Dissertations / Theses on the topic 'Circular flow analysis'

The flow around two identical circular cylinders, arranged in configurations where one of the cylinders is immersed in the wake of the other, is studied using numerical simulations. Two aspects of such flows were considered. The first is the stability of nominally two-dimensional time-periodic wakes to three-dimensional perturbations. We investigated flows around tandem and staggered arrangements with diverse centre-to-centre distances. Direct stability analysis and numerical simulations were employed, and the results are compared to those obtained for the flow around an isolated cylinder. The onsets of the three-dimensional instabilities were calculated and the unstable modes are fully described. In addition, we assess the nonlinear character of the bifurcations and physical mechanisms are proposed to explain the instabilities. The second aspect considered in this thesis is the flowinduced vibration experienced by a rigid cylinder when it is mounted on an elastic base and immersed in the wake of a fixed identical cylinder. Tandem arrangements with centre-to-centre distances varying from 1.5 to 8 cylinder diameters were tested. The flow was simulated using an Arbitrary Lagrangian-Eulerian approach that coupled the solution of the structure equations with that of the flow. Two- and three- dimensional simulations were performed to assess the mutual influence between the three-dimensional flow structures in the wake and the motion of the cylinder. The response of the downstream cylinder is compared to that of an elastically-mounted rigid isolated cylinder. Based on the simulation results we propose physical mechanisms to explain the origin of the excitation.

Orientador: Renato Bertolino Júnior<br>Banca: Haroldo de Mayo Bernardes<br>Banca: João Alberto Venegas Requena<br>Resumo: O presente trabalho tem por objetivo obter numericamente os valores das distribuições de pressões devidas a ação do vento e seus respectivos coeficientes de pressões de formas externos em torres de seção circular. As distribuições de pressões nas torres são determinadas através da simulação numérica, utilizando-se o programa ANSYS 9.0, considerando-se a interação fluido-estrutura. Para a simulação numérica, a geometria da torre foi modelada tridimensionalmente, considerando como fluido o ar no qual a edificação está inserida. As distribuições de pressão foram determinadas para relações geométricas em planta da torre, entre a altura e o diâmetro (h/d), para valores menores ou iguais a 10. Posteriormente, comparam-se os resultados numéricos obtidos na simulação através do ANSYS com os valores apresentados pela norma NBR-6123:1988, a fim de verificar a viabilidade da utilização da simulação numérica na obtenção das distribuições de pressão em outras estruturas.<br>Abstract: The present work has for objective to obtain the distributions pressures values the wind actions in tower with circular section. The values of the distributions pressures are obtained to the numeric simulation, using the ANSYS 9.0 software and considering the flow structure interaction. In the numeric simulation, the tower geometry was considered in 3D dimension, and the flowed it is the air. The distributions pressures were certain for geometry relationships between the height and the diameter (h/d), for values smaller or equal than 10. Later, the ANSYS numeric results are compared with the presents values by the NBR 6123:1998, in order to verify the viability numeric simulation used for obtaining the pressures distributions in other structures.<br>Mestre

Made available in DSpace on 2014-06-11T19:25:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-08-13Bitstream added on 2014-06-13T20:32:52Z : No. of bitstreams: 1 carrera_fh_me_ilha.pdf: 1664760 bytes, checksum: 5e03e489b4282bd00667bb00a9844991 (MD5)<br>PROPG<br>O presente trabalho tem por objetivo obter numericamente os valores das distribuições de pressões devidas a ação do vento e seus respectivos coeficientes de pressões de formas externos em torres de seção circular. As distribuições de pressões nas torres são determinadas através da simulação numérica, utilizando-se o programa ANSYS 9.0, considerando-se a interação fluido-estrutura. Para a simulação numérica, a geometria da torre foi modelada tridimensionalmente, considerando como fluido o ar no qual a edificação está inserida. As distribuições de pressão foram determinadas para relações geométricas em planta da torre, entre a altura e o diâmetro (h/d), para valores menores ou iguais a 10. Posteriormente, comparam-se os resultados numéricos obtidos na simulação através do ANSYS com os valores apresentados pela norma NBR-6123:1988, a fim de verificar a viabilidade da utilização da simulação numérica na obtenção das distribuições de pressão em outras estruturas.<br>The present work has for objective to obtain the distributions pressures values the wind actions in tower with circular section. The values of the distributions pressures are obtained to the numeric simulation, using the ANSYS 9.0 software and considering the flow structure interaction. In the numeric simulation, the tower geometry was considered in 3D dimension, and the flowed it is the air. The distributions pressures were certain for geometry relationships between the height and the diameter (h/d), for values smaller or equal than 10. Later, the ANSYS numeric results are compared with the presents values by the NBR 6123:1998, in order to verify the viability numeric simulation used for obtaining the pressures distributions in other structures.

The limited amount of natural resources on our planet has been actively discussed during the past decade. Recycling materials is becoming increasingly important in order to benefit the economy and the environment. The purpose of this study is to conduct a material flow analysis of the construction and demolition waste in the Helsinki metropolitan area to find out whether or not the goals set by the EU Waste Framework Directive can be reached by 2020. The study aims to map out the flows and suggest improvements wherever needed. The study is conducted by using a case study, HSY Ekomo, the first fully operational circular economy hub in Finland. The results show that both the municipality and private sector are well over the required goal of 70% recyclability rate of construction and demolition waste with a steady positive improvement from the first year of operations. The improvements were over 10% between the year 2016 and 2017. The private sector experiences some turbulence regarding legislation issues such as noise- and environmental permits which limits the economic benefit of recycling construction and demolition waste. Continued monitoring and faster adaption to international standards (such as the EU Waste Framework Directive) is required in order to be able to benefit the most economically and environmentally out of circular economic initiatives.<br>Den begränsade mängden naturresurser som existerar på vår planet har diskuterats under det senaste decenniet aktivt. Återvinning av material blir allt viktigare i dagens samhälle och vi kan se en trend var utvecklingen strävar efter beslut som har rötterna i cirkulär ekonomiskaprinciper. Resultatet av diskussionerna har blivit höga måtsättningar för medlemsländerna i Europeiska Unionen gällande återvinning var målet är att uppnå en återvinningsgrad på 70% innan 2020 för bygg- och rivavfall. Studien använder materialflödes analys (MFA) som metod för att kartlägga och kvantifiera flödnena av bygg- och rivavfall. Materialflödes analysen använder data från årsrapporter och statistik som blivit tillgängligt av HSY (statligt ägt bolag) samt av intervjuerna som utfördes på fältet. För att kvantifiera flödena på basis av den konceptuella modellen avnändes mjukvaran STAN. Avhandlingen strävar efter att ta första steget för att kartlägga materialflöden av bygg- och rivavfall i huvudstadsregionen (Helsingfors). Målet är att skapa en modell som kan användas som botten i framtida undersökningar och att kvantifiera modellen med existerande data för att se ifall målsättningarna stadgade av Europeiska Unionen kommer att uppnås innan 2020. Studien utfördes på cirkulär ekonomi stationen Ekomo för att kunna göra upp modeller för den privata sektorn och den kommunalla sektorn eftersom båda är verksamma på Ekomo. Resultaten av anvhandlingen var följande: Den privata sektorn och staten uppnår en återvinningsgrad på över 90% vilket är väl över stadgan satt av den Europeiska Unionen under året 2017 med en stadig utveckling från året innan med en väldigt liten andel som placeras på soptipp. Resultaten visar en stark utveckling av intresse från hushåll och företag för återvinning eftersom antalet kunder och lastbilar som besökt stationen ökat starkt under de senaste fem åren. Även om målsättningarna inom återvinning är uppnådda finns det ärenden som måste behandlas för att försäkra en fortsatt positiv utveckling. Den privata sektorn upplever att begränsade möjligheter för återanvänd krossbetong minskar efterfrågan på produkten, vilket gör den finansiellt svår att integrera i deras försälning. Buller- och miljötillstånd tvingar för tillfället bolagen att transportera bygg- och rivmaterialet utanför rivmålet, t.ex till Ekomo, för att krossas vilket ytterligare skapar finansiella problem för den privata sektorn. Lösningar för att göra återvinning av riv- och byggnadsmaterial för den privata sektorn lukrativare behövs för att inspirera flera organisationer att ansluta sig till arbete mot ett mera cirkulärt samhälle. Monitorering och snabbare anpassningsförmåga för internationella standarder krävs för att kunna utnyttja cirkulär ekonomiska initiativ på bästa möjliga sättet. För att komplettera avhandlingen skulle det vara intressant att se resultaten av en livcykelanalys (LCA) gällande samma flöden för att identifiera miljörelaterade problem och för att optimera flöden.

The current use of natural resources within the industry generally constitutes of linear systems of raw material extraction to waste formation. However, an increased awareness of sustainability issues has resulted in engagements to try to minimise the impacts on the environment that these linear systems impose. Circular Economy is a concept for a strategy that strives towards closing loops of material in society, and therefore reduce the need of raw material extraction and waste formation. Although Cir- cular Economy strives towards increasing the sustainability of a system, recent research has shown that circularity of material does not necessarily have to lower the environmental impact. Therefore there is a need for a method that can assess circularity from a holistic perspective to ensure the contribution of the Circular Economy strategy to a more sustainable society. The aim of the study is to create a framework that accounts for both conventional circular economy indicators and environmental impacts, and that helps set a strategy for companies to transform towards sustainable Circular Economy. The findings of the performed literature study resulted in the gathering of the most used assessment tools for assessment of circular economy in previous studies: Material Flow Analysis, Cumulative En- ergy Demand and Life Cycle Assessment. This set of tools is used to identify hot spots of impact of a product throughout the product lifetime and to set a strategy toward better practices of manufacturing companies. The study gives an example of practical implementation of the framework on a case study of brake caliper remanufacturing at Autoexperten, a chain of franchise concept garages owned by the parent company KGK. A Material Flow Assessment and a Life Cycle Assessment is performed on a scenario modeled to represent the current state of the case of remanufacturing at Autoexperten, and an alternative scenario that do not include the practice of remanufacturing. The results of the performed assessments concluded that the current state scenario is the most preferable alternative regarding energy use, material use and environmental impact. Therefore, the main recommendation in regards to business strategies for Autoexperten and KGK is to continue the practice of remanufacturing.<br>Dagens användning av naturresurser inom industrin utgörs i allmänhet av linjära system från utvinning av råmaterial till produktionen av avfall. En ökad medvetenhet om hållbarhetsfrågor har dock resulterat i engagemang för att försöka minimera den miljöpåverkan som dessa linjära system skapar. Cirkulär ekonomi är ett koncept för en strategi som strävar efter att cirkulera flöden av material i samhället och därmed minska behovet av råmaterialutvinning och avfallsbildning. Även om den cirkulära ekonomin strävar efter att öka hållbarheten inom ett system har ny forskning visat att cirkularet av material inte nödvändigtvis behöver minska miljöpåverkan inom ett system. Därför har det skapats ett behov av en metod som kan undersöka cirkuläritet från ett holistiskt perspektiv för att säkerställa att den cirkulära ekonomin verkligen bidrar till ett mer hållbart samhälle. Syftet med studien är att skapa ett ramverk som undersöker både konventionella indikatorer av cirkulär ekonomi och miljöpåverkan, och som också skapar en strategi för företag för att uppå hållbar cirkulär ekonomi. Resultatet av en litteraturstudie genererade en uppsättning av de mest använda utvärderingsverktygen för analys av cirkulär ekonomi bland tidigare studier: Materialflödesanalys, kumulativt energibehov och livscykelanalys. Den här uppsättningen av verktyg används i studien för att identifiera processer med speciellt hög påverkan i en produkts livscykel och för att skapa en strategi för bättre prestanda av tillverkande företag. Studien ger ett exempel på en praktisk implementering av ramverket på en fallstudie av renovering av bromsok på Autoexperten, en kedja med franchisekonceptgarage som ägs av moderbolaget KGK. En materialflödesanalys och en livscykelanalys utförs i studien på ett scenario som modelleras för att representera det rådande omständigheterna för renovering av bromsok hos Autoexperten, och ett alternativt scenario som inte inkluderar renovering av bromsok. Slutsatsen som kunde dras av resultaten av materialflödesanalysen och livscykelanalysen var att scenariot med de rådande omständigheterna för renovering av bromsok är det som är mest fördelaktigt vad gäller energianvändning, materialanvändning och miljöpåverkan. Därför är den huvudsakliga rekommendationen för skapandet av en affärsstrategi för Autoexperten och KGK att fortsätta med renoveringen av bromsok.

Ce projet de recherche s'articule autour des thématiques de l'économie circulaire et des petites économies insulaires. Ces territoires, bien que différents à plusieurs égards présentent tous des caractéristiques communes, loin de jouer en leur faveur. Celles-ci sont : leur petite taille, l'éloignement à leur métropole et une grande exposition aux aléas climatiques, dont les conséquences sur leurs économies sont directes. On constate toutefois au travers de l'état de l'art sur les petites économies insulaires une approche souvent fataliste de leur sort où ces territoires sont voués à subir les conséquences de leurs vulnérabilités inhérentes. Une solution potentielle pour une approche plus proactive serait l'application de l'économie circulaire, et particulièrement de l'écologie industrielle et territoriale. L'économie circulaire, vue comme un nouveau « business model soutenable » pourrait ainsi devenir un outil de transformation de ces spécificités en leviers de croissance et permettrait un changement de paradigme. Pour vérifier cette hypothèse, trois méthodologies seront utilisées: l'analyse du métabolisme territorial, l'utilisation d'indicateurs composites de résilience et de vulnérabilité et la recherche-action. Dans un souci de faisabilité, le cas de La Réunion (région ultrapériphérique) sera étudié mais les résultats se veulent applicables à l'ensemble des petites économies insulaires<br>This research centers on the circular economy and its impact on small island territories. The hypothesis stated is that implementing a circular economy can directly benefit these territories by turning their vulnerabilities (small size of their economy, remoteness, and exposure to climatic hazards) into levers of growth. To verify this hypothesis, I plan to conduct action research and answer the following question: Circular Economy in the Small Island States: A potential solution to their vulnerabilities? The Case of Reunion Island. Quantitative and qualitative data will be used to problem-solve and develop a model of circular economy for Reunion. The findings and model will be shared with other small island states in the hope of accelerating a paradigm shift across territories sharing the same characteristics

Material flows in Urban Metabolism play a key role for the purpose of building urban areas and growing the economy. There is lack of standard method for accounting of material flows within and across the boundaries of urban systems. This thesis aims to assess the Urban Metabolism of small-scale urban area through the application of the Economic Wide Material Flow Analysis and enhance the scope of the method by adding water flows, which could potentially become a basis for the development of the method in the future. First, the application of the Economic Wide Material Flow Analysis in urban areas was studied through a literature review and then the enhanced Economic Wide Material Flow Analysis was applied to Stockholm Royal Seaport using bottom-up data. Using bottom-up data resulted in detailed information, however, full comparison between urban areas was not possible due to data gaps. The results showed the importance of the method for enhancing Urban Metabolism analysis and amending resource management. Spotting available secondary and recycled resources in the socioeconomic system as a part of application of the method is beneficial to sustain the natural resources use. Since still the method is developing for small-scale urban areas, a mixture of this method and other recommended methods by having focus on data collection is suggested for integrating databases and comprehensive analysis.<br>Under de senaste decennierna har stadsområden expanderat snabbare än tidigare. Genom att öka människors tendens att bo i stora städer kommer naturresurser att behövas för att tillgodose stadsområdens växande behov. Materialflöden i stadsmetabolismen spelar en nyckelroll för att bygga miljövänligt och växande ekonomin. Det saknas en standardmetod för redovisning av materialflöden inom och över gränserna för stadssystem. Denna avhandling syftar till att utvärdera stadsmetabolismen genom att använda tillämpning av bred ekonomisk materialflödesredovisning och förbättra metodens omfattning genom att lägga till vatten- och genomströmningsflöden som potentiellt kan bli bas för utvecklingen av metoden i framtiden. Först studerades tillämpningen av ekonomiskt bred materialflödesredovisning i urbana områden genom litteraturöversikt och sedan tillämpades den förbättrade analysen av ekonomiskt bred materialflöde på Norra Djurgårdsstaden med hjälp av bottom-up data. Att använda bottom-up-data resulterade i detaljerad information, men fullständig jämförelse mellan stadsområden var inte möjlig på grund av dataklyftan Resultaten visade vikten av materialflödesredovisning för att förbättra urban metabolismanalys och ändra resurshantering. Att hitta tillgängliga sekundära och återvunna resurser i det socioekonomiska systemet som en del av tillämpningen av metoden är fördelaktigt för att upprätthålla användningen av naturresurser. Eftersom metoden fortfarande utvecklas för småskaliga stadsområden föreslås en blandning av denna metod och andra rekommenderade metoder såsom, livscykelbedömning, genom att fokusera på datainsamling för att integrera databas och omfattande analys.

La planète se trouve dans un état de dégradation des écosystèmes, d’épuisement des ressources, de tension démographique et d’urgence climatique particulièrement préoccupant. Le découplage de la consommation de matières premières avec l’activité économique est indispensable. En réduisant la pression sur la raréfaction des matières premières, l’économie circulaire peut participer à la lutte contre le dérèglement climatique. Bien que le recyclage ne puisse solutionner seul l’épuisement des ressources, il est indispensable de mettre en œuvre des solutions pour régénérer les matières présentes dans nos déchets. Or l’organisation actuelle de la filière de fin de vie ne semble pas répondre aux besoins de l’économie-monde.Le premier challenge pour déployer des solutions de recyclage en économie circulaire repose sur l’évaluation de la performance des scénarios de recyclage. La méthodologie proposée repose sur plusieurs outils d’analyse : analyse de flux de matières (MFA), Analyse de Cycle de Vie (ACV) et Analyse de coûts (LCC) dans un cadre technique de référence basé sur l’évaluation des écotechnologies (ETV). Ce travail s’applique en partenariat avec la société MTB. Trois axes de performances ont été retenus : technique, économique et environnemental.Cette évaluation multicritères, intégrés dans la démarche de conception de MTB, permet une communication sous la forme d’indicateurs clés de performances (KPI). Ces indicateurs supplémentaires permettent de quantifier rapidement l’éco-efficience d’un scénario, pour accompagner la prise de décisions des concepteurs lors de la construction de l'offre et du développement des solutions scénarios de recyclage<br>The planet is in a particularly worrying state of degradation of ecosystems, depletion of resources, demographic tension and a climate emergency. The decoupling of the consumption of raw materials with economic activity is a relevant action lever. By reducing the pressure on the scarcity of raw materials, the circular economy can participate in the fight against climate change. Although recycling alone cannot solve resource depletion, it is essential to implement solutions to regenerate the materials present in our waste. However, the current organization of the end-of-life sector does not seem to meet the needs of the world economy.The first challenge in deploying recycling solutions in the circular economy is based on evaluating the performance of recycling scenarios. The proposed methodology is based on several analytical tools: Material Flow Analysis (MFA), Life Cycle Assessment (LCA) and Life Cost Costing (LCC) in a technical reference framework based on the evaluation of environmental technologies (ETV). This work applies in partnership with the company MTB. Three performance axes were chosen: technical, economic and environmental.This multi-criterion assessment, integrated into the MTB design process, allows communication in the form of key performance indicators (KPI). By providing additional performance indicators it is possible to quickly quantify the eco-efficiency, to support decision-making by designers during the development of the recycling pathway

Este trabalho aborda o escoamento incompressível ao redor de um cilindro circular. A tese que se quer defender, com base em experimentos numéricos, é: A equação de Landau pode ser obtida a partir das equações de Navier-Stokes por uma análise de estabilidade não-linear global. A teoria produz um procedimento bem-definido para determinação dos coeficientes da equação de Landau, permitindo assim a sua interpretação como um modelo simplificado (equações reduzidas de Navier-Stokes) para a predição das forças aplicadas pelo fluido ao cilindro, que podem ser comparados com resultados experimentais. O modelo não-linear se baseia em uma teoria assintótica que, como se sabe, tem sua faixa de validade no espaço de parâmetros determinada a posteriori, por meio da própria comparação com dados de laboratório. Resultados na faixa 46 <= Re <= 80 são apresentados. Descobriu-se, que a faixa de aplicabilidade da teoria como aqui exposta é restrita, não excedendo em muito o valor crítico do número de Reynolds. Argumentos são expostos para justificar esta afirmação e possíveis maneiras de modificar a teoria para estender esta faixa são apresentadas. São reportados, ainda, teoria e resultados sobre um novo tipo de condição de contorno,denominado impedância fluida, que permite reduzir o tamanho do domínio de cálculo necessário para simulação de escoamentos externos, comparativamente à comumente utilizada condição de outflow. Neste caso, abordou-se a faixa 20 <= Re <= 600.<br>This work adresses the incompressible flow around a circular cylinder. What we want to prove, based on numerical experiments, reads: The Landau equation can be derived from the Navier-Stokes equations by means of a global nonlinear stability analysis. The theory leads to a procedure for calculating numerically the coefficients of these equation, thus permitting their interpretation as a simplified model - reduced Navier-Stokes equation - for the prediction of the forces applied by the fluid on the cylindrical structure, which can be compared against experimental data. The nonlinear model is based on an asymptotic theory which, as is known, has its validity range in the parameter space determined a posteriori. The focus lies in the range 46 <= Re <= 80. It was found that the theorys applicability range as presented here is restricted to a small neighborhood of Rec. This affirmation in justified and possible means of modifying the theory in order to enlarge this range are proposed. Theory and results concerning a new type of boundary condition called fluid impedance are also reported, permitting the reduction of the domain size necessary for simulating external flows, comparatively to the commonly used outflow condition. In this case, the range 20 <= Re <= 600 was considered.

The automotive industry is expected to transition from a net-consumer to a net-producer of aluminum scrap as aluminum-intensive vehicles (AIVs, i.e., Ford’s aluminum-bodied F-150) begin to reach end-of-life (EOL). In the past, the industry has downcycled aluminum scrap to meet the consumption demands of the automotive sector. With the shift to having a large supply of this scrap in the near future, the industry needs to recover and reuse EOL Al by utilizing a circular economic model, create value via an upcycling paradigm (vs downcycling). This work establishes a platform as to how the recycling industry can be restructured to create value in our waste streams and is organized in three segments: First, an analysis of the flow of automobiles at EOL was carried out from the perspective of recovery and reuse; a recycling rate for Al has been determined, and the factors that go into the dynamics of the recycling rate have been identified. Secondly, the current state of the market was surveyed to evaluate where improvements could be made to affect material collection and recovery. The latter led to compositional characterization of aluminum auto-shred to identify the alloys in the mixture, and thereby the needed intelligent sorting systems for upcycling. Thirdly, these results were used in a dynamic material flow model to predict how the composition of auto-shred will change due to increased aluminum usage and as a function of various end-of-life processing scenarios. The outcome and impact of this work is that we have established a platform that enables the ELV recycling industry to upcycle the large amount of Al that will be available in the near future. These results will be discussed and reviewed during this presentation.

Esta tese apresenta o estudo da transição para um escoamento tridimensional da esteira de um cilindro oscilando. Esta é a transição secundária do escoamento ao redor de um cilindro, sendo a primária a própria esteira de von Kármán. A investigação é realizada na mesma faixa de número de Reynolds (Re) que ocorre a transição da esteira de um cilindro fixo: 200 Re 400. O estudo envolve simulações numéricas diretas bi- e tridimensionais do escoamento incompressível ao redor de um cilindro oscilando usando o método dos elementos espectrais. A transição também é analisada através do estudo de estabilidade linear do escoamento. O método de Gaston Floquet é adequado para a análise de estabilidade a perturbações tridimensionais devido à periodicidade característica da esteira de von Kármán. Além disto, o método é mais geral e não é aplicado somente a equações autônomas com soluções periódicas: ele também pode ser usado em análises cujo campo base é estacionário como a análise da transição primária da esteira de um cilindro. Mostra-se que a transição da esteira para tridimensionalidade é influenciada pela oscilação do cilindro. As oscilações podem atrasar a transição quando em amplitudes baixas e com escoamento a um número de Reynolds até 260. Em outros casos, a transição é similar à observada no escoamento ao redor um cilindro fixo. Além disso, quando há mudança de padrões de desprendimento de vórtices devido às oscilações, desencadeiam-se modos instáveis diferentes dos observados na esteira de um cilindro fixo. A comparação dos resultados da análise de estabilidade de Floquet com simulações numéricas diretas e experimentos publicados mostra na maioria dos casos que, apesar de ser uma análise de estabilidade linear, muitas características da análise persistem além do limiar de estabilidade. As situações com discrepâncias são identificadas nesta tese, como padrão de desprendimento diferentes em simulações bi- e tridimensionais na mesma situação. As causa das discrepâncias são estudadas através das simulações numéricas diretas e considerações sobre o sistema linearizado e a abrangência da análise de estabilidade. Em adição, mostra-se que há um limiar de amplitude de oscilação acima do qual a dinâmica da esteira, e portanto a transição secundária, é afetada. Abaixo deste limiar, retoma-se o comportamento do escoamento ao redor de um cilindro fixo.<br>This thesis presents the investigation of the transition to a three-dimensional flow in the wake of an oscillating circular cylinder. This is the secondary transition of the flow around a circular cylinder, while the primary transition leads to the von Kármán wake. The investigative work is performed in the Reynolds number (Re) range which occurs the secondary transition of the wake o a circular cylinder: 200 Re 400. The study consists of two- and three-dimensional direct numerical simulations of the incompressible flow around an oscillating circular cylinder by means of the spectral/hp method. The transition is also analyzed through linear stability study of the flow. The Gaston Floquet method is an appropriate method for this linear stability analysis to three-dimensional perturbations due to the typical periodicity of the von Kármán wake. Furthermore, the Floquet method is of a general kind and it is not specifically applied to autonomous equation with periodic solutions: it can be employed in analysis with a stationary base flow like the primary transition of the wake of a circular cylinder. The thesis shows that the transition to a three-dimensional wake is affected by the cylinder oscillation. The oscillations can delay the transition when they have low amplitudes and the flow has Reynolds number below 260. In other situations, the transition is similar to that observed in the flow of a fixed circular cylinder. In addition, when there is a change in the vortex shedding pattern due to the oscillatory motion, the observed unstable modes are different than those in a wake of a fixed circular cylinder. The comparison of the results from the Floquet stabilty analysis with the ones from direct numerical simulations and published experiments shows that in most cases, despite the linearization for the stability analysis, many features of the analysis persist beyond the instability threshold. The discrepant features observed are specified in this thesis, e.g. vortex shedding patterns different in two- and three-dimensional simulations with the same parameters. The cause of the discrepancies are studied through direct numerical simulations and careful considerations on the linearized system and the range of the stability analysis. In addition, this thesis shows that there is a threshold amplitude of oscillation for which the wake dynamics, therefore the secondary transition, is affected. Below this threshold, the wake behaves the same way as in the flow around a fixed circular cylinder.

L'économie circulaire (EC) émerge depuis les années 2000 dans le débat public, en opposition à l'économie linéaire, modèle dominant aux limites économiques et écologiques reconnues. Cette thèse constitue une première confrontation opérationnelle de l'EC à un système socio-écologique dépendant de la pêche, le Pays de la Cornouaille en Bretagne. Le système est délimité dans sa façade maritime avec la pêche côtière, seule considérée comme production locale.L'approche est systémique, multidimensionnelle et dynamique. L'analyse comporte trois volets : le premier sur l'amont du circuit en mer, le deuxième sur l'aval du système à terre et le dernier sur le système complet. Premièrement, le coût caché des rejets est visualisé via une analyse comptable de flux de matière ("Material Flow Cost Accounting" MFCA) adaptée à la pêche, proposé comme outil pertinent pour améliorer la performance économique et environnementale des pêcheurs. Deuxièmement, l’analyse de flux révèle une forte dépendance des activités à terre vis-à-vis des importations et exportations de bioressources halieutiques malgré un apport significatif de la pêche côtière à l'économie locale. Troisièmement, des scenarii sur le sous-système Sardine, du "business as usual" a l'EC, servent à proposer une trajectoire alternative de développement basée sur un "panier" de biens et services territorialises et la construction d'une valeur territoire à partir de ressources halieutiques locales. Pour atteindre cette EC durable, il s'agira d'optimiser l'utilisation des ressources locales et diminuer les externalités négatives, en plus d'aller vers une gouvernance partagée, adaptée à l'échelle du système socio-écologique considéré<br>The years 2000 have favored the emergence of "Circular Economy" (CE) in the public debate, as opposed to the "linear economy", the dominant model that led to acknowledged economie and ecological limits. Our work is a first attempt to address the CE to a fishery-dependent socio-ecological System, the Cornouaille region in Brittany. The approach is systemic, multidimensional and dynamic. It implies the identification of marine boundaries, in which only Coastal fisheries are considered as a local production. The analysis is conducted along three main axes: an analysis of the upstream part at sea (fishing), an analysis looking at the downstream value chain, on land, and a third looking at the whole System. First, a Material Flow Cost Accounting (MFCA) analysis adapted to fisheries is proposed as a relevant tool to improve economy and environmental performance of fishers, providing evidence of hidden costs of fish discards.Second, the fish bioresource flow analysis indicates a strong dependency on importation and exportation flows to maintain land-based activities depending on sea products, albeit evidence of a significant contribution of Coastal fisheries to the local economy. Third, the exploration of the sardine sub-system through scenarii, ranging between from "business as usual" to those lined with CE, shows an alternative development trajectory, based upon a potential "basket of goods and services", a "territorial value", specifically linked to local fisheries. To achieve such a sustainable CE, we would need to not only aim at a more efficient use of local marine resources and decrease negative externalities, but also advocate for a shared governance, suited to the scale of the considered localised socio-ecological System

Dans le but de montrer l'influence de la morphologie fractale d'un agrégat sur son comportement thermophorétique, un nouveau dispositif expérimental a été développé ; le SpectroMètreThermophorétique Circulaire (SMTC). Cet instrument permet de mesurer la vitesse moyenne de thermophorèse des particules dans une zone de sélection comprise entre une plaque chaude et une plaque froide. Pour cela, nous avons développé une fonction de transfert spécifique au principe de l'instrument sur la base des travaux existant sur les analyseurs différentiels de mobilité électrique.Une qualification expérimentale du SMTC a été réalisée avec des billes de latex monodispersées de tailles comprises entre 64 nm et 500 nm. Le bon accord entre les vitesses de thermophorèse obtenues et la théorie de Beresnev et Chernyak (1995) nous a permis de valider le fonctionnement de l'instrument.Par la suite, nous avons comparé les vitesses de thermophorèse expérimentales obtenues avec le SpectroMètre Thermophorétique Circulaire pour des particules sphériques et des agrégats produits par un générateur d'aérosol à combustion. Contrairement aux résultats obtenus avec les billes de latex, nous observons une augmentation de la vitesse de thermophorèse des agrégats avec leur diamètre de mobilité électrique.Grâce à une étude morphologique des agrégats, nous avons remarqué que la vitesse de thermophorèse est dépendante du nombre de particules primaires de l'agrégat. Ces résultats expérimentaux confirment pour la première fois les données théoriques de Mackowski (2006)obtenues par des simulations Monte-Carlo. De plus, une comparaison avec les travaux de Messerer et al. (2003) montre que la vitesse de thermophorèse des agrégats semble indépendante de la taille des particules primaires.

Att kunna mäta vår materialanvändning är centralt i omställningen till ett resurseffektivare samhälle och en cirkulär ekonomi. Inom EU används Domestic Material Consumption (DMC) som indikator för materialanvändning. Den beräknas genom att addera de material som ett land utvinner, plus de material som importeras, minus de material som exporteras. Det finns kritik mot DMC då den endast tar hänsyn till vikten på import- och exportprodukter då de korsar landsgränsen. DMC inkluderar inte de uppströms material som gått åt för att producera en produkt, men som inte syns i slutprodukten (den så kallade materialryggsäcken).   Den ökade globaliseringen har för många länder lett till en förflyttning av produktion utomlands, och för att beräkna dessa länders totala materialanvändning krävs det att hänsyn tas till importerade och exporterade produkters materialryggsäck. Raw Material Consumption (RMC) är en indikator som tar hänsyn till materialryggsäcken, men den har idag ingen standardiserad beräkningsmetod. Både RMC och DMC används inom Agenda 2030 för att följa upp FN:s hållbarhetsmål 12 ”Hållbar konsumtion och produktion”, samt hållbarhetsmål 8 ”Anständiga arbetsvillkor och ekonomisk tillväxt”. Endast DMC används idag inom EU.   Syftet med projektet var att beräkna Sveriges materialanvändning med hjälp av indikatorn Raw Material Consumption (RMC), samt att identifiera styrkor och svagheter hos RMC. Eurostats RME-verktyg användes för att beräkna RMC. Enligt RMC ökade Sveriges totala materialanvändning från 198 miljoner ton råmaterialekvivalenter (RME) år 2008, till 221 miljoner ton RME år 2015, motsvarande 21,4 ton RME per capita 2008 till 22,6 ton RME per capita 2015. Resultaten jämfördes med resultat för Sveriges DMC som Statistiska Centralbyrån tagit fram. RMC och DMC gav liknande resultat för Sveriges totala materialanvändning. Detta tros bero på att materialryggsäcken för den svenska importen är ungefär lika stor som för exporten och att den största materialkategorin, icke-metalliska mineraler, utgör en liten del av vår handelsbalans och därför inte påverkas i någon större utsträckning när importerade och exporterade produkters materialryggsäck inkluderas. På materialkategorinivå är dock skillnaderna mellan RMC och DMC större.   Resultat från Eurostats RME-verktyg som tagits fram i denna studie, har jämförts med resultat som OECD och UNEP tagit fram för Sveriges RMC. De har använt en annan beräkningsmetod än den RME-verktyget tillämpar. Skillnaden i total RMC för de olika beräkningsmetoderna är mellan 11 % och 22 %. På materialkategorinivå är skillnaderna större, över 50 % för fossila bränslen exempelvis. Liknande resultat har påvisats i en studie som jämförde Österrikes RMC för år 2007 med olika beräkningsmetoder.   Både DMC och RMC kan användas som indikatorer för resurseffektivitet och cirkulär ekonomi, men vid jämförelse mellan länder är RMC teoretiskt en mer lämplig indikator. Detta eftersom många länder idag har flyttat stora delar av sin produktion utomlands, och DMC därför riskerar att ge en skev bild över resurseffektivitet och frikoppling, när materialryggsäcken inte inkluderas.<br>Being able to measure the amount of materials used in society, is central in the transition to a resource-efficient and circular economy. Within the EU, Domestic Material Consumption (DMC) is currently used as indicator for material use. It is calculated by adding the materials that a country extracts, plus the materials imported, minus the materials being exported. There is criticism of DMC, as a measure, since it only considers the weight of imported and exported goods when they cross the country border. It does not consider the upstream materials needed to produce a product, which are not represented in the final product (the so-called material backpack). Globalisation has led to a geographical disconnection in production and consumption, and to consider net-importing countries’ total material consumption, it is necessary to include traded product’s material backpack. Raw Material Consumption (RMC) considers the material backpack, but is currently without a standardised calculation method. Both RMC and DMC are used in Agenda 2030 to follow up the UN Sustainability Development Goal 12 "Sustainable Consumption and Production", as well as Goal 8 "Decent Work Conditions and Economic Growth". Only DMC is used today in the EU.   The aim of this project was to calculate Sweden’s material consumption, using the indicator Raw Material Consumption (RMC), as well as identifying strengths and weaknesses of RMC. For calculating RMC, Eurostat’s RME-tool has been used. According to RMC, Sweden's total material usage increased from 2008 when it amounted to 198 million tonnes of raw material equivalents (RME), to 221 million tonnes RME in 2015. There has also been an increase per capita: 21,4 RME per capita in 2008 to 22,6 RME per capita in 2015. These results have been compared with the results for Sweden's DMC, calculated by SCB. RMC and DMC gave similar results for Sweden's total material consumption. This is believed to be due to the similar size of the material backpack of imports and exports. Another reason is believed to be due to Sweden’s largest material category, non-metallic minerals, is a small part of our trade balance, and therefore is not affected when the material backpack is included. At the material category level, however, the differences between RMC and DMC are greater.   Results from Eurostat's RME tool, calculated in this study, have been compared with results presented by the OECD and UNEP. They have used a different calculation method for Sweden’s RMC than the RME tool applies. The difference in total RMC for different calculation methods is between 11 % and 22 %. At material category level, the differences are greater, more than 50 % for fossil fuels, for example. Similar results have been presented in a study over Austria's RMC for the year 2007, using different calculation methods.   Both DMC and RMC can be used as policy-support for resource efficiency, but RMC is theoretically a more suitable indicator for comparison of countries. This is since many countries today have moved a significant share of their production abroad, and DMC therefore risks displaying a false perception of resource efficiency and decoupling, when the material backpack is not included.

碩士<br>國立成功大學<br>航空太空工程學系<br>85<br>The major topic is to use numerical approach to simulate noise generated by flow past a blunt body.A two-dimensional circular cylinder is selected as our physical model.The far-field pressure distribution and the corresponding Fourier Spectra are analyzed.Moreover,the effects included various Mach number and Reynolds number are considered in the research.In the whole problem,we adapt an Upwind finitefinite volume method of third order accuracy and a three-stage Runge-Kutta time integration method of second order accuracy .Finally,we concentrate in the noise generatedin the flow field,Kirchhoff integral is used here

碩士<br>國立中興大學<br>機械工程研究所<br>81<br>The main purpose of this thesis is to analyze the flow field with the uniform flow over circular cylinders in various arrangements. The flow field is considered to be inviscid for high Reynolds number flows. By the satisfaction of the Kutta condition, the vortex shedding phenomena with fixed separation points behind the cylinders are carefully investigated. The global properties of the flow field are obtained from the numerical analysis. For solving the question, first, the surface vorticity method is applied to predict the solutions of the potential flow. Then the vortex shedding phenomenon at the separation points is simulated by the discrete vortex model. For more of analysis, we also try to analyze the interference effects of the wake flow for more than one cylinder case. 　　The predictions about the trend of the flow field in one circular cylinder are in good agreements with the other researches, but the values of CD and CL, as presented in this thesis, are lower than that from the experiments. For the cases of the two or three cylinders, the numerical scheme used in this dissertation predicts a reasonable results by comparing with the results from the flow visualizations and experiments except for the tandem arrangement of the two circular cylinders. 　　For the wake intrference study, it was found that the lift and drag forces of the downstream cylinder increase due to the effects of the upstream cylinder. As to the shedding frequency, flow effect to the Strouhal number is not obvious. It was found that the exist of upstream cylinder does not affect this quantity into large extent for the downstream cylinders.

碩士<br>國立交通大學<br>機械工程系<br>91<br>This thesis purposes to manufacture a micro fluidic device for observation and examination of the effects of surface tension, adhesive force and inertial force on the flow phenomena. Experimental results show that phenomena of vortex won’t be produced during the conditions of operation in the present study. Since the volume flow rate and cross- sectional area of the circular disc-shaped chamber influence the velocity and inertial force and then the flow phenomena will be affected, the Weber number decided from the geometric sizes of chamber seems more appropriate to interpret the flow phenomena under the conditions where the inertial force is significant. However, due to the adhesive force between solution and wall surface, kind of solution and depth will significantly affect the flow phenomena, Weber number couldn’t properly predict or explain the flow phenomena. And because the adhesive force influence apparently, in case of smaller surface tension of work fluid or not deep depth of micro channel a bubble may be formed prior to outlet of the chamber.

碩士<br>大葉大學<br>機械工程研究所碩士在職專班<br>94<br>ABSTRACT So far the most of table of circular saw on market is die-cast by aluminum alloy. That is because aluminum alloy not only has light weight, beautiful outlook, but also intensity quality. The aluminum alloy made table can have multi-shapes. Because the table of circular saw is to be with wide working area and thin thickness, many different shapes of ribs are usually used to increase its strength. However, this always develops quality problems, such as cracks, porosities, and shape changed. Therefore, how to develop a good designed aluminum alloy die casting product and also improve the die casting problem is need to be solve. This study will use mold-flow analysis to design the table mold of the circular saw. At first, we develop subsidiary institutions of table of circular saw, also take consider of the outlook and strength of the table to create its 3D model. Secondary, we use mold-flow analysis software at the mold developing stage to simulate how melt aluminum liquid fill-in metal mold. By this we can find out the better number and shape of entrances for melt aluminum liquid, and also the better design of ribs height on the table. Besides, we can estimate where the defects may happen by proper parametric inference. This helps us to decrease the risk, not just like the tradition way only rely on experiment experience, and also decrease problems on mold modification in future. Finally, we make molds according to the results of mold-flow simulations. After we finish die casting the table, we apply impact test on it to test its strength and precision on surface. Experiments show that the mold-flow analysis improves quality of the mold, decreases the defect rate of die-cast, and also the strength and precision of the table all meet our requirements. Key Words: circular saw, molding tool, die-cast, mold-flow analysis, entrances for melt aluminum liquid

碩士<br>中原大學<br>機械工程學系<br>87<br>Abstract The flow phenomena of the twin flow of a bubble driven fluid in a circular tube were analyzed in the present study. The effects to the flow field of the viscous fluid in a circular tube were examined under different values of Lambda (the width of bubble/the diameter of tube), the gas-liquid pressure difference and the capillary coefficient. The bubble equation used was from Pitts and the Galerkin method was used to obtain the approximate method of the viscous liquid flow field. The results showed that the liquid has fountain flow in front of the bubble with Lambda=0.715 , and the gas-liquid pressure difference versus capillary coefficient are negative proportional even with different values of Lambda in each case. The present study provides that an elementary result about the flow phenomenon of twin flow of a bubble driven fluid in a circular tube, and a reference to some relevant researches, such as the gas-assisted injection molding processes and the control of the biochemical liquid in a pipette, etc.

碩士<br>國立中興大學<br>機械工程學系所<br>94<br>This study investigates the long time characteristics of wake flow behind two side-by-side circular cylinders with different diameter ratios and at various net gaps. The switching characteristics of gap-flow, the phase characteristics of vortex structures and the locked-on characteristics of wakes flow will be emphasized. The experiments are performed in a low-speed recirculation water channel. Qualitative flow visualization and quantitative velocity measurements were performed by way of the laser sheet technique and the FLDV system, respectively. To acquire the phase information, the two velocity signals from FLDV and hot-film anemometer were taken simultaneously and analyzed by cross Wavelet transformation. In the following, some important results are concluded： (A)Cylinders with equal diameters 1.For the cases, Re＝2000, G/D1＝1.0〜1.5 and Re＝5000, G/D1＝0.75〜1.0, the gap-flow between two side-by-side circular cylinders switches intermittently. When the net gap ratio increases, the probability of the switching gap flow increases largely. However, the stably biased gap flow still occupies the most significant portion of the detecting time. 2.For the cases, Re＝2000, G/D1≧2.0 and Re＝5000、G/D1≧1.25, the gap flow becomes nearly parallel to the free-stream flow during most of the detecting time.(1)When the net gap ratio increases, the probability of the anti-phase vortex shedding decreases and the probability of the in-phase vortex shedding increases. Both of them approaches 10∼20％ till the net gap ratio is equal to 5(Re＝2000)or equal to 4(Re＝5000).(2)For the cases, Re=2000 and 5000, G/D1≧5.0, the flow patterns, in form of neither anti-phase shedding nor in-phase shedding, occur most frequently. (B)Cylinders with unequal diameters 1.For the case,D1＝2D2、G/D1＝0.75、Re＝2000, the following results will be summarized：(1)The ratio of the characteristic frequencies of the narrow and the wide wakes equals 3.3（fn/fw＝3.3）in case of no perturbation. When the large cylinder is perturbed at various excitation frequency, the bandwidth of double lock-on for both wakes occurs within the region fe/fos＝3.03〜3.18, indicating a subharmonic resonance.(2)When the large and the small cylinder are perturbed separately at various excitation frequencies, the double lock-on bandwidth of both wakes is located at fe/fos＝0.970〜1.02 and 0.848〜0.884, respectively.(3)Perturbations on the large cylinder can influence the narrow wake more efficiently. But perturbations on the small cylinder affect the wide wake more insignificantly.

碩士<br>中原大學<br>機械工程學系<br>87<br>The goal of the present work is to study the driven flow field in a circular tube at front of a long bubble. Show radius of curvature R*Sin(theta)=constant which is assumed by Pitts . Using uniform flow and source flow can proof R*Sin(theta)=constant. The number is 3.417. Image method can simulate the wall of circular tube. Finally, add fractional converge ratio lambda can perform driven flow field of a long bubble in the circular tube.

Numerical studies of two-dimensional laminar conjugate natural convection flow and heat transfer in horizontal annuli formed between inner heat generating solid cylinders and outer isothermal circular boundary are performed with and without the effect of surface radiation. The two configurations of the concentrically placed inner cylinder are a circular cylinder (CC configuration) and a square cylinder (SOS, i.e., Square-On-Side, configuration). The mathematical formulation consists of the continuity equation, momentum equations with Boussinesq approximation and the solid and fluid energy equations. Numerical solutions are obtained by discretising the governing equations on a collocated mesh (non-staggered mesh) and the pressure-velocity coupling is taken into account via the SIMPLE (Semi-Implicit Method for Pressure-Linked Equations) algorithm. A cylindrical polar coordinate system is employed for CC configuration and a Cartesian coordinate system is used for the SOS configuration. The convective terms are discretised with donor-cell differencing scheme and the diffusion terms, with central differencing scheme. The algebraic equations resulting from the discretisation of the governing equations are solved using the line by line TDMA (Tri-Diagonal Matrix Algorithm). A global iteration scheme over each time step is used for better coupling of temperature and the flow variables and steady-state solutions are obtained by time-marching. Steady-state results of conjugate pure natural convection are obtained for the volumetric heat generation and outer radius based Grashof number ranging from 104 to 1010, for solid-to-fluid thermal conductivity ratios of 1, 5, 10, 50 and 100, and for the aspect ratios of 0.2 and 0.4, with air as the working medium (Pr=0.708) for the CC and SOS configurations. The flow and temperature distributions are presented in terms of isotherms and streamline maps. Results are presented for several quantities of interest such as local and average Nusselt numbers on the inner and outer boundaries, dimensionless local temperatures on the inner boundary and dimensionless maximum and average solid cylinder temperatures. The results show that the flow in the annulus is characterized by double or quadruple vortex patterns. Of the dimensionless maximum solid temperature, average solid temperature and average inner boundary temperature, the first two are much sensitive to solid-to-fluid thermal conductivity ratio. Surface radiation effects are studied numerically in conjugation with natural convection. The coupling with surface radiation arises through the solid-fluid interface thermal condition. To account for the radiation effects, configuration factors among the subsurfaces of the inner and outer boundaries formed by the computational mesh are determined. Results are obtained for CC and SOS configurations for emissivities ranging from 0.2-0.8, with the other parameters as in pure natural convection case. It is found that even at low surface emissivity, radiation plays a significant role in bringing down the convective component and enhancing the total Nusselt numbers across the annulus. The presence of radiation is found to reduce the dimensionless temperatures inside the solid and homogenise the temperature distribution in the fluid. The radiative Nusselt number is about 50-70 % of the total Nusselt number depending on the radiative parameters chosen. This factor emphasizes the need for taking into account the coupling of radiation and natural convection for the accurate prediction of the flow and heat transfer characteristics in the annulus. The solution of the conjugate problem facilitates the determination of the solid temperature distribution, which is important in connection with the safety aspects of various thermal energy systems. Correlations as functions of Grashof number and thermal conductivity ratio are constructed for the estimation of various quantities of interest for the two configurations and aspect ratios for pure natural convection and for combined natural convection and radiation cases. The results are expected to be useful in the design of thermal systems such as spent nuclear fuel casks during transportation and storage, underground transmission cables and cooling of electrical and electronic components.

Numerical studies of two-dimensional laminar conjugate natural convection flow and heat transfer in horizontal annuli formed between inner heat generating solid cylinders and outer isothermal circular boundary are performed with and without the effect of surface radiation. The two configurations of the concentrically placed inner cylinder are a circular cylinder (CC configuration) and a square cylinder (SOS, i.e., Square-On-Side, configuration). The mathematical formulation consists of the continuity equation, momentum equations with Boussinesq approximation and the solid and fluid energy equations. Numerical solutions are obtained by discretising the governing equations on a collocated mesh (non-staggered mesh) and the pressure-velocity coupling is taken into account via the SIMPLE (Semi-Implicit Method for Pressure-Linked Equations) algorithm. A cylindrical polar coordinate system is employed for CC configuration and a Cartesian coordinate system is used for the SOS configuration. The convective terms are discretised with donor-cell differencing scheme and the diffusion terms, with central differencing scheme. The algebraic equations resulting from the discretisation of the governing equations are solved using the line by line TDMA (Tri-Diagonal Matrix Algorithm). A global iteration scheme over each time step is used for better coupling of temperature and the flow variables and steady-state solutions are obtained by time-marching. Steady-state results of conjugate pure natural convection are obtained for the volumetric heat generation and outer radius based Grashof number ranging from 104 to 1010, for solid-to-fluid thermal conductivity ratios of 1, 5, 10, 50 and 100, and for the aspect ratios of 0.2 and 0.4, with air as the working medium (Pr=0.708) for the CC and SOS configurations. The flow and temperature distributions are presented in terms of isotherms and streamline maps. Results are presented for several quantities of interest such as local and average Nusselt numbers on the inner and outer boundaries, dimensionless local temperatures on the inner boundary and dimensionless maximum and average solid cylinder temperatures. The results show that the flow in the annulus is characterized by double or quadruple vortex patterns. Of the dimensionless maximum solid temperature, average solid temperature and average inner boundary temperature, the first two are much sensitive to solid-to-fluid thermal conductivity ratio. Surface radiation effects are studied numerically in conjugation with natural convection. The coupling with surface radiation arises through the solid-fluid interface thermal condition. To account for the radiation effects, configuration factors among the subsurfaces of the inner and outer boundaries formed by the computational mesh are determined. Results are obtained for CC and SOS configurations for emissivities ranging from 0.2-0.8, with the other parameters as in pure natural convection case. It is found that even at low surface emissivity, radiation plays a significant role in bringing down the convective component and enhancing the total Nusselt numbers across the annulus. The presence of radiation is found to reduce the dimensionless temperatures inside the solid and homogenise the temperature distribution in the fluid. The radiative Nusselt number is about 50-70 % of the total Nusselt number depending on the radiative parameters chosen. This factor emphasizes the need for taking into account the coupling of radiation and natural convection for the accurate prediction of the flow and heat transfer characteristics in the annulus. The solution of the conjugate problem facilitates the determination of the solid temperature distribution, which is important in connection with the safety aspects of various thermal energy systems. Correlations as functions of Grashof number and thermal conductivity ratio are constructed for the estimation of various quantities of interest for the two configurations and aspect ratios for pure natural convection and for combined natural convection and radiation cases. The results are expected to be useful in the design of thermal systems such as spent nuclear fuel casks during transportation and storage, underground transmission cables and cooling of electrical and electronic components.

碩士<br>國立中央大學<br>土木工程學系<br>106<br>Rubber dams are widely used around the world for irrigation, water supply, flood control, scouring protection. This study integrated a Large Eddy Simulation (LES) model and the Volume of Fluid (VOF) method to investigate the free surface flows around a circular rubber dam. The simulation results were verified by the results of laboratory experiments. The numerical model was then used to examine the influences of Froude number, Reynolds number, depth ratio and blockage ratio on the hydrodynamic forces and discharge coefficients of the rubber dam. The results revealed that the drag coefficient decreased as the depth ratio increased. The flow rates over the crest of the dam were used to compute the discharge coefficients, and the computed discharge coefficient was different from the formula suggested by Matthew (1963) and Heidarpour & Chamani (2006) due to the backwater effect. The results of this study can be used for the structure design of circular rubber dam.

碩士<br>國立成功大學<br>環境工程學系<br>107<br>Assessing the Potential Value of Circular Practice in Taiwan’s Industrial Chains of Copper with Material Flow and Cost Analyses Tsung-Yen Tsai Pi-Cheng Chen Department of Environmental Engineering ＆ National Cheng Kung University SUMMARY The study shows the material flow and cost analyses for copper in Taiwan’s industrial chains. Then, the principle of circular economy is applied in this study to create or find the value of copper circulation. To illustrate current situation of copper consumption and quantify the cost and benefit for analyzing the value chain of copper, the material flow analysis and material flow cost accounting are implemented respectively. According to the results of material flow analysis show that the great amount of the cathode is imported, and the copper recycle is not complete in Taiwan. Furthermore, from the results of five hotspots that we screen out show that the amount of waste wire and cable can reach the profit standard for the copper smelting, but the vehicle can’t be reached. And the results of material flow cost accounting show that the main loss part of printed circuit board process is caused by etching and detection, the vehicle process is caused by the consumption of raw material and crushing/sorting. Finally, in conclusion, the study knows the current situation of copper are imported from the global supply chain, and the amount of waste wire and cable can be used as the raw material of the copper smelting plant. Considering the circular-economy scenario benefit, the printed circuit board industry and the vehicle industry are positive value of circular economy, but the heat-exchange equipment is negative value of circular economy. Key words：Copper, Circular economy, Material flow analysis, Cost-benefit analysis, Industrial chains   INTRODUCTION Taiwan is not a copper mine production country and the copper materials of domestic industries are imported from the global supply chain. Copper is a widely used metal and the manufacturing industries in Taiwan consume 1,694,273-ton copper in 2016. Recently, due to increasing the infrastructure construction for the United State policy after the 2016 election, the increased demand of copper leads the price rise from 4,645 USD/ton to 6,000 USD/ton. As to the copper depends on the global supply chain importing and the copper price has the trend of rise, this study analyzes the flow of copper in the Taiwan’s industrial chains. From the result of analysis, the purpose is to know the Taiwan’s main copper industry, find the recyclable amount and application of the copper and assess the value of copper circular. MATERIALS AND METHODS Copper is a critical material which means copper has great environmental impact, low resource efficiency, low economic benefit and high supply risk. To use copper efficiently, we investigate the circular economy’s potential for the copper in Taiwan. To know the circular economy’s potential for the copper, in this study, material flow analysis is implemented to illustrate current situation of copper consumption by the industries in Taiwan. Furthermore, we screen out the hotspots industries of copper for analyzing the value chain of copper to quantify the cost and benefit with material flow cost accounting. Finally, for these hotspots industries of copper that produce waste or waste raw material in the process, this study designs a high-cycle scenario based on the related technical literature. RESULTS AND DISCUSSION We divide the life cycle stages of copper into raw material, semi-finished products, products, use, and recycling resource and waste management. The results of material flow analysis show that the main items imported in raw material stage are cathode, the main items in semi-finished products stage are bare copper wire, followed by copper casting and copper foil. The main items in the products stage are cable, metal hand tool and metal mold. In the use stage, the main items are machine and architecture. However, in the recycling resource and waste management stage, the results show that the copper recycle is not complete in Taiwan. Then, we screen out five hotspots that are the copper recycle for waste wire and cable, printed circuit board byproduct, waste appliance, electronic product and the vehicle. The results of hotspots show that the waste parts of wire and cable, if used as copper smelting raw materials, it can be reaching the profit standard. But the recycle amount of the vehicle can not reach the profit standard for the smelting. The printed circuit board byproduct has the great amount of waste generated, it can develop the 3D printing to reduce the generation of waste. The development of IOT in the future will lead the increasing requirement of the electronic product and the copper. The main items of the waste appliance are air conditioner and fridge, the regeneration rate is 65.31% and 63.6% respectively. The results of hotspots with material flow cost accounting show that the main part of waste for the process in the industry. The main loss part of printed circuit board process is caused by etching and detection. The main loss part of vehicle process is caused by consuming raw material and crushing/sorting. The main loss part of heat-exchange equipment process is not much, we speculate the process and recycling technique is complete. The results of designing high-cycle scenario show that the different scenario can cause different circular economy value. It can be found the cost-effective recycling model. We compare the waste etching solution recycling scheme, the ion exchange combined with electrolysis is better than electrolysis. On the waste car recycling side, the manual selection is better than crusher. Considering the circular-economy scenario benefit, the result of cost and benefit analysis show that printed circuit board and vehicle are positive value. The value of copper is 395 NT million dollars and 1,135 NT million dollars respectively. On the other hand, the heat-exchange equipment is negative value. The loss value of copper is 344 NT million dollars. CONCLUSION In Taiwan’s copper industry chain, the great amount of copper materials is imported from the global supply chain, and there is a lack of information on the follow-up downstream of waste circulation. According to the analysis of the amount of the copper circulation and the circular pathway of hotspots in the copper material flow system, the amount of waste wire and cable can be used as the raw material of the copper smelting plant. On the circular-economy scenario benefit side, the printed circuit board industry and the automotive industry are in line with the cost-benefit of recycling, while the heat-exchange equipment is not in line with the cost-benefit of recycling.