京都大学 / 新制・課程博士 / 博士(工学) / 甲第24646号 / 工博第5152号 / 新制||工||1984(附属図書館) / 京都大学大学院工学研究科化学工学専攻 / (主査)教授 山本 量一, 教授 外輪 健一郎, 教授 松坂 修二 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Sediment pulses are defined as large amounts of loose sediment that are suddenly deposited in river corridors due to the action of external factors or processes of natural or anthropogenic origin. Such factors and processes include landslides, debris flows from tributaries, volcanic eruptions, dam removal projects, and mining-related activities. Their occurrence is associated with a surplus in sediment load to downstream reaches, and therefore, with severe channel aggradation and degradation, significant floodplain deposition, increase in flood frequency, damage of infrastructure, and impairment of aquatic habitats. The main objective of this research is to develop a better understanding of the fundamental mechanisms that govern the propagation of these sediment-flow hazards in alluvial sand-bed rivers. Specifically, the study presented herein is divided into three separate parts to achieve this overarching goal. First, a component intended to improve the numerical modeling of morphodynamic processes in alluvial sand-bed rivers by proposing a novel solution methodology that applies either the decoupled or the coupled modeling approach based on local flow and sediment transport conditions. Secondly, a detailed numerical analysis to characterize the behavior of fine-grained sediment pulses (i.e. composed of granular material in the sand size range) in alluvial sand-bed rives by identifying the properties of these types of pulses, as well as the characteristics of riverine environments, that are most relevant to their downstream migration. And lastly, a case study application to assess the effect of the magnitude, duration, and frequency of severe hydrologic events on the overall propagation behavior of fine-grained sediment pulses in alluvial sand-bed rivers. Ultimately, this research aims to contribute towards reducing the uncertainty associated with the impact of these phenomena, and hence, improving the resilience of rivers corridors. / Ph. D.

Optimization techniques are used to investigate changes in structural design which increase the energy absorbing capabilities of a marine vessel in a collision. The structural model of the vessel includes the stiffened shell, web frame supports, and rigid bulkheads. The failure criterion used is hull rupture, appropriate for tanker design. The collision scenario is a right angle strike by a rigid vertical bow midway between two rigid bulkheads. The stiffened shell is modelled as a series of longitudinal beams in plastic bending and plastic membrane tension. Optimization parameters included both the number and dimensions of the transverse web frames and longitudinal beams. The technique was applied to the redesign of a large oil tanker. Minimizing the weight with a constraint on the energy was superior to maximizing the energy with a weight constraint in both computation time and performance. Optimization increased the volume of the shell beams while decreasing their moment-of-inertia. In addition the volume and strength of the frame were decreased precipitating early development of membrane tension in the shell and spreading of damage throughout the compartment. An reduced the number of web frames from optimum design six to two and increased the energy absorbed before rupture by 130%. Lesser collisions energies were found for more conservative designs which included a set number of web frames and restrictions of other design parameters. The use of high strength steel was also investigated. / M.S.

Στον Πατραϊκό κόλπο έχουν γίνει πλήθος ερευνητικών εργασιών με διαφορετικά αντικείμενα. Στη Φυσική Ωκεανογραφία φαίνεται να εμφανίζεται ένα ερευνητικό κενό, που αφορά την προσομοίωση της κυκλοφορίας του νερού στην περιοχή. Το κενό αυτό προσπαθεί να καλύψει η εργασία αυτή, με απώτερο σκοπό την κατανόηση του υδροδυναμικού καθεστώτος της περιοχής μελέτης. Στην εργασία χρησιμοποιούνται όλες οι υφιστάμενες βιβλιογραφικές πηγές και μετρήσεις. Επίσης χρησιμοποιείται το μαθηματικό μοντέλο ΜΙΚΕ21 για την δυσδιάστατη προσομοίωση της κυκλοφορίας του νερού αφού πρώτα προηγήθηκε η βαθμονόμηση του. Το αποτέλεσμα της εργασίας αυτής οδηγεί στην κατανόηση της δυσδιάστατης υδροδυναμικής κυκλοφορίας του νερού, κυρίως στον Πατραϊκό κόλπο αλλά και στο Στενό Ρίου – Αντιρρίου και σε ένα μικρό τμήμα του Κορινθιακού κόλπου. / In the Patras gulf they have become many of inquiring work with different objects. In the Natural Oceanography it appears that is presented an inquiring void that concerns the simulation of circulation of water in the region. This project tries to cover this void, with final aim the comprehension of hydrodynamic arrangement of region of study. In the work are used all the existing bibliographic sources and measurements. Also is used mathematic model MIKE21 for the 2-dimensions simulation of water circulation. The result of this work leads to the comprehension of 2-dimensions hydrodynamic circulation of water, mainly to the Patras gulf but also to the channel Rio-Antirio and to a small part of Corinthian gulf.

Les vésicules sont des bicouches fermées de molécules tensioactives, remplies de liquide, à l'intérieur d'un autre liquide. Leur taille peut être comprise entre dix et 100 microns : elles sont alors dites géantes. Nous nous intéressons à la dynamique de deux de ces objets dans un cisaillement simple, c'est à dire l'écoulement d'un liquide situé entre deux plaques planes se translatant l'une par rapport à l'autre à vitesse et distance constante. Nous commençons par une étude asymptotique, pour des vésicules quasi-sphériques en interaction lointaine. Nous utilisons ensuite un code de calcul basé sur la méthode des éléments de frontière pour étudier le cas de vésicules moins sphériques et plus proches, et comparons les résultats obtenus avec des expériences. Nous présentons enfin comment cette étude peut être utilisée pour prédire certaines propriétés de diffusion d'une suspension de vésicules, dans le régime semi-dilué, où seul le détail des interactions à deux corps est considéré. / Vesicles are closed bilayers of tensioactive molecules, filled with liquid, inside another liquid. Their size can be between 10 and 100 microns : in this case, they are called giant vesicles. We study the dynamic of two of these objects in a simple shear flow, which is the one of a liquid sheared between two walls translating with respect to each other at a constant speed and distance. We begin by an asymptotic study, for quasispherical vesicles in the far field interacting regime. We then use a numerical code based on the boundary element method to study the case of less spherical and closer vesicles, and compare our results with experiments. We finish by presenting how this study can be used to predict some diffusing properties of a sheared suspension of vesicles, in the semidilute regime, where only the details of two body interactions are considered.

La texturation de surface est une thématique récente qui suscite un certain engouement pour les contacts dynamiques. Pendant de nombreuses années, les tribologues ont privilégié les surfaces lisses aux faibles rugosités pour limiter le frottement. Inspiré des rugosités de surface organisées observées dans la nature, les topologies de surfaces sont désormais axées sur la texturation et la structuration des rugosités. Fort de ce potentiel, de nombreuses études traitent, par une approche numérique, la modélisation de ces surfaces et les études expérimentales sont rares, avec une instrumentation souvent insuffisante pour appréhender tous les phénomènes physiques. Par une approche expérimentale, nous analysons le comportement des butées hydrodynamiques à faces parallèles partiellement texturées. Les 80 capteurs équipant le dispositif d'essais permettent d'apprécier avec rigueur la phénoménologie à l'interface du patin et du film lubrifiant. L'analyse met l'accent sur la capabilité de ce composant à être intégré dans un environnement industriel. Afin d'objectiver les résultats, les campagnes d'essais sont menées sur dix butées hydrodynamiques dont quatre sont munies de texturation. Une comparaison de ces butées facilite leur classement en termes de capacité de charge, de réduction de frottement ou encore de risque d'usure dans les phases de démarrage. Pour les configurations étudiées, les butées texturées ne peuvent concurrencer les butées à poches ou à plans inclinés du point de vue de la capacité de charge. En se référant à une butée à faces parallèles, les butées texturées permettent une réduction du frottement de 30% à faibles charges tandis que pour de fortes charges, les / Surface texturing is a recent topic which has raised a great interest in contact dynamics. For many years, engineers have favored smooth surfaces with low roughness in order to minimize friction losses. Inspired by textured surfaces which can be commonly found in nature, the research in surface topography is now focused on texturing and roughness characterization. Considering the great potential of surface texturing, many research studies analyze this subject, most commonly theoretically, while experimental works are often performed with inadequate equipment which does not allow a proper evaluation of the involved physical phenomena. This study uses an experimental approach in order to analyze the behavior of hydrodynamic thrust bearings with parallel textured pads. The experimental device is equipped with 80 sensors which allow a proper assessment of the phenomenology at the film/pad interface. This analysis focuses on the capability of this textured component to be integrated in an industrial environment. To objectify the results, the tests are conducted on ten hydrodynamic thrust bearings, among which four are textured. The comparison between the performances of these bearings facilitates their classification in terms of load-carrying capacity, friction loss and wears resistance during the start-up period. Results show that for the studied configurations, the textured thrust bearings cannot compete with pocketed or tapered land thrust bearings in terms of load-carrying capacity. In the case of parallel thrust bearings, surface texturing can help to reduce friction up to 30% at low loads while for heavy loads, their performance is equivalent or even lower than that of

Recent events regarding energy policies throughout the globe and advances in technology are making offshore wind farms become a reality. Most offshore wind farms are still, however, built close to land masses, and need to be rigidly attached to the seabed in one way or another. In many countries, both public and private entities are developing new concepts of floating platforms to overcome the thirty to thirty-five-metre depth limit. Some of these new platforms use and adapt previous Oil and Gas platform concepts, while others are built up from scratch. This Master Thesis covers a hydrodynamic and structural analysis of a new concrete floating platform concept developed for medium to deep waters. This work is based on data from experimental model-scale tests performed in a wave tank and from numerical models using linear potential theory, limited here only to regular wave trains. The study focused on the behavior of the heave plates attached to the platform: test data was analyzed in order to find indicators of the largest dynamic pressures on the plates when only motion data was available, and the structural behavior of the plates was studied under different static pressure distributions using a commercial Finite Element Method software. The results from these analyses show that the normal accelerations of the plates -assumed rigid- strongly correlate with the dynamic pressures measured; and that the general structural behavior of the plate, in terms of deformations and bending moments, is well captured when the hydrodynamic load distribution is simplified into a uniformly distributed load of the same magnitude. The results obtained will help reduce the computational effort currently needed in the design of these floating structures, especially at some stages, when numerous scenarios, load cases and combinations need to be studied.

O presente trabalho apresenta a primeira avaliação da hidrodinâmica do Saco do Mamanguá (RJ), com o objetivo de analisar o comportamento hidrodinâmico e o transporte de sedimentos da região, através do modelo hidrodinâmico Delft3D - FLOW e do modelo de ondas Delft3D - WAVE. Os resultados indicam que a hidrodinâmica do Saco do Mamanguá é grandemente influenciada pela ação do vento, principalmente pelos oriundos de sudoeste, seguido pela força da maré e dos gradientes de densidade, que juntos atuam no direcionamento e magnitude das correntes e trocas de volume entre a região e o oceano adjacente, sendo responsáveis também pelo transporte de sedimentos em suspensão da região. Os resultados do modelo numérico de ondas mostraram que estas não influenciam a hidrodinâmica da região. Através da comparação dos resultados do modelo numérico com os dados coletados na região, ele se mostrou satisfatório, principalmente em relação à hidrodinâmica, validando a correta representação dos padrões de circulação da área. Por fim, o trabalho demonstra que o Saco do Mamanguá é um ambiente de baixa energia, com correntes fracas, variando de bem misturado a estratificado em que, sua baixa dinâmica favorece a retenção de partículas em seu interior, porém a atuação do vento contribui para a exportação de material. / This study presents the first evaluation of hydrodynamics Saco do Mamanguá (RJ), with the aiming of analyze the hydrodynamics patters and sediment transport in the region using the hydrodynamic model Delft3D - FLOW and wave model Delft3D - WAVE. The results indicate that the hydrodynamics of Saco do Mamanguá is largely influenced by the wind, especially southwestern winds, followed by tide forces and density gradients which together will dictate direction and magnitude of current, the volume and mass exchanges between the study area and the adjacent ocean, and the suspended sediment transport. The results of the wave model showed that these did not influence the hydrodynamics of the region. The numerical model was proved be satisfactory, especially regarding the hydrodynamics patterns when compared to measured data, well representing the flow circulation of the area. Finally, the study demonstrates that Saco do Mamanguá is a low energy environment with low velocity currents, ranging from well mixed to stratified estuary. The low dynamic in the system favors particle retention in its interior although the performance of the wind contributes to the export of material.

O presente trabalho apresenta a primeira avaliação da hidrodinâmica do Saco do Mamanguá (RJ), com o objetivo de analisar o comportamento hidrodinâmico e o transporte de sedimentos da região, através do modelo hidrodinâmico Delft3D - FLOW e do modelo de ondas Delft3D - WAVE. Os resultados indicam que a hidrodinâmica do Saco do Mamanguá é grandemente influenciada pela ação do vento, principalmente pelos oriundos de sudoeste, seguido pela força da maré e dos gradientes de densidade, que juntos atuam no direcionamento e magnitude das correntes e trocas de volume entre a região e o oceano adjacente, sendo responsáveis também pelo transporte de sedimentos em suspensão da região. Os resultados do modelo numérico de ondas mostraram que estas não influenciam a hidrodinâmica da região. Através da comparação dos resultados do modelo numérico com os dados coletados na região, ele se mostrou satisfatório, principalmente em relação à hidrodinâmica, validando a correta representação dos padrões de circulação da área. Por fim, o trabalho demonstra que o Saco do Mamanguá é um ambiente de baixa energia, com correntes fracas, variando de bem misturado a estratificado em que, sua baixa dinâmica favorece a retenção de partículas em seu interior, porém a atuação do vento contribui para a exportação de material. / This study presents the first evaluation of hydrodynamics Saco do Mamanguá (RJ), with the aiming of analyze the hydrodynamics patters and sediment transport in the region using the hydrodynamic model Delft3D - FLOW and wave model Delft3D - WAVE. The results indicate that the hydrodynamics of Saco do Mamanguá is largely influenced by the wind, especially southwestern winds, followed by tide forces and density gradients which together will dictate direction and magnitude of current, the volume and mass exchanges between the study area and the adjacent ocean, and the suspended sediment transport. The results of the wave model showed that these did not influence the hydrodynamics of the region. The numerical model was proved be satisfactory, especially regarding the hydrodynamics patterns when compared to measured data, well representing the flow circulation of the area. Finally, the study demonstrates that Saco do Mamanguá is a low energy environment with low velocity currents, ranging from well mixed to stratified estuary. The low dynamic in the system favors particle retention in its interior although the performance of the wind contributes to the export of material.

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