Subsea pipelines are subjected to wave and steady current loads which cause pipeline stability problems. Current knowledge and understanding on the pipeline on-bottom stability is based on the research programmes from the 1980’s such as the Pipeline Stability Design Project (PIPESTAB) and American Gas Association (AGA) in Joint Industry Project. These projects have mainly provided information regarding hydrodynamic loads on pipeline and soil resistance in isolation. In reality, the pipeline stability problem is much more complex involving hydrodynamic loadings, pipeline response, soil resistance, embedment and pipe-soil-fluid interaction. In this thesis Computational Fluid Dynamics (CFD) modelling is used to investigate and establish the interrelationship between fluid (hydrodynamics), pipe (subsea pipeline), and soil (seabed). The effect of soil types, soil resistance, soil porosity and soil unit weight on embedment was examined. The overall pipeline stability alongside pipeline diameter and weight and hydrodynamic effect on both soil (resulting in scouring) and pipeline was also investigated. The use of CFD provided a better understanding of the complex physical processes of fluid-pipe-soil interaction. The results show that the magnitude of passive resistance is on the average eight times that of lateral resistance. Thus passive resistance is of greater significance for subsea pipeline stability design hence the reason why Coulomb’s friction theory is considered as conservative for stability design analysis, as it ignores passive resistance and underestimates lateral resistance. Previous works (such as that carried out by Lyons and DNV) concluded that soil resistance should be determined by considering Coulomb’s friction based on lateral resistance and passive resistance due to pipeline embedment, but the significance of passive resistance in pipeline stability and its variation in sand and clay soils have not be established as shown in this thesis. The results for soil porosity show that increase in pipeline stability with increasing porosity is due to increased soil liquefaction which increases soil resistance. The pipe-soil interaction model by Wagner et al. established the effect of soil porosity on lateral soil resistance but did not attribute it to soil liquefaction. Results showed that the effect of pipeline diameter and weight vary with soil type; for sand, pipeline diameter showed a greater influence on embedment with a 110% increase in embedment (considering combined effect of diameter and weight) and a 65% decrease in embedment when normalised with diameter. While pipeline weight showed a greater influence on embedment in clay with a 410% increase. The work of Gao et al. did not completely establish the combined effect of pipeline diameter and weight and soil type on stability. Results also show that pipeline instability is due to a combination of pipeline displacement due to vortex shedding and scouring effect with increasing velocity. As scoring progresses, maximum embedment is reached at the point of highest velocity. The conclusion of this thesis is that designing for optimum subsea pipeline stability without adopting an overly conservative approach requires taking into consideration the following; combined effect of hydrodynamics of fluid flow on soil type and properties, and the pipeline, and the resultant scour effect leading to pipeline embedment. These results were validated against previous experimental and analytical work of Gao et al, Brennodden et al and Griffiths.

FundaÃÃo de Amparo a Pesquisa do Estado do Piauà / O Nordeste do Brasil onde predomina o clima semiÃrido se caracteriza por ambientes de exploraÃÃo intensiva dos recursos naturais como a exploraÃÃo agrÃcola por pequenos produtores na forma de subsistÃncia. AÃÃes antropogÃnicas tÃm provocado limitaÃÃes na exploraÃÃo dos recursos naturais com consequentes perdas de solo e Ãgua e comprometimento da sustentabilidade ambiental das bacias hidrogrÃficas. Neste sentido, à fundamental a compreensÃo dos processos hidrossedimentolÃgicos, biolÃgicos e bioquÃmicos na definiÃÃo de estratÃgias para o melhor gerenciamento de pequenas bacias hidrogrÃficas e na definiÃÃo de planos de sustentabilidade dos agroecossistemas. Assim, teve-se como hipÃteses: (1) ecossistemas naturais do semiÃrido apresentam poucas perdas de sedimentos e nutrientes em decorrÃncia das chuvas, e tais sedimentos tÃm alta atividade microbiolÃgica em relaÃÃo aos solos de agroecossistemas tradicionais; (2) o estabelecimento de relaÃÃes entre variÃveis sedimentolÃgicas, microbiolÃgicas e bioquÃmicas à essencial para o entendimento e adoÃÃo de tÃcnicas de manejo sustentÃvel em agroecossistemas do semiÃrido; (3) a composiÃÃo mineralÃgica e os atributos fÃsicos dos sedimentos de arraste sÃo determinados pela erosividade das chuvas sobre os solos dos agroecossistemas. Para testar tais previsÃes objetivou-se: (a) quantificar a produÃÃo e caracterizar quÃmica, fÃsica e mineralogicamente os sedimentos de arraste de diferentes agroecossistemas do semiÃrido; (b) avaliar alteraÃÃes da atividade microbiolÃgica, da biomassa microbiana e da atividade enzimÃtica e quantificar a populaÃÃo de fungos micorrÃzicos arbusculares de sedimentos de arraste de diferentes agroecossistemas; (c) avaliar a granulometria dos sedimentos de arraste levando em consideraÃÃo a erosividade das precipitaÃÃes pluviomÃtricas; (d) relacionar a qualidade dos solos e dos sedimentos de arraste com os processos de degradaÃÃo, visando subsidiar o manejo mais sustentÃvel de agroecossistemas. Foram considerados os agroecossistemas de quatro microbacias hidrogrÃficas: (1) vegetaÃÃo de mata raleada (MR), com a manutenÃÃo de espÃcies vegetais com diÃmetro basal ≥ que 10 cm, e espÃcies de crescimento herbÃceo; (2) vegetaÃÃo nativa (MN), representando as condiÃÃes naturais de pequenas bacias rurais do semiÃrido brasileiro; (3) agrossistema com capim Andropogon gayanus Kunt (PAST); (4) agroecossistema com prÃtica usual da agricultura de subsistÃncia (AGRS). As microbacias estavam instrumetadas com pluviÃmetro tipo âVille de Parisâ, calha Parshall, coletores de sedimentos tipo armadilha (bed load), e pluviÃgrafo automÃtico. Os resultados obtidos permitem concluir: (1) a maior erodibilidade dos Vertissolos (das Ãreas de mata e pastagem) em relaÃÃo ao Luvissolo do sistema de agricultura de subsistÃncia promove maior produÃÃo de sedimentos de arraste, independentemente da vegetaÃÃo tÃpica do semiÃrido e dos sistemas tradicionais, e do nÃmero de eventos que geraram escoamento superficial; (2) a biomassa, a atividade microbiana e a perda de esporos de fungos micorrÃzicos arbusculares em sedimentos de arraste apresenta sensibilidade Ãs mudanÃas de uso da terra; (3) as fraÃÃes de quartzo e feldspato permite identificar neste mineral maior diversidade nos sistemas com Vertissolos (MN, MR e PAST) em relaÃÃo ao Luvissolo de AGRS, enquanto a identificaÃÃo de esmectitas e vermiculita em argilas tratadas de sedimentos das matas (MR e MN) e pastagem (PAST) caracteriza a drenagem deficiente daqueles em relaÃÃo a este sistema, cuja argila tratada revelou presenÃa de caulinita com picos mais elevados; (4) o Ca++ e K+ em quantidade nos sedimentos de arraste constitue uma importante reserva mineral para sua exploraÃÃo; (5) nÃo se verifica uma relaÃÃo direta entre a erosividade das chuvas (EI30) e a produÃÃo de areia e argila em sedimentos de arraste nos agroecossistemas de mata (MR e MN) e tradicionais (PAST e AGRS); (6) os agroecossistemas de mata (MR e MN) apresentam maiores teores de agregados estÃveis (AE) em relaÃÃo aos sistemas tradicionais (PAST e AGRS), favorecendo a qualidade biolÃgica dos solos; (7) tÃcnicas de manejo sÃo de grande importÃncia para o desenvolvimento de estratÃgias para a gestÃo de bacias hidrogrÃficas e na definiÃÃo de planos de sustentabilidade na regiÃo semiÃrida. / The Northeast of Brazil wich predominantes semiarid climate is characterized by intensive exploitation of natural resources and the environment for small farm producers in the form of subsistence. Anthropogenic activities have caused limitations in the exploitation of natural resources with consequent losses of soil and water and environmental sustainability commitment watershed. In this sense, it is fundamental to understanding the hydrosedimentological, biological and biochemical definition of strategies for better management of small watersheds and defines plans for sustainability of the agroecosystems. Thus, it was taken as hypotheses: (1) natural vegetation systems have small losses of sediment and nutrients due to rain, and the sediments have high microbial activity in relation to soils traditional agroecosystems; (2) the establishment of relationships between sedimentological, microbiological and biochemical variables is essential for the understanding and adoption of sustainable management techniques in semiarid agroecosystems; (3) the mineral composition and physical properties of the sediments produced by drag are determined by rainfall erosivity on soils of agroecosystems. To test these predictions the objectives were: (a) quantify the production and characterization of chemical, physical and mineralogical sediments by drag of differents semiarid agroecosystems; (b) evaluate changes in microbial activity, microbial biomass and enzyme activities and quantify the population of mycorrhizal fungi in sediment of differents agroecosystems; (c) evaluate the size of the sediments by drag considering the erosivity of rainfall; (d) relate the quality of soils and sediments by drag with degradation processes, to support sustainable management of agroecosystems. Systems the four watersheds were considered: (1) vegetation thinned forest (MR), with the maintenance of plant species with basal diameter ≥ 10 cm, and species of herbaceous growth; (2) native vegetation (MN), representing the natural conditions of small rural basins of the Brazilian semiarid; (3) agroecosystem with pasture Andropogon gayanus Kunt (PAST); (4) agroecosystem with usual practice subsistence agriculture (AGRS). The watersheds were instrumented with rain gauge type "Ville de Paris", gutters type Parshal, sediments collectors (bed load), and automatic meters. The results show: (1) the higher erodibility of Vertisols (forested areas and grassland) compared to Luvisol of subsistence agriculture promotes greater sediment produced by drag, regardless of typical vegetation of semiarid systems and traditional system and the number of events that promoted surface runoff ; (2) the biomass, microbial activity and the loss of spores of mycorrhizal fungi in sediments produced by drag shows sensitivity to changes in land use; (3) the fractions of quartz and feldspar mineral allows identifying this greater diversity in systems with Vertisols (MN, MR and PAST) in relation to Luvissol in the, while identification of vermiculite and smectite clays in sediments of treated samples of MR, MN and PAST characterizes those deficit drainage in relation to this system, which treated clay showed the presence of kaolinite with higher peaks; (4) the Ca+ + and K+ on sediment produced by drag constitutes an important reserve for mineral exploitation; (5) are not note a direct relationship between rainfall erosivity (EI30) and the production of sand and clay sediments produced by drag in agroecosystems (MR and MN) and traditional (PAST and AGRS); (6) the forest agroecosystems (MR and MN) have higher levels of stable aggregates (AE) compared to traditional systems (PAST and AGRS), favoring the biological quality of the soil; (7) management techniques are of great importance for the development of strategies for watershed management plans and the definition of sustainability in the semiarid region.

L’évaporation du carburant injecté dans une chambre de combustion est un phénomènecrucial dans un foyer aéronautique car elle détermine la quantité de vapeur qui sera ensuite brûléepour fournir de l’énergie au moteur. Cependant, ce phénomène reste mal décrit du fait desdifficultés de mesurer expérimentalement les taux d’évaporation des gouttes appartenant à unbrouillard. D’autre part, les hypothèses des modèles théoriques ne sont toujours pas représentativesdes conditions rencontrées dans les foyers de combustion.La thèse s’inscrit dans une démarche visant à étudier l’évaporation d’un groupe de gouttesdans un écoulement turbulent au moyen de la Simulation Numérique Directe (SND). En effet, lorsde l’évaporation de groupes de gouttes, des effets collectifs peuvent influer sur le taux d’évaporationde chaque goutte ou sur le taux d’évaporation global du nuage de gouttes. L’approche SNDpermet de quantifier précisément ces effets afin d’améliorer les modèles actuels d’évaporation.Dans un premier temps, des algorithmes ont été développés et utilisés dans une configuration1D sphérique pour décrire l’évaporation d’une goutte statique isolée et sans gravité. Puisdans un second temps, l’évaporation d’une goutte a été étudiée dans un écoulement laminaire.Une analyse des échanges de chaleur entre la goutte et le milieu extérieur ainsi que de la force detraînée exercée par l’écoulement laminaire sur la goutte a été effectuée. Dans cette partie, il a étémis en évidence que l’évaporation induit une diminution des échanges thermiques et de la traînée.Il a notamment été observé que dans certains cas de forte évaporation, la traînée de la gouttepeut devenir négative. Cela implique que l’évaporation peut être à l’origine d’un phénomène depropulsion de la goutte. Une analyse théorique permet de lier ce comportement à une asymétriedu débit d’évaporation. Dans un troisième temps, l’influence de la turbulence sur l’évaporationd’une goutte a été étudiée. Pour cela, un générateur de fluctuations turbulentes a été implémentéet des techniques de calculs parallèles ont été introduites pour réduire le temps des calculs. Celaa permis d’analyser les échanges thermiques et le comportement de la traînée d’une goutte eninteraction avec un écoulement turbulent. Il a été montré que ces deux grandeurs ont tendanceà être amplifiées par la turbulence. Enfin, dans un dernier temps, l’évaporation de groupes degouttes a été étudiée. Pour trois groupes de gouttes différents, les déplacements des gouttes ontété analysés avec les échanges de chaleur lorsque ceux-ci sont placés dans un écoulement laminaireou turbulent avec ou sans changement de phase. En présence d’évaporation, il a été mis enévidence que les déplacements sont différents des cas sans évaporation et donc que le changementde phase modifie les effets collectifs. De plus, ces effets de groupes ont aussi été observés sur leséchanges thermiques. / The vaporisation of injected fuel in a combustion chamber is a crucial phenomenon inan aeronautical motor because it determines the vapour quantity which will be burned to bringenergy to the motor. Still, this phenomenon is not well understood due to the difficulties tomeasure on experiments vaporisation rates of injected sprays. Moreover, hypothesis of theoriticalmodels are not representatives of conditions encountered in combustion furnaces.The thesis take place in an effort to analyse the evaporation of droplet groups in a turbulentflow by mean of Direct Numerical Simulation (DNS). Indeed, during droplet group evaporation,collective effects can modify single droplet rates of vaporisation and the group global rate ofvaporisation. The DNS approach should allows to quantify precisely this effect and leads to animprovement of actual models of evaporation.Firstly, algorithms are developped and used in a 1D spherical configuration to describe theevaporation of a single static droplet without gravity. Secondly, the vaporistion of a droplet in alaminar flow has been studied. The analysis focus on heat exchanges between the droplet and theexternal environment as well as the force exerced on the droplet by the laminar flow. In this part,it has been highlighted that the evaporation induced a decrease in thermal exchanges and drag.In some cases of strong evaporation, the drag of the droplet has been observed to be negative.It means that the evaporation can cause a propulsion phenomenon of the droplet. A theoriticalanalysis allows to link this behaviour to an asymetry of the vaporisation rate. Thirdly, a studyof the turbulence influence on the evaporation of a droplet has been carried out. A generator ofturbulent fluctuations has been implemented and parallel approaches have been introduced toreduced computational time. It allowes to analyse thermal exchanges and drag behaviour of adroplet interacting with a turbulent flow. The analysis showed that theses two variables increasewith turbulence. Lastly, the evaporation of groups of droplets has been studied. For three differentgroups of droplets, trajectories of droplets have been analysed with heat exchanges when they areput in a laminar or a turbulent flow with or without phase change. In presence of evaporation,the analysis pointed out that trajectories were different from cases whitout evaporation and sothat phase change modifies collective effects. Moreover, these collective effects have also beenobserved on thermal exchanges.

Most fighters use the convergent-divergent nozzle configuration to accelerate into the supersonic realm. This nozzle configuration greatly increases the thrust potential of the aircraft compared to the simpler convergent nozzle. The nozzle design is not only crucial for thrust, but also for the drag since the afterbody drag can be as high as 15% of the total. Engine manufacturers optimize the engine and the nozzle configurations for the uninstalled conditions, but these may not be optimal when the engine is installed in the aircraft. The purpose of this study is to develop a methodology to optimize axisymmetric nozzle settings in order to maximize the net thrust. This was accomplished by combining both simulations of thrust and drag. The thrust model was created in an engine performance tool, called EVA, with the installed engine performance of a low bypass turbofan jet engine at maximum afterburner power setting. The drag model was created with CFD, where the mesh was built in ICEM Mesh and the simulations were run with the CFD solver M-Edge. Five Mach numbers in the range from 0.6 to 1.6 were simulated at an altitude of 12 km. The results showed that the afterbody drag generally decreased when increasing jet pressure ratio at both subsonic and supersonic velocities. At subsonic conditions, increasing nozzle area ratio for underexpanded nozzles would decrease the drag. Increasing nozzle area ratio for fully expanded or overexpanded nozzles would instead increase the drag to an intermediate point from where it would decrease. At supersonic condition, increasing nozzle area ratio would generally cause reduction in drag for all cases. The optimization showed that a net thrust increase of 0.02% to 0.09% could be gained for subsonic conditions while the supersonic optimization had negligible gain in thrust.

The purpose of this investigation was to identify key design parameters that might significantly affect the response of span wire traffic light systems during extreme wind events. The performance of these systems was assessed through physical testing in an effort to quantify the effect of sag ratio, wire tension and wire clearance. The Wall of Wind experimental facility at Florida International University was utilized for testing the systems at different wind speeds and wind directions. The findings showed that, at all tested wind directions, lift, drag and tension forces increased with increasing wind speeds. On the contrary, increasing the wind speed resulted in higher inclination on the traffic lights, lower drag coefficients and higher lift coefficients. Overall, when the wind was approaching from the rear face of the traffic signals, increased drag coefficients were recorded. When the sag was set at 7% lower drag coefficients were observed.

Malgré un rôle important en physique, biologie et dans les processus industriels tels l’agroalimentaire et la dépollution de l’eau, la dynamique d'une particule colloïdale à proximité d'une interface fluide et ses interactions avec l’interface sont des phénomènes physiques encore débattus.Dans cette thèse, nous explorons la dynamique et l'interaction de particules colloïdales individuelles à proximité d'une interface air-eau à l’équilibre thermique.Afin de mener cette étude sans perturber le système expérimental, nous avons conçu et construit un microscope interférentiel à double onde adapté à l'interface air-eau. Contrairement à d'autres techniques expérimentales, notre configuration permet la mesure précise de la distance absolue entre particule l'interface sans nécessiter d’étalonnage ou d’hypothèse sur l'emplacement de l'interface. Nous avons ainsi pu obtenir des trajectoires hautement résolues de particules en 3D proches de l'interface, permettant la mesure précise des diffusions proche de l’interface et des interactions particules-interface.Le système montre deux profils d’énergie potentielle différents. Deux distances d’équilibre particule-interface sont ainsi observées. La plus grande peut être expliquée par la compétition des interactions de Van der Waals et électrostatiques avec la pesanteur. La distance d’équilibre plus courte ne peut s’expliquer que par la présence d’une interaction attractive supplémentaire. Les origines possibles de cette interaction sont discutées.En utilisant une nouvelle méthode d'analyse des déplacements quadratiques moyens des particules dans un potentiel générique, nous avons pu accéder aux coefficients de friction visqueuse des particules en fonction de la distance à l'interface. De manière singulière, l’interface air-eau se comporte comme une paroi liquide pour le mouvement des particules parallèlement à l’interface et comme une paroi solide pour le mouvement des particules perpendiculaire à l’interface. Ce résultat expérimental peut être partiellement rationalisé en considérant des modèles récents basés sur l’incompressibilité de surface. Cependant, certaines différences entre les expériences et les théories demeurent. Les coefficients de friction visqueuse sont plus importants que les prédictions hydrodynamiques et dépendent de la charge électrique des particules, ce qui suggère un possible rôle des phénomènes électrocinétiques.Enfin, le piégeage des particules à l'interface air-eau et leur angle de contact ont été mesurés tout en modifiant la force ionique de la solution aqueuse et en faisant varier l‘état de surface des colloïdes. / Despite the relevance to environmental, biological and industrial processes, the motion of a colloidal particle close to a fluid interface and the way it interacts with the water surface are still largely elusive and intriguing physical phenomena.In this thesis, we explore the motion dynamics and the interaction of individual colloidal particles close to an air-water interface in thermal equilibrium.In order to investigate them without perturbing or altering the experimental system, we designed and built a dual-wave reflection interference microscope working with an air-water interface geometry. Contrary to other established experimental techniques, our set-up allows accurate measurements of the absolute particle-interface distance and thus does not require any calibration or assumption to know the location of the interface. Highly resolved 3D particle trajectories close to the interface were obtained, from which information on particle diffusion close to the interface and particle-interface interactions are obtained.The system shows two different potential energy landscapes resulting in two different equilibrium particle-interface distances. The larger one can be fairly explained by Van der Waals and electrostatic interactions combined with gravity. The shorter one highlights the existence of an unexpected additional attractive interaction. The possible origins of such an interaction are discussed.Using a method of analysis of the particle mean square displacements in a generic potential we developed, we were able to access to particle drag coefficients as a function of the distance from the interface. Peculiarly, the air-water interface acts as a slip boundary for the particle motion parallel to the interface and as a no-slip boundary for the particle motion perpendicular to the interface. This experimental result can be partially rationalized considering recent models based on surface incompressibility. However, some discrepancies between experiments and theories remain. Experimental drag coefficients are larger than the hydrodynamic predictions and depend on the particle electrical charge, pointing therefore to a possible role of electrokinetic phenomena.Finally, the particle trapping at the air-water interface and its contact angle were observed while tuning the ionic strength of the aqueous solution and varying the surface state of the colloids.

The modern day tourists do not want to deal with the hassle of using a large number of travel guides and paper maps while travelling. They would prefer to be able to access required information via their mobile phones or Personal Digital Assistants (PDAs). We realise that the delivered information may be originally available in numerous information formats. To support the administrator of the tourist guides the programme is required to help sorting information from these different sources and to help inserting them into a system. Our goal with this project is to develop a software support for processing information import via a graphical user interface, to support the administrator in identifying and extracting the appropriate sight information from various resources. The interface also helps in transferring and storing the structured and unstructured data into the TIP database.

<p>At Saab Bofors Dynamics there are projects running which purpose are to develop simulators for various weapon systems like RBS 70. In order to manage creating real working simulators Saab Bofors Dynamics has to do more research and this final thesis is a part of this process.</p><p>This final thesis has been performed at Saab Bofors Dynamics in the department of modelling and simulation, RTRKM, in Karlskoga. The purpose was to develop a control algorithm which makes it possible for an aircraft to behave real when controlling through a joystick.</p><p>The conclusions show that further improvements are needed before the aircraft behaves entirely by the laws of physics. Among other things it is necessary to decrease the number of delimitations that have been done.</p>

<p>Att ha barn med drag av autism i klassrummet kräver att man kan förstå deras speciella kognitiva problem, som yttrar sig bland annat i nedsatt språkförståelse, nedsatt förmåga till social interaktion och en del avvikande beteenden. Jag har genom litteraturstudier, fältstudier i tre veckor på autismenhet, föreläsningar om autism, och egna erfarenheter gjort ett examensarbete om kommunikationoch pedagogiskt upplägg för det här handikappet. Arbetet handlar om hur de här barnen uppfattar kommunikation och vilka svårigheter omgivningen kan möta, samt vad den bör tänka på när man tar kontakt med de här barnen. Det pedagogiska upplägget handlar om hur arbetet i klassrummet kan underlättas för dem. Mina slutsatser är att med rätt hjälp och stöd kan de klara av en hel del.</p>

<p>The aim of this essay is to investigate how the author JT LeRoy (a. i. Laura Albert) questions and broadens the concept of authenticity in literature and authorship. My study is based on LeRoy’s novel Sarah [2000] and the collection of short stories The heart is deceitful above all things [2001], as well as articles written about the construction of Laura Albert’s alter ego JT LeRoy. I look for norms and boundaries in connection with authentic authors, identities, sex, gender and love. My method is that of a thematic analysis focusing on names, parenthood, religious beliefs and sub cultural norms and resistance. I am inspired by Michel Foucault’s thoughts on discourse, power and sexuality. My results are presented in a dialogue with previous readings and queer theory, foremost represented by Judith Butler. My general conclusion is that the literary texts, as well as the author represent a queer perspective, and that they therefore – in a heteronormative world view – are considered neither normal nor authentic.</p>