Esta dissertação apresenta uma modelagem matemática do escoamento laminar em tubos de paredes permeáveis aplicada à micro-filtração de suspensões. A modelagem utilizou-se da formulação integral das equações de conservação e de funções pré- estabelecidas para o representar os campos de velocidade e de concentração ao longo do tubo permeável. As equações integrais da quantidade de movimento e da conservação das espécies químicas forneceram duas equações diferenciais ordinárias de primeira ordem para as variáveis funcionais \"n (z)\" e \"m (z)\" presentes nas funções pré-estabelecidas. Para a solução destas equações optou-se pelo método de Runge-Kutta de quarta ordem devido a sua simplicidade e versatilidade conhecida da literatura. No entanto a equação para a conservação da quantidade de movimento apresentou grande instabilidade ao ser submetida à solução numérica, contornada a partir da imposição de diferentes formas de evolução para o campo de velocidade, através do funcional n(z) cujas formas de variação foram impostas segundo uma dependência linear, exponencial e polinomial. Por outro lado, a solução da equação para conservação das espécies foi numericamente convergente. De posse das funções pré-estabelecidas e ajustadas a partir da equação da conservação das espécies na forma integral, obtém-se neste trabalho os valores correspondentes para o adimensional de Sherwood, quantificando o processo de transferência de massa. Com os valores de Sherwood, os resultados desta modelagem foram comparados com os da literatura, Grober et al. (Apud Zeman & Zydney, 1996) e outros, e apresentaram-se de acordo para estudos de casos particulares, no intervalo de Peclet de 104 - 106 . / This dissertation presents a mathematical modeling of the larninar flow in permeable tubes applied to the micro-filtration of suspensions. The modeling uses of integral formulation of the conservation equations and of functions pre-established for to represent the fields of velocity and concentration along the permeable tube. The integral equations of the momentum and of conservation of the chemical species its supplied two differential ordinary equations if first order for the variables functional \"n(z)\" and \"m(z)\" presents in the pre-established functions. For the solution of these equations was opted for the method of Runge-Kutta of fourth order due to its simplicity and well-known versatility of the literature. However the equation for the conservation of the momentum presented great instability to be submitted to the numeric solution, outlined starting from the imposition forms different from evolution for the field of velocity, through the functional \"n(z)\" with lineal, exponential and polynomial dependence. However, the solution of the equation for conservation of the species was convergent numerical. Through of the pre-established functions and adjusted starting from the equation of the conservation of the species in the integral form, it was obtained in this work the corresponding values for the dimensionless of Sherwood, quantifying the process of mass transfer. With the values of Sherwood, the results of this modeling were compared with the one of the literature, Grober et al. (Apud Zeman & Zydney, 1996) and other, and they came of agreement for particular cases in the interval of Peclet of 104 the 106.

Submitted by Erika Demachki (erikademachki@gmail.com) on 2017-01-19T19:21:30Z No. of bitstreams: 2 Disssertação - Diego Emanoel Rodrigues - 2016.pdf: 4228559 bytes, checksum: e10d2a85e80b762539d34e79807b36d4 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-01-20T14:42:04Z (GMT) No. of bitstreams: 2 Disssertação - Diego Emanoel Rodrigues - 2016.pdf: 4228559 bytes, checksum: e10d2a85e80b762539d34e79807b36d4 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-01-20T14:42:04Z (GMT). No. of bitstreams: 2 Disssertação - Diego Emanoel Rodrigues - 2016.pdf: 4228559 bytes, checksum: e10d2a85e80b762539d34e79807b36d4 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-05-04 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Over time, the human societies have developed and increased their capacity of spatially reorganize the elements of the environment that surrounds them. Thus, the human intervention has become one of the engaging agents of the landscape, along with the physical and biological processes. This means that human activities influence and accelerate the erosion processes. Specifically, laminar erosion is a form of manifestation of the hydric erosion that occurs silently, depleting the soil fertility, gradually, over time. For this reason, Bertoni and Lombardi Neto (2014) emphasize that this type of erosion is one of the most dangerous, especially in countries with tropical climates. From this, we aim to do a diagnosis of natural susceptibility and of laminar erosion potential in the basin of the Ribeirão of Boqueirão, in the municipality of Davinópolis (GO), in order to investigate how the current land use/ vegetal cover influence to increase, mitigate or neutralize the natural susceptibility to laminar erosion in this basin. The methodology was based predominantly on adapting of the proposal of Salomão (1999), which determined a correlation matrix between the slopes declivity and the soil erodibility, for generating cartographic document indicating the natural susceptibility to laminar erosion. When it was overlaid on the map of land use / vegetal cover, resulted in the current potential map to laminar erosion. In the basin of Ribeirão of Boqueirão, which in general has dissected topography, we observed a high percentage of areas with high natural susceptibility to laminar erosion, which imposes restrictions for agricultural activities. The areas with lower natural susceptibility to laminar erosion are near to the main watercourse, in the central part of this basin. With respect to land use / vegetal cover, overall, it was not verified adoption of conservation measures and/ or harmonization of human activities to natural limitations to laminar erosion. Thus, the class I, with high laminar erosion potential, was mapped in 37.72% of the watershed area and, in general, points to areas where the land use is incompatible with natural limitations. In the meantime, the class II (medium potential) appeared in 45.33% of the watershed area, in which case there is incompatibility between the land use and natural susceptibility, which can be solved with the use of conservation practices. In the rest of the watershed, 16.95%, there is class III (low potential). The data presented show the need for planning that seeks to conserve the soil of this watershed, which also is one of the largest basins, fully located in the municipality of Davinópolis (GO). One should highlight that the families of farmers, when exploring the lands of this watershed, ensure their socio-economic reproduction and contribute to the economic dynamics of the municipality of Davinópolis, which has the agricultural production as an important pillar. / As sociedades humanas ao longo do tempo desenvolveram e aumentaram a sua capacidade de reorganizar espacialmente os elementos do meio que as envolve. Dessa forma, a intervenção antrópica se tornou um dos agentes dinamizadores da paisagem, juntamente com os processos físicos e biológicos. Isso implica dizer que as atividades humanas influem e aceleram os processos de erosão. Especificamente, a erosão laminar é uma forma de manifestação da erosão hídrica que ocorre de forma silenciosa ao depauperar a fertilidade do solo, de forma gradativa, ao longo do tempo. Por esse motivo Bertoni e Lombardi Neto (2014) enfatizam que esse tipo de erosão é uma das formas mais perigosas, especialmente, nos países de clima tropical. A partir disso se propôs realizar o diagnóstico da suscetibilidade natural e do potencial à erosão laminar na bacia hidrográfica do Ribeirão do Boqueirão, no município de Davinópolis (GO), com a finalidade de constatar como o atual uso da terra/cobertura vegetal influi para aumentar, amenizar ou neutralizar a suscetibilidade natural à erosão laminar nessa bacia hidrográfica. A metodologia se baseou, de forma predominante, na adaptação da proposta de Salomão (1999), que determinou uma matriz de correlação entre a declividade das encostas e a erodibilidade dos solos para a geração de documento cartográfico que indica a suscetibilidade natural à erosão laminar, que por sua vez, ao ser sobreposto ao mapa de uso da terra/cobertura vegetal, resulta no mapa de potencial atual à erosão laminar. Na bacia hidrográfica do Ribeirão do Boqueirão, que apresenta, de forma geral, relevo dissecado, observou-se elevado percentual de áreas com alto grau de suscetibilidade natural à erosão laminar, o que impõe restrições às atividades agrícolas. As áreas com menor suscetibilidade natural à erosão laminar se encontram próximas ao curso hídrico principal, na parte central dessa Bacia Hidrográfica. Quanto ao uso da terra/cobertura vegetal, não se verificou, de forma geral, adoção de medidas conservacionistas e/ou harmonização das atividades antrópicas às limitações naturais à erosão laminar. Assim, a classe I, de alto potencial à erosão laminar, foi mapeada em 37,72% da área da bacia hidrográfica e de forma geral aponta para regiões onde o uso da terra é incompatível às limitações naturais. Enquanto isso, a classe II (médio potencial) apareceu em 45,33% da área da bacia hidrográfica, e nesse caso ainda há incompatibilidade entre o uso da terra e a suscetibilidade natural, passível de ser resolvida com a utilização de práticas conservacionistas. O restante da bacia hidrográfica, 16,95%, se encontra a classe III (baixo potencial). Esses dados expostos revelam a necessidade de um planejamento que busque conservar o solo dessa bacia hidrográfica, que inclusive é uma das maiores bacias, integralmente localizadas no município de Davinópolis (GO). Destaca-se, ainda, que as famílias de agricultores, ao explorar as terras dessa bacia hidrográfica, garantem sua reprodução socioeconômica, além de contribuírem para a dinâmica econômica do município de Davinópolis, que tem na produção agropecuária um importante pilar de sustentação.

Diversas aplicações industriais utilizam escoamentos de fluidos viscoelásticos, e em muitos casos é necessário saber se os escoamentos propagam-se no estado laminar ou no turbulento. Embora a hidrodinâmica de fluidos viscoelásticos seja fortemente afetada pelo balanço entre forças inerciais e elásticas no escoamento, o efeito da elasticidade sobre a estabilidade de escoamentos inerciais não foi completamente estabelecido. Neste trabalho, estuda-se o que ocorre durante a transição laminar-turbulenta, investigando a convecção de ondas de Tollmien-Schlichting para o escoamento incompressível, para um fluido viscoelástico, entre placas paralelas, utilizando a equação constitutiva Giesekus. Para isto, adotou-se a simulação numérica direta para verificar a estabilidade dos escoamentos à perturbações não estacionárias deste fluido. Experimentos computacionais para verificação do código foram realizados. Com os resultados numéricos obtidos, foi possível verificar e analizar a estabilidade de escoamentos utilizando-se o modelo não newtoniano Giesekus. / Several industrial applications use viscoelastic fluid flows, and it is necessary to know if the flows propagate in the laminar or turbulent state. Although the hydrodynamics of viscoelastic fluids is strongly affected by the balance between inertial and elastic forces in the flow, the effect of elasticity on the stability of inertial flows has not been completely established. In this work we study what happens during the laminar-turbulent transition, investigating the convection of Tollmien-Schlichting waves for the incompressible flow, for a viscoelastic fluid, between parallel plates, using the constitutive equation Giesekus. For this, the direct numerical simulation was used to verify the stability of the flows to the non-stationary perturbations of this fluid. Computational experiments to verify the code were performed. With the numerical results obtained, it was possible to verify and analyze the stability of flows modelled by Giesekus non-newtonian model.

This is an experimental and theoretical study of a laminar separation bubble and the associated transition dynamics in its early stages. The separation of a laminar boundary layer from a solid surface is prevalent in very many flow situations such as over gas turbine blades (especially in the low-pressure turbine stage) and the wings of micro-aero-vehicles (MAVs) that operate at fairly low Reynolds numbers. Flow separation occurs in such cases due to the presence of an adverse pressure gradient. The separated shear layer becomes unstable due to the presence of an inflection point and presumably transitions to turbulence rapidly. Eventually, there is reattachment back to the solid surface further downstream, if conditions are right. The region enclosed by the shear layer is called a laminar separation bubble and has been a subject of many studies in the past. The present experiments have been conducted in a closed-circuit wind tunnel. A separation bubble was obtained on the upper surface of a flat plate by appropriately contouring the top wall of the tunnel. Four different techniques were used for qualitative and quantitative study viz. surface flow visualisation, smoke flow visualisation, surface pressure measurements and hotwire anemometry. Response of the bubble to both natural as well as artificial (impulsive excitation) disturbance environment has been studied. Linear stability analyses (both Orr-Sommerfeld and Rayleigh calculations), in the spatial framework, have been performed for the mean velocity profiles starting from an attached adverse pressure gradient boundary layer all the way up to the front portion of the separation bubble region (i.e. up to the end of the dead-air region where linear evolution of disturbances could be expected). The measured velocity profiles (both attached and separated) were fitted with analytical model profiles for doing stability calculations. A separation bubble consists of aspects of both wall-bounded and wall-free shear layers and therefore both viscous and inviscid mechanisms are expected to be at play. Most of the studies in the literature point to the inviscid instability associated with the shear layer to be the main mechanism. The main aim of the present work is to understand the exact origin of the primary instability mechanism responsible for the amplification of disturbances. We argue that at least up to the front portion of the bubble, the instability mechanism is due to the inflectional mode associated with the mean velocity profile. However, the seeds of this inviscid inflectional instability could be traced back to the attached boundary layer upstream of separation. In other words, the inviscid inflectional instability of the separated shear layer should be logically seen as an extension of the instability of the upstream attached adverse-pressure-gradient boundary layer. This modifies the traditional view that pegs the origin of the instability in a separation bubble to the free shear layer outside the bubble with its associated Kelvin-Helmholtz mechanism. Our contention is that only when the separated shear layer has moved considerably away from the wall (and this happens near the maximum height of the mean bubble) that a description by Kelvin-Helmholtz instability paradigm with its associated scaling principles could become relevant. We also propose a new scaling for the most amplified frequency for a wall-bounded shear layer in terms of the inflection point height and the vorticity thickness, and show its universality. Next, we theoretically investigate the role played by the re-circulating region of the separation bubble in the linear instability regime. In the re-circulating region near the wall, associated with the so-called wall mode, the production of disturbance kinetic energy is found to be negative. This is a very interesting observation which has been cursorily noted in earlier studies. Here we show that the near-wall negative production region exerts a stabilising influence on the downstream travelling disturbances. A theoretical support for such a mechanism to exist close to the wall is presented. It is shown that the stabilising wall-proximity effect is not a peripheral aspect but has a significant effect on the overall stability especially for the waves close to the upper neutral branch. We demonstrate the appropriateness of inviscid analysis for the stability of the separated flow velocity profile away from the wall, by comparing the numerical solutions of Rayleigh and Orr-Sommerfeld equations. Following this, the analytical consequences of the Rayleigh equation such as the inflection point criterion and the Fjortoft criterion are derived for the wall-bounded inflectional velocity profiles. Furthermore, we also discuss the relevance of the negative production region towards flow control and management for the wall-bounded flows. It appears fruitful to divide the separation bubble region into two parts with respect to the nature of disturbance dynamics: one outside the mean dividing streamline (which behaves as an amplifier) and the other inside the bubble corresponding to the re-circulating region (having oscillator type characteristics). To explore the oscillator-like behaviour of the bubble further, we have carried out spatio-temporal stability analysis of the reversed flow velocity profiles and determined the conditions for the onset of absolute instability. We contend that the presence of the negative production region for the upstream travelling waves has a restraining effect arresting the tendency of the flow (both wall-free and wall-bounded) to become absolutely unstable and thereby requiring a particular threshold of the backflow velocity to be crossed for its realisation. Moreover, the delay in the onset of absolute instability for a wall-bounded profile as compared to a free shear layer is attributed to a certain ‘negative-drag’ effect of the wall on the overall flow which increases the group velocities for the wall-bounded flows. A related theme in the literature regarding the dynamics of laminar separation bubbles is the so-called ‘bursting’ of the bubble wherein there is a sudden increase in the length and height of the bubble as some critical conditions are reached. Bubbles before bursting are termed as ‘short’ bubbles and those after bursting as ‘long’ bubbles. In this work, we provide a criterion to predict bursting which is a refinement over the existing criteria. The proposed criterion takes into account not just the length of the bubble but also the maximum height and it is shown to be more universal in differentiating short bubbles from the long ones, as compared to the other criteria. We also present a hypothesis regarding the sequence of events leading to bubble bursting by relating its onset to the instability of the re-circulating region. For this we observe that as the amount of backflow velocity is increased for a reversed flow velocity profile, the inflection point moves inside the mean dividing streamline and this happens before the onset of absolute instability. This causes a vorticity maximum to develop inside the re-circulating region which could lead to the instability of the closed streamlines with respect to two-dimensional cylindrical disturbances. The actual bursting process may be expected to involve non-linear interactions of the disturbances and the long bubble could be a nonlinearly saturated state of the instability of the re-circulating region. In order to explore the three-dimensionality associated with the bubble, extensive surface flow visualisation experiments have been performed. The surface streamline pattern is obtained for the entire span of the plate for three different freestream velocities. The patterns have been interpreted using topological ideas and various critical points have been identified. It is shown that the arrangement of critical points satisfies the ‘index theorem’ which is a topological necessity and the streamline patterns are ‘structurally stable’. An interesting observation from these patterns is the presence of three-dimensionality upstream of the separation line close to the wall even though the oncoming flow is nominally two-dimensional. Using the critical point theory, we propose a hypothesis which could be used to construct a semi-empirical model wherein the critical points are assigned with a quantity called ‘strength’ for determining the extent of upstream influence of a given separation line. Finally, we derive a necessary condition for the existence of inviscid spatial instability in plane parallel flows. It states that for spatial instability the curvature of the velocity profile should be positive in some region of the profile. This includes Rayleigh’s inflection point theorem (which was proposed and proved by Rayleigh for temporal instability) as a special case. It thus provides a rigorous basis for applying the inflection point criterion to the flows in the framework of spatial stability theory (which we have used extensively in the present thesis). Moreover, the condition derived here is more general as it also includes velocity profiles with the curvature positive everywhere which are excluded by Rayleigh’s theorem in the temporal framework. An example of such a profile is presented (Couette-Poiseuille flow with adverse pressure gradient) and it is shown that this flow is an exceptional case which is temporally stable but spatially unstable. Eigenvalue calculations as well as energy considerations suggest that the mechanism governing instability of this flow is inviscid and non-inflectional in character. This is a new result which could have important implications in understanding the instability dynamics of parallel flows.

Submitted by Laison Junio da Silva Furlan (laisonfurlan@gmail.com) on 2018-09-11T21:45:47Z No. of bitstreams: 1 dissertacao_final.pdf: 2611301 bytes, checksum: b4c51f4e16b1f3e612c4d3a044c777c5 (MD5) / Approved for entry into archive by Claudia Adriana Spindola null (claudia@fct.unesp.br) on 2018-09-12T11:25:26Z (GMT) No. of bitstreams: 1 furlan_ljs_me_prud.pdf: 2445202 bytes, checksum: 1f1f2699158710f217b33ed602d0f51e (MD5) / Approved for entry into archive by Claudia Adriana Spindola null (claudia@fct.unesp.br) on 2018-09-12T11:36:28Z (GMT) No. of bitstreams: 1 furlan_ljs_me_prud.pdf: 2445202 bytes, checksum: 1f1f2699158710f217b33ed602d0f51e (MD5) / Made available in DSpace on 2018-09-12T11:36:28Z (GMT). No. of bitstreams: 1 furlan_ljs_me_prud.pdf: 2445202 bytes, checksum: 1f1f2699158710f217b33ed602d0f51e (MD5) Previous issue date: 2018-08-02 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O presente trabalho investiga a transição laminar-turbulenta devido a ondas de Tollmien-Schlichting para o escoamento de Poiseuille incompressível, bidimensional, de um fluido viscoelástico, utilizando a equação constitutiva Giesekus. A Teoria de Estabilidade Linear e a Simulação Numérica Direta são utilizadas para verificar a estabilidade de escoamentos de fluidos viscoelásticos a perturbações não estacionárias. Na análise LST a equação de Orr-Sommerfeld é modificada para um fluido viscoelástico e resolvida pelo método da estimativa (Shooting). Enquanto que, na formulação DNS, as equações de Navier-Stokes, juntamente com a equação constitutiva Giesekus, são resolvidas utilizando métodos de diferenças finitas compactas de alta ordem. Com o objetivo de avaliar as curvas neutras de estabilidade e as taxas de amplificação, diferentes simulações numéricas são realizadas variando-se os parâmetros adimensionais no modelo Giesekus e comparando com o fluido Newtoniano. As técnicas LST e DNS mostraram-se ferramentas eficientes na análise espacial da estabilidade de escoamentos viscoelásticos do tipo Giesekus, permitindo uma melhor compreensão da influência dos parâmetros adimensionais desses escoamentos e contribuindo com resultados originais na verificação da estabilidade de escoamentos viscoelásticos utilizando o fluido Giesekus. / The present work investigates the laminar-turbulent transition due to Tollmien-Schlichting waves for the incompressible two-dimensional Poiseuille flow of a viscoelastic fluid, using the Giesekus constitutive equation. Linear Stability Theory and Direct Numerical Simulation are used to verify the stability of viscoelastic fluid flows to unsteady disturbances. In the LST analysis, the Orr-Sommerfeld equation is modified to a viscoelastic fluid and solved by Shooting method. Whereas, in the DNS formulation, the Navier-Stokes equations with the Giesekus constitutive equation are solved using high-order compact finite difference methods. In order to evaluate the neutral stability curves and the amplification rates, different numerical simulations are performed by varying the dimensionless parameters in the Giesekus model and their results are compared with the Newtonian fluid. The LST and DNS techniques proved to be efficient tools to the spatial stability analysis of viscoelastic fluid flows of the Giesekus type, allowing a better comprehension of the dimensionless parameters influence of those flows, contributing with originals results to verification of the viscoelastics fluid flows stability using Giesekus fluid. / FAPESP: 2017/11068-6

[pt] O presente trabalho consiste no projeto, construção e qualificação de um aparato para o estudo experimental de bolhas de separação laminar sobre uma placa plana. A previsão do comportamento das bolhas de separação é importante para o projeto de aeronaves, turbinas e geradores eólicos, pois o desprendimento dessas bolhas tem grande impacto na performance de aerofólios. A dinâmica das bolhas não é bem compreendida, além de ser difícil de ser capturada por simulações numéricas que utilizam modelagem da turbulência. Por isso, ensaios experimentais são muito utilizados para a calibração dos modelos utilizados em simulações de engenharia. Neste trabalho, foram criados equipamentos para simular experimentalmente bolhas de separação laminar sobre uma placa plana. Os dispositivos foram projetados para o canal de água do Laboratório de Engenharia de Fluidos da PUC-Rio. O gradiente de pressão necessário para induzir a separação da camada limite e consequente formação da bolha foi ajustado com uma parede falsa, de modo a criar um canal convergente-divergente com a placa plana. Foi projetado um mecanismo de sucção da camada limite na parede falsa para evitar a separação do escoamento nessa superfície. A localização e as vazões de cada ponto de sução foram determinadas com o auxílio de simulações numéricas. Também foi projetado e testado um sistema de sopro e sucção para a excitação de ondas de instabilidade do tipo Tollmien-Schlichting na camada limite da placa plana. O funcionamento de cada dispositivo foi avaliado através da medição da velocidade do escoamento. Para isso, foram empregadas técnicas de medição por velocimetría laser doppler e velocimetría por imagem de partículas. Os resultados obtidos validam o projeto e qualificam o aparato para o estudo de bolhas de separação laminar. / [en] The present work involves the design, construction and performance test of an apparatus for the investigation of laminar separation bubbles in a flat plate boundary layer. Laminar separation bubbles are relevant for many engineering applications and the dynamic of such bubbles has a strong impact on the performance of aircrafts and turbines. The separated boundary layer reattaches to the surface due to the laminar-turbulent transition in the bubble region. This dynamic process is highly challenging for flow simulation tools used for engineering purposes. Thus, there is a demand for experimental studies that can be used for calibration of models present in those simulation tools. To this end, an apparatus was designed and built for the water channel of the Laboratory of Fluid Engineering at PUC-Rio. The boundary layer separation on the flat plate was induced by imposing a constant adverse pressure gradient to the flow. To this end a false wall was built, in order to form a converging-diverging channel with the flat plate. Flow separation on the false wall was avoided using a suction mechanism that was designed to reduce locally the boundary layer thickness. Location of suction and suction flow rates were determined with aid of numerical simulations. In addition, it was designed and built a disturbance source to generate Tollmien-Schlichting waves in the boundary layer of the flat plate. This device was used to trigger the boundary layer transition in a controlled manner. All equipment were tested and their designs were validated against experimental measurements. Laser Doppler anemometry and Particle Image Velocimetry techniques were adopted for assessment of each equipment. Results validate the design and show that separation bubbles can be investigated in detail using this apparatus.

Submitted by Ellen Silva Gervazoni null (emillen_@hotmail.com) on 2016-08-25T17:45:32Z No. of bitstreams: 1 Disserataçaofinal_EllenGervazoni.pdf: 1426674 bytes, checksum: 25ce3b189028e33485b050b9f7676a94 (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-08-29T19:17:40Z (GMT) No. of bitstreams: 1 gervazoni_es_me_prud.pdf: 1426674 bytes, checksum: 25ce3b189028e33485b050b9f7676a94 (MD5) / Made available in DSpace on 2016-08-29T19:17:40Z (GMT). No. of bitstreams: 1 gervazoni_es_me_prud.pdf: 1426674 bytes, checksum: 25ce3b189028e33485b050b9f7676a94 (MD5) Previous issue date: 2016-06-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Diversos escoamentos de interesse prático são de fluidos viscoelásticos e muitas vezes é desejável saber se estes escoamentos propagam-se no estado laminar ou no turbulento. Embora a hidrodinâmica de fluidos viscoelásticos sejam fortemente afetadas pelo balanço entre forças inerciais e elásticas no escoamento, o efeito da elasticidade sobre a estabilidade de escoamentos inerciais não foi completamente estabelecida. No presente trabalho, estuda-se o que ocorre entre estes dois estados, na transição laminar-turbulenta. Especi- ficamente, é investigada a convecção de ondas de Tollmien-Schlichting para o escoamento incompressível de Poiseuille para um fluido viscoelástico, utilizando a equação constitutiva Oldroyd-B. Para isto, utiliza-se a Simulação Numérica Direta para verificar a estabilidade dos escoamentos de fluidos viscoelásticos a perturbações não estacionárias. Os resultados numéricos obtidos para escoamentos de fluidos viscoelásticos são comparados com os resultados de escoamentos de fluidos Newtonianos, que já estão bem documentados na comunidade científica. Além disso, uma equação de Orr-Sommerfeld modificada é deduzida para um escoamento viscoelástico utilizando a Teoria de Estabilidade Linear. / Several flows of practical interest are of viscoelastic fluids and it is often desirable to know if these flows are in a laminar or turbulent state. Although the hydrodynamics of viscoelastic fluids are strongly affected by the balance between inertia and elastic forces in the flow, the effect of elasticity on the stability of inertial flows has not been completely established. In this work is studied what happens between these two states, the laminar-turbulent transition. Specifically, it will be investigated the convection of Tollmien-Schlichting waves to incompressible Poiseuille flow of viscoelastic fluid, using the constitutive equation Oldroyd-B. For this, the analysis is carried out by means of Direct Numerical Simulation to verify the stability of the non-stationary disturbances viscoelastic fluids flows. The numerical results obtained for viscoelastic fluids flows are compared with the results of Newtonian fluids flows, which are already well documented in scientific community. In addition, an Orr-Sommerfeld modified equation is deducted for a viscoelastic flow using Linear Stability Theory.

Durante o processo de perfuração de poços de óleo e gás, em geral a passagem e oscilações da broca de perfuração provoca a ovalização das paredes do poço. O presente trabalho apresenta um estudo analítico e numérico do escoamento de fluido viscoplástico tipo Herschel-Bulkley através de três configurações de tubos de seções transversais elípticas: tubo elíptico, elíptico anular concêntrico e excêntrico. O objetivo desse estudo é analisar o efeito dos parâmetros geométricos do tubo, cinemáticos do escoamento e reológicos do fluido na perda de carga. A modelagem matemática foi realizada com base nas equações de balanço de massa e de quantidade de movimento e uma equação constitutiva para o tensor tensão do fluido. Para a solução analítica são utilizados os métodos de transformação de coordenadas e da folga variável modelando o escoamento como entre placas paralelas. Para a solução numérica é empregado o método de volumes finitos. As simulações numéricas são realizadas com o programa comercial PHOENICS-CFD. Para validar os resultados, são realizadas comparações com a literatura. Para cada geometria investigada foram obtidos os parâmetros de interesse na engenharia como: perfil de velocidade, vazão volumétrica, perfil das tensões e expressão para o fator de atrito. Os resultados para o duto anular circular concêntrico e excêntrico são corretamente reproduzidos quando a seção anular elíptica tende para a razão de aspecto unitária. / During the oil well drilling operations, the oscillations and the advancement of the drill makes the well takes an oval shape. This work presents an analytical and numerical study of the viscoplastic fluid flow of a Herschel-Bulkley fluid, through three types of elliptical cross sections ducts: elliptical, concentric and eccentric elliptical annulus. The objective is to analyze the effects of the pipe geometrical parameters, the kinematics of the flow and the fluid rheology over the pressure drop. The mathematical model was based on the mass and momentum balance equations and a constitutive equation expressing the stress tensor of the fluid. The analytical solutions employed were an analytical transformation of coordinates and other one based on in the slot flow model and the fluid flow was modeled as parallel plates in narrow annuli. For the numerical solution of the balance equations the finite volume method was used. The numerical simulations were carried out with PHOENICS-CFD. For validation of the results, comparisons with numerical and analytical results available in literature were done. Relevant engineering parameters were obtained, like velocity profiles, volumetric flow rate, shear stress profiles and an expression for the friction factor. The results for the concentric and eccentric circular annulus are adequately reproduced when the elliptical cross section tends towards unitary aspect ratio.

Durante o processo de perfuração de poços de óleo e gás, em geral a passagem e oscilações da broca de perfuração provoca a ovalização das paredes do poço. O presente trabalho apresenta um estudo analítico e numérico do escoamento de fluido viscoplástico tipo Herschel-Bulkley através de três configurações de tubos de seções transversais elípticas: tubo elíptico, elíptico anular concêntrico e excêntrico. O objetivo desse estudo é analisar o efeito dos parâmetros geométricos do tubo, cinemáticos do escoamento e reológicos do fluido na perda de carga. A modelagem matemática foi realizada com base nas equações de balanço de massa e de quantidade de movimento e uma equação constitutiva para o tensor tensão do fluido. Para a solução analítica são utilizados os métodos de transformação de coordenadas e da folga variável modelando o escoamento como entre placas paralelas. Para a solução numérica é empregado o método de volumes finitos. As simulações numéricas são realizadas com o programa comercial PHOENICS-CFD. Para validar os resultados, são realizadas comparações com a literatura. Para cada geometria investigada foram obtidos os parâmetros de interesse na engenharia como: perfil de velocidade, vazão volumétrica, perfil das tensões e expressão para o fator de atrito. Os resultados para o duto anular circular concêntrico e excêntrico são corretamente reproduzidos quando a seção anular elíptica tende para a razão de aspecto unitária. / During the oil well drilling operations, the oscillations and the advancement of the drill makes the well takes an oval shape. This work presents an analytical and numerical study of the viscoplastic fluid flow of a Herschel-Bulkley fluid, through three types of elliptical cross sections ducts: elliptical, concentric and eccentric elliptical annulus. The objective is to analyze the effects of the pipe geometrical parameters, the kinematics of the flow and the fluid rheology over the pressure drop. The mathematical model was based on the mass and momentum balance equations and a constitutive equation expressing the stress tensor of the fluid. The analytical solutions employed were an analytical transformation of coordinates and other one based on in the slot flow model and the fluid flow was modeled as parallel plates in narrow annuli. For the numerical solution of the balance equations the finite volume method was used. The numerical simulations were carried out with PHOENICS-CFD. For validation of the results, comparisons with numerical and analytical results available in literature were done. Relevant engineering parameters were obtained, like velocity profiles, volumetric flow rate, shear stress profiles and an expression for the friction factor. The results for the concentric and eccentric circular annulus are adequately reproduced when the elliptical cross section tends towards unitary aspect ratio.

Made available in DSpace on 2014-07-29T15:31:59Z (GMT). No. of bitstreams: 1 Dissertacao jose carlos de souza 2010.pdf: 4705890 bytes, checksum: 408747eceeb0ba0dbbc341572b418d4b (MD5) Previous issue date: 2010-03-05 / The watershed has been designed as units of planning and environmental management. Areas are easily definable and have the systemic character, where the elements of the landscape, been natural or man-made, are interrelated continually, outbreak changes of energy and matter. In the function of this character the basins are presented as an ideal units for the application of methodologies that aim contribute to the planning of the land use. The purpose of this paper is present the results of the evaluation of potential laminar erosion in the basin of Ribeirão Sozinha, in the Estado de Goiás, through the integrated analyses of the physical means and the application of the prediction model. The methodology was elaborate by Salomão (1999), is an approach with qualitative and aims specialize the fragilities of the soil to the slat erosion in the basin. The basin of the ribeirão Sozinha, has approximately 430 km2, in the lands of the municipality of Leopoldo de Bulhões, Anápolis, Goianápolis, Bonfinópolis, Goiânia, Senador Canedo, Caldazinha and Bela Vista de Goiás. The geology of the basin are composed for ortho and paraderivados granulites and the granitoids of the complex granulites Anápolis-Itauçu and metasedimentary rocks of the group Araxá Sul de Goiás. The geomorphology is characterized by regional surfaces of planning of units Goiano central plateau and plateau chastened of Goiânia. The basin is on the biome Cerrado, and the remain are found in the area there are the physiognomies of Mata Ciliar, Mata Seca, Cerradão, Cerrado sentido restrito e Campo Sujo. Were definite to the basin four class of soil erodibility, High, for the Inceptisols and Entisols; Medium for the Ultisols, Red Yellow Red and Red Oxisol with a medium texture sandy, Low, for the Oxisol of medium texture and clay Plinthosols Petric, and None, for Gelisols. The basin was spatialized in six class of the slope (0% 3%), (3,1% 8%), (8,1% 12%), (12,1% 20%), (20,1% 45) e ( > 45%). With the crossing of the class of erodibility with the slope, we found five class of susceptibility to erosion, that we present on the basin as a percent: Class I Extremely susceptibly (12,87%); Class II Much susceptibly (35,32%); Class III Moderately susceptibly (27,63%); Class IV a little susceptibly (23,92%) and Class V a little to none susceptibly (0,26%). The class to the susceptibility to the erosion was crossing with the class of land use (Agriculture, Pasture, Vegetation and Urban Areas) was obtain three class of the potential to the slat erosion on the Ribeirão Sozinha, high potential 29,84%, of the area of basin, incompatible uses, medium potential (55,74%), incompatible uses, with the possibility of interventions with conservation practice, low potential (14,04%) with compatible use. The area of this study composed the part east of the Goiânia, and is a dynamic area, with different uses, and accordingly this, need for implementation of tools that enable use planning and land use in order to reduce the land degradation by extensive slat erosion. / As bacias hidrográficas têm sido concebidas como unidades de planejamento e gestão socioambiental. São áreas facilmente delimitáveis e possuem uma característica sistêmica, onde os elementos da paisagem sejam eles naturais ou antrópicos, se inter-relacionam continuamente, deflagrando trocas de matéria e energia. Em função dessas características, as bacias se apresentam como unidades ideais para a aplicação de metodologias que visam contribuir para o planejamento de uso do e ocupação da terra. A proposta deste trabalho é apresentar os resultados da avaliação do potencial a erosão laminar na bacia do Ribeirão Sozinha, no Estado de Goiás, através da análise integrada do meio físico e da aplicação de modelo de previsão. A metodologia utilizada foi elaborada e apresentada por Salomão (1999), é uma abordagem de cunho qualitativo e visa especializar as fragilidades do solo a erosão laminar em uma bacia hidrográfica. A bacia do ribeirão Sozinha possui aproximadamente 430 km², abrangendo terras dos municípios de Leopoldo de Bulhões, Anápolis, Goianápolis, Bonfinópolis, Goiânia, Senador Canedo, Caldazinha e Bela Vista de Goiás. A geologia da bacia é composta pelos granulitos orto e paraderivados e ranitóides do Complexo Granulítico Anápolis-Itaúçu e rochas metassedimentares do Grupo Araxá Sul de Goiás. A geomorfologia é caracterizada por Superfícies Regionais de Aplainamento das unidades Planalto Central Goiano e Planalto Rebaixado de Goiânia. A bacia esta inserida nos domínios do bioma Cerrado, e os remanescentes encontrados na área se enquadram nas fisionomias Mata de Galeria, Mata Ciliar, Mata Seca, Cerradão, Cerrado sentido restrito e Campo Sujo. Foram definidas para a bacia quatro classes de erodibilidade do solo, Alta, para os Cambissolos e Neossolos Litolicos; Média, para os Argissolos Vermelho, Vermelho-Amarelo e Latossolos Vermelho de textura arenosa/média; Baixa, para os Latossolos Vermelho de textura média e argilosa e Plintossolos Pétricos; e Nula, para os Gleissolos. A bacia foi espacializada em seis classes de declividades (0% 3%), (3,1% 8%), (8,1% 12%), (12,1% 20%), (20,1% 45) e ( > 45%). Com o cruzamento das classes de erodibilidade com as de declividades, obteve-se cinco classes de suscetibilidade a erosão, que ficaram apresentadas na bacia nas seguintes porcentagens: Classe I Extremante suscetível (12,87%); Classe II Muito suscetível (35,32%); Classe III Moderadamente suscetível (27,63%); Classe IV Pouco suscetível (23,92%) e Classe V Pouco a não suscetível (0,26%). As classes de suscetibilidade a erosão foram cruzadas às classes de uso da terra (Agricultura, Pastagem, Vegetação e Área Urbana) e obteve-se três classes de potencial atual a erosão laminar na bacia do Ribeirão Sozinha, a saber: alto potencial, 29,84% da área da bacia, uso incompatível; médio potencial (55,74%), uso incompatível, com possibilidade de intervenções com práticas conservacionistas; baixo potencial (14,04%) com uso compatível ao recomendado. A área de estudo, compõe a parte leste da região metropolitana de Goiânia e se configura como uma área dinâmica, de múltiplos usos, e em função disso a necessidade da aplicação de instrumentos que viabilizem o planejamento de uso e ocupação da terra com vistas a se reduzir a degradação do solo por erosão laminar.