Ein neues, verallgemeinertes Modell für Blasenkoaleszenz und –zerfall wurde entwickelt. Es basiert auf physikalischen Überlegungen und berücksichtigt verschiedene Mechanismen, die zu Blasenkoaleszenz und –zerfall führen können. In einer ausführlichen Literaturrecherche wurden zunächst die verfügbaren Modelle zusammengestellt und analysiert. Es zeigte sich, dass viele widersprüchliche Modelle veröffentlicht wurden. Keins dieser Modelle erlaubt die Vorhersage der Entwicklung der Blasengrößenverteilungen entlang einer Rohrströmung für einen breiten Bereich an Kombinationen von Volumenströmen der Gas- und der Flüssigphase. Das neue Modell wurde ausführlich in einem vereinfachten Testsolver untersucht. Dieser erfasst zwar nicht alle Einzelheiten einer sich entlang des Rohres entwickelten Strömungen, erlaubt aber im Gegensatz zu den CFD-Simulationen eine Vielzahl von Variationsrechnungen zur Untersuchung des Einflusses einzelner Größen und Modelle. Koaleszenz und Zerfall kann nicht getrennt von anderen Phänomenen und Modellen, die diese widerspiegeln, betrachtet werden. Es bestehen enge Wechselwirkungen mit der Turbulenz der Flüssigphase und dem Impulsaustausch zwischen den Phasen. Da die Dissipationsrate der turbulenten kinetischen Energie ein direkter Eingangsparameter für das neue Modell ist, wurde die Turbulenzmodellierung besonders genau untersucht. Zur Validierung des Modells wurde eine TOPFLOW-Experimentalserie zur Luft-Wasser-Strömungen in einem 8 m langen DN200-Rohr genutzt. Die Daten zeichnen sich durch eine hohe Qualität aus und wurden im Rahmen des TOPFLOW-IIVorhabens mit dem Ziel eine Grundlage für die hier vorgestellten Arbeiten zu liefern, gewonnen. Die Vorhersage der Entwicklung der Blasengrößenverteilung entlang des Rohrs konnte im Vergleich zu den bisherigen Standardmodellen für Blasenkoaleszenz und -zerfall in CFX deutlich verbessert werden. Einige quantitative Abweichungen bleiben aber bestehen. Die vollständigen Modellgleichungen sowie eine Implementierung über „User-FORTRAN“ in CFX stehen zur Verfügung und können für weitere Arbeiten zur Simulation polydisperser Blasenströmungen genutzt werden.

In this study, commercially available Computational Fluid Dynamics (CFD) software, CFX-4.4 has been used for the simulations of aerosol transport through various aerosol-sampling devices. Aerosol transport was modeled as a classical dilute and dispersed two-phase flow problem. Eulerian-Lagrangian framework was adopted wherein the fluid was treated as the continuous phase and aerosol as the dispersed phase, with a one-way coupling between the phases. Initially, performance of the particle transport algorithm implemented in the code was validated against available experimental and numerical data in the literature. Code predictions were found to be in good agreement against experimental data and previous numerical predictions. As a next step, the code was used as a tool to optimize the performance of a virtual impactor prototype. Suggestions on critical geometrical details available in the literature, for a virtual impactor, were numerically investigated on the prototype and the optimum set of parameters was determined. Performance curves were generated for the optimized design at various operating conditions. A computational model of the Linear Slot Virtual Impactor (LSVI) fabricated based on the optimization study, was constructed using the worst-case values of the measured geometrical parameters, with offsets in the horizontal and vertical planes. Simulations were performed on this model for the LSVI operating conditions. Behavior of various sized particles inside the impactor was illustrated with the corresponding particle tracks. Fair agreement was obtained between code predictions and experimental results. Important information on the virtual impactor performance, not known earlier, or, not reported in the literature in the past, obtained from this study, is presented. In the final part of this study, simulations on aerosol deposition in turbulent pipe flow were performed. Code predictions were found to be completely uncorrelated to experimental data. The discrepancy was traced to the performance of the code's turbulent dispersion model. A detailed literature survey revealed the inherent technical deficiencies in the model, even for particle dispersion. Based on the results of this study, it was determined that while the code can be used for simulating aerosol transport under laminar flow conditions, it is not capable of simulating aerosol transport under turbulent flow conditions.

In this study, commercially available Computational Fluid Dynamics (CFD) software, CFX-4.4 has been used for the simulations of aerosol transport through various aerosol-sampling devices. Aerosol transport was modeled as a classical dilute and dispersed two-phase flow problem. Eulerian-Lagrangian framework was adopted wherein the fluid was treated as the continuous phase and aerosol as the dispersed phase, with a one-way coupling between the phases. Initially, performance of the particle transport algorithm implemented in the code was validated against available experimental and numerical data in the literature. Code predictions were found to be in good agreement against experimental data and previous numerical predictions. As a next step, the code was used as a tool to optimize the performance of a virtual impactor prototype. Suggestions on critical geometrical details available in the literature, for a virtual impactor, were numerically investigated on the prototype and the optimum set of parameters was determined. Performance curves were generated for the optimized design at various operating conditions. A computational model of the Linear Slot Virtual Impactor (LSVI) fabricated based on the optimization study, was constructed using the worst-case values of the measured geometrical parameters, with offsets in the horizontal and vertical planes. Simulations were performed on this model for the LSVI operating conditions. Behavior of various sized particles inside the impactor was illustrated with the corresponding particle tracks. Fair agreement was obtained between code predictions and experimental results. Important information on the virtual impactor performance, not known earlier, or, not reported in the literature in the past, obtained from this study, is presented. In the final part of this study, simulations on aerosol deposition in turbulent pipe flow were performed. Code predictions were found to be completely uncorrelated to experimental data. The discrepancy was traced to the performance of the code's turbulent dispersion model. A detailed literature survey revealed the inherent technical deficiencies in the model, even for particle dispersion. Based on the results of this study, it was determined that while the code can be used for simulating aerosol transport under laminar flow conditions, it is not capable of simulating aerosol transport under turbulent flow conditions.

In this Master´s thesis will be performed an analysis of thermal properties of synchronous machines in the program Ansys Workbench on a simplified model of synchronous traction motor. In the first section will be performed thermal analysis without cooling followed by analysis of air flow and finally thermal analysis with cooling for fan speed 1500 min-1 and 3000 min-1. The second section will describe the principle, construction and losses on the synchronous machine. The third chapter will describe concepts such as heat, temperature, heat transfer, types of the heat transfer, specific heat capacity, emisivity and thermal conductivity. The fourth chapter will introduce the program Ansys Workbench, finite element method and Ansys CFX. In the fifth chapter will be described how to perform thermal analysis on the created model of motor. The sixth chapter will describe how to analyze the air flow of the created model of motor. The flow analysis will be performed for fan speed 1500 min-1 and 3000 min-1. In the seventh chapter will be compared the results of the air flow and pressure field in the motor model. In the eighth chapter will be performed a thermal analyzis on the created motor model with cooling for fan speed 1500 min-1 and 3000 min-1. The nineth chapter will compare the results of temperatures and heat fluxes obtained from the thermal analysis witnout cooling, with cooling for fan speed 1500 min-1 and 3000 min-1 for full losses, half losses of continous running, and full losses of interrupt running for 9000 seconds (2 hours 30 minutes).

This master's thesis contains basic hydraulic calculations, design and optimalization of both the rotor and stator part of the axial pump. There is also included an analysis of the principle and function of hydrodynamic axial pumps. The last part of this work is focusing on the strength calculations and flow simulations using CFD.

Labyrinth seal force estimates are important to the prediction of the stability of turbomachinery. The force prediction methods fall into several categories: experiments, bulk flow analysis, and finite volume analysis. Finite volume analysis can be split into two subcategories: self-developed and commercial. In this research, a commercial computational fluid dynamics (CFD) program called ANSYS-CFX was used to predict the forces generated in a labyrinth seal whirling at specified speeds. The results were compared to data from VT-FAST, a bulk flow code, and TASCflow, another commercial CFD program. It was shown that there were discrepancies among the results, and several hypotheses were made as to the reason for these discrepancies. Additionally, ANSYS-CFX was used to study the effect of labyrinth seal eccentricity ratio on the resultant force generated. It was shown that the radial force component within the seal behaved linearly with respect to eccentricity ratio. However, the tangential force component had no distinguishable relationship with the eccentricity ratio. It was hypothesized that the lack of a relationship was caused by the small fluctuations in the inlet swirl. Although the inlet swirl varied very little at each eccentricity ratio, it was shown there was a relationship between the tangential force and inlet swirl. / Master of Science

O estudo da ventilação natural como forma de amenização climática tem sido tema de diversos trabalhos científicos apresentados em congressos e encontros da área de conforto ambiental tanto no país como no exterior. E segundo o Método de Givoni, em 74% das horas do ano, a ventilação natural é a principal estratégia de projeto para se obter o conforto térmico dos usuários na cidade de Aracaju SE. Assim sendo, tem-se como objeto desta pesquisa a ventilação natural nas habitações, e como objetivo geral um estudo do aproveitamento do vento para promover a ventilação natural em edificações residenciais na cidade de Aracaju, a fim de proporcionar melhores condições térmicas ambientais para os usuários sem a necessidade do condicionamento artificial do ar. O produto final consiste em recomendações de projeto baseadas nas pesquisas teóricas e simulações computacionais com o ANSYS CFX Computacional Fluid Dynamics Software que serviram de base para verificar a influência da ventilação natural na edificação por meio de propostas de alterações no projeto original. / Studies of natural ventilation as a way to minimize climate influences has been theme of several scientific papers presented in congresses and meetings concerning environmental comfort, in Brazil as well as in other countries. According to Givonis method, in 74% of the year hours, natural ventilation is the main strategy to obtain thermal comfort for the inhabitants of Aracaju (Sergipe capital city). Based on that information, the object of this research is the housing natural ventilation, and its general objective is a study of wind use to promote housing natural ventilation and provide better thermal comfort conditions of its users without the need of artificial air conditioning. The final product of this research consists in design recommendations based on theoretical research and computer simulations with ANSYS CFX Computacional Fluid Dynamics Software which became the base to verify the influence of natural ventilation in a building by proposing alterations in the original project.

O estudo da ventilação natural como forma de amenização climática tem sido tema de diversos trabalhos científicos apresentados em congressos e encontros da área de conforto ambiental tanto no país como no exterior. E segundo o Método de Givoni, em 74% das horas do ano, a ventilação natural é a principal estratégia de projeto para se obter o conforto térmico dos usuários na cidade de Aracaju SE. Assim sendo, tem-se como objeto desta pesquisa a ventilação natural nas habitações, e como objetivo geral um estudo do aproveitamento do vento para promover a ventilação natural em edificações residenciais na cidade de Aracaju, a fim de proporcionar melhores condições térmicas ambientais para os usuários sem a necessidade do condicionamento artificial do ar. O produto final consiste em recomendações de projeto baseadas nas pesquisas teóricas e simulações computacionais com o ANSYS CFX Computacional Fluid Dynamics Software que serviram de base para verificar a influência da ventilação natural na edificação por meio de propostas de alterações no projeto original. / Studies of natural ventilation as a way to minimize climate influences has been theme of several scientific papers presented in congresses and meetings concerning environmental comfort, in Brazil as well as in other countries. According to Givonis method, in 74% of the year hours, natural ventilation is the main strategy to obtain thermal comfort for the inhabitants of Aracaju (Sergipe capital city). Based on that information, the object of this research is the housing natural ventilation, and its general objective is a study of wind use to promote housing natural ventilation and provide better thermal comfort conditions of its users without the need of artificial air conditioning. The final product of this research consists in design recommendations based on theoretical research and computer simulations with ANSYS CFX Computacional Fluid Dynamics Software which became the base to verify the influence of natural ventilation in a building by proposing alterations in the original project.

Zur Verringerung von Schadstoffemissionen werden in Kaminöfen oft Keramikfilter integriert, die Staub und Ruß aus dem Abgas entfernen sollen. Die Filter beeinflussen jedoch die strömungsmechanischen, energetischen und chemischen Vorgänge im Feuerraum. Für die Auslegung und die praktische Anwendung der Filter ist die Kenntnis der Einflussgrößen und deren Umfang nötig. Mit Hilfe von experimentellen und numerischen Untersuchungen wurden die Stoff- und Energietransportvorgänge von zwei Kaminöfen charakterisiert. Zur Bestimmung der Massenabnahme von Holzscheiten kam eine neue, praktisch leicht umsetzbare Methode, basierend auf einer Schockkühlung mit flüssigem Stickstoff, zum Einsatz. Parallel dazu wurde die Massenabnahme der Holzscheite mit Hilfe einer Online-Massenbestimmung mittels Waage aufgezeichnet und ein Verfahren zur Bestimmung der Abbrandkinetik entwickelt. Die Schwierigkeiten der messtechnischen Erfassung und Auswertung der instationären Vorgänge wurden dargestellt und diskutiert. Für die zwei Kaminöfen sind numerische Simulationen mit der Software ANSYS CFX erstellt worden, die weitgehend auf realen Geometrien beruhen. Vergleichende null- und eindimensionale Simulationen mit unterschiedlichen Reaktionsmechanismen und gasförmigen Brennstoffen wurden realisiert und hinsichtlich ihrer Eignung für die Berechnung von Kaminöfen untersucht. Nach erfolgter Validierung wurde ein parametrisches Simulationsmodell eines Kaminofens erstellt. Mit diesem wurde eine Parameterstudie zur Untersuchung der Veränderung der Zielgrößen Heizleistung, Kohlenmonoxid- und Rußkonzentration sowie Gesamt- und Sekundärluftmassenstrom in Abhängigkeit der Parameter durchgeführt.

Zur Verringerung von Schadstoffemissionen werden in Kaminöfen oft Keramikfilter integriert, die Staub und Ruß aus dem Abgas entfernen sollen. Die Filter beeinflussen jedoch die strömungsmechanischen, energetischen und chemischen Vorgänge im Feuerraum. Für die Auslegung und die praktische Anwendung der Filter ist die Kenntnis der Einflussgrößen und deren Umfang nötig. Mit Hilfe von experimentellen und numerischen Untersuchungen wurden die Stoff- und Energietransportvorgänge von zwei Kaminöfen charakterisiert. Zur Bestimmung der Massenabnahme von Holzscheiten kam eine neue, praktisch leicht umsetzbare Methode, basierend auf einer Schockkühlung mit flüssigem Stickstoff, zum Einsatz. Parallel dazu wurde die Massenabnahme der Holzscheite mit Hilfe einer Online-Massenbestimmung mittels Waage aufgezeichnet und ein Verfahren zur Bestimmung der Abbrandkinetik entwickelt. Die Schwierigkeiten der messtechnischen Erfassung und Auswertung der instationären Vorgänge wurden dargestellt und diskutiert. Für die zwei Kaminöfen sind numerische Simulationen mit der Software ANSYS CFX erstellt worden, die weitgehend auf realen Geometrien beruhen. Vergleichende null- und eindimensionale Simulationen mit unterschiedlichen Reaktionsmechanismen und gasförmigen Brennstoffen wurden realisiert und hinsichtlich ihrer Eignung für die Berechnung von Kaminöfen untersucht. Nach erfolgter Validierung wurde ein parametrisches Simulationsmodell eines Kaminofens erstellt. Mit diesem wurde eine Parameterstudie zur Untersuchung der Veränderung der Zielgrößen Heizleistung, Kohlenmonoxid- und Rußkonzentration sowie Gesamt- und Sekundärluftmassenstrom in Abhängigkeit der Parameter durchgeführt.