Tese de mestrado integrado. Engenharia Química. Faculdade de Engenharia. Universidade do Porto. 2010

El objetivo principal de este trabajo es predecir la dispersión de un flujo bifásico en el lecho de un reactor de hidrodesulfuración. Se consideran propiedades físicas constantes, sin incluir reacciones químicas ni procesos de transferencia de calor ni materia. Dos herramientas de simulación diferentes se han utilizado en este estudio. Una de ellas es el software comercial Fluent, ampliamente utilizado en el campo de la Computación en Dinámica de Fluidos, en el que se han introducido nuevos modelos de arrastre y capilaridad no incluidos en la versión comercial del software. La segunda herramienta utilizada es el código doméstico Multiphase Flow Solver, escrito en lenguaje de programación Fortran, que ha sido desarrollado durante esta tesis doctoral, constituyendo un importante objetivo de la misma. Este código incorpora los modelos necesarios para describir los procesos físicos que describen el comportamiento de este tipo de flujos multifásicos y su dispersión en medios porosos. / The main objective of this work is to predict the two-phase flow dispersion in the bed of a hydrodesulfurization reactor. Physical properties are considered to remain constant, without including chemical reactions nor heat and mass transfer processes. Two different simulation tools have been used in this study. One of them is the commercial software Fluent, widely used in the field of Computational Fluid Dynamics, in which new drag and capillarity models not included in the commercial version of the software have been implemented. The second tool used is the domestic code Multiphase Flow Solver, written in Fortran programming language, which has been developed during this doctoral thesis, being one important goal of it. This code includes the models needed to describe the physical processes which describe the behavior of this type of multiphase flows and their dispersion in porous media.

In the post-operational phase of a Low/Intermediate-Low radioactive waste repository, gas will be generated in the caverns due to anaerobic corrosion of metals, and also chemical and microbial degradation of organic substances. Previous investigations on gas migration have indicated that discrete water conducting features (e.g. shear zones) are mainly responsible for gas transport from the caverns through the geosphere. Two phase flow processes occur in these water conducting features; the continuity and spatial distribution of pore spaces, the pore size distribution and the interfacial forces of the three phases gas-water-rock have a significant influence on gas transport.The main difficulties to be resolved when simulating two-phase flow processes in fractured rock are:- The description of the internal heterogeneity of the individual water conducting features. The influence of channelling along preferential flow paths is even more important than for single phase fluid flow, because gas transport takes place more or less exclusively along the most transmissive channels. - The determination of effective mass exchange coefficients of the relevant components of the system. Mass exchange may occur between three phases (gas-water-rock). It depends on the spatial distribution of water and gas along the water conducting features (i.e. specific surface of contact areas between phases), and on the solubility and diffusivity of the different components, but also on a couple of state variables of liquid phase (initial content of dissolve/free gas, initial pressure).The work presented in this thesis aims to improve the understanding of the physics of single and multiphase transport phenomena, to be able to develop a quantitative description of gas transport in shear zones to overcome in a satisfactory way the problems described above.

Orientador: Milton Mori / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-09-11T21:07:59Z (GMT). No. of bitstreams: 1 Bastos_JaciCarloSchrammCamara_M.pdf: 4360168 bytes, checksum: 100c57a7c93213cf37fcdab4ee05e24f (MD5) Previous issue date: 2005 / Resumo: A presente pesquisa apresenta a modelagem matemática e a simulação de uma operação de fluidização rápida em um longo duto cilíndrico vertical, operação importante em vários processos industriais, sendo que sua principal aplicação está vinculada ao craqueamento catalítico do petróleo para a conversão em gasolina. Tem como objetivos a obtenção de uma compreensão contínua e o conhecimento do desenvolvimento do escoamento gás-sólido, bem como a soma de experiências às pesquisas em escala industrial motivados pela possível predição do desempenho deste tipo de escoamento. O modelo tridimensional, turbulento e bifásico usado para a predição do escoamento gás-sólido, consiste num conjunto de equações de conservação da massa e momento para cada uma das fases, formuladas seguindo a aproximação Euleriana-Euleriana. As variáveis fluidodinâmicas foram estimadas pela solução do modelo, com o emprego de correlações empíricas da literatura e disponibilizadas pelo código computacional de CFD, para garantir o fechamento do modelo e sua solução numérica. Desde de que a predição da dinâmica do escoamento complexo, em dutos com alto fluxo ascendente de sólidos não é possível por meio somente de equações fundamentais, a maioria dos modelos requerem entradas empíricas, as quais somente são adquiridas com a experimentação. Estes dados foram obtidos dos estudos de PÄRSSINEN e ZHU (2001). A geometria e a malha numérica estrutural do duto vertical foram geradas pelo software (CAD) ICEM, subdividido em DDN (geometria) e Hexa (malha). A adaptação do modelo matemático para a geração do modelo numérico foi alcançada com o uso do simulador comercial CFX 5.7. Os resultados obtidos foram avaliados com respeito à teoria apresentada ao longo da dissertação, sendo finalmente feita uma comparação entre as predições numéricas com o modelo e dados experimentais da literatura / Abstract: The present research presents the mathematical modeling and the simulation of an operation of fast fluidization in a long vertical cylindrical duct line, which is an important operation in many industrial processes, where its main application is tied with the catalytic cracking of oil for gasoline synthesis. It has as objective the attainment of a continuous understanding and knowledge of the development of the gas-solid flow, as well as adding of experiences to research of industrial scale equipments motivated by the possibility of prediction of the performance of this type of flow. The three-dimensional, turbulent and two-phase model used for the prediction of the gas-solid flow, consists of a set of conservation equations of mass and momentum for each phase, which was formulated following the Eulerian-Eulerian approach. The fluid dynamics variables was estimated by the solution of the model with the use of correlations found in the literature and available in the computational CFD code, in order to guarantee the closure of the model and its numerical solution. Since the prediction of the dynamics of the complex flow in ducts with high ascending solid flow is not possible by solely using the basic equations, the majority of the models require the setting empirical, parameters which are acquired only with experimentation. These data were obtained from the studies of PÄRSSINEN and ZHU (2001). The geometry and the structural numerical mesh of the vertical duct was generated by the software (CAD) ICEM, subdivided in DDN (geometry) and Hexa (meshing). The adaptation of the mathematical model for the numerical model generation was reached with the use of the commercial simulator CFX 5.7. The results were evaluated with respect to the theory presented along this dissertation, where comparisons between the numerical predictions with the model and experimental data from the literature were performed. / Mestrado / Desenvolvimento de Processos Químicos / Mestre em Engenharia Química

Orientador: Milton Mori / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-14T18:54:23Z (GMT). No. of bitstreams: 1 Bastos_JaciCarloSchrammCamara_D.pdf: 4353350 bytes, checksum: 0de3633c8edcc4ae2ec7fc57a3b590d0 (MD5) Previous issue date: 2009 / Resumo: Apresenta-se nesta pesquisa uma análise experimental e numérica do comportamento da fase dispersa em um jato circular bifásico confinado e uma comparação com jato circular bifásico livre. Nas análises experimentais, uma câmara pentagonal em acrílico foi utilizada como sistema de confinamento para a obtenção de perfis axiais e radiais de velocidade média, flutuação de velocidade (RMS) e intensidade de turbulência. Estes dados foram analisados a fim de desenvolver uma análise completa da região desenvolvida do jato. Três diferentes jatos foram utilizados para a alimentação da fase gás no topo da câmara, mas apenas o jato central foi carregado com partículas entre 60 e 90µm de diâmetro. Os outros dois foram utilizados para proporcionar uma maior interação entre as fases no interior da câmara. A técnica óptica Phase Doppler Anemometry (PDA), foi empregada na medição da velocidade instantânea da fase sólida e do diâmetro das partículas nas diferentes posições axiais a partir do bico do jato. Nove casos de estudo distintos são investigados individualmente e, em seguida, comparados entre si. Estes casos fornecem informações importantes sobre o comportamento e o efeito do confinamento dos jatos sobre o transporte macrocóspico e turbulento das partículas entre o centro e as regiões de contorno do jato. As análises numéricas tratam da modelagem matemática tridimensional, turbulenta e transiente do escoamento no jato bifásico confinado. O modelo trata as fases gás e sólida a partir de uma abordagem Euleriana. O fechamento das equações de transporte foi realizado utilizando o modelo de turbulência de duas equações k-e para a fase gás e modelos de turbulência de zero-equação para a fase sólida, e ainda em alguns casos esta última apenas sofreu efeitos turbulentos advindos da fase contínua. A acurácia das previsões do modelo em um jato de partículas confinadas com as características médias no tempo, assim como os coeficientes da correlação de turbulência foram avaliados. Perfis radiais de velocidade média e fração volumétrica das partículas foram capturados em quarenta e dois níveis, subdivididos em nove casos e comparados aos dados experimentais adquiridos. O diâmetro médio das partículas utilizado nas simulações foi de 75µm e as velocidades iniciais utilizadas variam entre 3 e 11m/s no jato central. O modelo matemático previu um escoamento desenvolvido semelhante ao que foi encontrado experimentalmente. / Abstract: It is presented in this research an experimental and numerical analisys of the dispersed phase behavior in a circular confined two-phase jet and a comparison with circular free two-phase jet. In the experimental analysis, a pentagonal plexiglass chamber was used as confined system for the axial and radial profiles investigation of mean velocity, fluctuation velocity known as RMS velocity and turbulence intensity. These data were analyzed in order to develop a complete analysis in the developed region of the jet. Three different nozzles were used to feed the gas phase at the top of the chamber, but just the central nozzle was loaded with particles between 60 and 90µm of diameter. The other two were used to increase the interaction between the phases in the chamber. An optical technique known as Phase Doppler Anemometry was used to measure the instantaneous velocity of the solid phase and particle diameter in different axial positions of the jet nozzle. Nine different cases of study are investigated individually and then compared among each other. These cases provide important information about the jets behavior and the confinement effect on the macrocospic and turbulent transport of particles between the jet center and the jet contour regions. The numerical analysis deals with three-dimensional, turbulent and transient mathematical modeling of a confined two-phase jet flow. The model treats the gas and the solid phases from an Eulerian approach. The closure of the transport equations have been accomplished by using the k-e turbulence model for the gas phase and the zero-equation turbulence model for the solid phase, and in some cases the latter suffered turbulent effects occuring only from the continuos phase. The accuracy of the model predictions in a particle-laden confined jet with the characteristics as well as turbulence correlation coefficients have been evaluated. Radial mean velocity profiles for the solid phase were computed on forty two axial levels, subdivided in nine cases and compared to the obtained experimental data. The mean particle diameter used in the simulations was 75µm and the initial velocities used vary between 3 and 11m/s. The mathematical model predicted a flow development similar to that found experimentally. / Doutorado / Desenvolvimento de Processos Químicos / Mestre em Engenharia Química

Tesis por compendio / [EN] Listening, watching, reading and writing simultaneously in a foreign language is very difficult. On the one hand, there is a conflict of visual attention between viewing a video and completing a written activity at the same time. On the other hand, paying attention to the image, the audio, and the task simultaneously can lead to working memory overload. The aim of this thesis by publication was to develop a framework for using audiovisual comprehension questions imprinted in the video image in the form of subtitles and synchronized with the relevant fragments, for the purpose of foreign language learning and testing. Compared to viewings where the comprehension activity is available only on paper, this innovative technique may provide some benefits. For example, it could minimize the conflict in visual attention between watching the video and completing the task, by spatially and temporally approximating the questions and the relevant fragments. This methodology could be especially beneficial for adult students with a low level of language proficiency. A multiphase mixed methods design was employed. The investigation involved several interrelated studies, with the purpose of (a) ascertaining the opinions of specialists in teaching Spanish as a Foreign Language (SFL), Spanish linguistics and/or the use of technology, SFL university teachers, and adult SFL learners about this methodology, and (b) researching whether the viewing comprehension questions as video captions had an impact on test-takers' performance and visual behaviour in a SFL test. Overall, experts, SFL students and SFL teachers have positive opinions about this technique. Imprinted questions do not have a statistically significant effect on SFL learners' audiovisual comprehension test performance. However, imprinted questions increase the amount of time that test-takers watch the video in an statistically significant way. The main contribution of the thesis lies in the fact that we have formulated a framework for using audiovisual comprehension questions imprinted in the video image based on a thorough literature review and empirical research. / [ES] Escuchar, ver, leer y escribir simultáneamente en una lengua extranjera es muy complicado. Por una parte, existe un conflicto de atención visual entre ver un vídeo y completar una actividad escrita al mismo tiempo. Por otra parte, prestar atención a la imagen, al audio, y a la tarea simultáneamente puede llevar a la saturación de la memoria de trabajo. El propósito de esta tesis por compendio era desarrollar un marco teórico sobre el uso de preguntas de comprensión audiovisual sobreimpresas en la imagen del vídeo en forma de subtítulos y sincronizadas con los fragmentos relevantes para el aprendizaje y evaluación de lenguas extranjeras. En comparación con visionados donde la actividad de comprensión está disponible solo en papel, esta técnica innovadora podría aportar varios beneficios. Por ejemplo, podría reducir el conflicto de atención visual entre observar el vídeo y completar la tarea, al aproximar espacial y temporalmente las preguntas y los fragmentos relevantes. Esta metodología se considera especialmente beneficiosa para estudiantes adultos de niveles iniciales. Se utilizó un diseño mixto multifase. La investigación implicó la realización de varios estudios interrelacionados que tenían la finalidad de (a) conocer la opinión de expertos en didáctica del español como lengua extranjera (ELE), lingüística española y/o en el uso de la tecnología, profesores universitarios de ELE y estudiantes adultos de ELE sobre esta metodología, y (b) averiguar si las preguntas de comprensión sobreimpresas en el vídeo tenían algún impacto en el desempeño y la conducta visual de los examinandos en una prueba de ELE. Globalmente, los expertos, los estudiantes de ELE y los profesores de ELE tienen opiniones positivas sobre esta técnica. Las preguntas sobreimpresas no tienen un efecto estadísticamente significativo en el rendimiento de los examinandos en una prueba de comprensión audiovisual de ELE. Sin embargo, incrementan la cantidad de tiempo que los examinandos observan el texto audiovisual de forma estadísticamente significativa. La contribución principal de la tesis reside en el hecho de que hemos formulado un marco teórico sobre el uso de preguntas de comprensión audiovisual sobreimpresas en la imagen del vídeo sobre la base de una revisión exhaustiva de la literatura y una investigación empírica. / [CA] Escoltar, veure, llegir i escriure simultàniament en una llengua estrangera és molt complicat. D'una banda, existeix un conflicte d'atenció visual entre veure un vídeo i completar una activitat escrita al mateix temps. D'altra banda, prestar atenció a la imatge, l'àudio, i a la tasca simultàniament pot portar a la saturació de la memòria de treball. El propòsit d'aquesta tesi per compendi era desenvolupar un marc teòric sobre l'ús de preguntes de comprensió audiovisual sobreimpreses en la imatge del vídeo en forma de subtítols i sincronitzades amb els fragments rellevants per a l'aprenentatge i l'avaluació de llengües estrangeres. En comparació amb visionats en què l'activitat de comprensió està disponible només en paper, aquesta tècnica innovadora podria aportar diversos beneficis. Per exemple, podria reduir el conflicte d'atenció visual entre observar el vídeo i completar la tasca, en apropar espacialment i temporalment les preguntes i els fragments rellevants. Aquesta metodologia es considera especialment beneficiosa per a estudiants adults de nivells inicials. Es va utilitzar un disseny mixt multifase. La investigació va implicar la realització de diversos estudis interrelacionats que tenien la finalitat de (a) conèixer l'opinió d'experts en didàctica de l'espanyol com a llengua estrangera (ELE), lingüística espanyola i/o en l'ús de la tecnologia, professors universitaris d'ELE i estudiants adults d'ELE sobre aquesta metodologia, i (b) esbrinar si les preguntes de comprensió sobreimpreses al vídeo tenien algun impacte en el rendiment i la conducta visual dels examinands en una prova d'ELE. Globalment, els experts, els estudiants d'ELE i els professors d'ELE tenen opinions positives sobre aquesta tècnica. Les preguntes sobreimpreses no tenen un efecte estadísticament significatiu en el rendiment dels examinands en una prova de comprensió audiovisual de ELE. No obstant això, incrementen la quantitat de temps que els examinands observen el text audiovisual de manera estadísticament significativa. La contribució principal de la tesi rau en el fet que hem formulat un marc teòric sobre l'ús de preguntes de comprensió audiovisual sobreimpreses en la imatge del vídeo sobre la base d'una revisió exhaustiva de la bibliografia i una investigació empírica. / Casañ Núñez, JC. (2017). Un marco teórico sobre el uso de actividades de comprensión audiovisual con preguntas sobreimpresas en el vídeo y sincronizadas con los fragmentos relevantes para el aprendizaje y la evaluación de lenguas extranjeras: una investigación mixta multifase [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/90504 / TESIS / Compendio

This dissertation is a contribution to the development of a unified model of continuum mechanics, describing both fluids and elastic solids as a general continua, with a simple material parameter choice being the distinction between inviscid or viscous fluid, or elastic solids or visco-elasto-plastic media. Additional physical effects such as surface tension, rate-dependent material failure and fatigue can be, and have been, included in the same formalism. The model extends a hyperelastic formulation of solid mechanics in Eulerian coordinates to fluid flows by means of stiff algebraic relaxation source terms. The governing equations are then solved by means of high order ADER Discontinuous Galerkin and Finite Volume schemes on fixed Cartesian meshes and on moving unstructured polygonal meshes with adaptive connectivity, the latter constructed and moved by means of a in- house Fortran library for the generation of high quality Delaunay and Voronoi meshes. Further, the thesis introduces a new family of exponential-type and semi- analytical time-integration methods for the stiff source terms governing friction and pressure relaxation in Baer-Nunziato compressible multiphase flows, as well as for relaxation in the unified model of continuum mechanics, associated with viscosity and plasticity, and heat conduction effects. Theoretical consideration about the model are also given, from the solution of weak hyperbolicity issues affecting some special cases of the governing equations, to the computation of accurate eigenvalue estimates, to the discussion of the geometrical structure of the equations and involution constraints of curl type, then enforced both via a GLM curl cleaning method, and by means of special involution-preserving discrete differential operators, implemented in a semi-implicit framework. Concerning applications to real-world problems, this thesis includes simulation ranging from low-Mach viscous two-phase flow, to shockwaves in compressible viscous flow on unstructured moving grids, to diffuse interface crack formation in solids.