This study quantifies the influence of debris cages on critical submergence at vertical intakes in reservoir configurations. Four model debris cages were constructed of light panel material. A vertical intake protruding one pipe diameter above the floor of a model reservoir was tested in six configurations: open intake pipe, a debris grate placed directly over the intake pipe, and debris cages representing widths of 1.5*d and 2*d and heights of 1.5*c and 2*c, where d is diameter of the intake and c is height of intake above reservoir floor. A selection of top grating configurations and a submerged raft configuration were also tested for comparison. Testing of the model debris cages indicates that the roof or top grate of a debris cage dominates the influence a debris cage has on the reduction of critical submergence of air-core vortices. The side grates of a debris cage have some influence on the formation of vortices. The spacing of bars in the top grate has an influence on air-core vortex development. The presence of a debris cage at vertical intakes in still-water reservoirs reduces the critical submergence required to avoid air-core vortices and completely eliminates the air-core vortex for cases where the water surface elevation remains above the top grate of the debris cage. The potential exists for designing debris cages to fulfill a secondary function of air-core vortex suppression.

Grades da tomada dágua de usinas hidroelétricas são equipamentos de grande importância porque são responsáveis pela proteção das turbinas hidráulicas contra impacto de corpos flutuantes. Tais estruturas estão submetidas à ação de cargas dinâmicas oriundas do escoamento da água através das barras. O objetivo do presente trabalho é analisar grades submetidas à ação de fluxo de água. Ou seja, analisar as respostas da estrutura e o comportamento do escoamento da água utilizando os cálculos de dinâmica de estruturas acopladas às técnicas de dinâmica de fluidos computacional (CFD). Para a elaboração destas análises, foi utilizado o software comercial CFX versão 14. Tais análises foram elaboradas mediante o processo de interação fluido-estrutura. Primeiramente, um modelo estrutural simplificado das barras verticais das grades é elaborado a partir de dados de projetos conhecidos. A partir deste modelo define-se um volume de controle que representa o escoamento do fluido. Devido ao número de Reynolds calculado, utiliza-se o modelo de turbulência para obtenção dos resultados tais como tensões e deslocamentos nas barras verticais, e perfil de velocidades do escoamento. Considerando o modelo proposto, foram elaboradas análises com sete diferentes valores de velocidade de modo a comparar os dados calculados numericamente através do método de elementos finitos com valores obtidos experimentalmente. A partir do modelo verificado, é apresentada uma análise de uma grade inclinada submetida a um fluxo paralelo. / Trashracks are very important equipment because they are responsible for protecting turbines of hydroelectric plants against floating bodies. These structures are subjected to the action of dynamic loads due to the water flow through the vertical and horizontal bars. The objective of this study was to analyze trashracks submitted by action of water flow. In other words, to analyze the responses of the structure and the behavior of water flow using dynamic of structures calculations coupled with computational fluid dynamics techniques (CFD) for a turbulent regime, through the use of commercial software CFX version 14. This analysis is elaborated by the process of fluid structure interaction. First of all, a simplified structural model of vertical bars is defined from other similar projects. For this model is defined a volume of control that represents fluid flow. Due to the Reynolds number calculated, it is utilized a turbulence model in order to obtain the results. These results are: stresses and displacements of vertical bars; and profile of velocities of flow. The results are analyzed and discussed. After that, considering the simplified model, analyzes with seven different values of speed are executed in order to compare the results between the data calculated numerically by finite elements method, and the values obtained experimentally. Considering the model verified, an analysis, of an inclined trashrack subjected to a parallel flow, is presented.

Un des enjeux de la Directive Cadre sur l'Eau (2000) est de rétablir la migration piscicole aval à travers notamment une baisse de la mortalité des poissons au niveau des turbines des centrales hydroélectriques. Les grilles ichtyocompatibles constituent une des solutions possibles grâce à un arrêt physique des poissons couplé à un guidage vers un exutoire de contournement. Dans ce contexte, nous avons mené une étude expérimentale et numérique afin de caractériser différents types de grilles en termes de pertes de charge et de courantologie. Cela a permis de déterminer d'une part les pertes d'énergie liées à la proximité des barreaux pour diverses configurations et d'autre part les vitesses que les poissons sont susceptibles de rencontrer le long des grilles jusqu'à l'exutoire. Ces deux sujets complémentaires ont été abordés via l'utilisation de deux installations hydrauliques couplées à plusieurs systèmes de mesure adaptés à nos modèles de grille. Des mesures de hauteur d'eau ont permis d'établir des nouvelles lois de pertes de charge tandis que des mesures de vitesse avec des systèmes de vélocimétrie acoustique par effet Doppler (ADV) et de vélocimétrie par images de particules (PIV) ont permis de déterminer les angles pour lesquels les grilles satisfont les critères d'ichtyocompatibilité. Certains points de l'étude, liés à la caractérisation des exutoires notamment, ont été résolus grâce à des simulations numériques avec le logiciel OpenFOAM. L'ensemble des résultats obtenus a permis de dimensionner et de comparer les différentes solutions de grilles dans un cas de prise d'eau réel, soulignant ainsi les avantages et problématiques inhérents à chacune des solutions. / The Water Framework Directive (2000) particularly aimed at restoring the fish downstream migration and at preventing fish from being injured or killed in hydropower plant turbines. Fish-friendly trashracks, which physically stop fish and guide them towards bypasses, are one of the possible solutions.In this context, we have carried out an experimental and numerical study focused on the characterization of head losses and velocity distributions for various kinds of trashrack. This helped to quantify the energy loss due to the narrow bar spacing and to assess the magnitude of velocities that fish may face in different trashrack configurations. Two hydraulic installations coupled with several measurement devices allowed the study of both topics on model trashracks. Water depth measurements resulted in new head loss equations while velocity measurements with acoustic Doppler velocimetry (ADV) and particle image velocimetry (PIV) systems allowed the determination of fish-friendly angles in different trashrack configurations. Some other points of the thesis, concerning for instance bypasses, have been investigated with numerical simulations using OpenFOAM software. All the results allowed the conception and the comparison of various trashrack solutions for a real water intake case, highlighting the advantages and drawbacks relative to each of these solutions.