Este trabalho tem por objetivo formular um procedimento para a quantificação da vazão do ar promovida pela ação do vento no interior do edifício, em climas quentes. O procedimento é dividido em cinco partes: obtenção dos dados de vento, transposição dos dados de vento da estação meteorológica para a área de interesse, determinação dos coeficientes de pressão no edifício, determinação dos coeficientes de descarga das aberturas, e o cálculo da vazão no interior do edifício. Diversas ferramentas são apresentadas para a execução de cada etapa, e seu uso e parâmetros de entrada são discutidos. O uso de túnel de vento e a simulação com ferramentas de dinâmica dos fluidos computacional são apresentados em detalhes. O trabalho conclui que estão disponíveis aos projetistas um amplo conjunto de ferramentas para a predição da ventilação natural no interior do edifício, e que somente pelo seu uso criterioso, as conclusões são passiveis de uso no projeto arquitetônico. / The aim of this dissertation is to produce a procedure for wind-driven natural ventilation prediction, in hot climate building. The procedure is organized in five parts: wind data obtaining, topographic e roughness correction, pressure coefficient determination, discharge coefficient determination, and flow rate calculation inside the building. The dissertation presents some tools to execute each part of the procedure, and the specificities of those tools are discussed. Wind tunnel experiment and computation fluid dynamic simulation are presented in detail. The research conclusion is that designers have many tools avaliable to performe a natural ventilation prediction, but just concient use will produce reliable results for architectural design.

Sistemas pneumáticos de irradiação são instalações utilizadas em reatores nucleares de pesquisa. Sua função principal é de prover um meio rápido de envio de materiais para irradiação em posições localizadas nas proximidades do núcleo do reator. Durante sua utilização, cápsulas contendo os materiais de estudo são enviadas por meio de tubulações utilizando um fluido propulsor gasoso. Ao chegar à posição desejada, a cápsula sofre a exposição à radiação proveniente do reator possibilitando as transformações do material alocado em seu interior, porém como consequência da exposição também ocorre seu aquecimento térmico. Este trabalho estudou de forma numérica, utilizando a dinâmica dos fluidos computacional (CFD) e experimental, por meio de uma bancada de ensaios, o escoamento e transferência de calor durante o processo de irradiação. Os resultados encontrados demonstraram um aquecimento significativo para tempos de irradiação na ordem de 1 minuto considerando uma taxa de geração de calor constante, provocando a elevação da temperatura da cápsula a valores críticos para materiais de fabricação das cápsulas comumente utilizados como o polietileno de alta densidade (PEAD). Além disso, foram levantados os campos de velocidade, pressão e temperatura para o fluido propulsor e água de resfriamento no interior do tubo de irradiação que abriga a cápsula durante sua irradiação e avaliadas as respostas para diferentes modelos de turbulência nas simulações numéricas. Em função dos resultados obtidos concluiu-se que o estudo desenvolvido possibilitou exemplificar o processo de aquecimento das cápsulas e fornecer informações sobre as características do escoamento no interior do tubo de irradiação que abriga as cápsulas durante o processo de exposição. A utilização de diferentes modelos de turbulência nas simulações gerou resultados similares para o caso de estudo, porém pequenas variações em regiões de escoamento próximo à parede e em zonas de recirculação foram encontradas. / Pneumatic irradiation system facilities are used in nuclear research reactors. Its main function is to provide a fast means of sending materials to irradiation positions located near the reactor core. Capsules containing the sample materials are sent through pipes using a gaseous fluid propellant. Upon reaching the desired position, the capsule undergoes exposure to radiation from the reactor enabling the transformation of the material allocated inside, but as a consequence of exposure, its thermal heating also occurs. This study investigated numerically, using computational fluid dynamics (CFD), and experimentally the flow and heat transfer during the irradiation process. The results showed a significant heating for irradiation times on the order of 1 minute, considering a constant heat generation rate, thus causing increase in the capsule temperature up to critical values, for the materials that are commonly used for their manufacture. In particular, this is the case of the high density polyethylene (HDPE). Furthermore, the velocity, pressure and temperature fields were obtained for the propellant fluid and cooling water inside the irradiation tube house during its irradiation and the response of different turbulence modeling in the numerical simulations were analyzed. Based on the results obtained, it was possible to conclude that the developed study exemplified the heating process of the capsules and provided information about the characteristics of the flow inside the irradiation tube that houses the capsules during the exposure process. The use of different turbulence models in the simulations generated similar results for the study, however small variations in regions of flow near to the wall and inside recirculation zones were found.

Neste trabalho foram analisados diferentes parâmetros geométricos para canais de fluxo em células a combustível tipo PEMFC e sua influência no desempenho do sistema, utilizando a fluidodinâmica computacional. Na análise dos modelos matemáticos, verificou-se que o modelo de aglomerado inundado descreve com maior fidelidade o comportamento de células a combustível, enquanto as equações de Butler-Volmer não consideram as perdas por transporte de massa. Foram avaliadas as seções transversais retangular, trapezoidal e em degrau. O modelo com canais de seção retangular apresentou desempenho elétrico ligeiramente superior, porém os canais com seção trapezoidal propiciam um melhor gerenciamento de água. Em todos os aspectos estudados, os canais com seção em degrau se comportaram de forma análoga aos canais com seção trapezoidal, porém sua construção é menos complexa. Também foram analisadas as configurações serpentina e interdigitada em células de 5 cm², e sua influência na uniformidade da densidade de corrente. Não foram observadas diferenças significativas quanto à eficiência elétrica entre células com as duas configurações. A configuração interdigitada propiciou distribuição mais uniforme de geração de corrente, pois os reagentes são fornecidos em alta concentração por uma maior área da célula. Assim, esta configuração é preferível para aumento de escala. / In this work, different geometric parameters for PEMFC flow channels and their influence in cell performance were analyzed using computational fluid dynamics. At first, two mathematical models, the flooded agglomerate model and the Butler-Volmer equations, were compared. It was verified that the equations do not consider mass-transfer losses, while the agglomerate model describes the system more accurately. In a second analysis, rectangular, trapezoidal and step-shaped cross-sections were evaluated. The model with rectangular channels showed a slightly higher electrical performance; however, trapezoidal channels provided better water management. Cells with step-shaped cross-sections were found to be superior to those with trapezoidal channels, due to lower constructive complexity, even though their performance was similar to that of trapezoidal cross-sections in every aspect. Further studies analyzed serpentine and interdigitated channel patterns in 5 cm² cells and their influence in current density uniformity. Again, electrical performance was very similar for both patterns. However, the interdigitated pattern provided more spatial uniformity in current generation, because concentrated reactants are supplied to a wider area of the cell. Thus, this pattern is preferable for fuel cell scaling-up.

Na presente dissertação pretende-se mostrar a motivação, o planejamento e a metodologia usada para desenvolver o projeto e a implementação de um pacote aerodinâmico no veículo de competição da equipe EESC-USP Fórmula SAE da Escola de Engenharia de São Carlos. O principal objetivo no projeto da equipe é a dinâmica veicular. À partir disso, será projetado um pacote aerodinâmico a fim de gerar força de sustentação negativa ou downforce, melhorando a capacidade de tração dos pneus com o asfalto da pista e proporcionando maiores valores de aceleração lateral e velocidade nas curvas. Inicialmente é realizado um estudo para encontrar a melhor configuração nas simulações em dinâmica de fluidos computacional (CFD) a fim de otimizar a relação entre a fiabilidade dos resultados obtidos e o custo computacional deles. Também é feita uma descrição geral dos perfis aerodinâmicos a serem usados e um breve analise deles. Com base nesses resultados são projetados o diferentes dispositivos aerodinâmicos, onde são aplicadas estratégias de alto downforce a fim de otimizar o desempenho deles. Além disso, é realizado uma análise do comportamento aerodinâmico do veículo inteiro, com o intuito de integrar as diferentes componentes do carro que são influenciadas pela aerodinâmica. Também é feito um estudo em dinâmica veicular que visa entender o comportamento do carro em pista sob influência das forças aerodinâmicas. Finalmente, o modelo real do veículo é construído e é levado para pista a fim de realizar uma série de testes para validar os dados encontrados nas simulações. / In the present dissertation, it is intended to show the motivation, planning and methodology used to develop the design and implementation of an aerodynamic package in the EESSC-USP Formula SAE\'s race car of the Engineering School of São Carlos. The main objective of the team is vehicle dynamics. From this, an aerodynamic package is designed in order to generate negative lift forces known as downforce, improving the traction capacity between the tires and the asphalt of the track, and providing larger values of lateral acceleration and cornering speeds. Initially, a study to find the best configurations in CFD simulations is performed in order to optimize the rate between reliability of obtained results and computation cost. In addition, a general description and analysis of the aerodynamic profiles used is done. On basis in these results, several aerodynamic devices are designed, and some strategies of high downforce are applied to optimize its performance. Furthermore, an analysis of aerodynamic behavior of the entire vehicle is done with the purpose of integrating other components of the car influenced by aerodynamics. Also, a study about vehicle dynamics is done searching to understand the behavior of the car in track under the influence of aerodynamic forces. Finally, the real model of the race car is constructed and put on track in order to carry out several tests to validate found data in simulations.

Assim como um peixe pode aproveitar a energia dos vórtices formados por uma rocha em uma corredeira para economizar energia e produzir impulso, este trabalho tem por objetivo mostrar que os vórtices de von Kármán ou esteira de vórtices, desprendidos de um corpo cilíndrico colocado em um escoamento contínuo, com uma placa de um determinado comprimento, posicionada atrás desse corpo cilíndrico e com movimentos livres na horizontal, pode vibrar e produzir movimentos rotacionais, e por fim, uma frequência, com o objetivo de se aproveitar esse movimento para geração de energia. Para tanto, utilizou-se software CFD (Computational Fluid Dynamic), para observar e quantificar os movimentos produzidos pela placa. Observou-se também, entre três comprimentos de placa, com três velocidades diferentes, três números de Reynolds diferentes e com escoamentos laminar e turbulento, como as placas se comportam e qual delas produz movimento com maior frequência. Buscou-se também verificar a eficiência do movimento para números de Strouhal menores e iguais a 0,21. / Just as a fish can harness the energy of the vortices formed by a rock in the rapids to save energy and produce impulse this paper aims to show that the von Kármán vortex or wake vortex, detached from a cylindrical body placed in a flow continuous with a plate of a certain length, positioned behind this cylindrical body and freely moving horizontally, may vibrate and produce rotational movements, and finally, a frequency, in order to take advantage of this movement to generate power. Therefore, we used CFD software (Computational Fluid Dynamic), to observe and quantify the movements produced by the board. It was also observed between three plate lengths with three different velocities, three different Reynolds numbers and laminar and turbulent flow as the plates behave and which one produces motion with higher frequency. It sought to verify the efficiency of movement to lower Strouhal numbers and equal to 0.21.

De nos, jours avec la démocratisation des équipements électroniques et l’explosions des services informatiques proposés sur le web, la consommation des datacenters devient un enjeu énergétique et économique majeur. Ce terme qui peut être traduit par « centre de calcul », désigne les infrastructures qui hébergent et font fonctionner en permanence des serveurs informatiques. Son rôle est de fournir aux équipements électroniques un environnement thermique adapté, ainsi qu’une alimentation électrique stable de manière à assurer une très grande sécurité de fonctionnement. Mais l’activité permanente des serveurs génère de grandes quantités de chaleurs, et un refroidissement permanent est nécessaire. Cette étude à pour objectif de mieux comprendre les phénomènes physiques qui interviennent dans le fonctionnement des datacenters afin d’apporter des solutions pour optimiser leur fonctionnement et diminuer leur consommation. A l’aide de simulations numériques, nous étudions les écoulements d’air et les transferts de chaleur qui interviennent dans la salle informatique, et nous proposons un nouveau modèle numérique qui permet de simuler le comportement des serveurs de nouvelle génération. Puis, grâce à une méthode de type POD, couplée au logiciel TRNSYS, nous développons un modèle « transversal » capable de simuler le fonctionnement complet d’un centre de calcul depuis les équipements informatiques, jusqu’au système de production d’air froid. Finalement, ce dernier est employé pour concevoir et tester un système de régulation adaptatif qui permet de réduire significativement les consommations d’énergie. / Nowadays, with the constant evolution of Information Technology (IT) equipments, the energy consumption of datacenter over the world becomes a major concern. These infrastructures are designed to provide an adapted thermal environment and an uninterrupted power supply to the IT servers, in order to guarantee a high level of reliability. However, the constant activity of electronic equipments releases a large amount of heat, and requires a constant cooling. Thus the objective of this work is to study the physical phenomena involved in an operating datacenter, in order to optimize the process and to reduce its energy consumption. Using numerical simulation, we study the air flow and the heat transfers happening in the servers’ room. To quantify the impact of new generation servers on the cooling process, we propose a numerical model that simulates the behavior of “blade” server. Then, using a Proper Orthogonal Decomposition (POD) method linked to the software TRNSYS, we propose a new “transversal” model, that simulates a datacenter behavior from the servers to the cooling plant. This model is used to develop a new adaptive regulation strategy, which constantly optimizes the system in order to ensure a safe thermal environment, and provides large energy savings.

The airflow field and particle trajectories inside hard disk drive (HDD) are investigated in this study using commercial software Fluent and Gambit. Three-dimensional grids inside the HDD configuration are built using Gambit taking into account all the components and their geometric details. The airflow field inside HDD is simulated using three incompressible Navier-Stokes equations for various disk rotational speeds. The effects of using the various turbulence models inside the Fluent software such as the standard k - ε , RNG k - ε and Reynolds Stress Method on the computed airflow characteristics are also assessed. Steady flow fields and the effects of rotational speeds are assessed. Based on the computed steady airflow patterns, particle trajectories are computed using routines available in Fluent as well as special particle trajectory functions defined by the user via the user-defined functions. Particles of different sizes and materials are injected at various locations in the computed flow field and the corresponding particle trajectories are studied. Based on the investigation, the trajectory tends to be different according to sizes and materials. The present work forms a basis for further investigation of heat transfer processes inside the HDD to address thermal management issues and also the computation of unsteady flow fields in the HDD due to the movement of the actuator arm during data storage and retrieval / Singapore-MIT Alliance (SMA)

Die Arbeit befasst sich mit der Untersuchung des Kernformstofffließens als nichtnewtonsche Fluidströmung. Dazu werden verschiedene Formgrundstoffe und Kernformstoffe rheologisch untersucht. Als Bindersysteme kommen PUR Coldbox und Wasserglas zum Einsatz. Für diese Untersuchungen wird ein eigens für diesen Zweck entwickeltes Messgerät verwendet. Die gewonnenen Daten werden in ein numerisches Modell implementiert, welches mit den Methoden der numerischen Strömungsmechanik den Kernschießvorgang abbildet. Dabei kommt der Open Source CFD Code OpenFOAM zum Einsatz. Der Kernschießvorgang wird mit verschiedenen Kernkastengeometrien numerisch und experimentell untersucht und die Ergebnisse verglichen. Die Ergebnisse der rheologischen Untersuchungen zeigen deutlich den Einfluss der Beschaffenheit des Formgrundstoffes und des Bindersystems auf die Fließfähigkeit des Kernformstoffes. Der Vergleich zwischen Experiment und Simulation zeigt gute Übereinstimmung. Das formulierte Modell gibt die Möglichkeit, Probleme in der Kernqualität vorherzusagen.

The applicability of CFD codes for two-phase flows has always been limited to special cases due to the very complex nature of its interface. Due to its tremendous computational cost, methods based on direct resolution of the interface are not applicable to most problems of practical relevance. Instead, averaging procedures are commonly used for these applications, such as the Eulerian-Eulerian approach, which necessarily means losing detailed information on the interfacial structure. In order to allow widespread application of the two-fluid approach, closure models are required to reintroduce in the simulations the correct interfacial mass, momentum, and heat transfer. It is evident that such closure models will strongly depend on the specific flow pattern. When considering vertical pipe flow with low gas volume flow rates, bubbly flow occurs. With increasing gas volume flow rates larger bubbles are generated by bubble coalescence, which further leads to transition to slug, churn-turbulent, and annular flow. Considering, as an example, a heated tube producing steam by evaporation, as in the case of a vertical steam generator, all these flow patterns including transitions are expected to occur in the system. Despite extensive attempts, robust and accurate simulations approaches for such conditions are still lacking. The purpose of this dissertation is the development, testing, and validation of a multifield model for adiabatic gas-liquid flows at high gas volume fractions, for which a multiple-size bubble approach has been implemented by separating the gas structures into a specified number of groups, each of which represents a prescribed range of sizes. A fully-resolved continuous gas phase is also computed, and represents all the gas structures which are large enough to be resolved within the computational mesh. The concept, known as GENeralized TwO Phase flow or GENTOP, is formulated as an extension to the bubble population balance approach known as the inhomogeneous MUltiple SIze Group (iMUSIG). Within the polydispersed gas, bubble coalescence and breakup allow the transfer between different size structures, while the modeling of mass transfer between the polydispersed and continuous gas allows including transitions between different gas morphologies depending on the flow situations. The calculations were performed using the computational fluid dynamic code from ANSYS, CFX 14.5, with the support of STAR-CCM+ v8.06 and v9.02. A complete three-field and four-field model, including a continuous liquid field and two to three gas fields representing bubbles of different sizes, were first tested for numerical convergence and then validated against experimental data from the TOPFLOW and MT-Loop facilities.

Immer mehr Anwenderprogramme werden zum täglich genutzten Werkzeug des Ingenieurs zur Lösung vielfältiger Problemstellungen. Viele Aufgaben sind ohne die Computertechnik nicht mehr lösbar. Simulationen mit ein-, zwei- und allmählich zunehmend dreidimensionalen Programmen ermöglichen heute schon eine Komplexität der Betrachtung, die es ohne diese Programme nicht gäbe. Am Institut für Wasserbau und Technische Hydromechanik der TU Dresden werden daher verschiedene Praktika und Belege in Verbindung mit physikalischen Modellversuchen in die studentische Ausbildung integriert.