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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
551

The fall transition off Central California in 2002

O'Malley, Colleen M. 06 1900 (has links)
Approved for public release, distribution is unlimited / During the fall of 2002 the physical oceanographic conditions off Central California were monitored by means of CTD casts and VMADCP current measurements during two cruises. The first cruise, included 38 stations and one time series station. The second cruise was sponsored by the Naval Oceanographic Office (NAVOCEANOCEANO) and occupied nine sections along the coast. A total of 86 stations and two time series stations were occupied during the second cruise. CTD calibration and data processing methods are described. The isosteres, current vectors, and salinity distribution from the cruises provide a clear picture of the circulation pattern during the fall 2002. A strong shoreward, anticyclonic meander of the California current was observed. Although the meander itself did not cross the dynamic trough that separated inshore and offshore currents, at the point where the meander was adjacent to the trough, a ridge formed which transported Subarctic waters into the coastal zone. These fresh waters were advected to the north and south along the coast, depending upon the direction of nearshore currents. The observed mesoscale circulation showed the manner in which waters which are upwelled at the coast in summer are replaced by oceanic waters in the fall and winter. Analysis of the geography of the deep sound channel (DSC) during this period showed that the mean pressure of the DSC was at 586 dbar while the mean sound speed minimum was 1480 m/s. The minimum sound speed varied 3 m/s while the pressure of the minimum varied by 330 dbars. The shape of the pycnocline controlled the pressure and depth of the DSC in the region. / Ensign, United States Naval Reserve
552

Stored-grain Monitoring Utilizing Radio Wave Imaging

Asefi, Mohammad 20 June 2016 (has links)
Storage of large amounts of grain post-harvest is common during drying, distribution and preservation of crops. During storage, where grain is usually held in a large metallic container or bin, changes in temperature, moisture, and insect infestation can cause grain to spoil annual post-harvest crop losses are estimated up to 30% in some countries while Canadian losses of 2% exceed a billion dollars. Currently, locally-sensitive temperature and moisture sensors are a common way to monitor grain bins. Sensors are generally strung on heavy duty cables that can withstand the forces generated when unloading grain. This monitoring method provides a coarse sampling of the storage environment due to system cost and the fact that using many sensor cables would require significantly reinforcing the bin. Further, these cables are not suitable for monitoring stored crops that are dried by a combination of stirring and aeration. Over the past four years, I have developed multiple electromagnetic imaging based grain-monitoring systems with the goals of overcoming the deficiencies of existing sensor technology and allowing farmers and distributors a robust way to preserve our food stores and increase revenue. The proposed technology aims to produce global, quantitative images of grain properties throughout the bin from measurements taken by a few side-mounted antennas used to interrogate the bin contents. To develop this technology intensive research was put into the design of low profile, robust antennas as well as numerical analysis of the effects of different field distributions within conducting boundaries. Both electric and magnetic field sensitive antennas were built and tested in small lab-scale as well as full-scale grain bins to experimentally evaluate the performance of such imaging system. This thesis provides details on different system designs and analysis and describes the advantages and challenges associated with the techniques described. / October 2016
553

Secondary Clarifier Modeling: A Multi-Process Approach

Griborio, Alonso 08 May 2004 (has links)
The performance of settling tanks depends on several interrelated processes and factors that include: hydrodynamics, settling, turbulence, sludge rheology, flocculation, temperature changes and heat exchange, geometry, loading, the nature of the floc, the atmospheric conditions and the total dissolved solids concentration. A Quasi-3D (Q3D) clarifier model has been developed to include the following factors: axisymmetric hydrodynamics (including the swirl component), five types of settling (nonsettleable particles, unflocculated discrete settling, flocculated discrete settling, hindered settling and compression), turbulence, sludge rheology, flocculation with four classes of particles, temperature changes and surface heat exchange with the atmosphere, various external and internal geometry configurations, unsteady solids and hydraulic loading, the nature of the floc settling/interaction. The model includes: shear flocculation, differential settling flocculation and sweep flocculation. The Q3D model reproduces the major features of the hydrodynamic processes and solids distribution on secondary clarifiers. When the model is executed with the field derived settling characteristics, it can accurately predict the effluent and recirculation suspended solids concentrations. The model has been formulated to conserve fluid, tracer and solids mass. The model has been developed and tested using field data from the UNO Pilot Plant and the Jefferson Parish Waste Water Treatment Plant located at Marrero, Louisiana. A field testing procedure is presented that addressees all of the settling regimes that are encountered in a Secondary Settling Tank. Results obtained with the Q3D model indicate that the flocculation process plays a major role in the effluent suspended solids (ESS) on secondary clarifiers. The extent of actual flocculation depends on the design of the center well and on the concentration of the incoming mixed liquor suspended solids (MLSS). The center well promotes flocculation, but its most important benefit is the improvement on the tank hydrodynamics. The changes in temperature on secondary clarifiers play an important role on the performance of secondary settling tanks. The gravity induced radial velocities in the sludge blanket are higher than the radial velocities of the scraper in the region near the hopper, therefore the blades are not highly effective in conveying the solids in this region.
554

Dynamics of the Tsitsikamma current, with implications for larval transportof chokka squid (Loligo reynaudii) on the eastern Agulhas Bank

Hancke, Lisa January 2010 (has links)
Thesis (MTech (Oceanography))Cape Peninsula University of Technology, 2010 / The current dynamics along the Tsitsikamma coast is described from a combination of acoustic current measurements. satellite-tracked surface drifters and underwater temperature recordings made between November 2006 and March 2008. The Tsitsikamma coast is largely a Marine Protected Area (MPA) that protects a rich marine biodiversity. The nearshore currents are important in the dispersal of eggs and larvae of many marine species. including the paralarvae of the commercially caught chokka squid. LoNgo reynaudii. Changes in the environment, including the currents. can affect the successful recruitment of chokka squid, and can bring about large annual fluctuations in biomass that creates economic uncertainty in the squid fishery. Results confirm the existence of a predominantly alongshore current off the Tsitsikamma coast. At Middelbank eastward flow was slightly dominant, with a percentage occurrence of 58% vs. 41% westward flow near the surface. The percentage eastward flow decreased with depth, with 41% vs. 58% westward flow near the seabed. At Thyspunt westward and eastward flow occurred at near equal percentages. but westward flow was slightly dominant throughout the water column. The alongshore current was strongest near the surface during eastward flow (maximum = 141 crn.s1: average = 27 crn.s '). while westward surface currents were weaker (maximum velocity = 78 cm.s1: average = 19 crn.s1). Current speed generally decreased with depth and opposing surface and bottom currents, associated with a thermal stratified water column, were occasionally recorded. The nearshore flow regime was characterised by frequent barotropic alongshore reversals that occurred year round. An increase in strong eastward episodes, and opposing surface and bottom currents during spring and summer months have implications for the dispersal of squid paralarvae during the summer and winter spawning seasons. In summer, the combination of strong eastward pulses in the current and upwelling at the capes favoured dispersal onto the midshelf of the Agulhas Bank. In winter, alongshore oscillations without the offshore displacement associated with upwelling. restricted offshore dispersal which caused surface particles to be retained inshore. Drifter trajectories show that both the eastward and westward nearshore current can link the inshore spawning grounds with the nursery grounds, offshore on the central Agulhas Bank; and that passive, neutrally buoyant material in the surface layer can reach the vicinity of the cold ridge in as little as eight days. The wind-driven processes of upwelling and coastal trapped waves (CTWs). and the influence of the greater shelf circulation are discussed as possible driving forces of variability in the currents off the Tsitsikamma coast. The occurrence of coastal trapped waves during thermal stratification appears to drive the jet-like, eastward pulses in the current. and results suggest that the propagation of CTWs may regulate and even enhance upwelling and downwelling along the Tsitsikamma coast.
555

Numerical Methods for Studying Self-similar Propagation of Viscous Gravity Currents

Aditya Avinash Ghodgaonkar (6635993) 14 May 2019 (has links)
<div>A strongly implicit, nonlinear Crank-Nicolson-based finite-difference scheme was constructed for the numerical study of the self-similar behavior of viscous gravity currents. Viscous gravity currents are low Reynolds number flow phenomena in which a dense, viscous fluid displaces a lighter (usually immiscible) fluid. Under the lubrication approximation, the mathematical description of the spreading of these fluids is reduced to solving a nonlinear parabolic partial differential equation for the shape of the fluid interface. This thesis focuses on the finite-speed propagation of a power-law non-Newtonian current in a variable width channel-like geometry (a "Hele-Shaw cell'') subject to a given mass conservation/balance constraint. The proposed numerical scheme was implemented on a uniform but staggered grid. It is shown to be strongly stable, while possessing formal truncation error that is of second-order in space and it time. The accuracy of the scheme was verified by benchmarking it against established analytical solutions, which were obtained via a first-kind self-similarity transformation. A series of numerical simulations confirmed that the proposed scheme accurately respects the mass conservation/balance constraint. Next, the numerical scheme was used to study the second-kind self-similar behaviour of Newtonian viscous gravity currents flowing towards the end of a converging channel. Second-kind self-similar transformations are not fully specified without further information from simulation or experiment. Thus, using the proposed numerical scheme, the self-similar spreading and leveling leveling of the current was definitively addressed. The numerical results showed favorable comparison with experimental data.</div>
556

Signature calorimétrique de cohérence de phase quantique dans des anneaux mésoscopiques / Calorimetric signature of quantum phase coherence in mesoscopic rings.

Souche, Germain 22 September 2011 (has links)
Dans ce manuscrit, nous présentons des mesures haute résolution de chaleur spécifique Cp réalisées sur des anneaux mésoscopiques d'argent à très basses températures. Le but de cette expérience est de mettre en évidence une possible signature thermique due à la présence de courants permanents. Ce phénomène reste encore mal compris malgré de nombreuses expériences. Il existe en effet des contradictions entre les différents modèles théoriques et les résultats expérimentaux. L'approche thermique que nous exposons ici est un angle nouveau qui n'a jamais été exploré. Sous champ magnétique, une oscillation de période égale au quantum de flux Φ0=h/e (ou moitié) de Cp est attendue théoriquement. L'échantillon étudié est composé d'un grand nombre d'anneaux d'argent mésoscopiques déposés sur une membrane en silicium suspendue. Nous avons réalisé, à différentes températures, de multiples balayages en champ de la chaleur spécifique. Un traitement des signaux obtenus a ensuite été réalisé afin de repérer une éventuelle périodicité. Il a révélé la présence sur le signal de phase d'une oscillation de période h/2e n'apparaissant pas sur le module de la chaleur spécifique. Cette signature est maximale à 100mK. La fréquence et l'amplitude obtenues sont en accord avec les prédictions théoriques. La sensibilité atteinte est de ΔC~10^(-14)J/K sur le module (et de Δφ~10^(-2) degrés sur la phase) soit 10^(-21)J/K par anneau. Les résultats présentés ici apportent donc de nouveaux éléments dans l'analyse des courants permanents. / In this thesis, we report very high resolution specific heat measurements of normal metal mesoscopic silver rings at very low temperatures. The objective of this experiment is to measure the possible existence of thermal signatures due to the presence of persistent currents. This phenomenon is still misunderstood despite many measurements. Some contradictions exist between experimental results and the different theories. The thermal approach is a new point of view. Under magnetic field, the Cp variation is expected be periodic with the quantum of flux Φ0=h/e or half of the quantum of flux as it has been theoretically predicted. The studied samples is composed by a large number of silver rings with an electronic phase coherence length of few microns at low temperatures. They were deposited on the suspended membrane of a silicon sensor. We have realized, at different temperatures, a large number of identical scans of the heat capacity variation as a function of the applied field. A signal processing work on this data has then been realized to detect signal periodicities. It showed a difference between the module and the phase of the heat capacity. A peak can be observed on the FFT at a frequency corresponding to h/2e on the phase signal. The peak appears particularly at 100mK with a amplitude which is consistent with previous calculations. A sensitivity of ΔC~10^(-14)J/K on the module (Δφ~10^(-2) degrees on the phase) has been reached whether 10^(-21)J/K per ring. Thus, the presented experiences give new elements in the field of persistent currents.
557

Etude expérimentale et numérique des courants d'écrantages dans les aimants supraconducteurs à haute température critique REBCO / Experimental and numerical study of screening currents in REBCO high temperature superconducting magnets

Dilasser, Guillaume 11 October 2017 (has links)
L’industrialisation de la production des conducteurs utilisant les cuprates à haute température de transition pendant les deux dernières décennies offre aujourd’hui la possibilité de nouveaux développements dans le domaine du magnétisme supraconducteur. En particulier, nous nous intéressons ici aux applications des rubans supraconducteurs REBCO. Ceux-ci font partie des rares candidats disponibles à l’heure actuelle capables de fonctionner sous des inductions supérieures à 20 T aux températures de cryogénie classique (4,2 K), ce qui les rend quasiment incontournables dans le contexte des applications haut-champ. Parallèlement, leurs températures critiques élevées apportent également la possibilité de nouvelles conceptions d’aimants pouvant fonctionner à des températures allant jusqu’à 80 K environ. Ceci ouvre notamment la porte à de nouvelles options de cryogénie moins coûteuses, comme le refroidissement par azote liquide. Néanmoins, la mise en œuvre des rubans REBCO à l’intérieur de nouveaux aimants supraconducteurs se heurte dans certains cas au problème posé par les courants d’écrantages. Ce terme désigne les supercourants induits dans le matériau supraconducteur en réponse au champ extérieur. Ces courants parasites engendrent alors des perturbations sur le champ magnétique total produit par l’aimant : réduction de son amplitude, distorsions spatiales et instabilités temporelles. Ces multiples effets entrent généralement en collision avec les exigences sur la qualité de champ produite. Ainsi, comprendre le phénomène des courants d’écrantages, être capable de prédire sa dynamique et, idéalement, disposer de solutions afin d’y remédier, sont des tâches cruciales pour assurer la réussite des futurs projets d’aimants supraconducteurs REBCO. Cette thèse propose des éléments de réponse vis-à-vis de cette problématique. Le phénomène de courants d’écrantages y est tout d’abord approché de manière expérimentale au travers de la mesure de ses effets perturbateurs sur le champ magnétique de petits aimants tests REBCO. Les données expérimentales récoltées sont ensuite employées pour étayer le développement d’un modèle numérique de simulation magnétodynamique sous l’environnement open-source GetDP. Ce modèle est par ailleurs mis à l’essai avec de bons résultats dans le cas du dipôle 5,4 T EuCARD du CERN. Enfin dans une dernière partie, une investigation expérimentale est menée sur deux techniques capables de réduire, voire de supprimer intégralement, les impacts négatifs des courants d’écrantages sur le champ des aimants REBCO : le vortex shaking et l’overshoot en courant. Au travers de ces développements, cette thèse entend fournir aux concepteurs de futurs aimants supraconducteurs REBCO des moyens d’anticiper et de traiter les problèmes posés par les courants d’écrantages. / The industrialization of the production of high-transition temperature, cuprate-based conductors during the last two decades brings nowadays the possibility of new developments in the field of superconducting magnetism. In particular, we are interested here in the applications of superconducting REBCO tapes. Those belong to the few currently available candidates that are able to operate under magnetic induction above 20 T at classical cryogenic temperature (4.2 K), what makes them almost unavoidable in the scope of high-field applications. Besides, their high critical temperatures also bring the possibility for new magnet designs capable to operate up to temperatures of about 80 K. This notably opens the door to new, less expensive, cryogenic design options, like liquid nitrogen cooling.However, the practical implementation of REBCO tapes inside new superconducting magnets encounters a problem posed by screening currents. The latter term designates the supercurrents that are induced in the superconducting material in response to an external field. These parasitic currents then give rise to perturbations in the total magnetic field generated by the magnet: lowering of its magnitude, spatial distortions and time instabilities. Those various effects collide most of the time with the requirements on the produced field quality. Thus, understanding the phenomenon of screening currents, being able to predict its dynamic and, ideally, having of solutions to remedy this issue, are crucial tasks to ensure the success of future REBCO superconducting magnet projects.This Ph.D. work suggests some elements of answer with regard to this problematic. The phenomenon of screening currents is first approached experimentally, through the measurement of its disruptive effects of the magnetic field generated by small REBCO tests magnets. The experimental data gathered are then used to support the development of a numerical model for magnetodynamic simulations in the framework of the open-source environment GetDP. This model is furthermore tested with satisfactory results on the scenario of the 5.4 T EuCARD dipole developed by CERN. Finally, in a last section, an experimental investigation is conducted on two techniques capable at reducing, or even entirely suppressing, the negative impacts of the screening currents on the field of REBCO magnets: the vortex shaking and current overshoot.Across these developments, this Ph.D. work aims at providing the designers of future REBCO superconducting magnets with tools to anticipate and handle the issues caused by the screening currents.
558

Hydrodynamics of mangrove root-type models

Unknown Date (has links)
Mangrove trees play a prominent role in coastal tropic and subtropical regions, providing habitat for many organisms and protecting shorelines against storm surges, high winds, erosion, and tsunamis. The motivation of this proposal is to understand the complex interaction of mangrove roots during tidal flow conditions using simplified physical models. In this dissertation, the mangrove roots were modeled with a circular array of cylinders with different porosities and spacing ratios. In addition, we modeled the flexibility of the roots by attaching rigid cylinders to hinge connectors. The models were tested in a water tunnel for a range of Reynolds number from 2200 to 11000. Additionally, we performed 2D flow visualization for different root models in a flowing soap film setup. We measured drag force and the instantanous streamwise velocity downstream of the models. Furthermore, we investigated the fluid dynamics downstream of the models using a 2-D time-resolved particle image velocimetry (PIV), and flow visualization. The result was analyzed to present time-averaged and time-resolved flow parameters including the velocity distribution, vorticity, streamline, Reynolds shear stress and turbulent kinetic energy. We found that the frequency of the vortex shedding increases as the diameter of the small cylinders decreases while the patch diameter is constant, therefore increasing the Strouhal number, St=fD/U By comparing the change of Strouhal numbers with a single solid cylinder, we introduced a new length scale, the “effective diameter”. In addition, the effective diameter of the patch decreases as the porosity increases. In addition, patch drag decreases linearly as the spacing ratio increases. For flexible cylinders, we found that a decrease in stiffness increases both patch drag and the wake deficit behind the patch in a similar fashion as increasing the blockage of the patch. The average drag coefficient decreased with increasing Reynolds number and with increasing porosity. We found that the Reynolds stress (−u′v′) peak is not only shifted in the vortex structure because of shear layer interference, but also the intensity was weakened by increasing the porosity, which causes a weakening of the buckling of vorticity layers leading to a decline in vortex strength as well as increase in wake elongation. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection
559

Estudo da corrosão por interferência de corrente alternada em estruturas enterradas e desenvolvimento de metodologia para sua detecção / Study of corrosion by interference of alternating current in buried structures and development of methodology for detection.

Abud Filho, Sergio Eduardo 26 March 2015 (has links)
Dutos metálicos revestidos, enterrados e protegidos catodicamente, quando são instalados nas proximidades de linhas de transmissão e distribuição de energia elétrica, vêm apresentando problemas de corrosão, sendo esta atribuída às interferências de corrente alternada dispersas no solo. São muitos os critérios propostos na literatura para verificar se um duto está ou não sujeito a esse tipo de problema, mas tais critérios são contraditórios e ineficientes, uma vez que não levam em conta parâmetros termodinâmicos e não contemplam o acoplamento dos potenciais originados de corrente contínua com os potenciais oriundos de corrente alternada. O objetivo do presente trabalho foi estudar a corrosão causada por corrente alternada, selecionar um critério seguro de verificação da probabilidade de ocorrência dessa corrosão e desenvolver uma nova metodologia para a obtenção dos parâmetros necessários para a aplicação do critério proposto. Com base em uma ampla pesquisa bibliográfica, em resultados experimentais obtidos em laboratório e em campo, foi possível a seleção do seguinte mecanismo: a corrosão por corrente alternada é decorrente da oscilação do potencial da interface duto/solo que, dependendo do valor do pH nas suas vizinhanças, leva o sistema alternadamente ao domínio da corrosão e da imunidade ou alternadamente ao domínio da formação de óxidos (com e sem passivação) e da imunidade. Nessas condições, a corrosão do aço-carbono ocorre devido à irreversibilidade da reação Fe2+ + 2e- Fe, nos casos de alcalinização limitada, e à impossibilidade de formação de uma camada passiva protetora decorrente da flutuação de potencial entre o domínio de formação de óxidos e da imunidade, nos casos de alcalinização moderada. Como critério de verificação da ocorrência ou não de interferência de corrente alternada em dutos enterrados e catodicamente protegidos foi proposta, neste estudo, a obtenção da forma de onda do acoplamento entre os potencias originados de corrente contínua e os oriundos de corrente alternada sem a influência da queda ôhmica e a comparação do potencial de pico dessa forma de onda com o potencial estabelecido como limite aceitável do sistema de proteção catódica tradicional. Esta proposição foi feita com base na termodinâmica, o que garante que a previsão seja usada com mais segurança. Finalmente, foi desenvolvida uma sonda que, juntamente com uma instrumentação adequada, é capaz de fornecer a forma de onda do referido acoplamento em dutos enterrados e catodicamente protegidos, sem a interferência da queda ôhmica. / Corrosion problems have been observed in cathodically protected pipelines installed in the vicinity of high voltage power lines or electrical distribution systems. Many of these problems have been attributed to interferences coming from stray alternating currents. In the literature, there are many criteria proposed aiming at verifying the AC corrosion probability. However, such criteria are contradictory and ineffective since they do not take into account thermodynamic parameters and do not include the coupling of potential coming from direct current and the potential due to stray alternating current. The aim of this work was to study pipeline corrosion induced by stray alternating current, to select a safe criterion for the probability of this corrosion and to develop a new methodology for obtaining the required parameters for the application of the selected criterion. A broad literature review and the results obtained from a series of tests and analyses have allowed choosing the following mechanism: AC corrosion is a result of the fluctuation of the pipe/soil potential which, depending on the pH of the soil near the pipe, takes the system alternatively to the corrosion and to the immunity domains or alternatively to the oxide formation (with or without passivation) and to the immunity domains. Under these conditions, the corrosion of carbon steel occurs due to the irreversibility of the reaction Fe2+ + 2e- Fe reaction in cases of limited alkalinization and due to the impossibility of forming a protective passive layer caused by the potential fluctuation between the oxide formation and the immunity domains in cases of moderate alkalinization. In this study, a method to obtain the waveform of the AC+DC potential, without the ohmic drop, was proposed. The comparison of the peak potential of the AC + DC waveform with the potential value established as an acceptable threshold for traditional cathodic protection systems was used as a criterion for AC corrosion assessment. This criterion is proposed based on thermodynamic principles which ensure that the prediction is reliable. Finally, a probe was developed. This probe, along with a proper instrumentation, is able to provide the desired waveform for a safe application of the proposed criterion.
560

Dinâmica da interação da atividade de meso-escala da Corrente do Brasil com o fenômeno da ressurgência costeira ao largo de Cabo Frio e Cabo de São Tomé, RJ / Dynamics of meso-scale interactions activity between Brazil Current and coastal upwelling phenomenon off Cape Frio and Cape of São Tomé, RJ

Calado, Leandro 06 October 2006 (has links)
Os meandros da Corrente do Brasil ao largo do sudeste brasileiro s~ao singulares em termos de sua composic¸ ~ao termohalina. Estes v´ ortices, principalmente na regi~ao de Cabo Frio e Cabo de S~ao Tom´e, constituem um sistema integrado a ressurg^encia costeira e a pr´opria Corrente do Brasil, caracterizando um sistema din^amico que propomos denominar Corrente do Brasil-v ´ ortice-ressurg^encia. Apresentamos uma metodologia de construc¸ ~ao de modelos param´etricos das feic¸ ~oes oceanogr´aficas (ou Modelos de Feic¸ ~ao) que comp~oem o sistema. Estes modelos s~ao capazes de construir tridimensionalmente feic¸ ~oes oceanogr´aficas individuais a partir de dados sin´oticos de superf´?cie e fundo para elaborac¸ ~ao de campos iniciais de modelos num´ericos, com o objetivo de compreender a interac¸ ~ao do sistema din^amico Corrente do Brasil-v´ ortice-ressurg^encia. Atrav´es da simulac¸ ~ao num´erica dos campos iniciais baseados nos Modelos de Feic¸ ~ao investigamos o processo que conduz `a assimetria termohalina dos v´ ortices da Corrente do Brasil, acima descrita. Esta foi devida a aproximac¸ ~ao desses v´ ortices junto ao talude continental e ao ajustamento barocl´?nico das correntes `as menores profundidades. Verificamos, ainda, que a penetrac¸a~o da A´ gua Central do Atla^ntico Sul pela camada de Ekman de fundo n~ao tem efeito significativo na estrutura dos v´ ortices. Realizamos experimentosnum´ericos adicionais com o objetivo de investigar quais os tipos de instabilidade geof´?sica estariam envolvidas no fen^omeno do crescimento dos meandros e v´ ortices da Corrente do Brasil. Analisando os resultados atrav´es de c´alculos de convers~ao de energia pudemos concluir que o sistema Corrente do Brasil-v´ ortice-ressurg^encia apresenta instabilidade mista ( barotr ´opica e barocl´?nica). Contudo, verificamos quantitativamente que a instabilidade barocl´?nica foi dominante. O sistema, no entanto, mostrou-se sens´?vel `a ac¸ ~ao da tens~ao de cisalhamento do vento de nordeste na regi~ao e consequentemente `a ressurg^encia costeira. Interpretamos tal sensibilidade como fator respons´avel pela relev^ancia da instabilidade barotr ´opica no processo de crescimento dos meandros da Corrente do Brasil. Por fim, verificamos que um meandro cicl ^onico frontal, quase-estacion´ario, em condic¸ ~oes especiais de crescimento por mecanismo de instabilidade, pode auxiliar no estabelecimento da ressurg^encia costeira. O v´ ortice do Cabo de S~ao Tom´e simulado apresenta velocidade de fase muito baixa e cresce em direc¸ ~ao a oceano aberto, de forma praticamente perpendicular `a quebra de plataforma. Logo, o crescimento do vo´ rtice de Cabo de Sa~o Tome´ faz com que o mesmo advecte A´ gua Costeira para seu interior provocando, por continuidade, afloramento da A´ gua central do Atla^ntico Sul junto `a costa. Assim, podemos dizer que h´a, de fato, uma interac¸ ~ao entre o sistema costeiro e a atividade de meso-escala da Corrente do Brasil. / The Brazil Current meanders off the Brazilian southeast coast are unique in terms of their thermohaline structure. These eddies, especially off the Cape Frio and S~ao Tom´e region constitute an integrated system with the Brazil Current and the coastal upwelling, characterizing a dynamic system which we propose to nominate as Brazil Current-eddy-upwelling system. We present a methodology of parametric model construction of the oceanographic features (or Feature Models) which compose the inferred system . These models are capable of three-dimensionally building independent the relevant features from synoptic surface and bottom data in order to compose the initial fields for numerical models with the objective of understanding the dynamics of the interaction of Brazil Current-eddy-upwelling system. By means of numerical simulation usingthe initial fields based on the Feature Models, we investigated the process which conducts to the thermohaline asymmetry of the eddies in the Brazil Current as mentioned above. This is due to the baroclinic approximation of the currents to shallower depths. The penetration of the Central Water in the South Atlantic by the bottom Ekman layer does not have a significant effect on the eddy structure. Additional numerical experiments were carried out with the objective of unders tanding which of the geophysical instabilities were involved in the growth of the Brazil Current meanders and eddies. The results analyzed through calculation of energy conversion allowed us to conclude that the Brazil Current-eddie-upwelling system presents mixed instability (barotropic and baroclinic). However, the baroclinic instability is dominant and is mostly associated to the vertical shear of the oceanic currents. The system, however,was sensitive to the action of the northeast wind shear and consequently to the coastal upwelling. Such sensibility was interpreted as the main responsible for the relevance of barotropic instability in the growth process of meanders in the Brazil Current. Lastly, we verified that a quasi-stationary frontal cyclonic meander, in special growth conditions by instability mechanisms, mayhelp in establishing coastal upwelling. The simulated S~ao Tom´e Cape Eddy presented a very low phase velocity and grew towards the open sea, almost perpendicularly to the continental shelf break. Therefore, the growth of the S~ao Tom´e Cape Eddy advects Coastal Water into its center and, therefore, lead to upwelling of South Atlantic Central Water near the coast. We can therefore say that there are in fact interaction mechanisms between the coastal system and the meso-scale activity of the Brazil Current.

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