Les phénomènes d’interaction fluide-structure jouent un rôle important dans le calcul de tenue au séisme des assemblages combustibles. Afin de quantifier les marges de dimensionnement, le modèle de forces fluides utilisé doit être validé et affiné. Pour cela, des campagnes d’essais à l’échelle industrielle ont été réalisées en amont de la thèse. L’objectif ici est de contribuer à l’interprétation des essais industriels pour le cas stationnaire, et de valider les méthodes numériques permettant de simuler ce type d’écoulement. La problématique industrielle s'inscrit dans la tradition de l'étude des structures élancées sous écoulement axial. Le modèle de force fluide locale généralement utilisé, que nous appelons modèle de Taylor-Lighthill-Païdoussis (TLP), consiste en stationnaire à combiner un terme de force fluide potentielle, proportionnel à la courbure, et un terme de force fluide visqueuse, proportionnel à la pente. Des versions dynamiques de ce modèle ont été employées avec succès pour prédire le comportement vibratoire de cylindres flexibles en écoulement axial. Néanmoins, la littérature propose très peu de données de validation directe de cette représentation des forces fluides. Afin d’acquérir de telles données, pour le cas particulier d’un cylindre confiné dans un réseau de cylindres, un nouveau banc d’essai a été conçu et mis en place au laboratoire. Il s’agit d’un faisceau de 3x3 cylindres disposé dans une veine de soufflerie. Le cylindre central possède trois degrés de liberté : rotation, translation, flexion. Les efforts fluides résultants sont mesurés à l’aide d’une balance. Un modèle numérique similaire à la maquette est aussi réalisé et donne accès aux forces fluides locales. Les forces globales obtenues numériquement et expérimentalement sont comparables. Les forces locales obtenues dans les simulations numériques s’expliquent bien à l’aide du modèle TLP, en ignorant les effets de bord à l’entrée et à la sortie du faisceau. La transposition au cas industriel, de géométrie plus complexe, est réalisable par recalage des coefficients du modèle. / Fluid-structure interaction phenomena play a major role in the seismic design of fuel assemblies. In order to evaluate the design margins, the implemented model of fluid forces needs to be carefully assessed. Industrial-scale tests have been carried out with that purpose. Our goal is to contribute to their interpretation in the steady case, and to validate CFD methods usually applied to the type of flow at stake here. This fits in the tradition of the study of slender structures in axial flow. The local steady fluid forces decompose in a potential term, which is proportional to the curvature of the structure, and a viscous term, proportional to the angle of incidence. Adapted versions of this representation, which we call Taylor-Lighthill-Païdoussis (TLP) model, have proved successful in predicting the dynamic behaviour of flexible cylinders in axial flow. However, there is a lack in the literature of sound validation data for the fluid forces themselves. In order to gather such data, a new test rig has been designed and built. It consists in a 3x3 cylinder bundle confined in a wind tunnel. The central cylinder can be rotated, translated or bent. Resultant fluid forces are measured using a load cell. CFD calculations give access to the local fluid forces. CFD and experiments give similar results on the global fluid forces. The TLP model performs well at predicting the local fluid forces, except in the inlet and outlet regions. It can be fitted to the industrial case by adapting its coefficients.

Free fall is one of the important phases of the operation performed by the Special Forces paratroopers. Also civilian parachutists are performing free fall as a sport by doing aerobatic maneuvers when they reach the terminal velocity during falling before opening their parachutes. Vertical wind tunnels are used for training the parachutists and paratroopers. It is safe, cheap and more convenient when compared to jumping out of an airplane. This thesis consists of aerodynamic design of closed circuit, double return vertical wind tunnel with a flight section that can accommodate four paratroopers, aerodynamic design of a rotor straightener configuration axial flow fan and running CFD analysis of the axial flow fan for different operating conditions by FLUENT software.

Fluorescence correlation spectroscopy has become a standard technique for modern biophysics and single molecule spectroscopy research. Here is presented a novel widefield extension of the established single-point technique. Flow in microfluidic devices was used as a model system for microscopic motion and through widefield fluorescence correlation spectroscopy flow profiles were mapped in three dimensions. The technique presented is shown to be more tolerant to low signal strength, allowing image data with signal-to-noise values as low as 1.4 to produce accurate flow maps as well as utilizing dye-labeled single antibodies as flow tracers. With proper instrumentation flows along the axial direction can also be measured. Widefield fluorescence correlation spectroscopy has also been utilized to produce super-resolution confocal microscopic images relying on the single-molecule microsecond blinking dynamics of fluorescent silver clusters. A method for fluorescence modulation signal extraction as well as synthesis of several novel noble metal fluorophores is also presented.

Reversible axial flow fans are used as emergency ventilation fans to discharge the smoke generated on the probable fires occurring in the underground transportation systems and mines as quickly as possible, without causing any harm to people exposed to it. The fans which are placed in different configurations according to the location of fire must be able to work bi-directionally, namely reversible. Due to this fact, the blade profiles of the fan must possess the same aerodynamic performance while working on either discharge or suction condition of the fan, dictated by direction of the rotation. This manuscript consists of the computation of the aerodynamic performances of symmetrical blade profiles of fully reversible axial fans by computational fluid mechanics (CFD) methods, developing a methodology for the design of reversible axial fans and analysis of the designed fan with CFD methods. The aerodynamic performances of the blade cascades are evaluated using FLUENT 6.0 software for different Reynolds numbers, solidities and angle of attacks of the cascade. The results of these computations are embedded into the developed methodology. Performance analysis of the reversible axial flow fan, which is designed with the developed methodology, is done with CFD techniques.

[pt] O escoamento entre cilindros concêntricos com rotação do cilindro interno com a imposiçãao de um gradiente axial de pressão foi estudado experimentalmente. A razão de raios era (n)= 0, 64 e razão de aspecto era (r) = 265. O fator de atrito e campos de velocidade foram estudados para quatro rotações diferentes do cilindro interno e para os três regimes de escoamento, laminar, transição laminar- turbulento, e turbulento. Os Campos de velocidades foram obtidos através da técnica de Velocimetria por Imagem de Partículas (PIV). Os resultados para os fatores de atrito revelaram que a influência da rotação é mais pronunciada para regimes laminares e de transição. Para estes dois regimes o aumento observado foi de 100% de f/f0. Para o regime de escoamento turbulento, o aumento foi decrescendo gradativamente até o valor de 10% de f/f0 para Reaxial = 8458. Os campos de velocidade instantâneos relevaram padrões complexos do escoamento. Os perfis de velocidade axial médios tomavam uma forma achatada com o aumento da rotação do cilindro interno e do número de Reynolds axial. Para o regime de escoamento turbulento a influência da rotação do cilindro nos perfis de velocidade era pequena. / [en] The flow between concentric cylinders with an inner rotating cylinder with an imposed pressure-driven axial flow was studied experimentally. The radius ratio was (n) = 0, 64 and the aspect ration was (r) = 265. Friction factor and velocity fields were studied for four rotations of the inner cylinder and for laminar, transitional, and turbulent flow. Velocity fields were measure by Particle Image Velocimetry (PIV). The results for friction factor showed that the influence of the rotation is more apparent for laminar and transitional flow, increasing with the rotation of the inner cylinder. For these two flows, the increasing was 100% of f/f0. For turbulent flow, the increasing was gradualy decreasing to 10% of f/f0 for Reaxial = 8458. Instantaneous velocity fields showed complex flow patterns. The time average axial velocity profiles showed a top hat like form with the increasing of inner cylinder rotation and axial Reynolds numbers. For turbulent flow, the influence of rotation in the velocity profiles was small.

The diploma thesis consists of a theoretical part, which deals with the description of reversing turbocharger and its components. The following part is devoted to calculating the radial-axial compressor and turbine. It also performs a calculation of gear box and characteristics of the turbine.

Thesis (MScEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The main components of a micro gas turbine engine are a centrifugal or mixed-flow compressor, a combustion chamber and a single stage axial-flow or radial-flow turbine. The goal of this thesis is to formulate a design methodology for small axial-flow turbines. This goal is pursued by developing five design-related capabilities and applying them to develop a turbine for an existing micro gas turbine engine. Firstly, a reverse engineering procedure for producing digital three-dimensional models of existing turbines is developed. Secondly, a procedure for generating candidate turbine designs from performance requirement information is presented. The third capability is to use independent analysis procedures to analyse the performance of a turbine design. The fourth capability is to perform structural analysis to investigate the behavior of a turbine design under static and dynamic loading. Lastly, a manufacturing process for prototypes of a feasible turbine design is developed. The reverse engineering procedure employs point cloud data from a coordinate measuring machine and a CT-scanner to generate a three-dimensional model of the turbine in an existing micro gas turbine engine. The design generation capability is used to design three new turbines to match the performance of the turbine in the existing micro gas turbine engine. Independent empirical and numerical turbine performance analysis procedures are developed. They are applied to the four turbine designs and, for the new turbine designs, the predicted efficiency values differ by less than 5% between the two procedures. A finite element analysis is used to show that the stresses in the roots of the turbine rotor blades are sufficiently low and that the dominant excitation frequencies do not approach any of the blade natural frequencies. Finally prototypes of the three new turbine designs are manufactured through an investment casting process. Patterns made of an organic wax-like material and a polystyrene material are used, with the former yielding superior results. / AFRIKAANSE OPSOMMING: Mikro-gasturbiene-enjins bestaan uit 'n sentrifugaal- of ‘n gemende-vloeikompressor, 'n verbrandingsruim en 'n enkel-stadium-aksiaalvloei- of ‘n radiaalvloei-turbine. Die doel van hierdie tesis is om 'n ontwerpsmetodologie vir klein aksiaalvloei-turbines saam te stel. Hierdie doel word deur die ontwikkeling en toepassing van vyf ontwerpsverwante vermoëns nagestreef. Eerstens word 'n tru-waartse-ingenieursproses ontwikkel om drie-dimensionele rekenaarmodelle van die bestaande turbines te skep. Tweedens word 'n metode om kandidaatturbineontwerpe vanaf werkverrigtingsvereistes te verkry, voorgestel. Die derde ontwerpsvermoë is om die werksverrigting van 'n turbineontwerp met onafhanklike analises te evalueer. Die vierde ontwerpsvermoë is om die struktuur van 'n turbinelem te analiseer sodat die effek van statiese en dinamiese belastings ondersoek kan word. Laastens word 'n vervaardigingsproses vir prototipes van geskikte turbineontwerpe ontwikkel. Die tru-waartse-ingenieursproses maak gebruik van 'n koördinaat-meet-masjien en 'n CT-skandeerder om puntewolkdata vanaf die turbine in 'n bestaande mikro-gasturbiene-enjin te verkry. Die data word dan gebruik om 'n drie-dimensionele model van die turbine te skep. Die ontwerpskeppingsvermoë word dan gebruik om drie kandidaatturbineontwerpe vir die bestaande mikro-gasturbiene-enjin te skep. Onafhanklike empiriese en numeriese prosedures om die werkverrigting van 'n turbineontwerp te analiseer word ontwikkel. Beide prosedures word op die vier turbineontwerpe toegepas. Daar word gevind dat die voorspelde benuttingsgraadwaardes van die nuwe ontwerpe met minder as 5% verskil vir die twee prosedures. 'n Eindige-element-analise word dan gebruik om te wys dat die spannings in die wortels van die turbinelemme laag genoeg is, asook dat die dominante opwekkingsfrekwensies nie die lem se natuurlike frekwensies nader nie. Laastens word prototipes van die drie nuwe turbineontwerpe deur 'n beleggingsgietproses vervaardig. In die vervaardigingproses word die effektiwiteit van twee materiale vir die gietpatrone getoets, naamlik 'n organiese wasagtige materiaal en 'n polistireen-materiaal. Daar word bevind dat die gebruik van die wasagtige gietpatrone tot beter resultate lei.

[pt] O presente trabalho investigou a queda de pressão em escoamento através de um espaço anular com rotação do cilindro interno. A motivação para o trabalho veio da aplicação desta configuração em diversas situações de interesse industrial, como reatores químicos catalíticos, filtros e nas operações de perfuração de poços produtores de petróleo e gás. O estudo realizado foi conduzido em uma seção de testes especialmente projetada e construída, formando um espaço anular com razão de raios de 0,65 e com um comprimento de 256 diâmetros hidráulicos, suficiente para garantir o desenvolvimento hidrodinâmico do escoamento nos regimes laminar e turbulento. O trabalho investigou a queda de pressão ao longo do espaço anular como função da vazão, dada pelo número de Reynolds, e da rotação do cilindro interno, caracterizada pelo número de Reynolds rotacional. A faixa de números de Reynolds investigada foi de 260 a 10000, enquanto o Reynolds rotacional variou de 60 a 1000. Dois fluidos de trabalho foram utilizados nos testes: água e uma mistura de água e glicerina. Os resultados para a queda de pressão foram apresentados na forma de fatores de atrito hidrodinâmicos. Testes preliminares para o caso do cilindro interno sem rotação foram realizados e comparados com resultados da literatura, com o objetivo de validar a seção de testes e o procedimento experimental. Os resultados apresentados mostraram boa concordância com valores disponíveis na literatura tanto para o caso de escoamento laminar , quanto para escoamento turbulento. Para os casos de baixos números de Reynolds, os resultados mostraram que a rotação do cilindro interno provocava um pico na razão entre o fator de atrito com rotação e sem rotação para um valor do número de Reynolds da ordem de 500. Aumentos da ordem de 15% foram verificados. / [en] The present work investigated the pressure drop generated by the flow through an annular configuration with rotation of the inner cylinder. The motivation for the work comes from the several industrial application of the configuration, such as chemical reactors, filters and in drilling operations for oil and gas wells. The experimental study was conducted in a specially designed test section forming an annular space with radius ratio of 0.65 and a length equivalent to 265 hydraulic diameters, what guaranteed the hydrodynamic development of the flow for the laminar and turbulent regimes. The study investigated the pressure drop along the annular space as a function of the flow rate, given by the Reynolds number, and of the rotation of the inner cylinder, given by the rotational Reynolds number. The range of Reynolds number investigated was from 260 to 10,000, while the rotational Reynolds number was varied from 60 to 1,000. Two fluids were employed in the testes; water and a mixture of water and glycerol. The pressure drop results were presented in the form of dimensionless friction factors. Preliminary tests for the case of no rotation of the inner cylinder were compared with results available in the literature, in order to validate the test section and the experimental procedure. The results displayed good agreement with the literature for both laminar and turbulent regimes. For the low Reynolds number test cases, the results obtained have shown that the inner cylinder rotation induces a peak in the distribution of the ratio of friction factor to the friction factor without rotation. The peak, of about 15%, is found for Reynolds numbers of the order of 500.

Axial compressors are used in a wide variety of aerodynamic applications and are one of the most important components in aero-engines. The operability of compressors is however limited at low-mass flow rates by fluid dynamic instabilities such as stall and surge. These instabilities can lead to engine failure and loss of engine power which can compromise the aircraft safety and reliability. Therefore, a better understanding of how stall occurs and the causes behind its inception is extremely important. In the vicinity of the stall line, the flow field is inherently unsteady due to the interactions between adjacent rows of blades, formation of separation cells, and the viscous effects including shock-boundary layer interaction. Accurate modeling of these phenomena requires a proper set of stable and accurate boundary conditions at the rotorstator interface that conserve mass, momentum and energy, while eliminating false reflections. As a part of this effort, an existing 3D Navier-Stokes analysis for modeling single stage compressors has been modified to model multi-stage axial compressors and turbines. Several rotor-stator interface boundary conditions have been implemented. These have been evaluated for the first stage (a stator and a rotor) of the two stage fuel turbine on the space shuttle main engine (SSME). Their effectiveness in conserving global properties such as mass, momentum, and energy across the interface, while yielding good performance predictions has been evaluated. While all the methods gave satisfactory results, a characteristic based approach and an unsteady sliding mesh approach are found to work best. Accurate modeling of the formation of stall cells requires the use of advanced turbulence models. As a part of this effort, a new advanced turbulence model called Hybrid RANS/KES (HRKES) has been developed and implemented. This model solves Menter's k--SST model near walls and switches to a Kinetic Eddy Simulation (KES) model away from walls. The KES model solves directly for local turbulent kinetic energy and local turbulent length scales, alleviating the grid spacing dependency of the length scales found in other Detached Eddy Simulation (DES) and Hybrid RANS/LES (HRLES) models. Within the HRKES model, combinations of two different blending functions have been evaluated for blending the near wall model to the KES model. The use of realizability constraints to bound the KES model parameters has also been studied for several internal and external flows. The current methodology is used in the prediction of the performance map for the NASA Stage 35 compressor configuration as a representative of a modern compressor stage. The present approach is found to satisfactory predict the onset of stall. It is found that the rotor blade tip leakage vortex and its interaction with the shock wave is mainly the reason behind the stall inception in this compressor stage.

In this study, a variable pitch axial flow fan is designed and analysed for Ankara Wind Tunnel (AWT). In order to determine the loss caharacteristics of AWT, an algorithm is developed and the results are validated. Also some pressure and velocity measurements are made at the fan section to find the losses experimentally. After completion of the fan design, analyses are made at different volumetric flowrates and blade angles including the design point and the performance characteristics of the fan are obtained and thereafter the operating range of the tunnel is deterimened.