Multi-pantograph operation allows several short electric multiple unit (EMU) trainsets to be coupled or decoupled to adapt to daily or seasonal passenger-flow variation. Although this is a convenient and efficient way to operate rolling stock and use railway infrastructure, pantographs significantly influence each other and even significantly change the dynamic behaviour of the system compared to single-pantograph operation in the same condition. The multi-pantograph system is more sensitive and vulnerable than the single-pantograph system, especially at high operational speeds or with pantographs spaced at short distances. Heavy oscillation in the system can result in low quality of current collection, electromagnetic interference, severe wear on the contact surfaces or even structural damage. The mechanical interaction between the pantograph and the catenary is one of the key issues which limits the maximum operational speed and decides the maintenance cost.     Many researchers have paid a lot of attention to the single-pantograph operation and have made great progress on system modelling, optimizing, parameter studies and active control. However, how the pantographs in a train configuration affect each other in multi-pantograph operation and which factors limit the number of pantographs is not fully investigated. Nowadays, to avoid risking operational safety, there are strict regulations to limit the maximum operational speed, the maximum number of pantographs in use, and the minimum spacing distance between pantographs. With the trend of high-speed railways, there are huge demands on increasing operational speed and shortening spacing distance between pantographs. Furthermore, it is desirable to explore more practical and budget-saving methods to achieve higher speed on existing lines without significant technical modification.     In addition to a literature survey of the dynamics of pantograph-catenary systems, this thesis carries out a numerical study on multi-pantograph operation based on a three-dimensional pantograph-catenary finite element (FE) model. In this study, the relationship between dynamic performance and other parameters, i.e. the number of pantographs in use, running speed and the position of the pantographs, are investigated. The results show that the spacing distance between pantographs is the most critical factor and the trailing pantograph does not always suffer from deterioration of the dynamic performance. By discussing the two-pantograph operation at short spacing distances, it is found that a properly excited catenary caused by the leading pantograph and the wave interference between pantographs can contribute to an improvement on the trailing pantograph performance. To avoid the additional wear caused by poor dynamic performance on the leading pantograph and achieve further improvement at high speeds, it is suggested to use the leading pantograph as an auxiliary pantograph, which does not conduct any electric current and optimize the uplift force on the leading pantograph. After a brief discussion on some system parameter deviations, it is shown that a 30% of speed increase should be possible to achieve while still sustaining a good dynamic performance without large modifications on the existing catenary system. / <p>QC 20150928</p>

No description available.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21353号 / 工博第4512号 / 新制||工||1703(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 藤田 正治, 教授 中川 一, 准教授 竹林 洋史 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

No description available.

Helical heating coils are widely used in most conventional electric stoves for many years, these heating coils can reach 600-700°C, which is higher than the ignition point of oil and grease (about 400°C), leading to many fires. Pioneering Technology Inc. has developed a Safe-T Element plate to address such problem. The Safe-T Element plate is manufactured from Gray Cast Iron. However, these plates deform during its use. This study was carried out to investigate the current Safe-T Element design, both experimentally and numerically, in order to determine the root causes behind the deformation problem of the plate, and to suggest changes to the existing design in order to limit its distortion to acceptable targets. A chemical analysis was carried out to establish the type of material of the Safe-T Element plate. Chemical analysis showed that the material of the plate is cast iron. The microstructure of the plate was tested in order to examine its type and homogeneity. Tensile testing was carried to establish the grade of the material, and to calculate the value of its young's modulus and yield strength. Tensile testing indicated that the material of the Safe-T Element plate is close to Gray Cast Iron Class 40. Differential scanning calorimetry testing was carried out to investigate thermal stability of the plate material. This test indicated that material is thermally stable. Thermal cycling testing indicated that the root cause of the deformation problem is elastic thermal buckling. Temperature uniformity tests were carried out. More than 100°C temperature variation in the radial direction was observed. To address the distortion of the plate, an optimum geometry has been suggested based on the findings of the numerical investigation by removing the outer ring from the original design of the plate. / Thesis / Master of Applied Science (MASc)

In dieser Dissertation wird das kompressible, nicht-hydrostatische und dreidimensionale Modell All Scale Atmospheric Model (ASAM) für Grobstruktur- bzw. Large-Eddy-Simulationen (LES) angewendet, um lokale Inseleffekte in der karibischen Passatwindzone zu untersuchen. Da das Modell bis dato noch keine Anwendung im Bereich von LES feuchter atmosphärischer Grenzschichten und heterogener Oberflächen fand, wurden einige Bestandteile zum Modellcode hinzugefügt oder überarbeitet. Ein Hauptaugenmerk liegt dabei auf das Einbeziehen orographischer Strukturen mittels angeschnittener Zellen (engl. cut cells). Sowohl die räumliche und zeitliche Diskretisierung der Modellgleichungen als auch die nötigen physikalischen Parameterisierungen werden in einer umfassenden Modellbeschreibung zusammengefasst. Die Robustheit und Stabilität der Modellformulierung wird durch eine Reihe von Simulationen idealisierter Testfälle bestätigt. Large-Eddy-Simulationen werden für das Gebiet der Karibikinsel Barbados zur Untersuchung von Inseleffekten bezüglich Grenzschichtmodifikation, Wolkenbildung und vertikaler Durchmischung von Aerosolen durchgeführt. Durch das Vorhandensein einer topographisch strukturierten Inseloberfläche in der Mitte des Modellgebietes muss das Modellsetup offene seitliche Randbedingungen beinhalten. Damit das einströmende Windfeld konsistent mit der Dynamik einer turbulenten, marinen Grenzschicht ist, wird eine neue Methode implementiert und angewendet, welche auf Störungen des potentiellen Temperaturfeldes mittels finiter Amplituden basiert. Beobachtungen aus der SALTRACE-Messkampagne werden benutzt, um die Modellläufe anzutreiben. Die Ergebnisse einiger Sensitivitätstests zeigen Probleme der Modellierung im Bereich der \"Terra incognita\" auf. Dabei handelt es sich um die Modellierung auf räumlichen Skalen, welche zwischen denen von LES und wolkenauflösenden Modellen liegen. Außerdem werden Auswirkungen von entweder turbulent oder laminar anströmenden Windfeldern auf die Simulationsergebnisse untersucht. Besonders die Wolkeneigenschaften im Lee von Barbados werden in diesen Simulationen merklich beeinflusst. Ergebnisse einer weiteren Simulation mit einer sehr starken Passatinversion bringt deren Einfluss auf die Dicke und Höhe der simulierten Wolkenschichten zum Vorschein. Die Veränderung von Saharastaubschichten, welche Barbados über weiträumigen Transport über den Atlantik erreichen, wird analysiert. Die Auswirkungen beinhalten sowohl eine Ausdünnung und ein Absinken dieser Schichten als auch turbulenter Transport in Richtung Erdoberfläche. Die genaue Position der beeinflussten Schichten und die Stärke des turbulenten Mischens werden hauptsächlich von der atmosphärischen Schichtung, der Inversionsstärke und Windscherung gesteuert. Vergleiche zwischen den LES-Modellergebnissen und Daten aus Doppler-Windlidarmessungen zeigen gute Übereinstimmungen in der Formierung der konvektiven Strukturen tagsüber und des Vertikalwindfeldes. / In this thesis, the fully compressible, three-dimensional, nonhydrostatic atmospheric model called All Scale Atmospheric Model (ASAM) is utilized for large eddy simulations (LES) to investigate local island effects at the Caribbean. Since the model has not been applied to LES for moist boundary layers and heterogeneous surfaces so far, several parts are added to the model code or reworked. A special focus lies on the inclusion of orographical structures via the cut cell method. Spatial and temporal discretization as well as necessary physical parameterizations are summarized in a thorough model description. The robustness of the model formulation is confirmed by a set of idealized test case simulations. Large eddy simulations are performed for the area of the Caribbean island Barbados to investigate island effects on boundary layer modification, cloud generation and vertical mixing of aerosols. Due to the presence of a topographically structured island surface in the domain center, the model setup has to be designed with open lateral boundaries. In order to generate inflow turbulence consistent with the upstream marine boundary layer forcing, the newly developed cell perturbation method based on finite amplitude perturbations is applied. Observations from the SALTRACE field campaign are used to initialize the model runs. Several numerical sensitivity tests are carried out to demonstrate the problems related to \"gray zone modeling\" beyond LES scales or when the turbulent marine boundary layer flow is replaced by laminar winds. Especially cloud properties west of Barbados (downwind) are markedly affected in these simulations. Results of an additional simulation with a strong trade-wind inversion reveal its effect on cloud layer depth and height. The modification of Saharan dust layers reaching Barbados via long-range transport over the North Atlantic is analyzed. Effects of layer thinning, subsidence and turbulent downward transport near the layer bottom become apparent. The position of these layers and strength of downward mixing is found to be mainly controlled atmospheric stability, inversion strength and wind shear. Comparisons of LES model output with wind lidar data show similarities in the formation of the daytime convective plume and the vertical wind structure.

Cette étude concerne le transport de particules colloïdales en milieu poreux. Les colloïdes (particules de taille caractéristique inférieure au micron) se rencontrent dans de nombreux domaines de la vie quotidienne (encre, cosmétiques, ...), de la biologie (bactéries, virus, protozoaires, ...) et de l’ingénierie (filtration, hydrologie, génie civil, génie pétrolier, ...). De par leur taille et leur nature, l’étude de ces systèmes nécessite de s’intéresser aux interactions qui peuvent exister entre les particules elles mêmes mais aussi avec le milieu environnant. On cite particulièrement le cas d’écoulements dans des aquifères qui concernent le transport de contaminants d’origine biologique (bactéries, virus), d’origine chimique (hydrocarbures, polluants) ou d’origine minérale (argiles, métaux, ...). Dans chacun des cas cités, il est nécessaire de s’intéresser au transport et dépôt/décollement des particules pour mieux comprendre et modéliser les mécanismes mis en jeu. Une première partie du travail est consacrée à la mise en place et à la résolution d’un modèle macroscopique de dépôt de particules. La comparaison des résultats numériques avec des données expérimentales de la littérature a permis d’établir les relations existantes entre le facteur de retard et la force ionique d’une part et le nombre de Péclet d’autre part. La seconde partie du travail concerne l’étude, à l’échelle microscopique, du transport de particules colloïdales en présence de rugosités de surface (obstacle ou cavité). Les résultats mettent en évidence le rôle joué par ces rugosités de surface sur l’adsorption et désorption de particules sous l’influence des forces hydrodynamiques et des interactions physico-chimiques. / This study deals with the transport of colloidal particles in porous media. Colloids (particles with a characteristic size smaller than one micron) are found in daily life (ink, cosmetics ...) and in many fields of science and technology such as biology (bacteria, viruses, protozoa ...) and engineering (filtration, hydrology, civil engineering, petroleum engineering ...). Because of their size and nature, the study of these systems needs to focus on interactions that may exist between the particles themselves but also with the surrounding environment. This is particularly true in the case of transport of colloids in porous media where the particles characteristic dimension size is close to that of the porous medium. We mention especially the case of flow in aquifers that may affect the transport of contaminants of a biological origin (bacteria, viruses), chemical origin (hydrocarbons, pollutants) or minerals (clay, metals ...). In each case cited above, it is necessary to consider particles transport in porous media and their deposition/release to better understand and model the involved mechanisms. The first part of this work is devoted to the development and resolution of a macroscopic model of particle deposition. Comparison of numerical results with experimental data in the literature has established the existing relationships between a delay factor and both ionic strength and the Peclet number. The second part of the study deals with the study, at the microscopic level, of a colloidal particle transport taking into account DLVO forces for smooth and rough pore surfaces. Our results highlight the role played by surface roughness on the adsorption and desorption of particles under the influence of ionic strength and flow rate.

L'objectif de ce travail est d'étudier les détails des écoulements et des transferts thermiques induits par convection naturelle au sein d'un canal (simulation bidimensionnelle) et au sein d'une cavité cubique (simulation tridimensionnelle) munis de blocs chauffants. La chaleur dégagée par les blocs résulte d'une génération volumique uniforme de la chaleur, d'une température chaude constante ou d'un flux surfacique uniforme. On utilise l'air (Pr=0.72) comme fluide. Les paramètres de l'étude sont le rapport des conductivités thermiques du bloc solide et du fluide (0.1≤k*≤200), le nombre de Rayleigh (〖10〗^4≤Ra≤〖10〗^7) et la hauteur relative des blocs (1/8≤B≤1/2). La détermination des conditions de validité du modèle à blocs isothermes et du modèle à blocs libérant un flux surfacique uniforme, en fonction du rapport des conductivités thermiques et des autres paramètres du problème, compte parmi les principaux objectifs de ce travail. Les résultats obtenus montrent que l'écoulement et le transfert thermique ainsi que les conditions de validité des modèles mentionnés sont fortement influencés par les paramètres de contrôle et par la multiplicité de solutions trouvée en régime convectif. / The object of this work is to study the details of the flow and heat transfer induced by natural convection in a channel (2D simulation) and in a cubic cavity (3D simulation) containing heating blocks. The heat released by the blocks results from a uniform volumetric heat generation, a constant hot temperature or a uniform surface flux. Air (Pr=0.72) is used as working fluid. The parameters of the study are the thermal conductivities ratio of solid blocks and fluid (0.1≤k*≤200), the Rayleigh number (〖10〗^4≤Ra≤〖10〗^7) and the relative height of the blocks (1/8≤B≤1/2). Among the main objects of this work is the determination of the conditions of validity of the model with isothermal blocks and the model with blocks releasing a uniform surface flux, as functions of the thermal conductivities ratio and the other parameters of the problem. The results obtained show that the flow and heat transfer and the conditions of validity of the models mentioned are strongly affected by the control parameters and the multiplicity of solutions found in the convective regime.

L'utilisation massive des énergies fossiles est en grande partie responsable des émissions de gaz à effet de serre. De plus, la croissance de la demande énergétique et la raréfaction des ressources fossiles conduisent à l'accroissement du coût de l'énergie. La réponse à cette problématique passe par deux moyens d'action indissociables : la réduction des consommations énergétiques et le recours aux énergies renouvelables. La fenêtre pariétodynamique permet d’agir sur les deux postes principaux de déperdition thermique d’un bâtiment que sont les baies et la ventilation. Le principe de la fenêtre pariétodynamique étudiée est de faire circuler de l’air en convection forcée entre trois verres avant d’être restitué à l’ambiance intérieure du bâtiment. Cela permet à l’air de récupérer à la fois une partie des déperditions thermiques à travers la fenêtre et une partie de l’énergie solaire absorbée par les verres. Afin d’étudier le comportement thermo-aéraulique et les performances de la fenêtre, nous avons développé un modèle numérique de cette dernière. Un dispositif expérimental a été mis en place et utilisé afin de valider le modèle numérique et de comparer en conditions réelles les performances de la fenêtre étudiée à celles d’une fenêtre à double vitrage classique. Ces résultats expérimentaux ont été complétés par une étude paramétrique numérique réalisée pour différentes conditions climatiques et de fonctionnement. Les principaux enseignements issus de ces études expérimentales et numériques sont que le préchauffage de l’air se fait essentiellement dans la lame d’air intérieure, la température de la première lame d’air restant proche de celle de l’air extérieur. De plus, et contrairement aux températures de la face intérieure et de l’air soufflé, celle de la face externe de la fenêtre est peu impactée par les paramètres étudiés. Concernant le cadre de la fenêtre, nous avons observé que celui-ci bénéficie aussi des échanges thermiques avec l’air circulant, mais dans une moindre mesure. Cela contribue à rendre la fenêtre peu déperditive. Enfin, en couplant le modèle développé à un logiciel de simulation thermique dynamique, nous avons évalué le potentiel d’intégration de fenêtres pariétodynamiques dans une maison individuelle. Nous mettons ainsi en évidence que le besoin de chauffage est réduit d'environ 20 à 30 % par l’utilisation de fenêtres pariétodynamiques à la place de fenêtres à double vitrage classique. En été, si l’ambiance intérieure du bâtiment est plus fraîche que l’environnement extérieur, la fenêtre pré-rafraîchit l’air neuf entrant. / The massive use of fossil energies is largely responsible for greenhouse gas emissions. Moreover, the growth in energy demand and the depletion of fossil resources lead to an increase in energy costs. The response to this challenge requires two means of action which are linked : the reduction of energy consumption and the use of renewable energy. The airflow window acts on the two main ways of building heat losses that are windows and the ventilation. The principle of the studied airflow window is based on the circulation of fresh air, by forced convection, between the three glasses of the window before entering the building. This allows air to recover both a part of heat losses through the window and part of the solar energy absorbed by the glasses. To study the thermo-aeraulic behavior and thermal performances of the window, we have developed a numerical model of the studied airflow window. An experimental set up was used to validate the numerical model and compare, in real conditions, the studied window performances to the ones of a conventional double-glazed window. These experimental results were complemented by a numerical parametric study for different climatic and operating conditions.The main information from these experimental and numerical studies are that the preheating of the air takes place essentially in the inner air gap, temperature in the first air layer remaining close to the outdoor one. In addition, unlike the temperatures of the inside face and of the blown air, the outer face temperature of the window is not greatly affected by the studied parameters. On the window frame, we found that it also benefits of heat exchanges with the circulating air, but to a lesser extent. This makes the window energy efficient. Finally, by coupling the developed model to a thermal building simulation software, we evaluated the airflow windows integration potential in a house. We thus demonstrated that the heat load is reduced by about 20 to 30% by the use of airflow windows instead of conventional double-glazed windows. Moreover, in summer, when indoor is cooler than outdoor, we pointed out that the airflow window cools the incoming fresh air.

Neste trabalho apresentamos um estudo assintótico e numérico de escoamentos viscoelásticos com singularidades de tensão. Estas singularidades surgem como consequência de uma mudança abrupta nas condições de contorno, como no caso do stick-slip, ou devido a presença de quinas na geometria do problema, como no escoamento da contração. Para o problema stick-slip definimos o comportamento assintótico do fluido Oldroyd-B sobre um campo de velocidade Newtoniano. Esta análise foi feita com o método assintótico das expansões, que pode ser estendida para outros tipos de fluidos. O estudo assintótico do stick-slip com o modelo Oldroyd-B revelou que as equações deste modelo não estão bem definidas para este problema, pois este fluido estende o valor singular ao longo de toda a superfície livre, gerando resultados sem sentido físico. Além disso, os resultados assintóticos dos problemas stick-slip e da contração 4:1 foram verificados numericamente através da integração das equações constitutivas ao longo de linhas de corrente. Vale destacar que, além da tradicional formulação Cartesiana do tensor (CSF), também utilizamos a formulação natural do tensor (NSF), que tem a vantagem de capturar de modo mais acurado os resultados próximos às singularidades. Além do mais, desenvolvemos um método numérico para resolver as equações de Navier-Stokes combinadas com as equações constitutivas das formulações CSF e NSF para os modelos PTT e Giesekus nos dois problemas estudados. Vale ressaltar que, não há na literatura resultados numéricos, para o caso transiente, com a formulação NSF para os modelos PTT e Giesekus. Por fim, verificamos numericamente o comportamento assintótico das tensões próximo as singularidades, bem como a configuração das camadas limites para os problemas mencionados. / In this work we present an asymptotic and numerical study of viscoelastic flows with stress singularities. These singularities arise as a consequence of an abrupt change in the boundary conditions, as in the case of the stick-slip flow, or due to the presence of corners in the geometry of the problem, as in the contraction flow. For the stick-slip problem, we define the asymptotic behavior of the Oldroyd-B fluid over a Newtonian velocity field. This analysis was done with the method of matched asymptotic expansions, which can be extended to other types of fluids. The asymptotic study of the stick-slip flow for the Oldroyd-B model revealed that the equations of this model are not well defined for this problem, because this fluid extends the singularity throughout the free surface, generating results with no physical meaning. Besides that, the asymptotic results of the stick-slip and 4:1 contraction problems were verified numerically by integrating the constitutive equations along streamlines. It is worth mentioning that we performed asymptotic and numerical studies with the natural stress formulation (NSF) in addition to the Cartesian stress formulation (CSF). The NSF can capture the numerical results in a more accurate manner near singularities. Furthermore, we developed a numerical method to solve the Navier-Stokes equations combined with the constitutive equations of the CSF and NSF formulations for the PTT and Giesekus in the two problems studied. It is worth noting that there is no numerical results, for the transient case, with the NSF formulation for the PTT and Giesekus. Finally, we verified numerically the asymptotic behavior of stresses close to the singularities, as well as the configuration of the boundary layers for the problems mentioned above.