Das Ziel dieser Forschungsarbeit ist die Bestimmung charakteristischer aerodynamischer Koeffizienten im Schwebeflug mit Hilfe von Strömungssimulationen. Diese Koeffizienten werden für eine modellbasierte Regelung eines vollaktuierten Multikopters benötigt. Für die Simulationen wird aufbauend auf vorangegangenen Arbeiten ein ‚Sliding-mesh‘-Modell optimiert und einem ‚Overset-mesh‘-Modell gegenübergestellt. Die Verfahren werden anhand von Mess- sowie Referenzdaten hinsichtlich ihrer Rechenzeit und Genauigkeit verglichen. Die Messdaten werden im Rahmen dieser Arbeit ausgewertet. Die Referenzdaten stammen aus älteren Untersuchungen. Das ‚Overset-mesh‘-Verfahren liefert bei viermal höherer Rechenzeit gleichwertige adäquate Ergebnisse. Aus diesen Gründen werden anknüpfende Untersuchungen des Zeitverhaltens der Rotorschubkraft bei Drehzahländerungen mit dem ‚Sliding-mesh‘-Modell durchgeführt. Es wird beobachtet, dass die Schubkraft innerhalb der Simulation den Messdaten bei Drehzahlsprüngen vorauseilt.:1 Einleitung 1.1 Motivation 1.2 Zielsetzung und Aufbau der Arbeit 2 Theoretische Grundlagen 2.1 Strömungsmechanik 2.1.1 Grundgleichungen 2.1.2 Zusätzliche Gleichungen 2.1.3 Navier-Stokes-Gleichungen 2.1.4 Laminare und turbulente Strömungen 2.1.5 Grenzschicht 2.2 Numerische Strömungsmechanik 2.2.1 Numerische Diskretisierung 2.2.2 Numerische Lösungsmodelle 2.2.3 Turbulenzmodelle 2.3 Rotorströmungen 2.3.1 Strahltheorie 2.3.2 Numerische Rotorsimulation 3 Stand der Technik 3.1 Motivation 3.2 Rotorströmung 3.3 Aeroelastizität 3.4 Nachlaufströmung 4 Umsetzung 4.1 Modellbildung 4.1.1 ‚Sliding-mesh‘-Verfahren 4.1.2 ‚Overset-mesh‘-Verfahren 4.2 Validierung 4.2.1 ‚Sliding-mesh‘-Verfahren 4.2.2 ‚Overset-mesh‘-Verfahren 4.3 Modifikationen 4.3.1 ‚Sliding-mesh‘-Verfahren 4.3.2 ‚Overset-mesh‘-Verfahren 4.4 Auswertung 4.4.1 ‚Sliding-mesh‘-Verfahren 4.4.2 ‚Overset-mesh‘-Verfahren 5 Messaufbau und Messauswertung 5.1 Messaufbau 5.2 Messauswertung 5.2.1 Schubkraftverlauf 5.2.2 Drehmomentenverlauf 6 Zeitverhalten 6.1 Modellbildung 6.2 Auswertung Schubkraftverlauf 6.2.1 Drehzahlsprung 1 6.2.2 Drehzahlsprung 2 7 Zusammenfassung und Ausblick 7.1 Zusammenfassung 7.2 Ausblick

Este trabalho discute a questão da interação entre o casco do navio e o propulsor em funcionamento conjunto, e sua simulação por ferramentas computacionais. O texto se concentra em descrever os principais efeitos dessa interação, as principais dificuldades em se estimar esses efeitos, os métodos tradicionalmente usados, e como ferramentas computacionais podem ser aplicadas de maneira vantajosa. No texto também pode ser encontrada uma análise crítica dos métodos mais comuns e dos resultados, baseada em trabalhos de diversos autores, publicados nacional e internacionalmente. É apresentado o método dos volumes finitos, usado nesta pesquisa, algumas de suas particularidades principais, vantagens e desvantagens, e os resultados das simulações realizadas, interpretados à luz dos valores experimentais usados para comparação e das limitações do método dos Volumes Finitos. A comparação é feita analisando-se grandezas integrais, como a resistência do casco ou o empuxo do propulsor; e também as características do escoamento, como o perfil de velocidade na esteira, presença de vórtices, e outras estruturas típicas. Os resultados obtidos têm a mesma ordem de precisão dos que tem sido obtidos por outros pesquisadores, internacionalmente, e são coerentes qualitativamente; mas algumas questões referentes aos modelos físico e numérico escolhidos ainda limitam a precisão dos resultados e restringem sua adoção em atividades de engenharia. Entretanto, diversas características observadas no escoamento contribuem para aumentar o conhecimento de alguns fenômenos envolvidos no problema. / This work is about the hull and propeller interaction in joint functioning, and its simulation by computational tools. The text concentrates in describing the main effects of such interaction, the main difficulties in the estimation of these effects, the methods traditionally adopted, and how computational tools can be applied in advantageous way. A critical analysis of the most common methods and results, based on paperworks of several different authors worldwide, can also be found. The Finite Volumes method, used in this research, is presented - its main issues, advantages and disadvantages, and the simulations outcomes, compared to the experimental values and explained by the knowledge of the Finite Volumes method limitations. The comparison is made by means of both integral values, such as the hull\'s resistance or the propeller thrust; as well as the characteristics of the flow, like the wake velocity profile, presence of vortex, and other typical structures. The results shows the same error band than the ones which has been obtained by other researchers, worldwide, and most of the typical characteristics of the flow were observed. But some issues concerned to the chosen physical and numerical models still limit the precision of the outcomes, and restrict the application of such models at engineering activities. But several insights about the flow, obtained at this study, can be useful to the understanding of some phenomena involved in the propeller operation.

Este trabalho discute a questão da interação entre o casco do navio e o propulsor em funcionamento conjunto, e sua simulação por ferramentas computacionais. O texto se concentra em descrever os principais efeitos dessa interação, as principais dificuldades em se estimar esses efeitos, os métodos tradicionalmente usados, e como ferramentas computacionais podem ser aplicadas de maneira vantajosa. No texto também pode ser encontrada uma análise crítica dos métodos mais comuns e dos resultados, baseada em trabalhos de diversos autores, publicados nacional e internacionalmente. É apresentado o método dos volumes finitos, usado nesta pesquisa, algumas de suas particularidades principais, vantagens e desvantagens, e os resultados das simulações realizadas, interpretados à luz dos valores experimentais usados para comparação e das limitações do método dos Volumes Finitos. A comparação é feita analisando-se grandezas integrais, como a resistência do casco ou o empuxo do propulsor; e também as características do escoamento, como o perfil de velocidade na esteira, presença de vórtices, e outras estruturas típicas. Os resultados obtidos têm a mesma ordem de precisão dos que tem sido obtidos por outros pesquisadores, internacionalmente, e são coerentes qualitativamente; mas algumas questões referentes aos modelos físico e numérico escolhidos ainda limitam a precisão dos resultados e restringem sua adoção em atividades de engenharia. Entretanto, diversas características observadas no escoamento contribuem para aumentar o conhecimento de alguns fenômenos envolvidos no problema. / This work is about the hull and propeller interaction in joint functioning, and its simulation by computational tools. The text concentrates in describing the main effects of such interaction, the main difficulties in the estimation of these effects, the methods traditionally adopted, and how computational tools can be applied in advantageous way. A critical analysis of the most common methods and results, based on paperworks of several different authors worldwide, can also be found. The Finite Volumes method, used in this research, is presented - its main issues, advantages and disadvantages, and the simulations outcomes, compared to the experimental values and explained by the knowledge of the Finite Volumes method limitations. The comparison is made by means of both integral values, such as the hull\'s resistance or the propeller thrust; as well as the characteristics of the flow, like the wake velocity profile, presence of vortex, and other typical structures. The results shows the same error band than the ones which has been obtained by other researchers, worldwide, and most of the typical characteristics of the flow were observed. But some issues concerned to the chosen physical and numerical models still limit the precision of the outcomes, and restrict the application of such models at engineering activities. But several insights about the flow, obtained at this study, can be useful to the understanding of some phenomena involved in the propeller operation.

Several types of discrepancies have been examined between CFD simulations, wind tunnel measurements and real world conditions. The results of different wheel rotation methods show that while stationary approaches can often substitute real unsteady wheel rotation, they can also be very sensitive to the exact angular positioning of wheel rims. Using both measured and computed flow fields, the lower part of wheel wake was identified as a key area, showing differences between rotation methods and sources of simulation errors in general. It was also shown that the level of detail in tyre geometry and its deformation near contact patch do not have a large impact on accuracy. Due to the absence of tyre rotation, the tyre sidewall was identified as an important place of flow separation with large effect on flow field and forces. Angle of attack study confirmed that assessing purely straight-line drag causes its under prediction compared to real-world values. This judgement would however benefit from obtaining data in more adverse conditions compared to those currently available. Finally, tyre radial expansion was investigated, causing a drop in drag with increasing vehicle velocity and altering the flow around the rear bodywork. Ignoring this effect can therefore negatively influence the aerodynamic development of a vehicle.

The aim of this work is to create a computational model of radial industrial tumble dryers, to calculate and identify the amount of air that flows through the inside of the drum itself. The calculation will be performed via computational fluid dynamics (CFD). Furthermore, compile transient balance model of mentioned dryers. Perform simulation balance model and compare the results of simulations with experimental measurements. By comparing the experimental data and simulation to determine the degrees of freedom of balance model and evaluate their impact on the assembled transient model. For a better understanding of the drying process, there is constructed a system of differential equations describing heat and moisture within the material being dried on a simple model. In the section devoted to the computational analysis of fluid flow is analyzed existing geometry of the drum, which has a major impact on the flow of air inside the drum itself. Following describes how to simplify its complex geometry entering the computational fluid dynamics. Then, there is carried out a simulation of fluid flow inside the tumble dryers using MRF and Sliding Mesh models. Finally, there is an analysis of the data obtained and determined the average amount of air flowing through the drum itself. On the contrary, the aim of the work is not to create another text tool for students engaged in CFD theme.

<p dir="ltr">Precise measurement of the flowrate is crucial for both process control and energy consumption evaluation. The main aim of this work is to develop a methodology to calibrate mechanical flowmeters, designed to measure high viscosity fluids, in water. In order to accomplish this, a series of computational fluid dynamics (CFD) analysis are carried out to determine how the motion of the mechanical component varies with different flow rates of water and high viscosity fluids. This data is recorded and analyzed to develop calibration curves that relate the motion of the mechanical component the flow rates. From the calibration curves, it can be determined the required water flow rate to achieve the equivalent motion of the mechanical component in a specified viscosity. This method provides an efficient and cost-effective calibration process because it eliminates the need for calibrating using heated engine oil to achieve the fluid viscosity of the flow meter is designed. Flowmeter sensitivity analysis was also performed and it was observed that the motion of the mechanical component curves converges as the size of the flowmeter increases suggesting that the effect of viscosity on flowmeter sensitivity decreases as the size of the flowmeter is increased, likely due to reduced resistance to flow and smaller pressure drops. </p><p dir="ltr">The Kanbara Reactor ladle is a commonly used method in the steelmaking industry for hot-metal desulfurization pre-treatment. The impeller's configuration is pivotal to the reactor's performance, yet its precise function remains partially understood. This study introduces a 3-dimensional Volume-of-Fluid (VOF) model integrated with the sliding mesh technique, investigating the influence of five different impeller speeds. After Validating the model through experimental data, this numerical model is applied to investigate the typical developmental phenomena and the consequences of impeller speed variations on fluid flow characteristics, interface profile, and vortex core depth. The findings reveal that the rotational impeller induces a double-recirculation flow pattern in the axial direction due to the centrifugal discharging flow. With increasing impeller rotation speed, the vortex core depth also rises, emphasizing the substantial impact of impeller speed on vortex core depth.</p>

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Yes / A problem with 1-D water hammer modelling is in the application of accurate unsteady friction. Moreover, investigating the time response of fluid dynamics and unsteady turbulence structures during the water hammer is not possible with a 1-D model. This review article provides a summary of 1-D modelling using the recent finite volume approach and the discussion extends to a quasi-2-D model and historical developments as well as recent advancements in 3-D CFD simulations of water hammer. The eddy viscosity model is excellent in capturing pressure profiles but it is computationally intensive and requires more computational time. This article reviews 3-D CFD simulations with sliding mesh, an immersed solid approach, and dynamic mesh approaches for modelling valve closures. Despite prediction accuracy, a huge computational time and high computer resources are required to execute 3-D flow simulations with advanced valve modelling techniques. Experimental validation shows that a 3-D CFD simulation with a flow rate reduction curve as a boundary condition predicted accurate pressure variation results. Finally, a brief overview of the transient flow turbulence structures for a rapidly accelerated and decelerated pipe flow using DNS (Direct numerical simulation) data sets is presented. Overall, this paper summarises past developments and future scope in the field of water hammer modelling using CFD.

Les panneaux photovoltaïques ont pris ces dernières années une place importante dans le secteur de l’énergie. Les performances de ces panneaux dépendent notamment de la qualité et de l’homogénéité du silicium utilisé et des impuretés qu’il contient. Pour obtenir du silicium photovoltaïque, on peut utiliser un procédé de solidification dirigée afin d’obtenir un lingot de silicium de grade photovoltaïque à partir de silicium de grade métallurgique. Cette approche reste aujourd’hui difficile à simuler efficacement en raison de l’aspect multi-échelle du procédé et du suivi de l’interface mobile avec des transferts de masse et de chaleur à l’interface solide/liquide. Cette thèse présente la mise en œuvre d’une méthode originale de maillage glissant proposée pour réaliser un suivi adaptatif de l’interface mobile, afin d’améliorer l’efficacité des simulations. Dans un premier temps, la modélisation de la solidification dirigée d’un corps pur avec un tel maillage glissant est validée à l’aide d’une solution analytique dans une configuration diffusive de référence. L’impact de la méthode proposée est ensuite étudié dans une configuration de type Bridgman vertical en présence de convection naturelle dans la phase liquide. Dans un second temps, on s’intéresse à la ségrégation des impuretés dans cette même configuration. Pour cela, on propose une modélisation spécifique du rejet d’impuretés à l’interface, et on étudie l’impact sur les simulations de la méthode de maillage glissant proposée. Les résultats et les gains de performance pour les simulations sont discutés en faisant varier des paramètres de calcul et par comparaison avec des données de la littérature. / In recent years, photovoltaic panels took a key role in the energy sector. The efficiency of these panels depends notably on the quality of the processed silicon ingots and on their homogeneity regarding the impurities they include. In order to process photovoltaic silicon, one can use a directional solidification process to obtain a solar grade silicon ingot from a metallurgical grade silicon feedstock. This approach is still nowadays hard to simulate with efficiency because of the multi-scales aspects of the process and because of the front tracking of the interface, where some heat and mass transfer occurs. This thesis presents the implementation of an original moving mesh method, proposed in order to perform an adaptive front tracking of the moving interface. The aim is to improve the efficiency of the numerical simulations. In a first time, the directional solidification model of a pure substance with such a moving mesh is validated against an analytical solution based on a purely diffusive reference configuration. The influence of the proposed method is then studied on a vertical Bridgman configuration with natural convection in the liquid phase. In a second time, the segregation of impurities is considered in the same configuration. For this study, a specific model for the rejection of impurities is proposed at the solid/liquid interface, and the influence of the proposed moving mesh method on the results is as well explored. Finally, the results and the performance improvements for the numerical simulations are discussed through variations of the calculation parameters and through comparisons against data from the literature.

L'exploitation de l'énergie cinétique des courants marins ou fluviaux est une source d'énergie prometteuse et renouvelable. Les performances hydrodynamiques des hydroliennes sont à ce jour bien connues et l'attention se porte sur la compréhension des phénomènes de parc et l'interaction entre machines. Ce document présente la construction d'un modèle simplifié (ou méthode d'équivalence) pour les turbines à axe de rotation vertical. Une étape préliminaire consiste à valider l'utilisation de la méthode de maillage rotatif proposée par Code_Saturne (solveur CFD open source). La simulation de la turbine Darrieus/Achard A10 en 2D met en évidence une bonne concordance des mesures expérimentales (PIV). Cet outil sert dans une seconde étape à mettre au point un modèle simplifié de ces mêmes turbines. Celui-ci consiste à représenter la turbine dans l'écoulement par son équivalent en termes sources de quantité de mouvement sur la base d'une paramétrisation efficace des données empiriques. La méthode est validée pour une large plage de vitesses de rotation et de confinements, et sur plusieurs machines. La représentation du sillage par par les deux méthode de simulation est ensuite étudiée en détail. Des mesures par la technique de LDV dans le sillage proche d'un modèle réduit sont effectuées et établissent une référence expérimentale nécessaire pour ce type de machine. La dépendance forte des deux méthodes de simulation aux paramètres et aux modèles de turbulence est constatée. Deux phénomènes principaux sont relevés : la diffusion turbulente et les instabilités à grandes échelles. Des calculs de rendement sur des dispositions de machines variables illustrent l'applicabilité du modèle. Ils mettent notamment en avant l'effet positif de l'intensité turbulente ambiante sur le rendement dans un parc. / Harnessing kinetic energy from oceans or rivers is a promising source of renewable energy. The hydrodynamical performance of water turbines is well known and the focus is now on array optimization and turbine interaction. The present document aims to introduce a new modeling solution for vertical axis water current turbine of Darrieus/Achard type and its construction methodology. A preliminary stage consists in the validation of the new sliding mesh method available in Code_Saturne, EDF CFD open source solver. The good results obtained by comparison with PIV measurements on the Achard type turbine allow the use of this method as a reference tool. The second stage sees the construction of an equivalence model for the Darrieus turbine using momentum source terms. These terms are calculated thanks to an efficient parametrization of empirical data. The comparison of the model with full geometry calculation shows a good agreement in terms of power for a wide range of rotational velocity and blocking ratio. LDV measurements in the near wake of a small scale Achard turbine give a necessary reference set of data. The wake given by both simulations is strongly dependent of turbulence parameters or models, with the cohabitation of two main phenomena : momentum turbulent diffusion, and large scale fluctuations. To conclude, a calculation of the power output for several turbine distributions in an array illustrates the model capability.