekt där målet är att studera vanligt förekommande nedbrytningsmekanismer i vattenbyggnadskonstruktioner och att öka kunskapen om hur dessa och andra relaterade fenomen kan beskrivas med matematiska modeller. Målet är också att studera hur olika nedbrytningsmekanismer samverkar och att hitta lämpliga tillvägagångssätt att ta hänsyn till dessa interaktioner i modellerna. För detta ändamål presenteras en litteraturstudie avseende vanligt förekommande skador i vattenbyggnadskonstruktioner. Dessutom behandlar denna i vilka typer av vattenbyggnadskonstruktioner och var i dessa som de olika typerna av skador vanligtvis observeras. De matematiska modeller som presenteras i denna del av projektet är inriktade på långtidsabsorption av vatten i lufttillsatt betong samt på frysning i delvis vattenmättad lufttillsatt betong. Båda modellerna är baserade på en multifasbeskrivning av betong samt poromekanik för att beskriva det kopplade hydro-termo-mekaniska beteendet. Uppsatsen presenterar också några av de grundläggande koncepten gällande multifasmodellering av porösa material, inklusive diskretisering av modellerna genom användning av finita elementmetoden (FEM). Dessutom beskrivs de förenklingar som vanligtvis införs i de generella makroskopiska balansekvationerna för massa, energi och rörelsemängd då cementbaserade material modelleras. Simuleringsresultat från de utvecklade modellerna jämförs med försöksdata, fältmätningar samt andra simuleringsresultat från litteraturen för att verifiera modellerna samt visa hur de beter sig. Resultaten visar att båda modellerna ger tillfredställande resultat och kan användas för att uppskatta de långsiktiga fuktförhållandena i vattenbyggnadskonstruktioner samt frysinducerade töjningar i delvis vattenmättad lufttillsatt betong. Även om inga interaktioner mellan andra nedbrytningsmekanismer inkluderades i modellerna, så har utvecklingen samt användandet av dessa gett insikter gällande vilka parametrar som är viktiga att beakta i sådana vidareutvecklingar. Baserat på dessa insikter diskuteras också komplexiteten i att beskriva interaktionen mellan flertalet mekanismer i matematiska modeller. Det konstateras också att modeller som avses användas i dagligt ingenjörsarbete för livstidsbedömningar av vattenbyggnadskonstruktioner behöver förenklas. Däremot kan den typ av avancerade modeller som presenteras i denna uppsats användas som en grund för att studera vilka aspekter och parametrar som är viktiga att beakta i förenklade modeller. / <p>QC 20180403</p>

Dams in many countries are approaching their expected service life. Proper assessment of the aging dams structural health increase the knowledge of the current safety, and allow for better planning of renovation and rebuilding investments. The behavior of concrete dams is, to a great extent, governed by the ambient variation in temperature and water level. In cold regions, the ice sheet formed in the reservoir may subject a pressure load on the dams. Theoretically, this load has a significant impact on the structural behavior of dams. Despite this, the maximum magnitude, as well as the seasonal variation of the ice load, constitute the most considerable uncertainty in the safety assessment of dams. This thesis presents research that examines how to model the expected behavior of dams in cold climate. The underlying problem is to predict the response of dams due to variation in the external conditions. Since the ice load is such a vital part of the external conditions in cold climate, the understanding and modeling of ice loads have been given extra attention. Models suitable to predict the long-term behavior of dams can be divided between theoretical, data-based, and hybrid. Prediction accuracy is essential to set alert thresholds, and in that regard, the data-based models are generally superior. The major contribution of this thesis is the design and installation of a prototype ice load panel with direct measurement of the ice pressure acting on a dam. The panel is attached on the upstream face of the dam and is large enough so that the whole thickness of the ice sheet is in contact with the panel. The predicted ice load from the best available model that includes loads from both thermal events and water level changes did not correspond to the measured ice loads. As there are no validated models or measurement methods for ice load on the dam, continued research is necessary, both through further measurements to increase knowledge and development of models. / I många länder närmar sig vattenkraftsdammarna deras förväntade tekniska livslängd. Korrekt utvärdering av dammens strukturella status ökar kunskapen om det nuvarande säkerhetsläget och möjliggör för bättre planering av renoveringar och ombyggnadsinvesteringar. Betongdammarnas beteende styrs till stor del av variationen i omgivande temperaturer och vattennivå. I kalla regioner kan is som bildas i magasinet utsätta dammen för en tryckande last. Teoretiskt har denna belastning en betydande inverkan på dammarsstrukturella beteende. Trots detta är den maximala storleken såväl som säsongsvariationen för islasten en av de mest betydande osäkerheterna vidsäkerhetsbedömningen av dammar. Denna uppsats presenterar forskning som undersöker hur förväntat beteendehos dammar i kallt klimat kan modelleras. Den underliggande frågeställningen är att förutsäga en damms respons orsakad av variation i de yttre förhållandena. Extra fokus har lagts på förståelsen och modelleringen av islasten då den är en viktig del av de yttre förhållandena för dammar i kalla klimat. Modeller som är lämpliga för att förutsäga dammars beteende kan delas upp i teoretiska, databaserad, och hybridmodeller. Förutsägbarhetsnoggrannhet är avgörande för att ställa in varningsnivåer, och i det avseendet är de databaserade modellerna i allmänhet överlägsna. Det huvudsakliga bidraget från detta projekt är utvecklandet och installationen av en prototyp av en islast panel, fäst på en damms uppströmssida. Panelen mäter istrycket direkt mot dammen och är tillräckligt stor så att helaisens tjocklek förblir i kontakt med panelen. Panelen bidrar till ökad kunskap om säsongsvariationen i istryck och mekanismen för islaster orsakad av variation i vattennivån. Den predikterade islaten från den bästa tillgängliga islastmodellen som inkluderar termiska islaster och islaster från vattennivåförändringar överensstämmer inte med de uppmätta islastpanelen som uppmätts med panelen. Då det saknas validerade modeller eller mätmetoder för islast är det viktigt med fortsatt forskning, dels genom ytterligare mätningar för att öka kunskapen men även fortsatt modellutveckling. / <p>QC 20190926</p>

Since 1971, a number of flood frequency models have been developed for river basins in Malawi for use in the design of hydraulic structures, but the varied nature of their results have most often given a dilemma to the design engineer due to differences in magnitudes of calculated floods for given return periods. All the known methods for flood frequency analysis developed in country so far have not used a homogeneity test for the river basins from which the hydrological data has been obtained. This study was thus conducted with a view to resolving this problem and hence improve the design of hydraulic structures such as culverts, bridges, water intake points for irrigation schemes, and flood protection dykes. In light of the above, during the course of this study the applicability of existing methods in the design of hydraulic structures was assessed. Also, the study investigated how land use and land cover change influence the frequency and magnitude of floods in the study area, and how their deleterious impacts on the socio-economic and natural environment in the river basins could be mitigated / Environmental Sciences / M. Sc. (Environmental Management)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O emprego de materiais compósitos de matriz polimérica como reparo e reforço em estruturas nas indústrias do petróleo tem se tornado uma prática industrial comum. O uso destes reforços compreende desde o recobrimento de superfícies com defeitos, passantes ou não, até o reforço estrutural. Na última década, muitos estudos foram feitos para o desenvolvimento de uma metodologia alternativa para reforço e reparo de dutos com materiais compósitos. Recentemente, em 2006, o sistema ISO de normas técnicas apresentou a primeira especificação técnica de "Reparo em Compósitos para dutos das indústrias de Petróleo, Petroquímica e de Gás Natural Qualificação, projeto, instalação, testes e inspeção" ISO/PDTS 24817. O presente trabalho tem como objetivo o desenvolvimento de um sistema de reparo, utilizando materiais compósitos de matriz polimérica para o reparo e reforço estrutural de dutos e tubulações industriais, em conformidade com a Norma ISO 24817:2006. Foram desenvolvidos procedimentos para a confecção de corpos de prova destinados a ensaios mecânicos, e para aplicação do sistema de reparo. O sistema de reparo é destinado a defeitos tais como perda de espessura, amassamentos e danos transpassantes. Foi construída, em paralelo, toda a infraestrutura para a montagem de um laboratório destinado ao estudo de materiais compósitos, no Laboratório de Adesão e Aderência. São apresentados resultados de parte dos ensaios mecânicos necessários, comparação dos resultados obtidos com modelos teóricos e testes hidrostáticos. / The use of polymer matrix composites to repair and strengthen structures in the oil industry has become a common industry practice. The use of these reinforcements extends from covering surfaces with defects, through wall or not, to structural reinforcement. In the last decade, many studies have been done to develop an alternative approach to the strengthening and repairing of pipelines with composite materials. Recently, in 2006, the ISO system of technical standards presented the document technical support "Petroleum, petrochemical and natural gas industries Composite repairs for pipework Qualification, design, installation, testing and inspection" ISO/PDTS 24817. This study aims to develop a repair system using polymer matrix composite materials for repair and reinforcement of piping and pipelines in accordance with ISO 24817:2006. Procedures where developed for the confection of test specimens for mechanical testing, and application of the repair. The system is intended to repair defects such as thickness loss, gouges, and damage through wall or not. In parallel, an entire infrastructure was built for the conception of a laboratory for the study of composite materials at the Laboratory of Adhesion and Adherence. Here are presented the results of the required mechanical tests, the comparison results with theoretical models, and the hydrostatic testing.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O emprego de materiais compósitos de matriz polimérica como reparo e reforço em estruturas nas indústrias do petróleo tem se tornado uma prática industrial comum. O uso destes reforços compreende desde o recobrimento de superfícies com defeitos, passantes ou não, até o reforço estrutural. Na última década, muitos estudos foram feitos para o desenvolvimento de uma metodologia alternativa para reforço e reparo de dutos com materiais compósitos. Recentemente, em 2006, o sistema ISO de normas técnicas apresentou a primeira especificação técnica de "Reparo em Compósitos para dutos das indústrias de Petróleo, Petroquímica e de Gás Natural Qualificação, projeto, instalação, testes e inspeção" ISO/PDTS 24817. O presente trabalho tem como objetivo o desenvolvimento de um sistema de reparo, utilizando materiais compósitos de matriz polimérica para o reparo e reforço estrutural de dutos e tubulações industriais, em conformidade com a Norma ISO 24817:2006. Foram desenvolvidos procedimentos para a confecção de corpos de prova destinados a ensaios mecânicos, e para aplicação do sistema de reparo. O sistema de reparo é destinado a defeitos tais como perda de espessura, amassamentos e danos transpassantes. Foi construída, em paralelo, toda a infraestrutura para a montagem de um laboratório destinado ao estudo de materiais compósitos, no Laboratório de Adesão e Aderência. São apresentados resultados de parte dos ensaios mecânicos necessários, comparação dos resultados obtidos com modelos teóricos e testes hidrostáticos. / The use of polymer matrix composites to repair and strengthen structures in the oil industry has become a common industry practice. The use of these reinforcements extends from covering surfaces with defects, through wall or not, to structural reinforcement. In the last decade, many studies have been done to develop an alternative approach to the strengthening and repairing of pipelines with composite materials. Recently, in 2006, the ISO system of technical standards presented the document technical support "Petroleum, petrochemical and natural gas industries Composite repairs for pipework Qualification, design, installation, testing and inspection" ISO/PDTS 24817. This study aims to develop a repair system using polymer matrix composite materials for repair and reinforcement of piping and pipelines in accordance with ISO 24817:2006. Procedures where developed for the confection of test specimens for mechanical testing, and application of the repair. The system is intended to repair defects such as thickness loss, gouges, and damage through wall or not. In parallel, an entire infrastructure was built for the conception of a laboratory for the study of composite materials at the Laboratory of Adhesion and Adherence. Here are presented the results of the required mechanical tests, the comparison results with theoretical models, and the hydrostatic testing.

Dans le cadre de cette thèse, un ouvrage de type séparateur hydrodynamique est étudié pour répondre aux problématiques environnementales liées aux déversements de macro-déchets en mer. La première partie est destinée à l’analyse du fonctionnement hydraulique de l’ouvrage et son aptitude face au colmatage sur un pilote en laboratoire. Les données collectées vont ensuite permettre la validation d’une approche numérique capable de simuler l’écoulement. Cette technique est par la suite utilisée pour optimiser l’écoulement et la forme de la grille. Nous avons démontré, à partir de simulations numériques, l’intérêt d’une grille de type métal déployé pour obtenir des phénomènes d’agitations turbulentes et de gradient de pression important à l’amont de la grille. Ces phénomènes favoriseraient ainsi la dispersion des polluants et limiteraient les phénomènes de colmatage. La dernière partie de ce travail a été d’étudier le fonctionnement d’un ouvrage grandeur nature et d’observer son efficacité. / The installation of hydraulic structures to separate particles is a key element to improve the quality of water bodies. This PhD work focus on the study of a hydrodynamic separator used to capture large wastes before their discharge into the see. Tangential separation mechanism along a screen is used in this device. The first part of the work consists in studying the hydraulic behavior and the clogging effectiveness of the device with laboratory experiments. A CFD multiscale approach was developed in this work to optimize the shape of the screen in order to avoid clogging. This method, validated against experimental data, allows us to predict that expanded metal stripes are useful to develop turbulence and pressure gradients upstream the screen. This hydrodynamic phenomenon favor particles and pollutants ejection near the apertures. The last part of the work was to study the hydrodynamic behavior and the real efficiency with in situ experiments.

The object of this thesis is the evaluation of the restoration potential of small hydraulic structures for increasing water retention in river floodplain by using 2D HEC-RAS hydraulic model. A former millrace of the Rožnovská Bečva River was used for the design of restoration measures. The restoration proposal consists of partial modification of the current millrace and new close-to-nature watercourse in the agricultural floodplain. Restoration proposal also includes changes in land use, which consist of grassing and afforestation. The input data used for the hydraulic model are digital terrain model (5G) by ČÚZK, surface roughness parameter and mean hourly discharge data of 1997 (Q100) and 2007 (Q5) flood events provided by CHMI. The results of the hydraulic simulations point to the positive effect of proposed restoration measures especially in the change of flooded volumes (3x higher) and flooded areas (2x higher). The results indicate that restoration measures lead to the flooding from the newly designed watercourse that precedes the flooding from the Rožnovská Bečva River. This brings the possibility of more frequent occurrence of inundation events favourable for water retention in the river floodplain. Keywords: retention, floodplain, restoration, hydraulic structures, Rožnovská Bečva River,...

Tesis por compendio / The new legal regulations derived from climate change dictate that hydraulic structures must be designed to handle flood events associated with return periods up to 10,000 years. This obviously involves adapting the existing infrastructure to meet such requirements. In order to avoid risks in the restitution of the flow discharged to rivers, such as bank overflows or streambed erosion and scour processes, hydraulic design must be supported by reliable tools capable of reproducing the behavior of hydraulic structures. In the work presented herein, a fully three-dimensional CFD model to reproduce the behavior of different types of air-water flow in hydraulic structures is presented. The flow is assumed to be turbulent, isotropic and incompressible. Several RANS turbulence models are tested and structured rectangular meshes are employed to discretize the analyzed domain. The presence of two fluids is modeled using different VOF approaches and simulations are run using the PIMPLE algorithm. The model is implemented using the open-source platform OpenFOAM and its performance is compared to the commercial code FLOW-3D. The analysis is conducted separately on two different parts of hydraulic structures, namely: the spillway and the stilling basin. Additionally, a case of practical application, where the model reproduces the flow of a real-life case, is also presented in order to prove the suitability of the model to actual design cases. Mesh independence and model validation using experimental data are checked in the results of all the case studies. The sensitivity of the presented model to certain parameters is extensively discussed using different indicator variables. Among these parameters are turbulence closure, discretization scheme, surface tracking approach, CFD code or boundary conditions. Pros and contras of each of them are addressed. The analyzed turbulence models are the Standard k ¿ ¿, the Realizable k ¿ ¿, the RNG k ¿ ¿, and the SST k ¿ ¿. The discretization schemes under study are: a first-order upwind method, the second-order limited Van Leer method, and a second-order limited central difference method. The VOF approaches analyzed are the Partial VOF, as implemented in OpenFOAM, and the TruVOF, as implemented in FLOW-3D. In most cases, the Standard k ¿ ¿ model provides the most accurate estimations of water free surface profiles, although the rest of variables, with few exceptions, are better predicted by the RNG k ¿ ¿. The latter model generally requires slightly longer computation times. The SST k ¿ ¿ reproduces correctly the phenomena under study, although it generally turned out to be less accurate than its k ¿ ¿ counterparts. As regards the comparison among VOF approaches and codes, it is impossible to determine which one performs best. E.g. OpenFOAM, using the Partial VOF, managed to reproduce the in- ternal hydraulic jump structure and all derived variables better than FLOW-3D, using the TruVOF, although the latter seems to capture better the momentum transfer and so all derived variables. In the case of flow in stepped spillways, OpenFOAM captures better the velocity profiles, although FLOW-3D is more accurate when estimating the water free surface profile. It is worth remark- ing that not even their response to certain model parameters is comparable. E.g. FLOW-3D is significantly less sensitive to mesh refinement than OpenFOAM. Given the result accuracy achieved in all cases, the proposed model is fully applicable to more complex design cases, where stilling basins, stepped spillways and hydraulic structures in general must be investigated. / Las nuevas disposiciones legales derivadas del cambio climático dictaminan que las estructuras hidráulicas sean capaces de funcionar correctamente con eventos de inundación asociados a periodos de retorno de hasta 10,000 años. Esto, obviamente, implica adaptar la infraestructura existente para satisfacer dichos requerimientos. A fin de evitar riesgos en la restitución de los caudales vertidos al río, como desbordamientos o procesos erosivos y de socavación, el diseño hidráulico ha de sustentarse en herramientas fiables capaces de reproducir el comportamiento de las estructuras hidráulicas. En este trabajo, se presenta un modelo numérico CFD completamente tridimensional para reproducir el comportamiento de diferentes tipos de flujo aire-agua en estructuras hidráulicas. Se asume que el flujo es turbulento, isotrópico e incompresible. Diversos modelos de turbulencia RANS son contrastados y se emplean mallas estructuradas rectanuglares para discretizar el dominio analizado. La presencia de dos fluidos es modelada utilizando diferentes enfoques VOF y las simulaciones son ejecutadas empleando el algoritmo PIMPLE. El modelo es implementado mediante la plataforma de código abierto OpenFOAM y su respuesta es comparada con la del modelo comercial FLOW-3D. El análisis se lleva a cabo sobre dos partes diferentes de una estructura hidráulica, a saber, el aliviadero y el cuenco amortiguador, de forma separada. Además, un caso de aplicación práctica, donde el modelo reproduce el flujo en una estructura real, es presentado también a fin de probar la adecuación del modelo a casos de diseño aplicado. Se comprueban la independencia de la malla y la validación con datos experimentales de los resultados de todos los casos de estudio. La sensibilidad del modelo presentado a ciertos parámetros es analizada de forma exhaustiva empleando diferentes variables indicadoras. Los pros y contras de cada uno de éstos son planteados. Los modelos de turbulencia analizados son el Standard k-epsilon, el Realizable k-epsilon, el RNG k-epsilon y el SST k-omega. Los esquemas de discretización estudiados son: un método de primer orden upwind, uno de Van Leer de segundo orden y un esquema de segundo orden limitado de diferencias centradas. Los enfoques VOF analizados son el Partial VOF, implementado en OpenFOAM, y el TruVOF, implementado en FLOW-3D. En la mayoría de casos, el modelo k-epsilon aporta las estimaciones más precisas de perfiles de lámina libre de agua, pese a que el resto de variables, con alguna excepción, son mejor predichas por el RNG k-epsilon. Este modelo generalmente requiere mayores tiempos de cálculo. El k-omega reproduce correctamente los fenómenos bajo estudio, pese a que su precisión es generalmente más baja que la de los modelos k-epsilon. En lo que respecta a la comparación entre enfoques VOF y códigos, es imposible determinar cuál es el mejor. Por ejemplo, OpenFOAM, empleando el Partial VOF, logra reproducir la estructura interna del resalto hidráulico y todas las variables derivadas mejor que FLOW-3D, empleando el TruVOF, a pesar de que este último parece capturar mejor la transferencia de cantidad de movimiento y, por tanto, todas las variables derivadas. En el caso del flujo en aliviaderos escalonados, OpenFOAM captura mejor los perfiles de velocidad, pese a que FLOW-3D es más preciso en la estimación de los perfiles de lámina libre de agua. Conviene recalcar que ni tan sólo su respuesta a ciertos parámetros del modelo es comparable. Por ejemplo, FLOW-3D es significativamente menos sensible al refinado de malla que OpenFOAM. A la luz de la precisión de los resultados obtenidos en todos los casos, el modelo propuesto es completamente aplicable a casos de diseño más complejos, donde cuencos amortiguadores, aliviaderos escalonados y estructuras hidráulicas en general han de ser investigadas. / Les noves disposicions legals derivades del canvi climàtic dictaminen que cal que les estructures hidràuliques siguen capaces de funcionar correctament amb esdeveniments d'inundació associats a períodes de retorn de fins a 10,000 anys. Això, òbviament, implica adaptar la infraestrctura existent per satisfer aquests requeriments. A fi d'evitar riscs en la restitució dels cabals vessats al riu, com desbordaments o processos erosius i de socavació, el disseny hidràulic ha de recolzar-se en ferramentes fiables capaces de reproduir el comportament de les estructures hidràuliques. En aquest treball, es prsenta un model numèric CFD completament tridimensional per a reproduir el comportament de diferents tipus de flux aire-aigua en estructures hidràuliques. S'assumeix que el flux és turbulent, isotròpic i incompressible. Diferents models de turbulència RANS són contrastats i s'empren malles estructurades rectangulars per discretitzar el domini analitzat. La presència de dos fluids és modelada utilitzant diferents enfocaments VOF i les simulacions són executades emprant l'algorisme PIMPLE. El model és implementat mitjançant la plataforma de codi obert OpenFOAM i la seua resposta és comparada amb la del codi comercial FLOW-3D. L'anàlisi es du a terme sobre les diferents parts d'una estructura hidràulica, a saber, sobreeixidors esgraonats i vas esmorteïdor, de forma separada. A més, un cas d'aplicació pràctica, on el model reprodueix el flux a una estructura real, és presentat també a fi de provar l'adequació del model a casos de disseny aplicat. Es comproven la independència de la malla i la validació amb dades experimentals dels resultats de tots els casos d'estudi. La sensibilitat del model presentat a certs paràmetres és analitzada de forma exhaustiva emprant diferents variables indicadores. Els pros i contres de cadascun d'aquests són plantejats. Els models de turbulència analitzats són l'Standard k-epsilon, el Realizable k-epsilon, el RNG k-epsilon i l'SST k-omega. Els esquemes de discretització estudiats són: un mètode de primer ordre upwind, un de Van Leer de segon ordre i un esquema de segon ordre limitat de diferències centrades. Els enfocaments VOF analitzats són el Partial VOF, implementat en OpenFOAM, i el TruVOF, implementat en FLOW-3D. En la majoria de casos, el model Standard k-epsilon aporta les estimacions més precises de perfils de làmina lliure d'aigua, tot i que la resta de variables, amb alguna excepció, són millor predites pel RNG k-epsilon. Aquest model generalment requereix majors temps de càlcul. El k-omega reprodueix correctament els fenòmens sota estudi, tot i que la seua precisió és generalment més baixa que la dels models k-epsilon. Pel que fa la comparació entre enfocaments VOF i codis, és impossible determinar quin és el millor. Per exemple, OpenFOAM, emprant el Partial VOF, aconsegueix reproduir l'estructura interna del ressalt hidràulic i totes les variables derivades millor que FLOW-3D, emprant el TruVOF, tot i que aquest últim pareix capturar millor la transferència de quantitat de moviment i, per tant, totes les variables derivades. En el cas del flux en sobreeixidors esgraonats, OpenFOAM captura millor els perfils de velocitat, tot i que FLOW-3D és més precís en estimar els perfils de làmina lliure d'aigua. Cal deixar palès que ni tan sols la seua resposta a certs paràmetres del model és comparable. Per exemple, FLOW-3D és significativament menys sensible al refinament de malla que OpenFOAM. En base a la precisió dels resultats obtinguts en tots els casos, el model proposat és completament aplicable a casos de disseny més complexos, on vassos esmorteïdors, sobreeixidors esgraonats i estructures hidràuliques en general han de ser investigades. / Bayón Barrachina, A. (2017). Numerical analysis of air-water flows in hydraulic structures using computational fluid dynamics (CFD) [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/90440 / Compendio

Indiana University-Purdue University Indianapolis (IUPUI) / Hydraulic wind power transfer systems deliver the captured energy by the blades to the generators differently. In the conventional systems this task is carried out by a gearbox or an intermediate medium. New generation of wind power systems transfer the captured energy by means of high-pressure hydraulic fluids. A hydraulic pump is connected to the blades shaft at a high distance from the ground, in nacelle, to pressurize a hydraulic flow down to ground level equipment through hoses. Multiple wind turbines can also pressurize a flow sending to a single hose toward the generator. The pressurized flow carries a large amount of energy which will be transferred to the mechanical energy by a hydraulic motor. Finally, a generator is connected to the hydraulic motor to generate electrical power. This hydraulic system runs under two main disturbances, wind speed fluctuations and load variations. Intermittent nature of the wind applies a fluctuating torque on the hydraulic pump shaft. Also, variations of the consumed electrical power by the grid cause a considerable load disturbance on the system. This thesis studies the hydraulic wind power transfer systems. To get a better understanding, a mathematical model of the system is developed and studied utilizing the governing equations for every single hydraulic component in the system. The mathematical model embodies nonlinearities which are inherited from the hydraulic components such as check valves, proportional valves, pressure relief valves, etc. An experimental prototype of the hydraulic wind power transfer systems is designed and implemented to study the dynamic behavior and operation of the system. The provided nonlinear mathematical model is then validated by experimental result from the prototype. Moreover, this thesis develops a control system for the hydraulic wind power transfer systems. To maintain a fixed frequency electrical voltage by the system, the generator should remain at a constant rotational speed. The fluctuating wind speed from the upstream, and the load variations from the downstream apply considerable disturbances on the system. A controller is designed and implemented to regulate the flow in the proportional valve and as a consequence the generator maintains its constant speed compensating for load and wind turbine disturbances. The control system is applied to the mathematical model as well as the experimental prototype by utilizing MATLAB/Simulink and dSPACE 1104 fast prototyping hardware and the results are compared.