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In this project, the flow field characteristics of the simplified 2D rectangular primary sedimentation tank in Syvab wastewater treatment plant were achieved by a transient water-air two phases finite-volume method, applying Volume-Of-Fluid (VOF) model. RNG k-ε turbulence model was also employed to calculate the turbulent kinetic energy and its dissipation rate. The undesired hydraulic phenomenon for solid sedimentation was detected in original tank. To reduce the velocity and turbulence intensity of the influent, two categories of optimization methods were proposed, which are installing the baffle and changing the velocity inlet. The modifying effects of different methods were compared by the velocity profiles and the contours of kinetic energy. It turns out that both ways provide a preferred condition for particle settling. In the end, further research was forecasted and the work direction were given. / I detta projekt uppnåddes 2D modellering av avloppsflödesfältets karaktär hos en förenklade och rektangulär primära sedimenteringsbassäng, Syvab avloppsreningsverk, genom en transient-tvåfas-finita-volymmetoden med vatten och luft, som tillämpades med Volume-Of-Fluid (VOF) modellen. RNG k-ε turbulensmodellen användes även för att beräkna den kinetiska energin av turbulas och dess dissipationshastighet. Detta för att oönskade hydrauliska fenomen har uppmärksammats hos sedimenteringsbassängen hos avloppsreningsverket. För att minska flödeshastigheten och turbulens föreslås två optimeringsmetoder, vilket är att installera skärm och att ändra inloppets hastighet. Eeffekterna av de olika metoderna jämförs med hjälp av hastighets- och kinetisk energiprofiler. Det visar sig att båda metoderna kan ge gynsammare tillstånd för sedimentering av partikelar. Som avslutning ges prognos för den fortsatta forskningen och arbetsriktningen inom ämnet.

No description available.

Atualmente diversos produtos são fabricados por meio de injeção de polímeros, num processo denominado moldagem por injeção: material fundido é injetado em um molde no qual resfria e endurece. Contudo, ao contrário de outros processos de produção, a qualidade da peça criada por meio de moldagem por injeção não depende apenas do material e da sua forma geométrica, mas também da maneira na qual o material é processado durante a moldagem. Por esse motivo, o uso de modelagem matemática e simulações numéricas tem aumentado consideravelmente como maneira de auxiliar o processo de produção e tem-se tornado uma ferramenta indispensável. Desta forma, este projeto tem o propósito de simular o escoamento de fluidos durante a fase de preenchimento do processo de moldagem por injeção, utilizando o modelo 21/2-dimensional, composto por uma equação bidimensional para a pressão, conhecida como equação de Hele-Shaw, e uma equação tridimensional para a temperatura do fluido. Um modelo bidimensional para a temperatura é também desenvolvido e apresentado. Este projeto de doutorado propõe duas estratégias numéricas para a solução da equação de Hele-Shaw. A primeira delas é baseada em uma formulação euleriana do método Smoothed Particle Hydrodynamics, onde os pontos utilizados na discretização não se movem, e não há utilização de malhas. A segunda estratégia é baseada na criação de malhas dinamicamente construídas na região do molde que já encontra-se parcialmente cheio de fluido e subseqüente aplicação do método Control Volume Finite Element Method. Uma estratégia dinâmica do método semi lagrangeano é apresentada e aplicada à solução da equação bidimensional da temperatura. O projeto também pretende investigar três novas abordagens para o tratamento da superfície livre. Duas delas são baseadas na técnica Volume of Fluid e uma delas é uma adaptação meshless do método Front-Tracking. O comportamento não newtoniano do fluido é caracterizado por uma família de modelos de viscosidade. Testes numéricos indicando a confiabilidade das metodologias propostas são conduzidos / Currently, several plastic products are manufactured by polymer injection, in a process named injection molding: molten material is injected into a thin mold where it cools and solidifies. However, unlike other manufacturing processes, the quality of injection-molded parts depends not only on the material and shape of the part, but also on how the material is processed throughout the molding. For this reason, the use of mathematical modelling and numerical simulations has been increasing in order to assist in the manufacturing process, and it has become an essential tool. Therefore, this Sc.D. project has the purpose of simulating the fluid flow during the filling stage of the injection molding process, using the 21/2-dimensional model, compounded by a two-dimensional equation for the pressure field (also known as Hele-Shaw equation) and a three-dimensional equation for the temperature of the fluid. A simpler two-dimensional model for the temperature field is also derived and presented. This project proposes two novel numerical strategies for the solution of Hele-Shaw equation. The first one is based on an Eulerian formulation of the Smoothed Particle Hydrodynamics method, where the particles used in the discretization do not move along as the simulation evolves, thereby avoing the use of meshes. In the second strategy, local active dual patches are constructed on-the-fly for each active point to form a dynamic virtual mesh of active elements that evolves with the moving interface, then the Control Volume Finite Element Method is applied for the pressure field approximation. A dynamic approach of the semi-Lagrangian scheme is applied to the solution of the two-dimensional temperature equation. The project also assesses three new approaches for the treatment of the free surface of the fluid flow. Two of them are based on the Volume of Fluid technique and one of them is a meshless adaptation of the Front-Tracking method. The non-Newtonian behavior is characterized by a family of generalized viscosity models. Supporting numerical tests and performance studies, which assess the accuracy and the reliability of the proposed methodologies, are conducted

Cette thèse propose une modélisation numérique 2D des écoulements en zone de jet de rive avec un code Volume-Of-Fluid. Dans un premier temps, le détail de la structure interne de l’écoulement de jet de rive généré par l’effondrement d’un front d’onde turbulent sur une plage imperméable lisse est étudié. Le modèle numérique est ensuite étendu à la simulation des écoulements en milieu poreux internes à la plage. L’utilisation d’une unique équation de quantité de mouvement (VARANS) et de la méthode 1-fluide, permet de résoudre simultanément les écoulements de l’eau et de l’air à la surface et dans une plage perméable. Ce modèle a été confronté à une série de cas tests analytiques et à de récentes mesures expérimentales. Les résultats numériques montrent l’aptitude du modèle VOF-VARANS à reproduire les écoulements en zone de jet de rive sur une plage imperméable fixe. / A 2D numerical modeling of flows in the swash zone is proposed using a Volume-Of- Fluid code. The detailed flow structure of a bore-driven swash event over an impermeable beach is first studied. The numerical model is then developed to account for porous media flow within the beach. The unique VARANS momentum equation and 1-fluid method used allow to solve simultaneously both surface and subsurface flows of air and water phases in the swash zone. This model is validated against a series of analytical tests cases and confronted to recent experimental measurements. The numerical results highlight the ability of the VOF-VARANS model to reproduce swash flows over and within a permeable beach.

Cette thèse apporte une contribution à la simulation numérique de la construction de dépôts dans le cadre de la projection plasma type APS (Atmospheric Plasma Spraying). Ce travail est focalisé sur la construction d’un volume représentatif du revêtement en prenant en compte l’ensemble des phénomènes propres au procédé, tels que la nature de l’écoulement de gaz, la cinétique (multiphasique, mouillabilité) et la thermique (transferts thermiques, résistance thermique de contact, solidification) durant l’impact et l’empilement de particules. Une méthode numérique particulière, appelée VOF-SM (Volume Of Fluid - Sub Mesh), est développée. La simulation de l’impact d’un jet instationnaire et turbulent de plasma ArH2 sur un substrat a été réalisée pour définir la nature de l’écoulementen proche paroi et le transfert thermique entre cet écoulement et le substrat. Les phénomènes propres à l’impact de particules ont été intégrés au code de calcul Thétiset validés indépendamment par comparaison à des solutions analytiques et combinés par comparaison à un cas d’étude expérimentale millimétrique. Enfin, une étude d’impacts successifs de particules de Zircone Yttriée sur un substrat en acier a été menée, par une approche en similitudes thermique et cinétique pour pallier la difficulté de la résolution à petites échelles. / This PhD thesis is a contribution to the numerical simulation of the plasma sprayedcoating build-up by APS process (Atmospheric Plasma Spraying). This work focuses onthe build-up of a representative volume of the coat considering a great range of phenomenonappearing in APS process such as gas flow properties, kinetic (multiphase flow,wettability) and thermal (heat transfers, thermal contact resistance, solidification) duringthe impact and steaking of particles. An original numerical method, named VOF-SM(Volume Of Fluid - Sub Mesh) is developped. The simulation of the impact of an unsteadyand turbulent ArH2 plasma flow is carried out in order to define the gas flow closeto the wall and heat transferred to the substrate by the plasma. Specific phenomena of theimpact of particles were incorporated into the CFD code (Thétis) and validated independentlyby caparison with analytical solutions, then together combined by the comparisonto a millimeter size impact experimental data. Finally, a study of successive impacts ofYttria-Stabilized Zirconia particles onto a steel substrate was carried out by thermal andkinetic approach similarities to overcome the difficulty of resolving small scales.

[pt] No presente trabalho estudou-se numericamente a instabilidade das ondas na interface do escoamento estratificado de água e óleo em um canal plano. Esse padrão de escoamento, associado ao estágio inicial da formação de golfada, é comum em aplicações industriais, de áreas como produção de petróleo, nuclear, química e muitas outras. Através da introdução de perturbações controladas na interface do escoamento estratificado, analisou-se a evolução dessas perturbações à luz das teorias de estabilidade hidrodinâmica. Os experimentos numéricos foram realizados utilizando o método de Volume of Fluid (VOF) do simulador comercial ANSYS Fluent versão 15.0. Analisou-se o comportamento do escoamento em dois regimes distintos com relação a amplitude das ondas interfaciais. No primeiro regime, empregaram-se ondas pequenas o suficiente para que efeitos não lineares fossem desprezíveis. Os resultados obtidos apresentaram boa concordância com as previsões fornecidas por um solver das equações de Orr-Sommerfeld, para escoamento bifásico estratificado em um canal, indicando que a ferramenta numérica foi capaz de reproduzir o comportamento das ondas interfaciais. Mostrou-se que existe uma faixa de amplitudes, em torno de 0,2 porcento da altura do canal, a partir da qual os efeitos não lineares se tornam relevantes. No regime não linear foram avaliados diferentes cenários de interação não linear entre ondas, os quais geralmente são associados a transição do regime do escoamento estratificado para golfadas. Identificou-se o cenário mais relevante, analisando-se,a eficiência de cada uma dessas interações isoladamente. Observou-se que interações não lineares entre ondas de comprimento parecido são as que crescem mais rapidamente. Esse mecanismo parece ser dominante também na presença de um grande número de ondas, como é o caso esperado em um evento natural. Utilizou-se um modelo fracamente não linear, baseado nas equações de Stuart-Landau, para modelar o comportamento das ondas no escoamento, obtendo-se excelente concordância com os resultados das simulações. Isso é interessante do ponto de vista prático, pois sugere que modelos não lineares simples, como é o caso da equação de Stuart-Landau, podem ser implementados para melhorar as ferramentas utilizadas para prever mudanças de regime em escoamentos bifásicos. / [en] In the present work, the instability of waves at the interface of the stratified flow of water and oil in a plane channel was numerically studied. This flow pattern, which is associated with the initial stages of slug formation, is common in industrial application in areas such as oil production, nuclear, chemical and many others. Through the introduction of controlled perturbations at the interface of a stratified flow, the evolution of the perturbations was analyzed based on hydrodynamics stability theories. Numerical experiments were performed using the Volume of Fluid (VOF) method of the ANSYS Fluent release 15.0 commercial simulator. The behavior of the flow in two different regimes with respect to the amplitude of the interfacial waves was analyzed. In the first regime, small enough waves were employed so that non-linear effects were negligible. The results obtained presented good agreement with the predictions provided by a solver of the Orr-Sommerfeld equations for stratified two-phase flow in a channel, indicating that the numerical tool was able to reproduce the behavior of the interfacial waves. It was shown that there is a range of amplitudes, around 0.2 per cent of the channel height, above which the non-linear effects become relevant. In the nonlinear regime, different scenarios of nonlinear interaction between waves, which are usually associated with transition from stratified flow pattern to slug flow, were evaluated. The most relevant scenario was identified, based on the efficiency of each independent interaction. It was observed that non-linear interactions between waves of similar length present the fastest growth. This mechanism seems to be dominant also in the presence of a large number of waves, as present in natural events. A weakly nonlinear model, based on the Stuart- Landau equations, was employed to model the wave behavior in the flow, obtaining an excellent agreement with the results of the simulations. This is interesting from a practical point of view, since it suggests that simple nonlinear models, such as the Stuart-Landau equation, can be implemented to improve the tools used to predict regime changes in two-phase flows.

Ces travaux de thèse s'incrivent dans le cadre du traitement de gaz acides et captage CO2 dans les colonnes à garnissages structurés. Les gaz à traiter réagissent avec un liquide s'écoulant à contre-courant sur des plaques métalliques dont la compléxité géométrique permet d'accroître l'aire d'échange, et donc l'efficacité du procédé. Dans un contexte de modélisation multi-échelles des contacteurs à garnissages structurés, les écoulements gaz-liquide à la plus petite échelle géométrique des plaques de garnissages (de l'ordre de l'épaisseur du film liquide) sont étudiés, pour améliorer la compréhension et la modélisation des écoulements diphasiques et phénomènes de mouillage dans les garnissages. L'objectif final est de développer une méthodologie CFD pour reproduire des écoulements diphasiques 3D sur des géométries complexes telles que les plaques de garnissages. Pour ce faire, il est nécessaire de progresser en méthodes numériques et de proposer des méthodes expérimentales pour observer des écoulements de film liquide sur des géométries complexes. Ces travaux comprennent une partie numérique et une partie expérimentale. Un écoulement sur une plaque de garnissage structuré peut présenter des zones sèches, et donc des lignes de contact (dynamiques), ce qui présente un défi en simulation numérique à cause des différentes échelles de l'écoulement. La méthodologie employée ici en simulation numérique consiste à résoudre l'écoulement jusqu'à une échelle intermédiaire en modélisant les effets des plus petites échelles. Le code de calcul Two-Phase Level-Set a été utilisé et modifié dans ce but. Différentes méthodes level-set ont d'abord été testées de manière à identifier une méthode satisfaisante quant à la réduction des erreurs de conservation de masse, un problème rencontré en level-set. Il est ici montré que certaines combinaisons de schémas de discrétisation spatiale et temporelle permettent de réduire considérablement ces erreurs de conservation de masse. Après avoir réalisé de nombreux tests de validation, une nouvelle méthode numérique est proposée pour simuler les grandes échelles d'écoulements diphasiques 3D avec ligne de contact dynamique en level-set, dans des conditions réalistes. La méthode est ici validée pour des écoulements axisymétriques de gouttes simulés en 3D, en régime visqueux et en régime inertiel, et pour des écoulements de gouttes sur plan incliné. Les résultats sont en très bon accord avec d'autres travaux numériques et expérimentaux. Afin de faciliter l'utilisation de cette méthodologie pour des applications industrielles, un modèle sous-maille similaire a été implémenté dans un code VOF commercial; les résultats sont aussi en très bon accord avec d'autres travaux. En plus de ces développements numériques, une campagne expérimentale est mise en oeuvre pour observer des écoulements de film liquide sur une plaque de garnissage structuré. Les méthodes expérimentales employées sont d'abord testées et validées pour des écoulements de film plat ou ondulé sur plan incliné, et ensuite utilisées pour observer des écoulements de film sur des plaques de garnissage. L'épaisseur de film liquide est mesurée aux creux et aux crêtes des picots des plaques de garnissages, pour différents débits, par imagerie confocale chromatique. Des lois de puissance de l'épaisseur de film en fonction du Reynolds sont proposées; celles-ci sont très différentes suivant la position des relevés de mesure, aux creux ou aux crêtes des picots. La vitesse à l'interface de l'écoulement gaz-liquide est aussi mesurée, par PIV et PTV, en utilisant des particules hydrophobes. Les résultats montrent que le liquide a tendance à dévier du creux des canaux (corrugations), et la norme de la vitesse semblent présenter des extremums correspondant aux creux et crêtes des picots. [...] / The work described in this thesis is motivated by the use of structured packing columns in acid gas treatment and post-combustion CO2 capture. In a counter-current mode, flue gases react with the liquid that flows down over metal sheets, the geometrical complexity of which allows increasing the specific interfacial area, and thereby the overall efficiency of the process. In the context of multiscale modeling of structured-packing contacting devices, the focus in this work is on the gas-liquid flows at the smallest geometrical scale of packing sheets, of the order of the liquid film thickness, aiming to improve understanding and modeling of two-phase flows and wetting phenomena in structured packings. The ultimate objective is to build up a CFD methodology to reproduce 3D two-phase flows over complex surfaces such as structured packing sheets. For this purpose, progress is necessary both in pertinent computational methods and in the adaptation of experimental methods for observing liquid film flows over complex surfaces. This thesis therefore consists of computational and experimental parts. Flows over structured packing sheets may exhibit dry zones, and hence (moving) contact lines, the numerical simulation of which presents a computational challenge due to the disparity in length scales involved. Here, the methodology for large-scale numerical simulations of flows with moving contact lines consists in resolving the flow down to an intermediate scale and modeling effects of smaller ones. The parallelized freeware Two-Phase Level-Set has been extended for this purpose. First though, because some level-set methods have been reproached to yield mass conservation issues, an assessment is made of the mass conservation properties of a range of level-set methods. It is demonstrated that the combined use of some spatial and temporal discretization schemes allows to drastically reduce mass conservation errors in level-set methods. Having thus implemented a level-set method with satisfactory performance at such tests (and others), a novel numerical method is proposed to perform 3D large-scale simulations of flows with moving contact lines in level-set, under realistic conditions. Validation tests of axisymmetric droplet spreading in a viscous, and in an inertial regime, simulated in 3D, and sliding drops are shown to be in excellent agreement with prior experimental and numerical work. The results show that complex contact-line dynamics observed in prior experimental studies on sliding droplets can be simulated using the present large-scale methodology. To facilitate dissemination of this work in industrial applications, a similar subgrid model has been implemented in a commercial volume-of-fluid code; results of validation tests are shown to be in excellent agreement with other work. These computational developments are accompanied by an experimental campaign to observe liquid film flows over structured packing sheets. All experimental methods used herein are tested and validated for flat and wavy films down an inclined plane before being used for observing liquid film flows over packing sheets. The film thickness is measured at local troughs and crests of small-scale corrugations of the structured packing sheet, for different flow rates, by Chromatic Confocal Imaging. Power laws of the Reynolds number for the mean liquid film thickness are suggested, with significant differences for measurements at crests compared to that at troughs. Interface velocity measurements are also performed by PIV and PTV using hydrophobic particles. Results reveal that the liquid tends to deviate from troughs of large-scale corrugations, and seems to exhibit local extrema of the velocity magnitude corresponding to troughs and crests of small-scale corrugations. [...]

Atualmente diversos produtos são fabricados por meio de injeção de polímeros, num processo denominado moldagem por injeção: material fundido é injetado em um molde no qual resfria e endurece. Contudo, ao contrário de outros processos de produção, a qualidade da peça criada por meio de moldagem por injeção não depende apenas do material e da sua forma geométrica, mas também da maneira na qual o material é processado durante a moldagem. Por esse motivo, o uso de modelagem matemática e simulações numéricas tem aumentado consideravelmente como maneira de auxiliar o processo de produção e tem-se tornado uma ferramenta indispensável. Desta forma, este projeto tem o propósito de simular o escoamento de fluidos durante a fase de preenchimento do processo de moldagem por injeção, utilizando o modelo 21/2-dimensional, composto por uma equação bidimensional para a pressão, conhecida como equação de Hele-Shaw, e uma equação tridimensional para a temperatura do fluido. Um modelo bidimensional para a temperatura é também desenvolvido e apresentado. Este projeto de doutorado propõe duas estratégias numéricas para a solução da equação de Hele-Shaw. A primeira delas é baseada em uma formulação euleriana do método Smoothed Particle Hydrodynamics, onde os pontos utilizados na discretização não se movem, e não há utilização de malhas. A segunda estratégia é baseada na criação de malhas dinamicamente construídas na região do molde que já encontra-se parcialmente cheio de fluido e subseqüente aplicação do método Control Volume Finite Element Method. Uma estratégia dinâmica do método semi lagrangeano é apresentada e aplicada à solução da equação bidimensional da temperatura. O projeto também pretende investigar três novas abordagens para o tratamento da superfície livre. Duas delas são baseadas na técnica Volume of Fluid e uma delas é uma adaptação meshless do método Front-Tracking. O comportamento não newtoniano do fluido é caracterizado por uma família de modelos de viscosidade. Testes numéricos indicando a confiabilidade das metodologias propostas são conduzidos / Currently, several plastic products are manufactured by polymer injection, in a process named injection molding: molten material is injected into a thin mold where it cools and solidifies. However, unlike other manufacturing processes, the quality of injection-molded parts depends not only on the material and shape of the part, but also on how the material is processed throughout the molding. For this reason, the use of mathematical modelling and numerical simulations has been increasing in order to assist in the manufacturing process, and it has become an essential tool. Therefore, this Sc.D. project has the purpose of simulating the fluid flow during the filling stage of the injection molding process, using the 21/2-dimensional model, compounded by a two-dimensional equation for the pressure field (also known as Hele-Shaw equation) and a three-dimensional equation for the temperature of the fluid. A simpler two-dimensional model for the temperature field is also derived and presented. This project proposes two novel numerical strategies for the solution of Hele-Shaw equation. The first one is based on an Eulerian formulation of the Smoothed Particle Hydrodynamics method, where the particles used in the discretization do not move along as the simulation evolves, thereby avoing the use of meshes. In the second strategy, local active dual patches are constructed on-the-fly for each active point to form a dynamic virtual mesh of active elements that evolves with the moving interface, then the Control Volume Finite Element Method is applied for the pressure field approximation. A dynamic approach of the semi-Lagrangian scheme is applied to the solution of the two-dimensional temperature equation. The project also assesses three new approaches for the treatment of the free surface of the fluid flow. Two of them are based on the Volume of Fluid technique and one of them is a meshless adaptation of the Front-Tracking method. The non-Newtonian behavior is characterized by a family of generalized viscosity models. Supporting numerical tests and performance studies, which assess the accuracy and the reliability of the proposed methodologies, are conducted

Aufgrund fluiddynamischer Effekte bei der Schnellerwärmung für die Warmumformung wird die Applikation der Technologie erschwert. Die vorliegende Arbeit thematisiert diesen Effekt und evaluiert die Triebkräfte sowohl numerisch als auch im Experiment. Aufbauend darauf werden Vermeidungsstrategien aufgezeigt und experimentell validiert um eine Verschiebung der Beschichtung zu verhindern. Es können insbesondere die temperatursensitive Marangonikraft als auch die magnethydrodynamische Wirkung der Lorentzkraft bei einer induktiven Erwärmung als Haupttriebkräfte identifiziert werden, die sich aufgrund identischer Kraftvektorrichtungen überlagern und verstärken. Es hat sich gezeigt, dass für den vorliegenden Fall einer 20-30 μm dünnen AlSi-Beschichtung die Marangonikraft gegenüber der Lorentzkraft um einen Faktor von mindestens 68 überwiegt. Ein vergleichbarer Effekt ist auch bei konduktiver Erwärmung zu beobachten. Hinsichtlich möglicher Vermeidungsstrategien einer globalen Beschichtungsverschiebung bietet die Applikation von lokalen Flussbarrieren mittels Laser, Induktion oder Walztexturierung, sowie das Vermeiden einer freien Flüssigkeitsoberfläche durch Aufbringen einer Zusatzbeschichtung, das größte Potential. In der zweiten Versionierung der Dissertationsschrift wurde auf S. IV im Vorwort, sowie auf S.72, Kapitel 4.2 eine ergänzende Nennung eines Instituts und Kooperationspartners hinzugefügt. / The application of fast heating technologies for hot forming is hindered by fluiddynamic effects and a resulting coating shift. Present thesis investigates this effect to evaluate the driving forces numerically as well as experimentally. Based on this evaluation, strategies are developed and investigated to avoid a global displacement of the AlSi-coating. In case of inductive fast heating the main driving force is represented by a superposition of Lorentzian forces as well as surface tension related Marangoni forces with a force vector pointing from hot to cold regions on the blank. The numerical evaluation shows that in case of 20-30 μm thin layers of AlSi the Marangoni force is at least 68 times higher than the Lorentz force and therefore represents the main driving force. A comparable effect is observable in case of conduction heating. Local flow barriers realized by Laser, inductive heating or texturing as well as the avoidance of a free liquid-surface due to application of additional coating layers show huge potential to prevent a global coating flow.