Submitted by EVANDRO FERNANDES DA CUNHA (evandro.cunha@unesp.br) on 2018-11-18T20:13:14Z No. of bitstreams: 1 Tese Evandro Cunha.pdf: 10054124 bytes, checksum: f324825069efc486e2637a46c1b85371 (MD5) / Approved for entry into archive by Cristina Alexandra de Godoy null (cristina@adm.feis.unesp.br) on 2018-11-21T15:21:55Z (GMT) No. of bitstreams: 1 cunha_ef_dr_ilha.pdf: 10054124 bytes, checksum: f324825069efc486e2637a46c1b85371 (MD5) / Made available in DSpace on 2018-11-21T15:21:55Z (GMT). No. of bitstreams: 1 cunha_ef_dr_ilha.pdf: 10054124 bytes, checksum: f324825069efc486e2637a46c1b85371 (MD5) Previous issue date: 2018-07-31 / Esta tese de doutorado traz uma abordagem experimental sobre mecanismos de geração, desenvolvimento e propagação em canal de instabilidade na superfície livre de um escoamento de fluido não-Newtoniano. Estas instabilidades, quando evoluem para um padrão estável, exibem comprimento, amplitude e celeridade bem definidos, sendo denominadas roll waves. Na literatura existe uma lacuna no que diz respeito às medições destes fenômenos em condições controladas de laboratório, e com pouquíssimos registros, quando presentes em eventos naturais. Assim, buscou-se neste trabalho projetar e implementar um aparato experimental operacional e de baixo custo com o objetivo de gerar e aferir tais instabilidades, sob condições controladas e sem a influência de vibrações externas (canalete posicionado sobre uma mesa inercial), seguindo metodologia de ensaio proposta e testada. O fluido teste utilizado foi o gel de carbopol 996, que apresentou boa estabilidade e propriedades reológicas aderentes ao modelo de Herschel-Bulkley, tal qual as lamas encontradas em pés de barragens, lamas oriundas de fluxos hiperconcentrados ou de corridas propriamente ditas. Um sistema de sucção-recalque, através de uma bomba hidráulica de cavidade progressiva, impulsionava o gel para o canal de ensaio, garantindo fluxo contínuo do material em regime de recirculação. Para gerar as instabilidades na superfície livre, foi imposta, a montante do canal, uma perturbação, por meio de um pulso de ar controlado em intensidade e frequência. Após evolução e estabilização, a onda (roll wave) era aferida por meio de sistema de medição ultrassônico na configuração de pulso-eco e, seguindo metodologia inovadora proposta nesta tese, por meio de técnica fotométrica em função da absorção luminosa de um corante (azul de metileno) adicionado ao fluido teste em escoamento. Para confirmação da qualidade dos resultados obtidos pela aplicação das técnicas de medição experimental, foram feitas confrontações entre as técnicas experimentais propostas e entre estas e um modelo numérico, desenvolvido pelo grupo de pesquisa. Por fim, foram testados dois estudos de caso de formação e propagação de roll waves no canal, o primeiro visando a obtenção e tratamento das amplitudes em diversos pontos ao longo do canal, e, no segundo, a influência da frequência de perturbação sobre a amplitude da roll wave, todos para cenários experimentais com números de Froude superiores ao Froude mínimo, condição necessária à geração do fenômeno. / This doctoral thesis brings an experimental approach on generation, development and propagation mechanisms of instabilities free-surface flows of a non-Newtonian fluid. When these instabilities evolve to a stable pattern, they display well-defined length, amplitude and celerity, being denominated as roll waves. There is a great gap in literature concerning experimental data. Few experiments are found relating laboratory measurements of these phenomena in controlled conditions; this is also true when it comes to in situ measurements from natural events. Thus, the aim of this project was to design and implement a low cost operational experimental apparatus to generate and measure such instabilities under controlled conditions, isolated from external vibration influences. This project follows a previous methodology developed which was tested and approved. Carbopol gel 996 was used as test fluid, presenting good stability and rheological properties matching to Herschel-Bulkley model, oftenly used for modeling industrial sludge, slurry fluids, natural mud, among others. A hydraulic circuit was installed in which a progressive cavity hydraulic pump pushed the gel to the inlet of the testing channel, ensuring continuous flow of material, capturing the fluid at the channel outlet. A free-surface disturbance was imposed to the flow through a controlled pulse of air (intensity and frequency) on the upstream flow to produce the free-surface instabilities. After evolution and stabilization, the wave (roll wave) was measured through ultrasonic measurement system in the pulse-echo configuration and also through photometric technique using light absorption by a dye (methylene blue) added to the test fluid. Confrontations of the experimental data were made among the proposed experimental techniques and also with numerical simulations developed by the research group in order to assess the quality of the results obtained by the application of the experimental measurement techniques. Lastly, two case studies of formation and propagation of roll waves were tested: the first one aimed to obtain and process the amplitudes in several points along the channel; the second one, the influence of frequency of disturbance over the amplitude of the roll wave was studied. All the experimental scenarios were tested for Froude number over the minimum value necessary for the generation of the phenomenon.

Ce manuscrit de thèse rapporte quelques études méthodologiques sur la régionalisation du climat par l’approche dynamique. Le domaine géographique couvre une large zone allant du milieu de l’Atlantique Nord à l’Europe de l’Est, et du Sahel à l’Arctique. La quête à tout prix d’une amélioration du climat régional n’est pas au cœur du manuscrit. Pourtant, l’accent est mis sur trois points clefs, généralement rencontrés par toutes tentatives de régionalisation du climat. Le premier point concerne le schéma d’imbrication : imbrication du sens unidirectionnel du GCM vers le RCM (one-way nesting, OWN) ou bidirectionnelle entre le GCM et le RCM (two-way nesting, TWN). Le deuxième point examine la réalisation technique d’imbrication, qui est généralement une opération de relaxation newtonienne ajoutée aux équations pronostiques du modèle. Le troisième point est sur l’effet du raffinement de maille dans le RCM. L’esprit général du manuscrit consiste à conceptualiser et réaliser des simulations numériques pour traiter ces trois points avec astuces afin de les isoler et quantifier. Le modèle de circulation générale LMDZ est utilisé pour l’ensemble des expériences. Il joue à la fois le rôle du GCM et celui du RCM. Dans les deux cas, il conserve strictement ses paramétrisations physique et sa configuration dynamique, ainsi que tous les forçages ou paramètres externes. La stratégie d’expérimentation, qualifiée comme Master versus Slave, consiste à réaliser des simulations sous deux protocoles reliés l’un et l’autre : « DS-300-to-300 » désigne Downscaling du GCM à 300 km de résolution horizontale au RCM qui est identique au GCM, aussi à 300 km de résolution spatiale ; « DS-300-to-100 » désigne Downscaling de 300 km (GCM) à 100 km (RCM). Il est clair que « DS-300-to-300 » est un cadre idéalisé, particulièrement approprié pour évaluer l’effet de l’opération de relaxation. Le protocole « DS-300-to-100 », soustrait du « DS-300-to-300 », permet d’évaluer très précisément l’effet de la résolution du RCM augmentée. Dans chaque protocole, deux schémas de communication entre le RCM et le GCM ont été implémentés, l’un (OWN) est la méthodologie classique du sens unique qui consiste à piloter le RCM par les sorties du GCM, l’autre (TWN) est d’établir un échange mutuel entre les deux modèles. Le climat régional est sensible au choix des schémas de communication entre le RCM et le GCM, surtout aux moyennes latitudes. TWN apporte une nette amélioration sur la représentation des informations frontalières. Au niveau des modes régionaux de circulation atmosphérique, exprimés en structures d’EOF, OWN et TWN sont tous deux capables de les reproduire, mais avec de légères déformations dans l’espace. La relaxation newtonienne, largement utilisée dans la régionalisation du climat, permet au RCM de bien suivre la trajectoire synoptique du GCM. Pourtant, la concomitance temporelle et la ressemblance spatiale sont dépendantes des variables considérées, des saisons, des régimes de temps, et des échelles spatio-temporelles de circulations atmosphériques. Des cas de dé-corrélation sont remarquables quand la circulation dominante de la région est de petites échelles. Le raffinement de maille augmente la liberté du RCM à développer sa dynamique interne, surtout aux petites échelles, mais aussi à l’ensemble du spectre de la circulation à travers l’interaction des échelles. Ainsi le RCM devient plus indépendant et s’écarte davantage du GCM. Cette thèse, autour des aspects méthodologiques de la régionalisation du climat, aide à avoir une meilleure compréhension sur la pratique. Elle adresse aussi un message de précaution à la communauté RCM et l’invite à bien vérifier leur méthodologie de régionalisation. / The work developed in this thesis explores through methodological modelling studies the current techniques of climate regionalization. In this case, the regionalization focuses on a geographical domain covering from the North Atlantic to Eastern Europe longitudinal wise, and from the Sahel to the Arctic as a latitudinal interval. The aim of this thesis is not the improvement of regional climate modelling per se, but tackling three key questions that are commonly met by all attempts when trying to improve climate regionalization. Firstly, the choice and advantages of the nesting scheme: one-way nesting (OWN) versus two-way nesting (TWN). Secondly, the evaluation of the nesting method, which is generally a Newtonian relaxation operation added to the prognostic equations of the model. And finally, the consequences of the mesh refinement in Regional Circulation Models (RCM). The objective of this manuscript consists in conceptualizing and carrying out numerical simulations to answer these three questions by isolating each individual effect and quantifying the consequences of each of the effects. The general circulation model LMDZ is used for all experiments. It is able to play the role of the General Circulation Model (GCM) and the RCM, keeping the same physical parameterizations and the same dynamical configuration, as well as the same external forcings and model parameters. Our experimental set-up, referred as “Master versus Slave”, consists on two related protocols: “DS-300-to-300” and “DS-300-to-100”. The former implies the downscaling of the GCM at 300 km of horizontal resolution while the RCM has the identical resolution of 300 km. The latter implies the downscaling from 300 km (GCM) to 100 km (RCM). We have assumed the “DS-300-to-300” as an idealized framework, particularly appropriate to evaluate the relaxation operation effect. In parallel, the “DS-300-to-100” protocol, subtracted from the “DS-300-to-300”, allows assessing the effect of the increased resolution for the RCM. In each protocol, two communication schemes between the RCM and the GCM have been implemented. The first one -OWN- is the classic one-way methodology to control the RCM by the outputs of the GCM. The second one -TWN- is used to establish a mutual exchange between the two models (RCM and GCM). This thesis has found that climate regionalization is highly sensitive to the choice of the communication scheme between the RCM and the GCM, especially at mid-latitudes. TWN clearly improves the representation at the boundaries. For the regional atmospheric circulation modes, expressed in EOF structures, both OWN and TWN are able to reproduce them, but with a slight deformation in space. Newtonian relaxation, widely used in climate regionalization, allows the RCM to follow the GCM’s synoptic trajectory. However, temporal concomitance and spatial resemblance of the two depend on the variables considered, on the particular seasons selected, on the weather regimes, and on the spatiotemporal scales of atmospheric circulation. De-correlation cases are remarkable when the dominant circulation on a regional scale is small. Moreover, mesh refinement increases the freedom of the RCM to develop its internal dynamic circulation, especially at small scales, and also across the whole spectrum of circulation regimes through the scales in which the RCM operates. Thus, when resolution increases, the RCM becomes more independent from the GCM behavior and the model results deviate significantly from the GCM. Focused on the methodological aspects of climate regionalization, this thesis helps to gain a better understanding on the regionalization practice. Il also sends a precautionary message to the RCM community, kindly inviting to verify their regionalization strategy.

Une étude théorique et expérimentale de la convection de Rayleigh-Bénard pour un fluide non-Newtonien rhéofluidifiant a été effectuée. L’approche théorique consiste en une analyse linéaire et faiblement non linéaire de l’instabilité thermo-convective d’une couche horizontale d’un fluide non-Newtonien, d’étendue supposée infinie dans le plan horizontal, chauffée par le bas et refroidie par le haut. Le comportement rhéofluidifiant est décrit par le modèle de Carreau. Pour ce modèle, les conditions critiques d’instabilité du régime conductif sont les mêmes que pour un fluide Newtonien. L’objectif de l’analyse faiblement non linéaire consiste à déterminer d’une part la valeur critique du degré de rhéofluidification à partir duquel la bifurcation primaire devient sous critique et d’autre part l’influence de rhéofluidification sur la sélection du motif de convection au voisinage des conditions critiques, en tenant compte d’un éventuel glissement à la paroi, d’une conductivité thermique finie de celle-ci et de la thermodépendance de la viscosité. Les conséquences sur le champ de viscosité et l’évolution du nombre de Nusselt sont caractérisées. L’approche expérimentale consiste à visualiser par ombroscopie les motifs de convection qui se développent dans une cellule cylindrique. Deux rapports d’aspect ont été considérés : AR = 3 et AR = 4. Les fluides utilisés sont des solutions aqueuses de Xanthan à différentes concentrations. L’influence du degré de rhéofluidification combiné avec la thermodépendance de la viscosité sur le domaine de stabilité des rouleaux et des hexagones ainsi que sur la zone de transitions rouleaux hexagones est mise en évidence / Theoretical and experimental study of Rayleigh-Bénard convection in a non-Newtonian shear-thinning fluid was performed. The theoretical approach consists in a linear and a weakly nonlinear of thermo-convective instability in a horizontal layer of a non-Newtonian fluid, assumed infinite in extent, heated from below and cooled from above. The rheological behavior of the fluid is described by the Carreau model. For this rheological model, the critical threshold is the same as for a Newtonian fluid. The objective of the weakly non linear analysis is to determine on one hand the critical value of the shear-thinning degree above which the bifurcation becomes subcritical and on the other hand, the influence of shear-thinning effects on the pattern selection near the onset, taking into account the possibility of wall slip, a finite thermal conductivity of the walls as well as the thermo-dependency of the viscosity. The impact on the viscosity field and on the evolution of the Nusselt number are characterized. The experimental approach consists in visualizing the convection patterns using the shadowgraph method in a cylindrical cell. Two aspect ratios were considered : AR = 3 and AR = 4. The fluids used are aqueous solutions of xanthan-gum at different concentrations. The influence of shear-thinning effects combined with the thermo-dependency of the viscosity on the stability domain of rolls and hexagons as well as on the transition between rolls and hexagons is highlighted

Fluidos Não-newtonianos estão presentes em grande quantidade na natureza e em muitas aplicações industriais. Tais fluidos apresentam uma variedade de comportamentos específicos. Dentre eles podemos citar: elasticidade, plasticidade, viscosidade variando com a taxa de deformação, tixotropia. Esta tese de doutorado apresenta um recente modelo para Fluidos Estruturados Tixotrópicos (de Souza Mendes, 2009), no qual baseasse nas tradicionais equações de balanço de momentum e massa, em uma equação constitutiva de Maxwell-b modificada e uma equação de evolução para o nível de estrutura do material. Na equação constitutiva de Maxwell-b modificada, tempo de relaxação e viscosidade estrutural são funções da estrutura do material. A equação evolutiva para o parâmetro de estruturação prevê efeitos de tixotropia, dependentes do tempo de equilíbrio do material. As equações que constituem o modelo mecânico para Fluidos Estruturados Tixotrópicos são aproximadas numericamente através do Método de Elementos Finitos de Galerkin Mínimos-quadrados (GLS). Tal método adicionou termos dependentes de malha ao método clássico de Galerkin, de forma a aumentar a estabilidade da formulação original, proporcionando compatibilizar os sub-espaços de velocidade e pressão. São investigados escoamentos creeping flow de Fluidos Estruturados Tixotrópicos em dois problemas clássicos de engenharia: em torno de um cilindro confinado entre duas placas e em uma expansão planar abrupta. Parâmetros relevantes ao modelo são variados em faixas pertinentes ao problema físico simulado e os resultados demonstraram uma boa capacidade de previsão. / Non-Newtonian fluids are present in large quantities in nature and in many industrial applications. Such fluids exhibit a variety of specific behaviors. Among them we can mention: elasticity, plasticity, viscosity varying with the strain rate, thixotropy, etc. This thesis presents a new model for thixotropic Structured Fluids (de Souza Mendes, 2009), in which were a basis in traditional balance equations of mass and momentum, the constitutive equation of Maxwell-type and an evolution equation for the level structure of the material. In the modified constitutive equation of Maxwell-b, relaxation time and structural viscosity are functions of material structure. The structure parameter evolutive equation provides effects of thixotropy, dependent on the equilibration time of the material. The equations which constitute the mechanical model for Structured Thixotropic fluids are approximated numerically using the Galerkin Least-squares Finite Element Method (GLS). Such a method added mesh dependent terms to the classical method of Galerkin in order to increase the stability of the original formulation, providing compatibility between sub-spaces of velocity and pressure. Are investigated Structured Thixotropic Fluids creeping flow in two classical problems in engineering: around a cylinder confined between two plates and in a planar abrupt expansion. Relevant parameters to the model are varied in pertinent ranges to physical problem simulated and the results demonstrated a good predictive capability.

Made available in DSpace on 2015-05-08T14:59:45Z (GMT). No. of bitstreams: 1 Arquivototal.pdf: 1419023 bytes, checksum: 1bf50c9a366f8d01e4a2a3efdb0a5526 (MD5) Previous issue date: 2012-09-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this study the forced convection in the laminar flow in simultaneous developing is studied by applying the Generalized Integral Transform Technique to provide a hybrid analytical solution for the fields of velocity, pressure and temperature in circular ducts. The Continuity, Navier-Stokes, Poisson and Energy equations are formulated using primitive variables,knowing that the Poisson Equation was obtained from some mathematical manipulation made on the Navier-Stokes equations. The integral transformation is done in the Momentum equation in x, Poisson and energy equations, and the resulting equations are solved using the IMSL, DBVPFD subroutines and recovering the original potential for each profile studied. In this way it is possible to find a solution to the system by means of an expansion in terms of convenient eigenfunctions, to circular ducts, the eigenfunctions will be Bessel functions. In the following, some results from a practical point of view will be calculated and exhibited graphically such as: The Nusselt number, the f Re value, the study of the convergence profile of the velocity field, the mean velocity, the temperature, the mean temperature, pressure and the mean pressure in the middle of the duct will be analyzed. The results will be compared with the ones found in the literature to validate and adjust the model. / No presente trabalho a convecção forçada interna no escoamento laminar em desenvolvimento simultâneo é estudada aplicando a Técnica da Transformada Integral Generalizada para produzir um solução híbrida para os campos de velocidade, pressão e temperatura em dutos circulres. As equações da Continuidade, de Navier-Stokes, de Possion e da Energia são formuladas utilizando variáveis primitivas, sabendo-se que a equação de Poisson foi obtida a partir de algumas manipulações matemáticas feitas na equação de Navier-Stokes. A transformação integral é aplicada nas equações da quantidade de movimento na direção x, de Poisson e na equação da energia, e as equações resultantes são resolvidas com a subrotina numérica do IMSL, DBVPFD recuperando o potencial original para cada perfil em estudo. Assim é possível encontrar uma solução para o sistema de equações em termos de um expansão de autofunções, que para dutos circulares, as autofunções serão funções de Bessel. Em seguida resultados de interesse prático são calculados e exibidos graficamente como: número de Nusselt e f Re e estudos da convergência dos perfis de velocidade,velocidade média, temperatura, temperatura média, pressãoo e pressão média no centro do duto são analisados. Os resultados são comparados com os dados disponíveis na literatura para validação e ajustes do modelo.

Made available in DSpace on 2015-05-08T15:00:09Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 727146 bytes, checksum: 486fc97b94f3c34e9b689dd0ebc1b729 (MD5) Previous issue date: 2010-09-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this paper the Generalized Integral Transform Technique is employed to produce hybrid solutions for the velocity and pressure fields of a newtonian fluid in two dimensional flow. The problem is formulated by using primitive variables and the necessary mathematical manipulations were used to obtain the Poisson equation for the pressure field. The momentum equations in the axial direction of flow and Poisson are transformed to remove the transversal dependency. The resulting transformed fields are solved with the IMSL numerical subroutine, DBVPFD. The obtained results for the longitudinal velocity profile at the center of the channel are compared with the available data in the open literature for validation and model fitting. Even so, studies are carried out about the convergence of the solution for the velocity profile in the centerline as well as testing different values of the scale factor of axial coordinate for the choice of a factor which can fit perfectly for comparison with available data. Interest practical datas such as: friction factor and mean velocity are obtained along the duct for a entry condition into the parallel flow channel (v = 0). / No presente trabalho a Técnica da Transformada Integral Generalizada é empregada para produzir soluções híbridas para os campos de velocidade e pressão de um fluido newtoniano no escoamento bidimensional. O problema é formulado a partir da utilização das variáveis primitivas e as manipulações matemáticas necessárias foram usadas para a obtenção da equação de Poisson para o campo de pressão. As equações da quantidade de movimento na direção axial do escoamento e a de Poisson são transformadas para a retirada da dependência transversal. Os campos transformados resultantes são resolvidos com a subrotina numérica do IMSL, DBVPFD. Os resultados obtidos para o perfil de velocidade longitudinal no centro do canal são comparados com os dados disponíveis na literatura aberta para validação e ajustes do modelo. Ainda assim, são realizados estudos de convergência da solução para o perfil de velocidade no centro, bem como testes em diferentes valores do fator de contração de escala da coordenada axial para a escolha de um fator que melhor se ajuste a comparação com os dados disponíveis. Dados de interesses práticos, tais como: fator de atrito e velocidade média são obtidos ao longo do duto para uma condição de entrada no canal do escoamento paralelo (v = 0).

Made available in DSpace on 2014-06-11T19:29:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2003-07-30Bitstream added on 2014-06-13T20:48:14Z : No. of bitstreams: 1 santos_fl_me_ilha.pdf: 5580224 bytes, checksum: 7664797be424662e0d0d1021e9ee4dc5 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Em função da concentração de material sólido, misturas resultantes de argila e água conferem, via de regra, propriedades não-Newtonianas. Essa concentração passa a variar com a granulometria e a composição do mineral do sedimento, bem como com a qualidade da água. Algumas tentativas foram feitas na busca de melhor explicar a reologia e a dinâmica global dessas misturas nessa última década, notadamente no contexto de lavas torrenciais e misturas hiperconcentradas. Essa dissertação de mestrado tem por objetivo desenvolver uma caracterização reológica de misturas sólido-líquido (água+argila caulinítica e água+areia fina+argila caulinítica) com diferentes concentrações em volume (Cv) para as quais são determinadas, a partir de ensaios de reometria de precisão, as propriedades tais como a viscosidade aparente, tensão crítica de cisalhamento e curva de tensão de cisalhamento x taxa de deformação. Verificou-se, em condições controladas, a influência da temperatura, pH e concentração em volume (Cv) sobre a curva reológica dessas misturas, além de eventuais fenômenos de tixotropia e modo de preparo. O modelo reológico melhor ajustado para as argilas foi o de Herschel-Bulkley ( ( )n τ =τ c + k γ& ), onde: τ é a tensão de cisalhamento; τc é a tensão crítica (ou rigidez inicial); k é um termo de consistência (viscosidade aparente); n é o índice de escoamento; e dy γ& = du é a taxa de deformação. Obtém-se também, a partir de uma análise quantitativa global, leis de evolução dos diversos parâmetros reológicos em função da concentração em volume. Após a etapa de caracterização física e reológica das misturas, realizaram-se, sob condições controladas, ensaios dinâmicos através de escoamentos de lamas em canal inclinado. Nesses ensaios foram medidos os parâmetros lâmina normal, vazões... ; n is flow index; and dy γ& = du is shear rate. It is also obtained, from a global quantitative analysis, evolution laws of the several rheologics parameters in function of the solid volume concentration. After the stage of rheological and physical characterization of mixing samples, dynamics experiments were made, under controlled conditions, than the flow of mud was observed in the open channel. These analyses were made in order to examine the behavior of parameters such as: normal depth, discharge and velocities. In fact, the experience showed that is possible to deduce wall friction laws from the rheological proprieties based on high mud concentrated suspensions and the dynamic of these muds.

Orientador: Geraldo de Freitas Maciel / Banca: Cassio Roberto Macedo Maia / Banca: Mônica Feijó Naccache / Resumo: Rompimentos de Barreira são fenômenos caracterizados por um campo de escoamento inicialmente represado e submetido nos instantes subseqüentes a uma liberação abrupta. Diversos modelos matemáticos e leis de comportamento reológico podem ser associados a este problema e cada um deles deve ser estudado e compreendido de maneira a predizer, a partir de testes físicos e numéricos, sua adequação à descrição da evolução espaço-temporal de frentes resultantes deste fenômeno, tipo ruptura de barragem, retendo água , rejeitos ou materiais de reologia complexa. O desenvolvimento de técnicas analíticas possibilitou entender de maneira impar o desenvolvimento desses fenômenos, porém, a difícil obtenção de dados que alcançassem consonância com aqueles obtidos experimentalmente, demonstrava a fragilidade desse tipo de análise perante a descrição de sistemas dinâmicos complexos. Sendo assim, optou-se pela tentativa de recriar estes fenômenos a partir de técnicas que utilizassem a manipulação de equações governantes completas. Sistemas contínuos podem ser analisados através de aproximações discretas, resultando em valores realísticos, muito próximos aos obtidos experimentalmente, e a capacidade computacional atual, permite diminuir sensivelmente os erros envolvidos, aumentando cada vez mais a consistência física destes métodos. Neste trabalho utilizou-se o software comercial ANSYS-CFX para simular os fenômenos de ruptura de barreira, configurando a reologia de dois materiais, o Carbopol 940 representando um material de reologia complexa (Herschel-Bulkley) e o Glicerol (Newtoniano), esses dados foram então confrontados com os obtidos experimentalmente através de um modelo em escala reduzida. Campos de velocidade, pressão e evolução temporal das frentes foram analisadas, verificando-se valores com grande consonância entre numérico e experimental, mostrando uma grande consistência física dos métodos utilizados / Abstract: The Dam Break problem is a phenomenon characterized by a flow field initially dammed and submitted in the subsequent moments of an abrupt release. Various mathematical models and laws of rheological behavior may be associated with this type of problem and each must be studied and understood in order to predict from physical and numerical tests the temporal evolution of their fronts resulting from this phenomenon, type Dan Break problems, retaining water or rheology complex materials. The development of analytical techniques enabled the understanding the development of these phenomena, however, the difficulty to obtain a reach agreement data with those obtained experimentally, showed the fragility of this type of analysis to the description of complex dynamic systems. But, it was decided by attempt of recreate these phenomena from techniques that use the manipulation of complete government equations. Continuous systems can be analyzed by discrete approximations, leading to realistic values, very close to those obtained experimentally, and current computational capacity, enables to reduce the errors involved significantly, increasing the consistency of these physical methods. This work used the commercial software ANSYSCFX to simulate the phenomena of breaking the barrier, setting the rheology of two materials, the Carbopol 940 representing a material of complex rheology (Herschel-Bulkley) and glycerol (Newtonian), these data were then compared with those obtained experimentally using a model in scale. Fields of velocity, pressure and temporal evolution of the fronts were analyzed. Found very similar values between numerical and experimental simulations, showing the physical consistency of the methods used / Mestre

Orientador: Geraldo de Freitas Maciel / Banca: Edson Del Rio Vieira / Banca: Jefferson B. Libardi Liborio / Resumo: Esta dissertação de mestrado traz à discussão o comportamento reológico de misturas formadas por água+colóides+detritos (areia fina), visando entender e esclarecer os processos físicos e mecânicos, tais como sedimentação e ressuspensão de materiais inertes no seio da massa fluida não-newtoniana (água+colóides), bem como verificar a validade ou adeqüabilidade do modelo reológico de Herschel-Bulkley (modelo previamente investigado e validado para misturas compostas de água+colóides) para misturas viscoplásticas com presença de grãos. A variação das propriedades reológicas das misturas, em função das características físicas dos grãos (diâmetro, massa específica e área superficial), é investigada, e um modelo de estimativa de tensão crítica é apresentado. Ademais foram realizados ensaios preliminares de escoamento de fluidos hiperconcentrados em canais inclinados, na tentativa de calibrar uma lei de atrito. Dentro dessas perspectivas, a dissertação é composta de 6 Capítulos com um denso Estado da Arte que descreve os fenômenos e mecanismos que regem os escoamentos desse tipo de compósito. Com base na literatura estudada e, a partir da análise dos resultados experimentais, pôde-se concluir que, para misturas compostas de água+colóides+detritos, o comportamento reológico das misturas é o mesmo que aquele do fluido intersticial (água+colóides), desde que a homogeneidade da mistura seja garantida (não ocorrência de sedimentação e ressuspensão sucessivas). Neste caso, o modelo reológico de Herschel-Bulkley continua sendo válido para explicar as curvas de escoamento ou de fluxo das misturas viscoplásticas com grãos. Para misturas que apresentem os fenômenos de sedimentação e ressuspensão, o modelo de Bagnold, adaptado a fluidos hiperconcentrados... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work retakes the discussion about the rheological behavior of mixtures composed by water+ kaolinitic clay+fine sand in order to investigate the physical and mechanical processes such as sedimentation and suspension of inert materials into the non-Newtonian or interstitial fluid (water+colloids), as well as verify the adaptability of the Herschel-Bulkley rheological model (model previously investigated and validated for composed mixtures of water+ kaolinitic clay) for explain the viscoplastic+coarse materials rheological properties. The variation of the rheological properties of the mixtures in function of the coarse material characteristics (diameter, specific mass and superficial area) was investigated and a model predicting yield stress was proposed. Furthermore, some tests were performed in an inclined canal to determine a friction law for this kind of fluids. Inside of these perspectives, this dissertation is composed of 6 Chapters whit a dense State of the Art describing the phenomena and their mechanisms were pointed up. Based on literature and from the experimental results, one could concluded that the viscoplastic + coarse material mixtures behavior is the same of the interstitial fluid one, since that the homogeneity of the mixture is guaranteed (not occurrence of successive sedimentation and resuspension). In this case, Herschel-Bulkley rheological model is still valid to explain the curves of flow of the viscoplastic + coarse material. For mixtures that present the phenomena of sedimentation and resuspension, Bagnoldþs model, adapted to the hyperconcentrated fluids, describes well the variations of rheological parameters in function of the shear rates applied. Finally, it could be concluded that the experiments of free surface in canals, despite partial, can... (Complete abstract click electronic access below) / Mestre

Dissertation submitted in fulfilment of the requirements for the degreerequirements Master of Technology: Civi Engineering in the Faculty of Engineering at the Cape Peninsula University of Technology Supervisor: APN. Sutherland Co-supervisor: Prof. R. Haldenwang Cape Town October 2013 / The reliable prediction of pressure drop versus flow rate for non-Newtonian pipe flow is important in many industrial processes. In laminar flow scale up is straightforward, but transitional velocity and turbulent flow predictions remain a practical problem. Various theoretical models exist, but nothing in literature shows conclusively which of these is the most reliable and consistent, nor is it evident what effect the choice of rheological model has on the predictions. The aim of this work was to i) evaluate the influence of different rheological models when used in existing prediction techniques for non-Newtonian flow ii) characterise each material type using selected (commonly used) rheological models and iii) predict laminar, transitional and turbulent pipe flow characteristics for each material type using existing prediction techniques, for comparison with experimental results. Only time-independent, homogeneous, non-Newtonian fluids in pipe sizes from 13mm to 200mm were investigated. Rheological models and laminar flow predictions used only the power law, Bingham plastic, Herschel-Bulkley, Casson and Hallbom yield plastic models. The techniques used to predict transitional velocity were Ryan & Johnson, Metzner-Reed, Hedström intersection method, Slatter and Hallbom. For turbulent flow the Newtonian approximation, Dodge & Metzner, Wilson & Thomas, Slatter, Hallbom modified Wilson & Thomas and the Bowen correlation methods were used. The study documents the relevant theory and presents an assessment of the influence of rheology on pipe flow predictions, summarised in terms of the practical performance of the various rheological model/prediction method combinations for the different materials. In laminar flow at practical pseudo shear rates (8V/D; taken as 40s-1) the choice of rheological model does not significantly influence pressure drop predictions. For yield-pseudoplastic materials (eg. kaolin) the Hedström intersection and the Slatter Reynolds number method with Bingham plastic or Casson rheology predicted transitional velocity most accurately. For Bingham plastic materials (eg. bentonite) the best predictions were obtained using the Metzner & Reed Reynolds number with Bingham plastic rheology, although similar results were observed for this technique with all rheologies. The transitional velocity for pseudoplastic materials (eg. CMC) was best predicted by the Slatter and Metzner & Reed Reynolds number methods, using power law or Casson rheology. For turbulent flow of yield pseudoplastic materials the Slatter method using the Casson rheology gave the most accurate predictions overall. Turbulent flow of Bingham plastic materials was best predicted by the Slatter, Hallbom pseudo fluid Nikuradse and Dodge & Metzner methods, using Bingham plastic, Casson or yield plastic rheology. For pseudoplastic materials the Slatter and Wilson & Thomas methods were the most accurate, when used with yield plastic or power law rheology. Transitionalal velocity and turbulent flow predictions for materials with a yield stress vary significantly with rheological model. Laminar data should therefore be examined thoroughly and rheological models fitted with care. For pseudoplastic fluids there is little difference in predictions between the various techniques as long as power law rheology is used.