Escoamentos bifásicos estão presentes em diversos processos naturais e industriais, como na indústria de petróleo. Podem apresentar-se em diferentes configurações topológicas, ou, padrões de escoamento, entre eles o escoamento estratificado ondulado e o estratificado com mistura na interface. Os escoamentos bifásicos estratificados óleo-água têm sido utilizados como uma forma conveniente de evitar a formação de emulsões de água em óleo em oleodutos e possuem uma ocorrência comum em poços de petróleo direcionais. Quando a onda interfacial ultrapassa determinado limite geométrico e cinemático, surge o fenômeno do entranhamento de gotas, representado por misturas entre as fases junto à interface que promovem um aumento na queda de pressão. Modelos têm sido apresentados pela literatura na tentativa de descrever o fenômeno do entranhamento de gotas. Neste trabalho é apresentada uma nova proposta de modelagem matemática unidimensional para o entranhamento de gotas com o objetivo de melhorar a previsão dos parâmetros envolvidos, em especial, da fração volumétrica de óleo e da queda de pressão bifásica. Também foi utilizada simulação numérica computacional, CFD (Computational Fluid Dynamics), com o uso de software comercial para obtenção dos valores dos parâmetros do escoamento estratificado ondulado óleo-água (fração volumétrica de óleo, queda de pressão, amplitude e comprimento da onda interfacial). Os resultados da modelagem fenomenológica para entranhamento e os de CFD foram comparados com bancos de dados experimentais. Os resultados em CFD mostram concordância com os resultados experimentais, tanto na análise qualitativa das propriedades geométricas das ondas interfaciais, quanto na comparação direta com os dados para fração volumétrica e queda de pressão. Os resultados numéricos da modelagem fenomenológica para fatores de entranhamento apresentam boa concordância com dados da literatura. / Two-phase flows are present in many natural and industrial processes, such as in the oil industry. They may be found arranged in several flow patterns, including the wavy stratified flow and the stratified with mixing at the interface. The stratified oil-water flow has been used as a convenient way to avoid the formation of emulsions of water in oil and have a common occurrence in directional oil wells. When the interfacial wave exceeds a certain geometric and kinematic limit the phenomenon of drop entrainment arises at the interface, causing an increase of pressure drop. Models have been presented in the literature in an attempt to describe the phenomenon of drop entrainment. In this work, we present a new method for the one-dimensional mathematical modeling of entrainment in order to improve the prediction of oil volume fraction and pressure drop. It was also used a commercial computational fluid dynamics tool (CFD) to obtain the values of flow parameters of wavy stratified oil-water flow, such as oil volume fraction, pressure drop, amplitude and length of the interfacial waves. The results of the phenomenological modeling for entrainment and CFD were compared with experimental databases. The CFD results are in agreement with the experimental results in both the qualitative analysis of the geometric properties of the interfacial waves and in direct comparison with oil-volumetric-fraction and pressure-drop data. The numerical results of the phenomenological model for entrainment factors are in agreement with data from the literature.

Neste trabalho estudou-se o comportamento reológico e morfológico da mistura polimérica imiscível de polipropileno e poliamida. Como resultado deste estudo obtiveram-se valores de tensão interfacial entre 10mN/m e 13mN/m. A tensão interfacial diminuiu em até 87% quando a mistura é compatibilizada com polipropileno maleado. A análise morfológica no regime de viscoelasticidade linear quando avaliada uma morfologia de emulsão de poliamida em polipropileno revelou diâmetro médio da fase dispersa entre 1,5µm e 20µm. O diâmetro das gotas da fase dispersa diminuiu com a adição de polipropileno maleado chegando a reduções de até 98%, mantendo-se constante a concentração da fase dispersa. No regime de viscoelasticidade não linear foram testados modelos para avaliar o comportamento da mistura em fluxos de cisalhamento e extensão, sendo que somente para os fluxos de extensão foi obtida boa correlação dos resultados experimentais com as previsões teóricas. / Rheological and morphological behaviour of polypropylene and polyamide polymer blend was studied. The values of interfacial tension were obtained between 10mN/m and 13mN/m. The interfacial tension decreased in 87% for compatibilized blend. Morphology analysis for linear viscoelastic regime shows dispersed drop diameter between 1,5µm and 20µm. The diameter of the drops decreased with the addition of maleic polypropylene reducing until 98%, keeping constant the concentration of the disperse phase. In non linear viscoelastic regime different models were tested to evaluate the behavior of the blends in shear and elongacional flows. However, only the elongacional flow results were acquired with theoretical - experimental corroboration.

[pt] O atual esgotamento de campos de petróleo tradicionais tem aumentado a demanda pela produção e transporte óleos não convencionais, que podem possuir uma alta viscosidade dinâmica. Neste contexto, o estudo do escoamento simultâneo de gás e óleos viscosos em tubulações é de grande importância para a indústria de Óleo e Gás. Simulações numéricas uni-dimensionais desempenham um papel essencial nestes estudos, especialmente aquelas baseadas no Modelos de Dois-Fluidos 1D, cuja solução numérica em malhas refinadas consiste na Metodologia de Captura de Regimes. O propósito deste trabalho é utilizar esta abordagem para reproduzir dados experimentais de escoamentos óleo viscoso-gás em golfadas e estratificado ondulado em um duto horizontal em escala laboratorial. Para aprimorar os resultados desta metodologia, dados experimentais foram usados conjuntamente com um procedimento de otimização e uma versão simplificada do Modelos de Dois-Fluidos 1D para criar duas novas expressões para o fator de atrito interfacial, as quais mostraram maior eficiência que correlações padrão da literatura. O efeito da introdução da pressão dinâmica, difusão axial de quantidade de movimento e tensão interfacial dinâmica no Modelo de Dois-Fluidos 1D foi analisado. Resultados de gradiente de pressão e de fração volumétrica de líquido (histogramas, valores médios e perfis transientes) foram comparados com dados experimentais. Observou-se, com o auxílio de análises de boa-colocação, que a pressão dinâmica e as novas expressões para o fator de atrito interfacial fornecem resultados satisfatórios. / [en] The current depletion of traditional oil fields is increasing the demand for the production and transport of unconventional oils, which might possess a high dynamic viscosity. In this context, the study of the simultaneous flow of gas and viscous oils in pipelines is of paramount importance for the Oil and Gas industry. One-dimensional numerical simulations play a key role in such studies, especially the ones based on the 1D Two-Fluid Model, whose numerical solution in fine meshes consists in the Regime Capturing Methodology. The purpose of this work is to use this approach for reproducing the experimental data of isothermal slug and stratified wavy viscous oil-gas flows in a horizontal laboratory-scale pipe. For improving the results of the methodology, experimental data were used together with an optimization procedure and a simplified version of the 1D Two-Fluid Model for successfully creating two new expressions for the interfacial friction factor, which showed better efficiency than standard literature correlations. The effect of introducing a dynamic pressure, axial momentum diffusion and dynamic interfacial shear in the 1D Two-Fluid Model was examined. Results of pressure gradient and liquid holdup (histograms, mean values and transient profiles) were compared against experimental data. It was seen, with the aid of well-posedness analyses, that the dynamic pressure and the new expressions for the interfacial shear stress provided satisfactory results.

Made available in DSpace on 2014-12-17T14:13:33Z (GMT). No. of bitstreams: 1 ElquioEO_TESE.pdf: 1649953 bytes, checksum: 1098cd34b1d3e6c9a180949d25fa8185 (MD5) Previous issue date: 2010-06-07 / Universidade Federal do Rio Grande do Norte / The aim of this work was to perform the extraction and characterization of xylan from corn cobs and prepare xylan-based microcapsules. For that purpose, an alkaline extraction of xylan was carried out followed by the polymer characterization regarding its technological properties, such as angle of repose, Hausner factor, density, compressibility and compactability. Also, a low-cost and rapid analytical procedure to identify xylan by means of infrared spectroscopy was studied. Xylan was characterized as a yellowish fine powder with low density and poor flow properties. After the extraction and characterization of the polymer, xylan-based microcapsules were prepared by means of interfacial crosslinking polymerization and their characterization was performed in order to obtain gastroresistant multiparticulate systems. This work involved the most suitable parameters of the preparation of microcapsules as well as the study of the process, scale-up methodology and biological analysis. Magnetic nanoparticles were used as a model system to be encapsulated by the xylan microcapsules. According to the results, xylan-based microcapsules were shown to be resistant to several conditions found along the gastrointestinal tract and they were able to avoid the early degradation of the magnetic nanoparticles / O presente trabalho teve como objetivo a extra??o e caracteriza??o do pol?mero de xilana a partir de res?duos de sabugo de milho e a produ??o de microc?psulas a partir deste pol?mero. O primeiro passo foi a extra??o da xilana em meio alcalino e caracteriza??o deste pol?mero quanto as suas propriedades tecnol?gicas (?ngulo de repouso, fator de Hausner, densidade, compressibilidade e compactabilidade), bem como a elabora??o de uma procedimento r?pido e barato para a identifica??o deste pol?mero atrav?s de espectroscopia de absor??o na regi?o do infravermelho. O pol?mero de xilana foi caracterizado como sendo um p? de cor amarelada de baixa densidade e com propriedades de escoamento pouco favor?veis. Ap?s a obten??o e caracteriza??o do pol?mero, microc?psulas de xilana foram preparadas atrav?s da reticula??o polim?rica interfacial e caracterizadas a fim de se obter sistemas multiparticulados gastroresistentes. O trabalho foi delineado buscando-se os melhores fatores na t?cnica de prepara??o das microc?psulas, assim como o estudo do processo, aumento de escala e avalia??o biol?gica. Nanopart?culas magn?ticas foram utilizadas como sistema modelo a ser encapsulado pelas microc?psulas ? base de xilana. Os resultados obtidos demonstraram que as microc?psulas de xilana s?o resistentes ?s diversas condi??es encontradas ao longo do trato gastrintestinal e foram capazes de evitar a degrada??o pr?via das nanopart?culas magn?ticas in vitro

O interesse na utilização de fibras naturais com matrizes poliméricas para a preparação de compósitos espalhou-se rapidamente ao longo dos últimos anos. No entanto, a adesão interfacial entre a fibra e a matriz tem ainda de ser aperfeiçoada. Para melhorar a adesão entre os constituintes e, consequentemente as propriedades mecânicas e térmicas dos materiais, duas abordagens foram investigadas: a irradiação por feixe de elétrons e a mercerização. Este trabalho descreve a fabricação e caracterização de biocompósitos de polietileno de alta densidade e fibra do ouriço da castanha do Brasil que foram preparadas por duas metodologias diferentes: a primeira foi irradiar o compósito com 150 kGy e a segunda foi irradiar a matriz com 15 kGy e então produzir o compósito. Para ambas as metodologias foram utilizadas fibras naturais mercerizadas e não mercerizadas. O efeito dos tratamentos estudados para melhorar a adesão entre a fibra e a matriz polimérica foi avaliado através de caracterizações mecânica, química, térmica e morfológica. Com base neste estudo, observou-se que a fibra do ouriço da castanha do Brasil é um material tecnicamente viável para uso como reforço em compósitos poliméricos. Observou-se que o processo de irradiação da matriz seguida da produção dos compósitos é um método eficaz para melhorar as propriedades térmicas e mecânicas dos compósitos biopoliméricos e que, quando comparado com o processo de mercerização, esse método pode ser considerado mais ambientalmente correto (sem produtos químicos e sem geração de resíduo), mais barato e mais simples. / The interest in the use of natural fibres with polymeric matrix for the preparation of composite spread rapidly over the last years. However, the interfacial adhesion between the fiber and the matrix has to be improved. To improve the adhesion between the constituents and consequently the mechanical and thermal properties of materials, two approaches were investigated: electron beam irradiation and mercerization. This paper describes the fabrication and characterization of biocomposites compounds with high density polyethylene and fibre from Brazil nut pod that were prepared by two different methods: the first irradiating the composite with 150 kGy and the second was radiating matrix with 15 kGy and then produce the composite. For both methodologies, natural fibers, mercerized and non-mercerized were used. The effect of the treatments to improve adhesion between the fiber and the polymer matrix was evaluated through mechanical, chemical, thermal and morphology charcterization. Based on this study, it was observed that fibre from Brazil nut pod is a technically viable material for use as reinforcement in polymer composites. It was observed that the process of matrix irradiation followed by the composite fabrication is an effective method for improving the thermal and mechanical properties of the composites, when compared with mercerization process, this method can be considered more environmentally friendly (no chemicals, and without generating waste), cheaper and simpler.

Escoamentos bifásicos estão presentes em diversos processos naturais e industriais, como na indústria de petróleo. Podem apresentar-se em diferentes configurações topológicas, ou, padrões de escoamento, entre eles o escoamento estratificado ondulado e o estratificado com mistura na interface. Os escoamentos bifásicos estratificados óleo-água têm sido utilizados como uma forma conveniente de evitar a formação de emulsões de água em óleo em oleodutos e possuem uma ocorrência comum em poços de petróleo direcionais. Quando a onda interfacial ultrapassa determinado limite geométrico e cinemático, surge o fenômeno do entranhamento de gotas, representado por misturas entre as fases junto à interface que promovem um aumento na queda de pressão. Modelos têm sido apresentados pela literatura na tentativa de descrever o fenômeno do entranhamento de gotas. Neste trabalho é apresentada uma nova proposta de modelagem matemática unidimensional para o entranhamento de gotas com o objetivo de melhorar a previsão dos parâmetros envolvidos, em especial, da fração volumétrica de óleo e da queda de pressão bifásica. Também foi utilizada simulação numérica computacional, CFD (Computational Fluid Dynamics), com o uso de software comercial para obtenção dos valores dos parâmetros do escoamento estratificado ondulado óleo-água (fração volumétrica de óleo, queda de pressão, amplitude e comprimento da onda interfacial). Os resultados da modelagem fenomenológica para entranhamento e os de CFD foram comparados com bancos de dados experimentais. Os resultados em CFD mostram concordância com os resultados experimentais, tanto na análise qualitativa das propriedades geométricas das ondas interfaciais, quanto na comparação direta com os dados para fração volumétrica e queda de pressão. Os resultados numéricos da modelagem fenomenológica para fatores de entranhamento apresentam boa concordância com dados da literatura. / Two-phase flows are present in many natural and industrial processes, such as in the oil industry. They may be found arranged in several flow patterns, including the wavy stratified flow and the stratified with mixing at the interface. The stratified oil-water flow has been used as a convenient way to avoid the formation of emulsions of water in oil and have a common occurrence in directional oil wells. When the interfacial wave exceeds a certain geometric and kinematic limit the phenomenon of drop entrainment arises at the interface, causing an increase of pressure drop. Models have been presented in the literature in an attempt to describe the phenomenon of drop entrainment. In this work, we present a new method for the one-dimensional mathematical modeling of entrainment in order to improve the prediction of oil volume fraction and pressure drop. It was also used a commercial computational fluid dynamics tool (CFD) to obtain the values of flow parameters of wavy stratified oil-water flow, such as oil volume fraction, pressure drop, amplitude and length of the interfacial waves. The results of the phenomenological modeling for entrainment and CFD were compared with experimental databases. The CFD results are in agreement with the experimental results in both the qualitative analysis of the geometric properties of the interfacial waves and in direct comparison with oil-volumetric-fraction and pressure-drop data. The numerical results of the phenomenological model for entrainment factors are in agreement with data from the literature.

Neste trabalho estudou-se o comportamento reológico e morfológico da mistura polimérica imiscível de polipropileno e poliamida. Como resultado deste estudo obtiveram-se valores de tensão interfacial entre 10mN/m e 13mN/m. A tensão interfacial diminuiu em até 87% quando a mistura é compatibilizada com polipropileno maleado. A análise morfológica no regime de viscoelasticidade linear quando avaliada uma morfologia de emulsão de poliamida em polipropileno revelou diâmetro médio da fase dispersa entre 1,5µm e 20µm. O diâmetro das gotas da fase dispersa diminuiu com a adição de polipropileno maleado chegando a reduções de até 98%, mantendo-se constante a concentração da fase dispersa. No regime de viscoelasticidade não linear foram testados modelos para avaliar o comportamento da mistura em fluxos de cisalhamento e extensão, sendo que somente para os fluxos de extensão foi obtida boa correlação dos resultados experimentais com as previsões teóricas. / Rheological and morphological behaviour of polypropylene and polyamide polymer blend was studied. The values of interfacial tension were obtained between 10mN/m and 13mN/m. The interfacial tension decreased in 87% for compatibilized blend. Morphology analysis for linear viscoelastic regime shows dispersed drop diameter between 1,5µm and 20µm. The diameter of the drops decreased with the addition of maleic polypropylene reducing until 98%, keeping constant the concentration of the disperse phase. In non linear viscoelastic regime different models were tested to evaluate the behavior of the blends in shear and elongacional flows. However, only the elongacional flow results were acquired with theoretical - experimental corroboration.

Master of Science / Department of Mechanical and Nuclear Engineering / Kevin B. Lease / This research was intended to measure the interfacial shear strength between fiber/ matrix systems and to investigate the relation between structure-mechanical properties and performance of fiber/matrix systems. This work conducted a systematic study on model fiber/matrix systems to enhance the fundamental understanding on how variation of polymeric compositions (and hence, different structures), different curing conditions, and fiber surface treatments influence the interactions between the fiber and matrix. In order to measure the interfacial shear strength of fiber/matrix systems, the microdroplet technique was used. In this technique a polymer droplet was deposited on a fiber in the liquid state. Once the droplet was cured a shear force was applied to the droplet in order to detach the droplet from the fiber. The amount of the force needed to de-bond the droplet was directly related to the strength of the bonds formed between the fiber and matrix during the curing process. In addition, the micro-droplet technique was used to evaluate effects of different crosslinker ratio of fiber/ matrix system and also to see if different curing conditions affect the interfacial shear strength of fiber/ matrix system. Surface treatment was also conducted to evaluate its effects on the interfacial shear strength of the fiber/ matrix system using microdroplet technique. The interfacial shear strength of fiber/ matrix system increased along with the increase of crosslinker ratio to a limiting value, and it decreased as long as the crosslinker ratio increased. Curing condition also caused the interfacial shear strength of fiber/ matrix system to increase when it was cured at higher temperature. Fiber surface treatment exhibited a significant effect to the interfacial shear strength as well as the fiber/ matrix contact angle measurement.

The objective of this study was to characterize non-wetting fluid in multi-phase systems comprising a range of fluid and porous medium properties. Synchrotron X-ray microtomography was used to obtain high-resolution, three-dimensional images of fluids in natural porous media. Images were processed to obtain quantitative measurements of fluid distribution, morphology, and interfacial area. Column-flooding experiments were conducted with four enhanced-solubilization (ES) solutions to examine their impact on entrapped organic liquid. Mobilization caused a change in organic-liquid morphology and distribution for most experiments. The effect of ES-solution flooding on fluid-fluid interfacial area was similar to that of water flooding. Organic-liquid mobilization was observed at total trapping numbers that were smaller than expected. This was attributed to pore-scale mobilization of blobs that were re-trapped prior to being eluted from the column. Pore-scale mobilization was also observed during water-flooding experiments for which trapping numbers varied over several orders of magnitude. Water-flooding and surfactant-flooding experiments were compared to investigate the impact of interfacial tension, viscosity, and fluid velocity on entrapped organic liquid. For similar total trapping numbers, flooding at larger velocities appeared to have a greater effect on the distribution of non-wetting blobs than lowering interfacial tension or increasing the viscosity of the wetting fluid. The fluid-normalized interfacial area was generally independent of the total trapping number. Finally, the impact of fluid type on the interfacial area between different pairs of non-wetting fluids was investigated during drainage and imbibition in four natural porous media. Interfacial areas were similar among all fluid pairs for a given porous medium. They were also similar for drainage and imbibition conditions. The maximum specific interfacial area (A(m)) was determined to quantify the magnitude of interfacial area associated with a given porous medium. The value of A(m) was larger for the media with smaller median grain diameters. Therefore, physical properties of the porous medium appear to have a greater influence on the magnitude of specific total interfacial area for a given saturation than fluid properties or wetting-phase history.

In the thesis explicit dual parabolic-elliptic models are constructed for the Konenkov flexural edge wave and the Stoneley-type flexural interfacial wave in case of thin linearly elastic plates. These waves do not appear in an explicit form in the original equations of motion within the framework of the classical Kirchhoff plate theory. The thesis is aimed to highlight the contribution of the edge and interfacial waves into the overall displacement field by deriving specialised equations oriented to aforementioned waves only. The proposed models consist of a parabolic equation governing the wave propagation along a plate edge or plate junction along with an elliptic equation over the interior describing decay in depth. In this case the parabolicity of the one-dimensional edge and interfacial equations supports flexural wave dispersion. The methodology presented in the thesis reveals a dual nature of edge and interfacial plate waves contrasting them to bulk-type wave propagating in thin elastic structures. The thesis tackles a number of important examples of the edge and interfacial wave propagation. First, it addresses the propagation of Konenkov flexural wave in an elastic isotropic plate under prescribed edge loading. For the latter, parabolic-elliptic explicit models were constructed and thoroughly investigated. A similar problem for a semi-infinite orthotropic plate resulted in a more general dual parabolic-elliptic model. Finally, an anal- ogous model was derived and analysed for two isotropic semi-infinite Kirchhoff plates under perfect contact conditions.