Pressure swirl atomizers are commonly used in IC, aero-engines, and liquid propellant rocket combustion. Understanding the atomization process is important in order to enhance vaporization, mitigate soot formation, design of combustion chambers, and improve overall combustion efficiency. This work utilizes non-invasive techniques such as ultra -speed imaging, and Phase Doppler Particle Anemometry (PDPA) in order to investigate the cascade atomization process of pressure-swirl atomizers by examining swirling liquid film dynamics and the localized droplet characteristics of the resulting hollow cone spray. Specifically, experiments were conducted to examine these effects for three different nozzles with orifice diameters .3mm, .5mm, and .97mm. The ultra-speed imaging allowed for both visualization and interface tracking of the swirling conical film which emanated from each nozzle. Moreover, this allowed for the measurement of the radial fluctuations, film length, cone angle and maximum wavelength. Radial fluctuations are found to be maximum near the breakup or rupture of a swirling film. Film length decreases as Reynolds number increases. Cone angle increases until a critical Reynolds number is reached, beyond which it remains constant. A new approach to analyze the temporally unstable waves was developed and compared with the measured maximum wavelengths. The new approach incorporates the attenuation of a film thickness, as the radius of a conical film expands, with the classical dispersion relationship for an inviscid moving liquid film. This approach produces a new long wave solution which accurately matches the measured maximum wavelength swirling conical films generated from nozzles with the smallest orifice diameter. For the nozzle with the largest orifice diameter, the new long wave solution provides the upper bound limit, while the long wave solution for a constant film thickness provides the lower bound limit. These results indicate that temporal instability is the dominating mechanism which generates long Kelvin Helmholtz waves on the surface of a swirling liquid film. The PDPA was used to measure droplet size and velocity in both the near field and far field of the spray. For a constant Reynolds number, an increase in orifice diameter is shown to increase the overall diameter distribution of the spray. In addition, it was found that the probability of breakup, near the axis, decreases for the largest orifice diameter. This is in agreement with the cascading nature of atomization.

The primary motivation for this work was to predict the conditions that would yield minimum drag for a small Ram-Air Turbine used to provide a specified power requirement for a small flight test instrument called the Boundary Layer Data System. Actuator Disk Theory was used to provide an analytical model for this work. Classic Actuator Disk Theory (CADT) or Froude’s Momentum Theory was initially established for quasi-one-dimensional flows and inviscid fluids to predict the power output, drag, and efficiency of energy-extracting devices as a function of wake and freestream velocities using the laws of Conservations of Mass, Momentum, and Energy. Because swirl and losses due to the effects of viscosity have real and significant impacts on existing turbines, there is a strong motivation to develop models which can provide generalized results about the performance of an energy-extractor, such as a turbine, with the inclusion of these effects. A model with swirl and a model with losses due to the effects of viscosity were incorporated into CADT which yielded equations that predicted the performance of an energy-extractor for both un-ducted and ducted cases. In both of these models, for this application, additional performance parameters were analyzed including the drag, drag coefficient, power output, power coefficient, force coefficient, and relative efficiency. For the un-ducted CADT, it is well known that the wake-to-freestream velocity ratio of 1/3 will give the maximum power extraction efficiency of 59.3%; this result is called the Betz limit. However, the present analysis shows that reduced drag for a desired power extraction will occur for wake-to-freestream velocity ratios higher than the value of 1/3 which results in maximum power extraction efficiency. This in turn means that a turbine with a larger area than the smallest possible turbine for a specified power extraction will actually experience a lower drag. The model with the inclusion of swirl made use of the Moment of Momentum Theorem applied to a single-rotor actuator disk with no stators, in addition to the laws of Conservation of Mass, Momentum, and Energy from the CADT. The results from the model w/swirl showed that drag remains unchanged while power extracted decreases with the addition of swirl, with swirl effects becoming more severe for tip speed ratios below about 5. As for CADT, reduced drag for a specified power extraction can be achieved when the wake-to-freestream velocity ratio is higher that than which provides maximum power extraction efficiency. The model w/losses due to viscosity incorporated the losses into the Conservation of Energy relationship. The results from the model w/losses showed that there is a distinct wake-to-freestream velocity ratio at which minimum drag for a specified power output is achieved, and that this velocity ratio is usually—but not always—higher than that for which the power extraction efficiency is a maximum. It was concluded that a lower drag for a specified power output of an energy-extractor can usually be achieved at a wake-to-freestream velocity ratio higher than that which produces the v maximum power extraction efficiency. The latter condition, known as the Betz limit for CADT, and which defines the minimum size for a turbine to provide a specified power extraction, is therefore not the correct target design condition to achieve lowest drag for a small Ram-Air Turbine to power BLDS.

The demand for more power and performance from electronic equipment has constantly been growing resulting in an increased amount of heat dissipation from these devices. Thermal management of high-density power control units for hybrid electric vehicles is one such application. Over the last few years, the performance of this power control unit has been improved and size has been reduced to attain higher efficiency and performance causing the heat dissipation as well as heat density to increase significantly. However, the overall cooling system has remained unchanged and only the heat exchanger corresponding to the power control unit (PCU) has been improved. This has allowed the manufacturing costs to go down. Efforts are constantly being made to reduce the PCU size even further and also to reduce manufacturing costs. As a consequence, heat density will go up (~ 200 – 250 W/cm2) and thus, a better high performance cooler/heat exchanger is required that can operate under the existing cooling system design and at the same time, maintain active devices temperature within optimum range (<120 – 125 °C) for higher reliability. The aim of this dissertation was to study the various cooling options based on jet impingement, mini-channel, ribbed mini-channel, phase change material and double sided cooling configurations for application in hybrid electric vehicle and other similar consumer products and perform parametric and optimization study on selected designs. Detailed experimental and computational analysis was performed on different cooling designs to evaluate overall performance. Severe constraints such as choice of coolant, coolant flow-rate, pressure drop, minimum geometrical size and operating temperature were required for the overall design. High performance jet impingement based cooler design with incorporated fin-like structures induced swirl and provided enhanced local heat transfer compared to traditional cooling designs. However, the cooling scheme could manage only 97.4% of the target effectiveness. Tapered/nozzle-shaped jets based designs showed promising results (~40% reduction in overall pressure drop) but were not sufficient to meet the overall operating temperature requirement. Various schemes of mini-channel arrangement, which were based on utilizing conduction and convection heat transfer in a conjugate mode, demonstrated improved performance over that of impingement cooling schemes. Impingement and mini-channel based designs were combined to show high heat transfer rates but at the expense of higher pressure drops (~5 times). As an alternate, mini-channel based coolers with ~1.5 mm size channels having trip strips or ribs were studied to accommodate the design constraints and to enhance local as well as overall heat transfer rates and achieve the target operating temperature. A step by step approach to the development of the heat exchanger is provided with an emphasis on system level design. The computational based optimization methodology is confirmed by a fabricated test bed to evaluate overall performance and compare the predicted results with actual performance. Additionally, one of the impingement based configuration (Swirl-Impingement-Fin) developed during the course of this work was applied to the internal cooling of a turbine blade trailing edge and was shown to enhance the thermal performance by at least a factor of 2 in comparison to the existing pin-fin technology for the conditions studied in this work. / Ph. D.

The urgent need to reduce green house gas emissions from the transport sector, particularly from heavy-duty trucks, has underscored the importance of developing more efficient internal combustion engines. Using computational fluid dynamics (CFD), this work investigated the impact of valve seat geometry on in-cylinder swirl, addressing a gap in research. Additionally, the suitability of steady-state simulations for providing valid qualitative data on port flow was assessed. To answer both research questions, two approaches were followed: steady-state port flow RANS simulations, and transient RANS simulations in a running engine setup. The results from the steady-state simulations highlighted the limitations of this approach to qualitatively predict swirl, as this quantity is highly dependent on the mesh. Despite these limitations, the steady-state simulations were still able to capture the trade-off between swirl and discharge coefficient, outlined in the literature. Transient simulations revealed that in-cylinder swirl is affected by the geometry of the valve seats. It was found that valve seats that direct the flow towards the liner, while avoiding strong flow separation tend to promote higher swirl, whereas valve seats that induce strong flow separation lead to lower swirl ratios. Despite the trade-off between swirl and volumetric efficiency, the volumetric efficiency losses were found to be practically negligible. The study emphasizes the need for a more comprehensive set of simulations, including more valve lifts and pressure ratios. Given the unsuitability of the steady-state simulations to predict swirl trends, future investigations should focus on replacing this approach by transient simulations with steady-state geometry and boundary conditions, properly addressing flow time-dependency at relatively low computational cost, and facilitating validation with experimental data.

Thermische Energiespeicher tragen u. a. zur Erhöhung der Versorgungsicherheit in der Fernwärmeversorgung und zur Effizienzsteigerung des Fernwärmesystems (z. B. Flexibilisierung der Erzeuger, Speicherung überschüssiger Wärme, besserer hydraulischer Betrieb) bei. Dafür eignen sich Druckbehälter, sog. schlanke Heißwasserspeicher (Speichertyp b1). Die oben genannten Vorteile setzen einen effizienten Speicherbetrieb (niedrige interne und externe Speicherverluste) voraus. Dieser Beitrag beschäftigt sich mit der Minimierung der internen Verluste durch die Verbesserung des thermischen Schichtungsverhaltens. Eine thermische Schichtung mit einem möglichst schmalen Übergangsbereich zwischen heißer und kalter Zone ist ein Indikator für geringe Mischvorgänge während der Beladung. Die Minimierung dieser Mischungsvorgänge bei der Beladung nimmt eine Schlüsselrolle bei der Minimierung der internen Speicherverluste ein. Lohse und Brähmer untersuchten die Beladung mit herkömmlichen radialen Diffusor in schlanken Heißwasserspeicher mit numerischer Strömungssimulation. Die Arbeiten identifizieren aufgrund der schlanken Speicherform nachteilige Strömungseffekte wie z. B. einen ausgeprägten Wandstrahl. Dieser Wandstrahl regt Mischvorgänge an und damit steigen die internen Speicherverluste. Zur Überwindung dieser Strömungsproblematik schlägt die Beladung mit Drall vor. Die Untersuchungen von Oestreich zeigten das Strömungsverhalten im Diffusor und im Speicher, die Auswirkungen auf die thermische Schichtung sowie die Vorteilhaftigkeit. Dieser Beitrag soll eine detailliertere Beschreibung der Strömungsvorgänge liefern. Dieses Wissen ist unbedingt notwendig, um die Ursachen und Wirkungen bei der Beladung mit Drall und beim Aufbau der thermischen Schichtung besser zu verstehen. Die Modellierung und Simulation des Diffusors bzw. des Speichers erfolgen mit ANSYS CFX. Zur Auflösung turbulenter Strukturen findet die Large Eddy Simulation Anwendung. Dieser Artikel präsentiert erstmalig die Wirbelstrukturen im Diffusor mit Leitelementen zur Drallerzeugung. Die Speicherströmung weist ein ähnliches Verhalten zu bekannten Dichteströmungen (z. B. Lappen-Kluft-Struktur, Instabilitäten in den freien Scherschichten) auf, was bisher nicht bekannt war. Hohe Peclet-Zahlen (hohe Advektionsströme) im Speichermodell führen zu numerischer Instabilität der Simulation und erfordern deshalb erhöhten Diskretisierungsaufwand. / Thermal energy storage systems contribute, among other things, to increasing the security of supply in the district heating system and to improving the efficiency of the district heating system (e.g., making the generators more flexible, storing waste heat, better hydraulic operation). Pressure vessels, so-called slim hot water storage tanks (storage type b1) are suitable for this purpose. The above mentioned advantages require efficient storage operation (low internal and external storage losses). This paper deals with the minimization of internal losses by improving the thermal stratification behavior. Thermal stratification with a thermocline between hot and cold zone as narrow as possible is an indicator of low mixing processes during loading. Minimizing these mixing processes during loading takes a key role in minimizing internal storage losses. Lohse and Brähmer investigated loading with conventional radial diffuser in slim hot water storage tanks with numerical flow simulation. The work identifies adverse flow effects due to the slim tank shape, such as a wall jet. This wall jet stimulates mixing processes and thus increases the internal storage losses. To overcome this flow problem, Findeisen et al. proposes swirl loading. The investigations of Oestreich et al. showed the flow behavior in the diffuser and in the storage, the effects on the thermal stratification as well as the advantageousness. This paper aims to provide a more detailed description of the flow processes. This knowledge is essential to better understanding the causes and effects of swirl loading and the structure of thermal stratification. Modeling and simulation of the diffuser and storage, respectively, are performed using Ansys CFX. Large eddy simulation (LES) is applied to resolve turbulent structures. This paper presents for the first time the vortex structures in the diffuser with internal elements for swirl generation. The storage flow exhibits similar behavior to known density flows (e.g., head and nose formation, instabilities in the free shear layers), which was previously unknown. High Peclet numbers (high advection currents) in the storage model lead to numerical instability of the simulation and therefore require increased discretization efforts.

Cette thèse est une contribution à l’étude des flammes de méthane turbulentes non prémélangées en rotation, dites swirlées, avec ou sans enrichissement en oxygène de l’oxydant. L’étude se focalise sur la stabilité de la flamme, les émissions polluantes et la dynamique du jet en non réactif et réactif. Notre dispositif expérimental se compose d’un brûleur à swirler coaxial avec injection radiale de méthane au voisinage de la sortie du brûleur. Ce dernier est confiné dans une chambre de combustion. La teneur en oxygène dans l’oxydant, le nombre de swirl géométrique et la richesse globale à l’injection sont les principaux paramètres qui peuvent être précisément contrôlés. La stabilité de la flamme est caractérisée par chimiluminescence OH*. Les émissions polluantes sont mesurées par des analyseurs en ligne via un prélèvement dans les gaz brûlés. La dynamique du jet est caractérisée principalement par PIV stéréoscopique dans un plan longitudinal et plusieurs plans transverses. La diffusion du méthane dans le jet swirlé est abordée qualitativement par fluorescence induite par laser de l’acétone dans un plan. À ce jour, peu de travaux portent sur la caractérisation notamment dynamique de ces flammes swirlées avec enrichissement en O2. La mise en rotation du jet est à l’origine d’une zone de recirculation centrale qui favorise la stabilisation de la flamme en régime pauvre et à grand nombre de Reynolds. L’étude des émissions polluantes montre que les régimes de combustion à l’air pour lesquels la flamme est liftée stable sont aussi ceux qui produisent du CO et du CH4 résiduel en des quantités non négligeables. L’enrichissement en oxygène permet alors de convertir les imbrûlés et ce pour de faibles enrichissements tout en améliorant la stabilité de flamme via une diminution de la hauteur d’accrochage et des fluctuations associées comme le confirment de précédentes études. L’augmentation des NOx par la voie thermique a été quantifiée pour des enrichissements en oxygène inférieurs à 30 % vol. L’étude systématique en non réactif et réactif apporte des détails sur la topologie tridimensionnelle du jet swirlé suivant les paramètres de l’étude. L’étude de la décroissance des vitesses et de la décroissance du nombre de swirl dans la direction de l’écoulement permetde mettre en évidence l’effet de la flamme sur le jet swirlé. Un couplage entre l’évolution du taux d’entraînement par la recirculation externe et les émissions polluantes est mis en évidence pour expliquer l’évolution des NOx suivant la richesse globale à l’injection. Nous avons proposé une modélisation des écoulements swirlés qui repose sur les écoulements à vorticité hélicoïdale afin d’identifier les caractéristiques principales des structures hélicoïdales au sein de l’écoulement. / This thesis is a contribution to the study of turbulent non-premixed swirling methane flames with or without oxygen addition in the oxidizer. The study deals with the flame stability, the pollutant emissions and the jet dynamic behaviour in non-reacting and reacting conditions. The burner, operating in a combustion chamber, consists of two concentric tubes with a swirler placed in an annular arrangement, which supplied the oxidant flow (air or oxygen-enriched air). The central pipe delivers fuel (methane) radially just below the burner exit plane. The oxygen content in the oxidizer, the geometric swirl number and the global equivalence ratio are the main parameters, which can be precisely set. OH* chemiluminescence imaging is used to characterize flame stability. Multi-gas analyzers are used to measure pollutant emissions in the exhaust gas. The flow is characterized using stereoscopic PIV measurements in different longitudinal and transverse planes. A qualitative study dealing with the methane diffusion imaging is also conducted by use of acetone planar laser-induced fluorescence. Up to now only few studies have examined the dynamic behavior of this type of swirled flames with oxygen addition. Introducing swirl allows creating a central recirculation zone which favors lean flame stabilization at higher Reynolds numbers. The mapping of the combustion regimes combined with the pollutant emission results show that the stable lifted flames are related to high CO and residual CH4 emission levels in the exhaust gas. Oxygen addition, even by a few percent, allows improving CO and unburned hydrocarbons conversion and increasing flame stability at the same time via a decrease of liftoff heights and the related fluctuations. The NOx emissions increase via the thermal pathway with increasing the oxygen-enrichment rate up to 30 % vol. A comparative study in non-reacting and reacting conditions is conducted to give insight into the tridimensional flow field topology varying the above-mentioned parameters. Mean streamwise velocity and swirl number decay rates show the flame effects on the flow dynamics. A coupling mechanism between the entrainment rate of the surroundings via the external recirculation and the pollutant emissions is proposed to explain the NOx emission trend with the global equivalence ratio. A model is also proposed based on the helical vortices to identify the main features of helix structures in the jet in non-reacting and reacting conditions.

L’évolution des turboréacteurs vers des taux de dilution toujours plus importants est associée à de nouvelles problématiques. Parmi elles, le raccourcissement de l’entrée d’air et de la tuyère est associé à une diminution du gain apporté par les traitements acoustiques de nacelle. La contribution des traitements situés dans l’espace entre la soufflante et le stator redresseur (OGV) va donc prendre de l’importance par rapport à l’ensemble des traitements. Cette zone, également appelée “interstage”, est caractérisée par une forte giration de l’écoulement moyen due à l’entraînement du fluide par le rotor. L’objectif de ce travail est de développer un modèle analytique afin d’évaluer l’effet de la giration sur le comportement des traitements acoustiques dans l’interstage, ainsi que sur le bruit à large-bande rayonnant en amont dû à l’interaction de la turbulence en aval de la soufflante avec les aubes des stators (OGV). Dans un premier temps, l’évolution de petites perturbations dans écoulement moyen tournant et cisaillé dans un conduit rigide est étudiée. Après avoir introduit les équations ainsi que les hypothèses du problème, l’analogie acoustique de Posson & Peake [122] est présentée. L’effet de la giration sur le contenu modal dans un conduit rigide est mis en évidence pour plusieurs types d’écoulements tournants. En particulier, le décalage des fréquences de coupures est étudié. L’étude est ensuite étendue au cas d’un conduit annulaire traité acoustiquement. Une attention particulière est portée sur la condition aux limites à appliquer aux parois du conduit. Dans ce cadre, une correction due aux effets centrifuges est apportée à la condition aux limites de Myers [101]. Une extension du modèle de Brambley [24] est aussi proposée afin de prendre en compte l’effet de l’épaisseur de la couche limite aux parois du conduit dans le cas tournant. Les effets combinés de la rotation et de la condition aux limites sur le contenu modal sont ensuite étudiés. En outre, une relation de dispersion pour les modes de surfaces en présence d’écoulement tournant est développée. À partir des développements précédents, un modèle de transmission acoustique est proposé afin d’évaluer l’effet de la giration sur le comportement des traitements acoustiques. La méthode repose sur le principe de raccordement modal appliqué à la conservation du débit massique et de l’enthalpie totale aux interfaces séparant les sections rigides et traitées. Une nouvelle méthode de projection basée sur les propriétés des polynômes de Chebyshev est proposée. À partir de ce modèle, l’efficacité des traitements acoustiques est étudiée pour différents écoulements tournants. Enfin, un modèle de prédiction du bruit à large-bande d’interaction rotor-stator est établi à partir de l’analogie de Posson & Peake [122], dans le but de prendre en compte l’effet de la giration sur la puissance acoustique rayonnée en amont. Le terme source est calculé selon le formalisme de Posson et al. [120]. Le modèle ainsi développé permet de prendre en compte une évolution radiale des paramètres géométriques et des propriétés statistiques de la turbulence incidente. Le modèle est ensuite évalué sur le cas test NASA SDT pour différents régimes et géométries. / The advent of modern turbofan engines such as UHBR goes along with new issues. Amongst others, the shortening of the inlet and exhaust yield a relatively higher importance of the liners located inside the interstage, where the flow is highly swirling. The present work aims at developing analytical models to assess the effect of the swirl both on the behavior of the interstage liners and on the upstream radiation of the fan-OGV interaction broadband boise. The evolution of small fluctuations in a rigid annular duct containing a swirling and sheared mean flow are studied first. After having introduced the governing equations and the main assumptions, the acoustic analogy of Posson & Peake [122] tailored to an annular duct with swirl and shear is presented. The effect of the swirl on the modal content in a rigid annular duct is highlighted for different types of swirl. In particular the shift of the cut-on thresholds is studied. Then, the modal analysis is extended to a duct with lined walls. A particular attention is paid on the boundary condition. Notably, a correction of the classical Myers boundary condition [101] is proposed to account for the centrifugal effects. An extension of Brambley’s boundary condition [24] is also derived to account for the boundary layer thickness to first order. The effect of both the swirl and the boundary condition on the modal content are studied. Besides, a dispersion relation for the surface waves is derived for the corrected Myers boundary condition. Based on the previous modal analyses, a transmission tool is developed to assess the effect of the swirl on the efficiency of a liner. The method, which relies on the mode-matching approach, is based on the conservation of the total enthalpy and the mass flow at the interfaces between the rigid and the lined sections. Due to the nature of the eigenfunctions, a new projection method based on the Chebyshev polynomial properties is proposed. Thanks to this model, the absorption is assessed for different types of swirl. Finally, a rotor-stator interaction broadband noise prediction model is derived from Posson & Peake’s acoustic analogy [122], to account for the effect of the swirl on the upstream radiated acoustic power. The source term is computed according to Posson et al.’s model [120]. It allows considering a radial variation of the geometry and the statistical properties of the incident turbulence. The model is assessed on the NASA SDT test case and the effect of the swirl is evaluated for several stator geometries and regimes.

O projeto de pesquisa propôs avaliar a metodologia de Simulação de Escalas Adaptativas (SAS) para descrever escoamentos turbulentos e não-reativos utilizando estudos de casos característicos, amplamente documentados, os quais possuem comportamentos do escoamento distintos presentes em diferentes regiões de uma câmara de combustão. O primeiro estudo de caso foi a análise do escoamento sobre um degrau, em que foi avaliada a capacidade do modelo Simulação de Escalas Adaptativas, frente aos modelos de Navier-Stokes com Média de Reynolds (RANS) e Simulação de Grandes Escalas (LES) e aos dados experimentais, em prever a distribuição de pressão, ponto de recolamento e de perfis de velocidade ao longo do domínio após a separação. Pode-se notar que o modelo SAS apresentou resultados praticamente idênticos aos resultados obtidos pelo modelo RANS com relação à distribuição de pressão e a posição ponto de recolamento. Porém, os perfis de velocidade apresentaram algumas discrepâncias com relação aos perfis de velocidade dos modelos RANS e LES e dos resultados experimentais. Um segundo estudo de caso foi a análise do escoamento através de um turbilhonador, em que a capacidade do modelo SAS foi avaliada, comparando seus resultados com os resultados do modelo de Navier-Stokes Não-Estacionárias com Média de Reynolds (URANS) e com os dados experimentais, em prever perfis de velocidade em regiões de recirculação presentes neste estudo de caso. Pode-se observar que ambos os modelos conseguiram prever as principais estruturas de recirculação do escoamento, porém, os perfis de velocidade apresentaram significativas discrepâncias com relação aos dados experimentais. Em seguida, foram feitas comparações entre os modelos SAS e URANS com relação à previsão da precessão central de vórtice e de estruturas de vórtices, das quais foi observado que o modelo SAS apresenta uma maior capacidade para prever estas estruturas em relação ao modelo URANS. / The research project aimed to evaluate the Scale-Adaptive Simulation (SAS) methodology to describe turbulent and non-reactive flows using characteristic, widely documented, case studies, which have distinct flow behaviors present in different regions of a chamber of combustion. The first case study was the analysis of a flow over a backward-facing step, from which the Scale-Adaptive Simulation (SAS) model capacity was evaluated, compared to the Reynolds Averaged Navier-Stokes (RANS) and Large-Eddy Simulation (LES) models and experimental data, in order to predict the pressure distribution, reattachment point and velocity profiles throughout the domain after separation. It can be noticed that the SAS model presented results almost identical to the results obtained by the RANS model in relation to the pressure distribution and reattachment position. However, the velocity profiles presented some discrepancies in respect to RANS and LES velocity profiles and the experimental results. A second case study was the analysis of the flow through a swirler, from which the capacity of the SAS model was evaluated, comparing its results to the results of the Unsteady Reynolds Averaged Navier-Stokes (URANS) model and with the experimental data, to predict velocity profiles in recirculation regions present in this case study. It can be observed that both models were able to predict the main recirculation structures of the flow, however, the velocity profiles presented significant discrepancies in relation to the experimental data. Then, comparisons were made between the SAS and URANS models in respect to the prediction of vortex precession vortex core and vortex structures, from which it was observed that the SAS model presents a greater capacity to predict these structures in relation to the URANS model.

Esta tese apresenta um modelo matemático para simulação numérica do escoamento com turbilhonamento (swirl) em tochas de plasma térmico de arco não transferido que operam em corrente contínua, assim como os resultados obtidos com as simulações para estudo de casos. O modelo magneto-hidrodinâmico (modelo MHD) bidimensional permitiu simular a interação entre o escoamento e o arco elétrico usando uma configuração axissimétrica, que abrange as seguintes regiões: entrada do gás; interior da tocha; jato de plasma livre no ambiente. O modelo foi implementado num código numérico baseado no Método dos Volumes Finitos para a solução numérica das equações governantes. Para os estudos foram simulados casos com diferentes condições operacionais (vazão de gás; intensidade de corrente elétrica; gases plasmogênicos: ar e argônio; intensidade de turbilhonamento). A fim de verificar a qualidade do modelo, alguns resultados foram comparados com a literatura e apresentaram boa concordância: a maior diferença obtida entre valores de temperatura experimentais e valores calculados foi -10%, e a média das diferenças obtidas nas comparações foi de aproximadamente ±3,2%. Os perfis de temperatura e de velocidade obtidos para a região do arco e para o jato de plasma resultante permitiram o estudo do comportamento do escoamento na tocha de plasma em diferentes condições. Conclui-se que o modelo desenvolvido é apto à realização de investigações numéricas do escoamento em tochas de plasma e dos efeitos do turbilhonamento na interação arco/escoamento. / This thesis presents a mathematical model for numerical simulation of swirling flow in DC non-transferred arc thermal plasma torches, as well as the results obtained from simulations to case studies. The two-dimensional magnetohydrodynamic model (MHD model) allowed simulate the interaction between the flow and the electric arc using an axisymmetric configuration, covering the following areas: gas inlet; inside the torch; free jet of plasma in the environment. The model was implemented in a computer code based on the Finite Volume Method (FVM) to enable the numerical solution of the governing equations. For the study, cases were simulated with different operating conditions (gas flow rate; electric current intensity; plasmogenic gases: air and argon; swirl intensity). In order to verify the quality of the model, some results were compared with the literature and showed good agreement: the biggest difference between experimental temperature values and calculated values was 10%, and the average of the differences obtained in the comparisons was approximately ±3.2%. The resulting profiles of temperature and velocity obtained for the region of the arc and the plasma jet allowed the study of the flow behavior in the plasma torch in different conditions. It is concluded that the model developed is able to carry out numerical investigations of the flow in plasma torches and the effects of swirl in the interaction arc/flow.

In this thesis, the concept of style transfer for visual storytelling is introduced. Style transfer for visual storytelling is the process of identifying a definitive style of a source, such as an artist or culture, and applying the features of that style to a target, such as a character which has a different style. As a proof of concept, the style of the American film director Tim Burton is transferred to a character from Hindu mythology, Yamah. The style transfer is done based on the concept of 'Pattern Language' introduced by Christopher Alexander et al., in his book, 'A Pattern Language'. A set of patterns is developed based on the source and target. The target is then designed based on the patterns. The design is then visualized in a suitable medium.