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Estudo de modelo hidrodinâmico unidimensional aplicado a um trecho de canal do Córrego do Gregório em São Carlos, SP / One-dimensional study of hydrodynamic model applied to a channel stretch of stream of Gregório in São Carlos, SPAlmeida, Rodrigo Martins de 09 October 2013 (has links)
O presente trabalho reporta o esforço empenhado para relacionar nível d\'água e vazão, fazendo uso exclusivamente de medições de nível, em campo, durante a passagem de ondas de cheia através de um trecho de canal prismático situado no perímetro urbano da cidade de São Carlos, SP denominado Córrego do Gregório. Montagens para coleta de dados em campo foram testadas e foi utilizada a modelagem hidrodinâmica 1-D para a resolução das equações de Saint-Venant, através do método implícito de quatro pontos de Preissmann. Apesar do potencial do método, já apontado por alguns autores, o presente trabalho reporta dificuldades na realização de medições e também problemas na modelagem de trecho de canal com características muito particulares. Várias análises foram realizadas tais como a verificação do número de passos de tempo necessário para minimização dos efeitos da condição inicial imposta (IQ1), a verificação da celeridade de uma onda de cheia analisando os picos dos eventos e assim determinar o coeficiente de cisalhamento de Manning proposto por Aricò, Nasello e Tucciarelli (2009) e o método implícito na resolução das equações de SV proposto por Jin, Coran e Cook (2004), que funciona como um filtro baseado no número de Froude (condição do tipo de escoamento) também foi testado. Durante o evento do dia 23/03/2013 foi estimado as velocidades em campo. Para cada um dos 12 eventos registrados foi realizado uma simulação utilizando o modelo hidrodinâmico e o melhor resultado foi utilizado em uma segunda simulação para comparar as lâminas d\'água observadas e calculadas. Ao analisar o quanto os valores de erros máximos absolutos (ERMAX1 e ERMAX2) representam em relação ao máximo registro obtido no evento, em porcentagem, têm-se eventos com 3,6% até valores absurdos de 27,1%. Assim, trata-se de um trabalho teórico-experimental que oferece subsídios importantes para futuros trabalhos nessa direção. / This work reports the committed effort to relate water level and flow, using exclusively field measurements of level, during the passage of flood waves through a prismatic channel stretch located on the surroundings of São Carlos - SP called stream of Gregório. Assembles for data gathering in the field were tested and it was used 1-D hydrodynamic modeling for solving equations of Saint-Venant, through the four points Preissmann implicit method. Despite the potential of this method, as pointed out by some authors, this study reports difficulties in performing measurements and to model a channel stretch with very particular characteristics. Several analyzes were performed such as checking the number of time steps needed for minimizing the effects of the initial condition imposed (IQ1), verifying the celerity of a full wave analyzing the peaks of events and so to be able to determine the Manning friction coefficient proposed by Arico et al. (2009) and the implicit method to solve the S-V equations proposed by Jin, Coran e Cook (2004), which acts as a filter based on the Froude number (condition-type flow), was also tested. During the event of the day 23/03/2013 was estimated speeds in the field. For each of the 12 recorded events a simulation was made using a hydrodynamic model and the best result was used in a simulation to compare the second water depths observed and calculated. By analyzing how the values of maximum absolute errors (ERMAX1 and ERMAX2) account for the highest recording obtained at the event, in percentage, have been events with 3.6% until absurd values from 27.1%. So, it is a theoretical-experimental that offers important information for future work in this direction.
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Estudo de modelo hidrodinâmico unidimensional aplicado a um trecho de canal do Córrego do Gregório em São Carlos, SP / One-dimensional study of hydrodynamic model applied to a channel stretch of stream of Gregório in São Carlos, SPRodrigo Martins de Almeida 09 October 2013 (has links)
O presente trabalho reporta o esforço empenhado para relacionar nível d\'água e vazão, fazendo uso exclusivamente de medições de nível, em campo, durante a passagem de ondas de cheia através de um trecho de canal prismático situado no perímetro urbano da cidade de São Carlos, SP denominado Córrego do Gregório. Montagens para coleta de dados em campo foram testadas e foi utilizada a modelagem hidrodinâmica 1-D para a resolução das equações de Saint-Venant, através do método implícito de quatro pontos de Preissmann. Apesar do potencial do método, já apontado por alguns autores, o presente trabalho reporta dificuldades na realização de medições e também problemas na modelagem de trecho de canal com características muito particulares. Várias análises foram realizadas tais como a verificação do número de passos de tempo necessário para minimização dos efeitos da condição inicial imposta (IQ1), a verificação da celeridade de uma onda de cheia analisando os picos dos eventos e assim determinar o coeficiente de cisalhamento de Manning proposto por Aricò, Nasello e Tucciarelli (2009) e o método implícito na resolução das equações de SV proposto por Jin, Coran e Cook (2004), que funciona como um filtro baseado no número de Froude (condição do tipo de escoamento) também foi testado. Durante o evento do dia 23/03/2013 foi estimado as velocidades em campo. Para cada um dos 12 eventos registrados foi realizado uma simulação utilizando o modelo hidrodinâmico e o melhor resultado foi utilizado em uma segunda simulação para comparar as lâminas d\'água observadas e calculadas. Ao analisar o quanto os valores de erros máximos absolutos (ERMAX1 e ERMAX2) representam em relação ao máximo registro obtido no evento, em porcentagem, têm-se eventos com 3,6% até valores absurdos de 27,1%. Assim, trata-se de um trabalho teórico-experimental que oferece subsídios importantes para futuros trabalhos nessa direção. / This work reports the committed effort to relate water level and flow, using exclusively field measurements of level, during the passage of flood waves through a prismatic channel stretch located on the surroundings of São Carlos - SP called stream of Gregório. Assembles for data gathering in the field were tested and it was used 1-D hydrodynamic modeling for solving equations of Saint-Venant, through the four points Preissmann implicit method. Despite the potential of this method, as pointed out by some authors, this study reports difficulties in performing measurements and to model a channel stretch with very particular characteristics. Several analyzes were performed such as checking the number of time steps needed for minimizing the effects of the initial condition imposed (IQ1), verifying the celerity of a full wave analyzing the peaks of events and so to be able to determine the Manning friction coefficient proposed by Arico et al. (2009) and the implicit method to solve the S-V equations proposed by Jin, Coran e Cook (2004), which acts as a filter based on the Froude number (condition-type flow), was also tested. During the event of the day 23/03/2013 was estimated speeds in the field. For each of the 12 recorded events a simulation was made using a hydrodynamic model and the best result was used in a simulation to compare the second water depths observed and calculated. By analyzing how the values of maximum absolute errors (ERMAX1 and ERMAX2) account for the highest recording obtained at the event, in percentage, have been events with 3.6% until absurd values from 27.1%. So, it is a theoretical-experimental that offers important information for future work in this direction.
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Extensões em problemas de corte: padrões compartimentados e problemas acoplados / Extensions for cutting stock problems: compartmentalized cutting patterns and integrated problemsLeão, Aline Aparecida de Souza 08 February 2013 (has links)
Nesta tese é abordado o problema da mochila compartimentada e o problema de corte de estoque unidimensional acoplado ao problema dimensionamento de lotes. Para o problema da mochila compartimentada é apresentada a versão unidimensional e proposta a versão bidimensional, denominados como problema da mochila compartimentada unidimensional e problema da mochila compartimentada bidimensional, respectivamente. Para o problema de corte de estoque acoplado ao dimensionamento de lotes são apresentadas três variações: uma máquina para produzir um tipo de objeto; uma máquina para produzir vários tipos de objetos; múltiplas máquinas para produzir vários tipos de objetos. Algumas formulações matemáticas de programação inteira e inteira-mista, decomposições dos problemas em problema mestre e subproblemas e heurísticas baseadas no método geração de colunas são propostas para os problemas da mochila compartimenta e o problema acoplado. Em específico, para o problema acoplado são aplicadas decomposições Dantzig-Wolfe, que podem ser por período, por máquina ou por período e máquina. Além disso, uma heurística baseada em grafo E/OU é proposta para o problema da mochila compartimentada bidimensional / In this thesis we present the constrained compartmentalized knapsack problem and the one dimensional cutting stock problem integrated with the capacitated lot sizing problem. For the constrained compartmentalized knapsack problem, the one dimensional version is presented and the two dimensional version is proposed, called one-dimensional compartmentalized knapsack problem and two-dimensional compartmentalized knapsack problem, respectively. For the cutting stock problem integrated with the capacitated lot sizing problem three variations are considered: one machine to produce one type of object; one machine to produce multiple types of objects; multiple machines to produce multiple types of objects. Some integer and mixed programming formulations, decompositions of the problems in master problem and subproblems and heuristics based on column generation method are proposed for the compartmentalized knapsack problem and the cutting stock problem integrated with the capacitated lot sizing problem. In particular, the period, the machine, and the period and machine Dantzig- Wolfe decompositions are applied for the integrated problem. Moreover, a heuristic based on the graph AND/OR is proposed for the two-dimensional compartmentalized knapsack problem. Computational results show that these mathematical formulations and methods provide good solutions
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Herbert Marcuse: utopia e dialética da libertação / Herbert Marcuse: utopia and dialectics of liberationBarros, Joy Nunes da Silva 08 December 2009 (has links)
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Previous issue date: 2009-12-08 / Secretaria da Educação do Estado de São Paulo / The present dissertation mainly aims at analyzing the concept of utopia in the work of Herbert Marcuse, taking as a guiding hypothesis the assertion that the faith Modernity has in the progress brought by clarification seems to have faded and therewith the great projects of social emancipation will no longer find a place in directing political struggles in modern times. This hypothesis will be analyzed in the light of Marcusean thinking, perceiving it as a consequence of what the author denominated one dimensional society, a social configuration, product of the development of Modernity, which has been able to absorb all forms of thinking that are contrary to it and impose itself as the only reality possible. Thus, the issue that directs the development of this master s thesis is the endeavor to clarify the philosophical status that the concept of utopia occupies in Herbet Marcuse's thinking, which has close ties with Hegelian Dialectics, as well as the correlation between utopic thinking and political action from the perspective of the Frankfurt philosopher / A presente dissertação tem como objetivo principal analisar o conceito de utopia na obra de Herbert Marcuse, tomando como hipótese norteadora a asserção de que a fé ostentada pela Modernidade no progresso trazido pelo esclarecimento parece ter se esmorecido e com isso os grandes projetos de emancipação social passam a não encontrar mais lugar no direcionamento das lutas políticas no tempo hodierno. Essa hipótese será analisada à luz do pensamento marcusiano, entendendo-a como uma consequência daquilo que o autor denominou sociedade unidimensional, uma configuração social, produto do desenvolvimento da Modernidade, que se tornou capaz de absorver todas as formas de pensamento que lhe são contrárias e impor-se como única realidade possível. Neste sentido, a questão que direciona o desenvolvimento desta dissertação é a de buscar esclarecer o estatuto filosófico que o conceito de utopia ocupa no pensamento de Herbert Marcuse, que mantém estreito vínculo com a dialética hegeliana, assim como a correlação entre o pensamento utópico e a ação política a partir da obra do filósofo frankfurtiano
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Single crystal growth and magnetic heat transport study of the spin chain compound Sr₂CuO₃ / Croissance cristalline et étude des propriétés de transport thermique d’origine magnétique du composé à chaines de spins Sr₂CuO₃Beesetty, Neela Sekhar 10 July 2015 (has links)
Le transport thermique dû à des excitations magnétiques dans les composés 1D contenant des chaines et échelles de spins fait actuellement l’objet d’une collaboration fructueuse entre chimistes et physiciens du solide. Le composé à chaines de spins Sr₂CuO₃, qui est un excellent exemple de chaine de type Heisenberg antiferromagnétique de spins S = ½, présente une conductivité thermique anisotrope due à des excitations magnétiques le long des chaines, appelées spinons. Afin de comprendre les mécanismes de diffusion responsables de la conduction thermique magnétique observée, nous avons introduit du désordre dans les chaines en effectuant des substitutions chimiques sur les ions qui composent celles-ci. En appliquant la méthode de croissance dite de “zone solvante” (traveling solvent floating zone method) nous avons élaboré des monocristaux de grande pureté de Sr₂CuO₃ substitués, d’une part par des ions Ca²⁺ (S = 0) qui viennent remplacer des ions Sr²⁺ (S = 0) e, situés en dehors des chaines, créant ainsi un désordre dans les liaisons ; et d’ autre part, des cristaux du même composé, substitué par des ions nickel Ni²⁺ (S = 1) qui prennent cette fois la place des ions Cu²⁺ (S = ½) dans les chaines, introduisant du désordre dans la distribution des sites. Après caractérisation des cristaux par les techniques traditionnelles de diffraction X et chimiques, nous avons fait une étude systématique de leurs propriétés magnétiques et thermiques. Des mesures Raman, de susceptibilité magnétique et de chaleur spécifique ont confirmé l’existence du désordre attendu, et ont suggéré que la substitution par le nickel amenait une rupture des chaines alors que celle par le calcium introduisait des défauts dans les chaines. Par ailleurs, à l’aide de mesures de RMN du ⁶³Cu, nous avons pu observer l’ouverture d’un gap de spins dans le spectre d’excitation des spinons, lié au désordre crée. L’analyse des courbes de conductivité thermique semble indiquer la présence d’une forte interaction spinon-phonon qui limite la conduction thermique à basse température. On notera, en particulier, que pour de forts taux de substitution en calcium, la conductivité thermique croit avec la température, mettant ainsi en évidence l’origine magnétique, associée aux spinons, de la conduction thermique. / Heat transport due to magnetic excitations in strongly correlated electronic materials containing low dimensional spin structures such as chains and ladders is an emerging field of research due to a fruitful collaboration between condensed matter physicists and solid state chemists. The spin chain compound Sr₂CuO₃, which is known to be the best realization of the S = ½ Heisenberg antiferromagnetic model, exhibits anisotropic thermal conductivity due to magnetic excitations, called spinons, of the spin chains. In order to understand its magnetic thermal conduction and the nature of scattering mechanisms involved, we have induced disorder into the chain structure by carrying out chemical substitution. Employing the sophisticated traveling solvent floating zone method we have grown high purity single crystals of Ca-substituted Sr₂CuO₃, in which Ca²⁺ (S = 0) ions substitute Sr²⁺ (S = 0) ions situated off the spin chains in the lattice creating a bond disorder, and Ni-substituted Sr₂CuO₃ in which Ni²⁺ (S = 1) ions substitute Cu²⁺ (S = ½) ions in the spin chains creating a site disorder. After characterizing the crystals using standard techniques, we have performed a systematic study of their magnetic and thermal properties. Raman spectra, magnetic susceptibility and specific heat measurements performed on these crystals confirmed the introduction of the anticipated disorder, suggesting that the substituted Ni atoms lead to breaking of the spin chains, and the Ca atoms act as effective in-chain defects. We observed the phenomenon of opening of a spingap in the otherwise gapless spinon excitation spectrum due to the induced disorder using ⁶³Cu NMR measurements. Our analysis of the thermal conductivity measurements points towards the presence of a strong spinon-phonon scattering that limits heat conduction at low temperatures. Remarkably, substituting high concentrations of Ca, we observed that thermal conductivity increases linearly with temperature, revealing the intrinsic magnetic thermal conduction due to spinons.
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Estudo do fenômeno de formação e colapso de macro cavidades em líquidos / Study of the phenomenon of formation and collapse of macro cavities in liquidsPereira, Pedro Augusto Fernandes 02 April 2014 (has links)
A cavitação e a dinâmica de bolhas são tópicos bastante recorrentes na literatura, devido sobretudo a seus efeitos em diversos tipos de fenômenos, como transferência de calor e escoamento em tubos. Considerando fases líquidas, sabe-se que estas estruturas de cavidade estão normalmente associadas ao equilíbrio metaestável, alcançado devido a quedas locais de pressão ou ao superaquecimento de uma substância pura (ou quase). Nestes casos é necessária a inicialização da mudança de fase através de algum mecanismo adequado, o qual gera uma sequência rápida de fenômenos. Apesar de comumente associado a danos, recentemente vários estudos vêm mostrando aplicações práticas deste tema, além de um campo ainda pouco explorado, que é o das macro cavidades. Essas cavidades podem ser geradas através do aquecimento de água a baixa pressão, sob condições específicas, criando sequências explosivas e formando movimentos como pistão para a água no interior de um invólucro convenientemente dimensionado. Este fenômeno mostra-se semelhante em diversos aspectos às micro cavidades, mais especificamente às cavidades próximas a superfícies livres, embora, sem dúvida, em escala muito maior. Os aspectos mencionados foram filmados com câmeras de alta velocidade e as características observadas foram comparadas com aquelas observadas em micro escala. Vários testes foram desenvolvidos de forma a melhor entender a dinâmica da formação e colapso dessas estruturas, sobretudo levando em conta um comportamento mais unidimensional para a evolução da bolha. Através de várias aproximações e análise de diferentes hipóteses para a variação de pressão e para a força de resistência, soluções analíticas e numéricas foram obtidas para a força exercida no fundo do contêiner e para a expansão e colapso das bolhas ao longo do tempo. As soluções propostas, em comparação com os dados experimentais, mostraram boa concordância entre si, sugerindo que os aspectos fundamentais da dinâmica da cavidade foram devidamente considerados e quantificados. / Cavitation and bubble dynamics are fairly recurring topics in literature, mostly due to their effects in various types of phenomena such as heat transfer and flow in pipes. Considering liquid phases, it is known that these cavity structures are normally associated with the metastable equilibrium, reached due to local pressure drop or overheating of a pure substance (or nearly so). In these cases, the phase change require a startup via some appropriate mechanism, which generates a fast sequence of phenomena. Although commonly associated with damage, recently several studies shown practical applications of these topics, and a still little explored field emerged, which is the field of macro cavities. These cavities can be generated by heating water at a low pressure, under specific conditions, creating an explosive sequences and forming piston like movements for the water inside a properly scaled casing. This phenomenon appears to be similar in many aspects to micro cavities, more specifically for cavities near free surfaces, although, without doubt, on a much larger scale. The mentioned aspects were filmed with high-speed cameras and the main features were compared with those observed in micro scale. Several tests have been developed to better understand the dynamics of the formation and collapse of these structures, especially taking into account a more one-dimensional behavior to the evolution of the bubble. Through various approximations, and analysis of different assumptions for the variation of pressure and the resistance force, analytical and numerical solutions were obtained for the force exerted on the bottom of the container and the expansion and collapse of bubbles over time. The proposed solutions in comparison with experimental data showed good agreement between each other suggesting that the fundamental aspects of the dynamics of the cavity were properly considered and quantified.
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Evaluating Innovative Nutrient Management Options and Seasonal Groundwater Recharge Dynamics in an Agricultural Source Water Protection AreaBrook, Jacqueline Marie 29 August 2012 (has links)
This thesis presents two interrelated studies that consider nutrient management and seasonal changes in recharge on agricultural lands within the context of source water protection. The research focuses first on the management of the risk to groundwater quality through the implementation of various nutrient management practices and secondly considers the dynamic nature of the transport pathway to the groundwater system associated with seasonal changes in climate and hydrology. The combined results provide insight into several of the key factors influencing the protection of groundwater sources within the agricultural landscape.
Field work was completed between 2009 and 2010 on an agricultural field near the City of Woodstock, Ontario. The site is located within a source water protection area; the two-year travel time zone of the Thornton Well Field which represents the primary water supply for the City of Woodstock and which has experienced chronic increases in nitrate concentrations over the last few decades. The wells are completed in glacial overburden consisting of intermingling sand and gravel till aquifers which overly a limestone bedrock aquifer. Agricultural best or beneficial management practices (BMPs) field have been implemented and monitored since 2004. The BMPs were adopted in order to reduce nitrogen losses to the aquifer, and consisted of a reduction in nitrogen fertilizer application rates over a series of agricultural fields located near the well
The first study is a one year experiment designed to compare alternative nutrient management practices for corn. Combinations of fertilizer treatments with or without a legume cover crop (red clover) were assessed. The fertilizer treatments studied were: a polymer coated urea (slow-release fertilizer) applied at planting, a conventional urea applied at planting, side-dress treatment of a solution of urea and ammonium nitrate in water containing 28% nitrogen with two different application rates applied in the early summer, and a control. The legume cover crop was incorporated in the soil in the previous fall, and acts as a slow release fertilizer as nitrogen is made available to the following crop as the plants decompose. Treatments were compared based on crop yield, overall economic return, and the potential for nitrate leaching. The potential for nitrate leaching was evaluated with bi-weekly shallow soil core during the growing season, and deep soil cores taken before planting, after harvest and the following spring. The deep cores allowed changes in nitrate storage below the rooting zone to be assessed.
The results of this study highlight the importance of timing of fertilizer applications and rate of fertilizer applications. Treatments which provide a delay in the release or application of fertilizer, the polymer-coated urea, the calculator-rate side-dress and the clover cover crop, were found to be advantageous. The polymer-coated urea treatments and side-dress treatments were found to reduce leaching compared to the conventional urea treatment. Treatments with the clover cover crops were not found to reduce crop yields or increase leaching potential, and lower fertilizer costs associated to this practice were found to have a positive economic effect. Plots treated with the high-rate side-dress fertilizer application lost more nitrate to the subsurface compared to the other treatment options, and an economic disadvantage was observed as yields did not compensate for higher fertilizer costs. The study highlights the advantages of the different treatments under study, which may be used to inform policy makers and farmers in the selection of economically and environmentally sustainable nutrient management BMP options.
Groundwater monitoring at the site over the years has indentified interesting recharge dynamics, particularly in the vicinity of an ephemeral stream which develops annually during spring and winter melt events in a low lying area of the study site. It was hypothesized that rapid recharge could occur beneath the stream allowing for surface water to quickly reach groundwater, posing a threat to municipal water wells. The current framework of source water protection does not take into account the potential risk posed by this type recharge event. At this field site, rapid infiltration associated with this type of event may pose a risk to drinking water quality due to the proximity of the stream to the pumping wells and the nature of the aquifer.
The second study examines rapid groundwater recharge processes beneath the ephemeral stream during the course of a spring melt in 2010. The goals of the study were to quantify recharge at one location beneath the stream and to assess whether temperature variations above the water table can be used as a tracer to reasonably estimate recharge during a short live recharge event. A novel housing for the temperature sensors was designed in order to deploy and position them into gravelly materials within the vadose zone, which reduced the potential for the formation of preferential pathways and permitted the retrieval of the sensors at a later date. Field data were collected during the course of the spring melt period from a network of groundwater monitoring wells and subsurface temperature sensors. Spatial and temporal changes in groundwater geochemistry, hydraulic head and temperature were were used to characterize recharge dynamics at the field site. Recharge beneath a segment of the ephemeral stream was quantified through the numerical analysis of the field data using Hydrus 1-D, a one-dimensional numerical model designed to simulate soil water flow and heat transport in variably saturated porous media. Site specific data were used to create the model domain, provide estimates of physical parameters, and to define initial and time variable boundary conditions. Model parameters were first calibrated by simulating periods where it was expected that soils would be gravity drained with minimal soil water flow, and then further refined by simulating the period when the ephemeral stream was present. A final set of parameters was determined, and the initial gravity drained conditions were re-simulated. The model was able to reproduce field observations under different flow scenarios using the final set of parameters, suggesting that the conceptual model and final model domain representative of the actual field conditions. The successful simulation of the field data sets under the different flow scenarios also increases confidence in the uniqueness of the model results. The model estimated that 0.15 m of recharge occurred beneath the instrumented site during the period between March 9th and March 22nd of 2010 when the ephemeral stream was present. This represents approximately a third of the expected total annual recharge for this location. Regional changes in hydraulic head, groundwater temperature and groundwater chemistry provided additional insight into the dynamic nature of the recharge process during the spring meld period and further illustrated the spatial variability of the aquifers’ response to the stream. The study found that the use of temperature as a tracer provided useful and quantifiable insight into recharge phenomena. The results of this study suggest that high rates of rapid recharge occur beneath the ephemeral stream, and are spatially variable. This type of focused infiltration that occurs during the spring melt may represent a risk to municipal water quality if the infiltrating waters are carrying contaminants.
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Nonlinear liquid sloshing in a 3D tank with bafflesWu, Chih-Hua 09 July 2010 (has links)
Liquid sloshing with unrestrained free surface in a moving container is associated with various engineering problems, such as tankers on highways, liquid oscillations in large storage tanks caused by earthquakes, sloshing of liquid cargo in ocean-going vessels, and the motion of liquid fuel in aircraft and spacecraft. The purpose of this study is to develop a three-dimensional (3D) numerical wave tank with or without internal structures to investigate the mechanism of liquid sloshing and the interaction between the fluid and internal structures. The developed 3D time-independent finite difference method is applied on solving liquid sloshing in tanks with or without the influence of baffles under the ground motion of six-degrees of freedom. The 3D Navier-Stokes equations were solved and transformed to a tank-fixed coordinate system, and the fully nonlinear kinematic and dynamic free surface boundary conditions for fluid sloshing in a rectangular tank with a square base were considered. The fluid is assumed incompressible in this study. The complicated interaction in the vicinity of the fluid-structure interface was solved by implementing one dimensional ghost cell approach and the stretching grid technique near the fluid-structure boundaries were used to catch the detailed evolution of local flow field. A PC-cluster was established by linking several single computers to reduce the computational times due to the implementation of the 3D numerical model. The Message Passing Interface (MPI) parallel language and MPICH2 software were utilized to code the computer codes and to carry out the circumstance of parallel computation, respectively.
The developed numerical scheme was verified by rigorous benchmark tests. Not only the reported analytical, numerical and experimental studies were compared with the present numerical results, the experimental investigation was also involved in the present work to further validate the accuracy of the numerical scheme. All the benchmark tests of this study showed excellent accuracy of the developed numerical scheme. For a tank without internal structures, the coupled motions of surge and sway are simulated with various excitation angles, excitation frequencies and water depths. The characteristics of sloshing waves are dissected in terms of the classification of sloshing wave types, sloshing amplitude, beating phenomenon, sloshing-induced forces and energy transfer of sloshing waves. Six types of sloshing waves, named single-directional, diagonal, square-like, swirling-like, swirling and irregular waves, were found and classified in the present study and the occurrence of these waves are tightly in connection with the excitation frequency of the tank. The effect of excitation angle on the characteristics of sloshing waves is explored and discussed, especially for swirling waves. The spectral analyses of sloshing displacement of various sloshing waves are examined and a clear evidence of the correlation between sloshing wave patterns and resonant modes of sloshing waves are demonstrated. The mechanism of switching direction of swirling waves is discussed by investigating the situation of circulatory flow, the instantaneous free surface, the gravitational effect and the instantaneous direction of external forcing. The coupling effects of heave, surge and sway motions were also included in this study and the result showed an unstable influence of heave motion on the kinematic and dynamic characteristics of sloshing waves when the vertical excitation frequency of the tank is twice as large as the fundamental natural frequency. Except irregular waves, the other types of sloshing waves are converted into swirling waves due to the effect of heave motion.
The study related to tuned liquid damper (TLD) in 2D and 3D tanks were considered. A comprehensive investigation for a 2D tank with vertically tank bottom-mounted baffles (baffled tank) are demonstrated and discussed with respect to the influence of baffle height on the natural mode of the tank, the evolution of vortices and vortex shedding phenomenon, the relationship between the vortex shedding frequency and the excitation frequency of the tank, the vortex size generated in the vicinity of the baffle tip, the interaction of vortices inside the tank. The baffle height shows a significant influence on the shift of the first natural frequency of the baffled tank and the liquid depth also plays an important part in determining this influence. In other words, the shift of the first natural mode due to various baffle height is varied with water depths. The design of two baffles separated by 0.2 times the tank breadth is an efficient tool to not only reduce the sloshing amplitude but switch the first natural frequency of the tank. The sloshing displacement is affected distinctly by different numbers of baffles mounted vertically on the tank bottom. The more baffles mounted onto the tank bottom, the smaller the sloshing displacement is presented in both the transient and steady-state periods. The processes of the evolution of vortices near the baffle tip are categorized into four phases: the formation of separated shear layer and generation of vortices, the formation of a vertical jet and shedding of vortices, the interaction between shedding vortices and sloshing flow (the generation of snaky flow) and the interaction between snaky flow and sloshing waves. Vortex shedding phenomenon due to stronger vertical jets occurs when the excitation frequency is close to the first natural mode of the baffled tank. The size of the vortex generated near the baffle tip is discussed and the vortex size is closely correlated with the baffle height.
Two types of 3D tuned liquid dampers, a vertically tank bottom-mounted baffle and a vertical plate, are discussed for a tank under coupled surge-sway motions. The wave types of diagonal and single-directional waves switch to the swirling type due to the influence of the baffle. The phenomenon of square-like waves or irregular waves coexisting with swirling waves is found in the baffled tank under diagonal excitation. The baffle and the vertical plate mounted parallel to the east (west) wall of the tank can effectively reduce the sloshing amplitude when the excitation angle is between 0 degree and 10 degree and the corresponding sloshing displacement in the sway (z) direction becomes more dominant with the increase of the excitation angle. The shift of the first natural mode of the baffled tank due to various baffle heights in the x direction is dominated in this design of baffled tank. The length of the plate can cause a significant influence on not only the variation of the natural frequencies but the type of the sloshing waves. The influence of the vertical plate on the irregular waves is insignificant and several peaks appear in the spectral analysis of the sloshing displacement for the irregular waves and the numbers of peaks are more than that of the baffled tank.
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The Effect Of Basin Edge Slope On The Dynamic Response Of Soil DepositsCiliz, Serap 01 February 2007 (has links) (PDF)
The effects of basin edge slope on the dynamic response of soil deposits are assessed by using one-dimensional and two-dimensional numerical analyses. 24 basin models having trapezoidal cross section are generated to represent different geometries (basin depth, basin edge slope) and soil type. Harmonic base motions with different predominant periods (Tp) are used in the analyses.
The results indicate that, for a constant basin edge slope and a constant ratio of fundamental period of site to the predominant period of base motion (Tn/Tp), the response is almost the same for different soil types, basin depths and base motions.
In the sloping edge region, one-dimensional response analysis predictions are found to be conservative compared to two-dimensional analysis predictions / however beyond this region they are unconservatively biased by a factor as high as 1.5. The sloping edge region and the horizontal region of the basin are denoted by normalized distance (ND) values varying from 0 to 1 and 1 to 2 respectively. The critical region where maximum amplification observed falls in the range of ND=1.0 to ND=1.5 for basins having slopes greater than 30o. The lower boundary of the critical region is shifted towards as low as ND=0.2 for basins having slopes less than 30o.
For a constant value of Tn/Tp, the increase in the amplification is smooth for basins with gentle slopes as compared to basins with steep slopes for the region where ND~1. For a basin and earthquake couple approaching to resonance state (Tn/Tp=1), the amplification for the region where ND is greater than 1 is found to be as high as 100% of that is found for the region where ND~1.
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One-Dimensional Quantum Magnets in Cuprates: Single Crystal Growth and Magnetic Heat Transport Studies / Eindimensionale Quantenmagnete in Kupraten: Einkristallzucht und Untersuchungen von Magnetischem WärmetransportRibeiro, Patrick 22 July 2008 (has links) (PDF)
This experimental work focusses on the magnetic thermal conductivity, κ_mag, of the one-dimensional two-leg spin ladder system Sr_14Cu_24O_41 and the spin chain system SrCuO_2. These two S = 1/2 antiferromagnetic Heisenberg compounds possess enormous magnetic contributions to the heat transport which in some cases exceed the phonon contributions by more than one order of magnitude. Despite of intense ongoing experimental and theoretical investigations, the underlying mechanism of the magnetic heat transport remains unclear. The study of κ_mag aims a better understanding of the basic physics which determine mobility, scattering and dissipation of the dispersing magnetic excitations. The most important tool used in this study is to selectively influence the structure and the electronic and magnetic properties of the compounds through doping. For this purpose single crystalline samples were produced using the Traveling Solvent Floating Zone technique, a crucible-free technology, which allows the growth of centimeter sized single crystals of high quality. In particular, the successful growth of large quantities of the hole-free ladders La_4Sr_10Cu_24O_41 allowed the realization of inelastic neutron scattering and, for the first time, the acquisition of the complete magnetic excitation spectrum of the spin ladder, composed not only by the triplon band, but also by the two-triplon continuum, permitting an accurate determination of the coupling constants in this system. The importance of the cyclic-exchange, previously unclear, was asserted. In order to study the scattering mechanisms of the magnetic excitations (triplons) off static defects in the two-leg ladder Sr_14Cu_24O_41, this compound was doped with tiny amounts of Zn. Occupying the Cu site in the ladders, the Zn plays the role of a non-magnetic defect, imposing an upper limit to the mean free path of the triplons. The thermal conductivity of Sr_14Cu_(14−z)Zn_zO_41, with z = 0, 0.125, 0.25, 0.5 and 0.75, shows a strong decrease of both the phononic and magnetic contributions with increasing z value. In particular, the decrease of the magnetic part indicates an increased scattering of the triplons off Zn defects. The analysis of κ_mag, using a kinetic model, allows the extraction of the triplon mean free path l_mag. This quantity was successfully correlated to the mean Zn-Zn distance along the ladders, confirming the validity of the employed kinetic model and corroborating results of previous works. In SrCuO_2, the magnetic contribution to the thermal conductivity appears as a hump-like anomaly on the high-T back of the low-T phonon peak. In order to better separate the magnetic contribution from the phononic background, small amounts of Sr were substituted by the smaller and lighter Ca, leading, on the one hand, to an increased scattering of the phonons and consequently to a suppression of the phononic thermal conductivity. On the other hand, since Ca is isovalent to Sr, no significant changes of the magnetic properties of the system are expected: a magnetic peak belonging to κ_mag should appear. Measurements of the thermal conductivity of Sr_(1−x)Ca_xCuO_2 for x = 0, 0.0125, 0.025, 0.05 and 0.1 show indeed a systematic decrease of the phonon thermal conductivity with increasing x. However, against initial expectations, no magnetic peak appears. Instead, the magnetic thermal conductivity decreases at intermediate and low temperatures with increasing doping level, indicating a strong influence of the Ca dopant on the magnetic system. Surprisingly, no changes of κ_mag occur at higher temperatures, where κ_mag remains constant for all doping levels. To explain this intriguing temperature and doping dependence of κ_mag, three scenarios are proposed. One of the scenarios is based on the phenomenon of mutual spinon and phonon heat transport, the so called spin-phonon-drag mechanism. Another scenario assumes an effective scattering of spinons off Ca defects. In a third scenario, the appearance of a gap in the doped compounds is considered. The obvious effect of the Ca dopant on the magnetic thermal conductivity motivated a more detailed investigation of the doping dependence of electronic and magnetic properties in Sr_(1−x)Ca_xCuO_2. NMR data reveal the presence of a magnetic gap for the x = 0.1 compound. The doping dependent evolution of the specific heat at low-T is consistent with this result. Furthermore, susceptibility data may be explained within a segmentation of the spin chains, which in turn can be also related to the opening of a gap. These results strongly support that the reduction of κ_mag in the Ca doped compounds is related to a smaller number of magnetic excitations participating in the heat transport due to the presence of the gap. A possible reduction of the chain length, as suggested by the susceptibility data, is also consistent with the scenario of a reduced κ_mag due to an increased scattering of magnetic excitations. In spite of these partially consistent results, there are still no clear-cut explanations for the evolution of κ_mag upon doping. In particular, it cannot be completely ruled out that a fraction of the Ca dopant goes into the chains, a point which has to be urgently clarified in order to allow a correct interpretation of the data.
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