Konvektions- und Erstarrungsvorgänge sind sowohl in natürlichen als auch in technischen Prozessen von grundlegender Bedeutung und stehen dabei miteinander in komplexer Wechselwirkung. Die vorliegende Arbeit beschreibt die Entwicklung eines experimentellen Aufbaus, mit dem sich vielfältige Formen dendritischer Erstarrung und thermosolutaler Konvektion in optisch transparenten Materialsystemen initiieren lassen. Besonderes Augenmerk liegt dabei auf der Implementierung optischer Messtechnik und automatisierter Bildauswertung. Die hier entwickelte komplexe Bildverarbeitung erlaubt die simultane Anwendung verschiedener Verfahren der Strömungs- und Temperaturmessung: Eine automatisierte Bildsegmentierung quantifiziert unterschiedliche Feststofffraktionen; mittels Lagrangian Particle Tracking (LPT) werden die Trajektorien frei beweglicher Kristalle bestimmt und Particle Image Velocimetry/Thermometry (PIV/T) misst Strömungs- und Temperaturfeld im Fluid. Für die simultane Verwendung dieser Verfahren unter Minimierung von Quereffekten stellt die vorliegende Arbeit eine Reihe von Erweiterungen und Neuentwicklungen oben genannter Standardverfahren vor: Mit dem neuartigen Ansatz des Spectral Random Masking kann das Geschwindigkeitsfeld einer (unmaskierten) Teilchenfraktion (PIV-Tracer) ohne den Einfluss einer zweiten (maskierten) Teilchenfraktion (Blasen oder Feststoffpartikel) bestimmt werden. Dieser neuartige Algorithmus maskiert entsprechende Bildbereiche mittels zufälliger Intensitätsmuster und vermeidet so Probleme herkömmlicher Verfahren. Die Verwendung von Thermochromic Liquid Crystal (TLC)-Partikeln als Strömungstracer ermöglicht zusätzlich zur Particle Image Velocimetry (PIV) die Visualisierung des Temperaturfeldes mittels Liquid Crystal Thermometry (LCT). Um dabei genaue quantitative Messungen bei Anwesenheit mehrerer Feststofffraktionen zu erreichen, wurde eine neue Methode der Farbinterpolation entwickelt. Diese generiert RGB-Bilder, welche nur die Färbung der TLC-Partikel repräsentieren. Die anschließende Verarbeitung von RGB-Tripeln und räumlichen Farbabhängigkeiten durch ein künstliches neuronales Netz (KNN) ermöglicht es, verlässliche globale Temperaturfelder zu bestimmen. Die Kombination dieses KNN-Systems mit einem entsprechenden Kalibrierverfahren verbessert dabei die Genauigkeit und den messbaren Temperaturbereich der Liquid Crystal Thermometry (LCT) im Vergleich zu herkömmlichen Verfahren. Mit dem hier etablierten experimentellen Aufbau und Messschema können quantitative globale Studien zur gegenseitigen Beeinflussung von Erstarrung und Strömung unter simultaner Betrachtung verschiedener Feldgrößen durchgeführt werden. Damit ist ein tieferes Verständnis der komplexen physikalischen Vorgänge möglich. Die vorliegende Arbeit demonstriert dies anhand einer experimentellen Studie über die doppelt-diffusive Konvektion während der Kristallisation einer wässrigen Ammoniumchloridlösung NH4Cl(aq).:Zusammenfassung Danksagung 1. Einleitung 2. Physikalische Grundlagen 2.1. Konvektion 2.1.1. Freie thermische Konvektion 2.1.2. Doppelt-diffusive Konvektion 2.2. Erstarrung 2.3. Wechselwirkung zwischen Erstarrung und Strömung 3. Methoden der bildgebenden optischen Messtechnik 3.1. Digitale Bildverarbeitung 3.2. Optische Strömungsmessung 3.2.1. Particle Image Velocimetry 3.2.2. Lagrangian Particle Tracking 3.3. Liquid Crystal Thermometry 3.3.1. Farbkalibrierung 3.3.2. Simultane Temperatur- und Strömungsmessung 3.4. Bisheriger Einsatz optischer Messtechniken für Erstarrungsexperimente 4. Experimenteller Aufbau 4.1. Ammoniumchlorid als transparentes Modellsystem 4.2. Messzelle 4.3. Labortechnik 4.3.1. Temperaturmesstechnik 4.3.2. Temperaturregelung 4.3.3. Temperaturregime und experimenteller Ablauf 4.4. Bildgebung 4.4.1. Laser-Lichtschnittverfahren 4.4.2. Durchlichtverfahren 4.4.3. LED-Lichtschnittverfahren 4.4.4. Kombinationsmöglichkeiten und Einsatz der Bildgebungsverfahren 5. Implementierung und Weiterentwicklung der digitalen Bildverarbeitung 5.1. Detektion und Quantifizierung verschiedener Feststofffraktionen 5.1.1. Bildsegmentierung 5.1.1.1. Statische Hintergrundmaskierung 5.1.1.2. Dynamische Segmentierung 5.1.2. Bestimmung der Feststoffanteile 5.1.3. Quantifizierung der Bewegung der äquiaxialen Kristalle 5.2. Bestimmung des Geschwindigkeitsfeldes der kontinuierlichen Phase 5.2.1. Spectral Random Masking 5.2.2. PIV-Analyse der kontinuierlichen Phase 5.3. Messung des Temperaturfeldes der kontinuierlichen Phase 5.3.1. Farbinterpolation mittels maskierter Faltung 5.3.2. Kalibrierung der Liquid Crystal Thermometry 5.3.2.1. Bestimmung des Farbspiels der TLC-Partikel 5.3.2.2. Temperaturmessung mittels künstlicher neuronaler Netze 5.3.3. Anwendung und Genauigkeit der Temperaturmessung 5.4. Simultane Quantifizierung von Erstarrung, Strömung und Temperatur 6. Demonstration der Messtechnik anhand ausgewählter Experimente 6.1. Analyse globaler Merkmale der Erstarrungsexperimente 6.1.1. Entwicklung verschiedener Konvektionsregime 6.1.2. Wachstum verschiedener Kristallfraktionen 6.2. Bedingungen lokaler äquiaxialer Erstarrung 6.2.1. Äquiaxiales Kristallwachstum infolge lokaler Unterkühlung 6.2.2. Nukleation äquiaxialer Kristalle durch kolumnares Kristallwachstum 6.3. Erkenntnisgewinn und Möglichkeiten der Experimente 7. Zusammenfassung und Ausblick 7.1. Bewertung des experimentellen Aufbaus und der entwickelten Messtechnik 7.2. Optimierungsmöglichkeiten der Messtechnik 7.3. Möglichkeiten und Bedeutung zukünftiger experimenteller Untersuchungen A. Technische Zeichnungen B. Materialeigenschaften der verwendeten NH4 Cl-Lösungen C. Weiterführende Details der Temperaturmessung und -regelung C.1. Kalibrierung der Thermoelemente C.2. Kalibrierung der Thermistoren C.3. Entwicklung und Einrichtung eines Peltier-Luftkühlers D. Weiterführende Details und Illustrationen der entwickelten Bildverarbeitung D.1. Verwendete Python Bibliotheken D.2. Signalflussplan des Spectral Random Masking D.3. Particle Image Velocimetry/Thermometry D.4. Empfindlichkeitsanalyse des künstlichen neuronalen Netzes D.5. Abschätzung der Genauigkeit der LCT während der Experimente E. Erstarrungsexperimente E.1. Lichtschnittbeleuchtung E.1.1. Thermisch stabile Schichtung E.1.2. Thermisch instabile Schichtung E.1.3. Thermisch neutrale Schichtung E.2. Hintergrundbeleuchtung und doppelwandiger Behälter E.2.1. Thermisch stabile Schichtung E.2.2. Thermisch instabile Schichtung Symbolverzeichnis Indexverzeichnis Abkürzungsverzeichnis Literatur Selbstständigkeitserklärung / Convection and solidification processes are of fundamental importance in both natural and technical processes and are subject to complex interaction. The present work presents the development of an experimental setup to initiate various forms of dendritic solidification and thermosolutal convection in optically transparent material systems. Special attention is given to the implementation of optical measurement techniques and automated image processing. The complex image processing developed here allows the simultaneous application of different methods for flow and temperature measurement: An automated image segmentation quantifies different solid fractions; with Lagrangian Particle Tracking (LPT) the trajectories of free moving crystals are determined and Particle Image Velocimetry/Thermometry (PIV/T) measures flow and temperature field in the fluid. For the simultaneous use of these methods while minimizing cross-effects, this thesis illustrates a number of extensions and new developments of the above mentioned standard methods: With the novel approach of Spectral Random Masking the velocity field of an unmasked particle fraction (PIV tracer) can be determined without the influence of a second (masked) particle fraction (bubbles or solid particles). This novel algorithm masks corresponding image areas by random intensity patterns and thus avoids typical problems of conventional methods. The use of Thermochromic Liquid Crystal (TLC) particles as flow tracers enables the visualization of the temperature field by Liquid Crystal Thermometry (LCT) in addition to flow measurements by Particle Image Velocimetry (PIV). To achieve accurate quantitative measurements in the presence of several solid fractions, a new method of color interpolation was developed. This method generates RGB-images, which only represent the coloration of the TLC particles. The subsequent processing of RGB triples and spatial color dependencies using an artificial neural network (ANN) allows to determine reliable global temperature fields. The combination of this ANN system with a corresponding calibration procedure improves the accuracy and measurable temperature range of the LCT compared to conventional methods. With the experimental setup and measurement scheme established here, quantitative global studies on the mutual influence of solidification and flow can be performed under simultaneous consideration of different physical quantities. Compared to previous studies, this allows a deeper understanding of the complex physical processes. The present work demonstrates this with an experimental study of double diffusive convection during crystallization of an aqueous ammonium chloride solution NH4Cl(aq).:Zusammenfassung Danksagung 1. Einleitung 2. Physikalische Grundlagen 2.1. Konvektion 2.1.1. Freie thermische Konvektion 2.1.2. Doppelt-diffusive Konvektion 2.2. Erstarrung 2.3. Wechselwirkung zwischen Erstarrung und Strömung 3. Methoden der bildgebenden optischen Messtechnik 3.1. Digitale Bildverarbeitung 3.2. Optische Strömungsmessung 3.2.1. Particle Image Velocimetry 3.2.2. Lagrangian Particle Tracking 3.3. Liquid Crystal Thermometry 3.3.1. Farbkalibrierung 3.3.2. Simultane Temperatur- und Strömungsmessung 3.4. Bisheriger Einsatz optischer Messtechniken für Erstarrungsexperimente 4. Experimenteller Aufbau 4.1. Ammoniumchlorid als transparentes Modellsystem 4.2. Messzelle 4.3. Labortechnik 4.3.1. Temperaturmesstechnik 4.3.2. Temperaturregelung 4.3.3. Temperaturregime und experimenteller Ablauf 4.4. Bildgebung 4.4.1. Laser-Lichtschnittverfahren 4.4.2. Durchlichtverfahren 4.4.3. LED-Lichtschnittverfahren 4.4.4. Kombinationsmöglichkeiten und Einsatz der Bildgebungsverfahren 5. Implementierung und Weiterentwicklung der digitalen Bildverarbeitung 5.1. Detektion und Quantifizierung verschiedener Feststofffraktionen 5.1.1. Bildsegmentierung 5.1.1.1. Statische Hintergrundmaskierung 5.1.1.2. Dynamische Segmentierung 5.1.2. Bestimmung der Feststoffanteile 5.1.3. Quantifizierung der Bewegung der äquiaxialen Kristalle 5.2. Bestimmung des Geschwindigkeitsfeldes der kontinuierlichen Phase 5.2.1. Spectral Random Masking 5.2.2. PIV-Analyse der kontinuierlichen Phase 5.3. Messung des Temperaturfeldes der kontinuierlichen Phase 5.3.1. Farbinterpolation mittels maskierter Faltung 5.3.2. Kalibrierung der Liquid Crystal Thermometry 5.3.2.1. Bestimmung des Farbspiels der TLC-Partikel 5.3.2.2. Temperaturmessung mittels künstlicher neuronaler Netze 5.3.3. Anwendung und Genauigkeit der Temperaturmessung 5.4. Simultane Quantifizierung von Erstarrung, Strömung und Temperatur 6. Demonstration der Messtechnik anhand ausgewählter Experimente 6.1. Analyse globaler Merkmale der Erstarrungsexperimente 6.1.1. Entwicklung verschiedener Konvektionsregime 6.1.2. Wachstum verschiedener Kristallfraktionen 6.2. Bedingungen lokaler äquiaxialer Erstarrung 6.2.1. Äquiaxiales Kristallwachstum infolge lokaler Unterkühlung 6.2.2. Nukleation äquiaxialer Kristalle durch kolumnares Kristallwachstum 6.3. Erkenntnisgewinn und Möglichkeiten der Experimente 7. Zusammenfassung und Ausblick 7.1. Bewertung des experimentellen Aufbaus und der entwickelten Messtechnik 7.2. Optimierungsmöglichkeiten der Messtechnik 7.3. Möglichkeiten und Bedeutung zukünftiger experimenteller Untersuchungen A. Technische Zeichnungen B. Materialeigenschaften der verwendeten NH4 Cl-Lösungen C. Weiterführende Details der Temperaturmessung und -regelung C.1. Kalibrierung der Thermoelemente C.2. Kalibrierung der Thermistoren C.3. Entwicklung und Einrichtung eines Peltier-Luftkühlers D. Weiterführende Details und Illustrationen der entwickelten Bildverarbeitung D.1. Verwendete Python Bibliotheken D.2. Signalflussplan des Spectral Random Masking D.3. Particle Image Velocimetry/Thermometry D.4. Empfindlichkeitsanalyse des künstlichen neuronalen Netzes D.5. Abschätzung der Genauigkeit der LCT während der Experimente E. Erstarrungsexperimente E.1. Lichtschnittbeleuchtung E.1.1. Thermisch stabile Schichtung E.1.2. Thermisch instabile Schichtung E.1.3. Thermisch neutrale Schichtung E.2. Hintergrundbeleuchtung und doppelwandiger Behälter E.2.1. Thermisch stabile Schichtung E.2.2. Thermisch instabile Schichtung Symbolverzeichnis Indexverzeichnis Abkürzungsverzeichnis Literatur Selbstständigkeitserklärung

[pt] O medidor de vazão de fluido multifásico (MM) se desenvolveu impulsionado principalmente pela necessidade da indústria de óleo e gás em medir a vazão da produção dos poços que comumente é composta por petróleo, gás e água. Em outubro de 2015, a Agência Nacional de Petróleo, Gás Natural e Biocombustíveis (ANP) publicou o Regulamento Técnico de Medição de Fluido Multifásico para Apropriação de Petróleo, Gás Natural e Água que apresenta os requisitos através de planos que as empresas operadoras de óleo e gás precisam preparar e submeter para obter a autorização para aplicar o MM na medição para apropriação. Contudo, esse regulamento não especifica a metodologia que deve ser utilizada no denominado plano de verificação de desempenho para avaliar desempenho do MM no campo, cabendo a cada operadora desenvolver a sua metodologia para esse fim e apresentar a ANP. Este trabalho propõe e aplica uma metodologia para verificação de desempenho para MM com resultados de testes realizados em laboratório com fluidos reais e em campo de produção de petróleo e gás. É observado que testes com tempo curto de duração, inferior a 1000 segundos, tendem a gerar incertezas mais elevadas do que testes com longa duração, com mais de 1000 segundos, como os realizados na plataforma. Sendo assim, os resultados de incerteza de medição maiores gerados no laboratório com tempos de integração curtos podem ser considerados mais conservativos que os resultados dos testes realizados na plataforma. / [en] The multiphase flowrate (MM) was driven by the necessity of the oil and gas industry to measure the production flow of the wells that are commonly composed of oil, gas and water. In October 2015, the National Agency for Petroleum, Natural Gas and Biofuels (ANP) published the Technical Regulation for Measurement of Multiphase Fluid for Petroleum, Natural Gas and Water produced, which presents the requirements through plans that oil and gas companies need to prepare and submit for authorization to apply the MM in the measurement for allocation. However, this regulation does not specify the methodology that should be used in the so-called performance verification plan to evaluate the performance of the MM in the field, it being incumbent on each operator to develop its methodology for this purpose and present the ANP. This work proposes and applies a methodology for performance verification for MM with test results performed in the laboratory with real fluids and in oil and gas field. It was observed that short duration tests, below 1000 seconds, tend to generate higher uncertainties than long tests, higher than 1000 seconds, such as those performed on the platform. Thus, the higher measurement uncertainty results generated in the laboratory with short integration times can be considered more conservative than the results of the tests performed in the platform.

Two and three-phase flow processes involving gas, liquid and solid, are common in nature and industry, and include some of the most complex and poorly-understood transport problems. In this research hydrodynamics, heat and mass transfer processes in complex two and three-phase flows were investigated. The interfacial surface area concentration in a short vertical column subject to the through flow of fiber-liquid-gas slurry was experimentally measured using the gas absorption technique. The experimental data were statistically analyzed for parametric effects, and were empirically correlated. The absorption of a gaseous species by a slurry droplet with internal circulation and containing reactive micro-particles was simulated, and parametrically studied. The micro-particles were found to enhance the absorption rate. The absorption rate was sensitive to droplet recirculation, and shrinkage of particles with time resulted in declining absorption rates. The transport of soot particles, suspended in laminar hot gas flowing in a tube, was modeled and parametrically studied. Due to coupled thermal radiation and thermophoresis, a radially-nonuniform temperature profile develops, leading to sharp, non-uniform radial soot-concentration profiles. The assumption of monodisperse particles leads to over-prediction of thermophoresis. The transport and removal of particles suspended in bubbles rising in a stagnant liquid pool were modeled based on a Eulerian – Monte Carlo method. The bubble hydrodynamics were treated in Eulerian frame, using the Volume-of-Fluid (VOF) technique, while particle equations of motion were numerically solved in Lagrangian frame. The bubbles undergo shape change, and have complex internal circulation, all of which influence the particle removal. Model predictions were also compared with experimental data. Using a resemblance between two-phase flow in microchannels, and in large channels at microgravity, a simple Weber number-based two-phase flow regime map was developed for microchannels. Based on the available air-water experimental data, a criterion for the prediction of conditions that lead to flow regime transition out of the stratified-wavy flow pattern in horizontal annular channels was proposed. The thermocapillary effects on liquid-vapor interface shape during heterogeneous bubble ebullition in microchannels were analytically studied.

In power plants using large utility coal-fired boilers for generation of electricity the coal is pulverised in coal mills and then it has to be pneumatically transported and distributed to a larger number of burners (e.g. 30-40) circumferentially arranged in several rows around the burning chamber of the boiler. Besides the large pipework flow splitting devices are necessary for distribution of an equal amount of pulverised fuel (PF) to each of the burners. So called trifurcators (without inner fittings or guiding vanes) and ''riffle'' type bifurcators are commonly used to split the gas-coal particle flow into two or three pipes/channels with an equal amount of PF mass flow rate in each outflow cross section of the flow splitting device. These PF flow splitting devices are subject of a number of problems. First of all an uneven distribution of PF over the burners of a large utility boiler leads to operational and maintenance problems, increased level of unburned carbon and higher rates of NOX emissions. Maldistribution of fuel between burners caused by non uniform concentration of the PF (particle roping) in pipe and channel bends prior to flow splitting devices leads to uncontrolled differences in the fuel to air ratio between burners. This results in localised regions in the furnace which are fuel rich, where insufficient air causes incomplete combustion of the fuel. Other regions in the furnace become fuel lean, forming high local concentrations of NOX due to the high local concentrations of O2. Otherwise PF maldistribution can impact on power plant maintenance in terms of uneven wear on PF pipework, flow splitters as well as the effects on boiler panels (PF deposition, corrosion, slagging). In order to address these problems in establishing uniform PF distribution over the outlet cross sections of flow splitting devices in the pipework of coal-fired power plants the present paper deals with numerical prediction and analysis of the complex gas and coal particle (PF) flow through trifurcators and ''riffle'' type bifurcators. The numerical investigation is based on a 3-dimensional Eulerian- Lagrangian approach (MISTRAL/PartFlow-3D) developed by Frank et al. The numerical method is capable to predict isothermal, incompressible, steady gas- particle flows in 3-dimensional, geometrically complex flow geometries using boundary fitted, block-structured, numerical grids. Due to the very high numerical effort of the investigated gas-particle flows the numerical approach has been developed with special emphasis on efficient parallel computing on clusters of workstations or other high performance computing architectures. Besides the aerodynamically interaction between the carrier fluid phase and the PF particles the gas-particle flow is mainly influenced by particle-wall interactions with the outer wall boundaries and the inner fittings and guiding vanes of the investigated flow splitting devices. In order to allow accurate quantitative prediction of the motion of the disperse phase the numerical model requires detailed information about the particle-wall collision process. In commonly used physical models of the particle-wall interaction this is the knowledge or experimental prediction of the restitution coefficients (dynamic friction coefficient, coefficient of restitution) for the used combination of particle and wall material, e.g. PF particles on steel. In the present investigation these parameters of the particle-wall interaction model have been obtained from special experiments in two test facilities. Basic experiments to clarify the details of the particle-wall interaction process were made in a test facility with a spherical disk accelerator. This test facility furthermore provides the opportunity to investigate the bouncing process under normal pressure as well as under vacuum conditions, thus excluding aerodynamically influences on the motion of small particles in the near vicinity of solid wall surfaces (especially under small angles of attack). In this experiments spherical glass beads were used as particle material. In a second test facility we have investigated the real impact of non-spherical pulverised fuel particles on a steel/ceramic target. In this experiments PF particles were accelerated by an injector using inert gas like e.g. CO2 or N2 as the carrier phase in order to avoid dust explosion hazards. The obtained data for the particle-wall collision models were compared to those obtained for glass spheres, where bouncing models are proofed to be valid. Furthermore the second test facility was used to obtain particle erosion rates for PF particles on steel targets as a function of impact angles and velocities. The results of experimental investigations has been incorporated into the numerical model. Hereafter the numerical approach MISTRAL/PartFlow-3D has been applied to the PF flow through a ''riffle'' type bifurcator. Using ICEM/CFD-Hexa as grid generator a numerical mesh with approximately 4 million grid cells has been designed for approximation of the complex geometry of the flow splitting device with all its interior fittings and guiding vanes. Based on a predicted gas flow field a large number of PF particles are tracked throughout the flow geometry of the flow-splitter. Besides mean quantities of the particle flow field like e.g. local particle concentrations, mean particle velocities, distribution of mean particle diameter, etc. it is now possible to obtain information about particle erosion on riffle plates and guiding vanes of the flow splitting device. Furthermore the influence of different roping patterns in front of the flow splitter on the uniformness of PF mass flow rate splitting after the bifurcator has been investigated numerically. Results show the efficient operation of the investigated bifurcator in absence of particle roping, this means under conditions of an uniform PF particle concentration distribution in the inflow cross section of the bifurcator. If particle roping occurs and particle concentration differs over the pipe cross section in front of the bifurcator the equal PF particle mass flow rate splitting can be strongly deteriorated in dependence on the location and intensity of the particle rope or particle concentration irregularities. The presented results show the importance of further development of efficient rope splitting devices for applications in coal-fired power plants. Numerical analysis can be used as an efficient tool for their investigation and further optimisation under various operating and flow conditions.

The transport or the separation of solid particles or droplets suspended in a fluid flow is a common task in mechanical and process engineering. To improve machinery and physical processes (e.g. for coal combustion, reduction of NO_x and soot) an optimization of complex phenomena by simulation applying the fundamental conservation equations is required. Fluid-particle flows are characterized by the ratio of density of the two phases gamma=rho_P/rho_F, by the Stokes number St=tau_P/tau_F and by the loading in terms of void and mass fraction. Those numbers (Stokes number, gamma) define the flow regime and which relevant forces are acting on the particle. Dependent on the geometrical configuration the particle-wall interaction might have a heavy impact on the mean flow structure. The occurrence of particle-particle collisions becomes also more and more important with the increase of the local void fraction of the particulate phase. With increase of the particle loading the interaction with the fluid phase can not been neglected and 2-way or even 4-way coupling between the continous and disperse phases has to be taken into account. For dilute to moderate dense particle flows the Euler-Lagrange method is capable to resolve the main flow mechanism. An accurate computation needs unfortunately a high number of numerical particles (1,...,10^7) to get the reliable statistics for the underlying modelling correlations. Due to the fact that a Lagrangian algorithm cannot be vectorized for complex meshes the only way to finish those simulations in a reasonable time is the parallization applying the message passing paradigma. Frank et al. describes the basic ideas for a parallel Eulererian-Lagrangian solver, which uses multigrid for acceleration of the flow equations. The performance figures are quite good, though only steady problems are tackled. The presented paper is aimed to the numerical prediction of time-dependend fluid-particle flows using the simultanous particle tracking approach based on the Eulerian-Lagrangian and the particle-source-in-cell (PSI-Cell) approach. It is shown in the paper that for the unsteady flow prediction efficiency and load balancing of the parallel numerical simulation is an even more pronounced problem in comparison with the steady flow calculations, because the time steps for the time integration along one particle trajectory are very small per one time step of fluid flow integration and so the floating point workload on a single processor node is usualy rather low. Much time is spent for communication and waiting time of the processors, because for cold flow particle convection not very extensive calculations are necessary. One remedy might be a highspeed switch like Myrinet or Dolphin PCI/SCI (500 MByte/s), which could balance the relative high floating point performance of INTEL PIII processors and the weak capacity of the Fast-Ethernet communication network (100 Mbit/s) of the Chemnitz Linux Cluster (CLIC) used for the presented calculations. Corresponding to the discussed examples calculation times and parallel performance will be presented. Another point is the communication of many small packages, which should be summed up to bigger messages, because each message requires a startup time independently of its size. Summarising the potential of such a parallel algorithm, it will be shown that a Beowulf-type cluster computer is a highly competitve alternative to the classical main frame computer for the investigated Eulerian-Lagrangian simultanous particle tracking approach.

Reservoir testing and analysis are fundamental tools in understanding reservoir hydraulics and hence forecasting reservoir responses. The quality of the analysis is very dependent on the conceptual model used in investigating the responses under different flowing conditions. The use of reservoir testing in the characterization and derivation of reservoir parameters is widely established, especially in conventional oil and gas reservoirs. However, with depleting conventional reserves, the quest for unconventional reservoirs to secure the increasing demand for energy is increasing; which has triggered intensive research in the fields of reservoir characterization. Gas hydrate reservoirs, being one of the unconventional gas reservoirs with huge energy potential, is still in the juvenile stage with reservoir testing as compared to the other unconventional reservoirs. The endothermic dissociation hydrates to gas and water requires addressing multiphase flow and heat energy balance, which has made efforts to develop reservoir testing models in this field difficult. As of now, analytically quantifying the effect on hydrate dissociation on rate and pressure transient responses are till date a huge challenge. During depressurization, the heat energy stored in the reservoir is used up and due to the endothermic nature of the dissociation; heat flux begins from the confining layers. For Class 3 gas hydrates, just heat conduction would be responsible for the heat influx and further hydrate dissociation; however, the moving boundary problem could also be an issue to address in this reservoir, depending on the equilibrium pressure. To address heat flux problem, a proper definition of the inner boundary condition for temperature propagation using a Clausius-Clapeyron type hydrate equilibrium model is required. In Class 1 and 2, crossflow problems would occur and depending on the layer of production, convective heat influx from the free fluid layer and heat conduction from the cap rock of the hydrate layer would be further issues to address. All these phenomena make the derivation of a suitable reservoir testing model very complex. However, with a strong combination of heat energy and mass balance techniques, a representative diffusivity equation can be derived. Reservoir testing models have been developed and responses investigated for different boundary conditions in normally pressured Class 3 gas hydrates, over-pressured Class 3 gas hydrates (moving boundary problem) and Class 1 and 2 gas hydrates (crossflow problem). The effects of heat flux on the reservoir responses have been addressed in detail.

O interesse na medição do perfil de velocidade na área de fluidodinâmica tem crescido nos últimos anos devido a evolução das técnicas de medição. Nesse contexto, a técnica ultrassônica tem se destacado por ser não intrusiva, não invasiva e funcionar mesmo em fluidos opacos. Neste trabalho foi investigado a técnica de ultrassom Doppler para medição de perfis de velocidade, utilizando equipamentos ultrassônicos para ensaios-não-destrutivos (END). Tais equipamentos são mais acessíveis do que equipamentos convencionais de medição de velocidade por ultrassom. Também foi proposto o uso da técnica de autocorrelação estendida (EAM), para medição de velocidades além do limite de Nyquist. Essa restrição existe na grande maioria dos medidores, que utilizam a técnica convencional de autocorrelação (ACM). O EAM combina o ACM com o método da correlação cruzada (CCM), outro estimador amplamente conhecido, mas que não é muito utilizado devido a seu alto custo computacional. Desta forma, o EAM consegue medir velocidades maiores com um custo computacional intermediário, que não é tão baixo quanto o ACM e nem tão alto quanto o CCM. Para adquirir e processar os dados obtidos, foi desenvolvido um sistema para aquisição e processamento dos sinais baseado na linguagem LabView. O pulsador ultrassônico END e os estimadores de velocidade por EAM, CCM e ACM foram validados medindo o perfil de velocidade em um cilindro girante, capaz de fornecer velocidades controladas de fácil solução analítica. Os resultados mostram erros médios quadráticos abaixo de 2%, validando o equipamento e a técnica. O EAM também mediu velocidades acima no limite de Nyquist com um desempenho computacional de 9 vezes maior do que o CCM. Na segunda parte deste trabalho, a técnica ultrassônica de medição de velocidade foi aplicada para medição de escoamentos multifásicos em tubulações, tema de grande interesse da indústria de petróleo e gás. Um escoamento vertical líquido-gás-sólido foi analisado com o mesmo equipamento END. Primeiramente, o perfil de velocidade do escoamento liquido-sólido em regime laminar, foi medido e validado utilizando um equipamento Coriolis como referência. Em seguida, foram realizados testes adicionando gás ao escoamento. As velocidades superficiais de líquido e gás foram variadas para gerar os padrões de escoamento tipo bolhas dispersas, intermitente e intermitente aerado. Os resultados foram comparados a imagens de uma filmadora de alta velocidade. Foram obtidos parâmetros como perfil de velocidade das bolhas dispersas, velocidade do filme de líquido e velocidade da mistura dependendo do padrão de escoamento analisado. Assim, a medição de velocidade por ultrassom Doppler, utilizando um equipamento de END, foi aplicado com sucesso em dois problemas de fluidodinâmica. / Interest in knowing the instantaneous velocity profile in fluid dynamics has grown in recent years as new flow visualization techniques are improving. In this context, the ultrasonic Doppler velocity profiler (UVP) has desirable characteristics, as it is non-invasive, works with opaque liquids, and it is portable and easy to install if compared with other velocity profiler methods. In this work, the use of nondestructive ultrasonic devices in the UVP field is investigated. NDT systems are widely available and have lower cost if compared to traditional ultrasonic velocity profiler systems. The use of an extended autocorrelation method (EAM) for ultrasonic velocity estimation beyond Nyquist limit are also evaluated. The Nyquist limit causes a restriction on the maximum measurable velocity of the traditional autocorrelation method (ACM), present in most of ultrasonic velocity profiler systems. EAM combines the ACM technique with cross-correlation method (CCM) which is a well-established velocity estimator that does not suffer with Nyquist limit. However, the technique has a high computational cost that limits real time applications. EAM has the advantage of measure velocities beyond the Nyquist limit but with a lower computational cost than CCM. To evaluate the NDT device and the velocity estimation techniques ACM, CCM and EAM, a data acquisition system and a signal-processing unit based on LabView language were developed. The velocity profile of a rotating cylinder was used to validate all measurements. The techniques ACM, CCM and EAM successfully measured velocities within Nyquist limit with less than 2% deviation, validating the NDT system. EAM also measured velocities beyond Nyquist limit with a computational performance 9 times faster than CCM. The ultrasonic technique was also applied to measure the velocity profile of a multiphase flow in a pipeline, which are of great interest in oil and gas industry. Tests within a multiphase flow composed by different combinations of oil/sand/nylon-particles and gas were conducted in a vertical rig. A high-speed camera was used to validate the measurements. First the ultrasonic velocity profile measured was validated in a liquid-solid flow by using a Coriolis flowmeter as a reference. Next, superficial liquid and gas velocity were controlled to obtain different flow patterns such as bubbly flow and slug flow. The technique measured the bubbles velocity, the mixture velocity and the liquid film velocity depending on the flow pattern. Finally, the ultrasonic NDT system was successfully applied to investigate two different fluid engineering problems.

CNPq; FUNTEF-PR / Sensores wire-mesh (WMS) são capazes de gerar imagens da seção transversal de escoamentos multifásicos e tem sido amplamente utilizados para investigar fenômenos de escoamentos em plantas piloto. Tais dispositivos são capazes de medir parâmetros de escoamento tais como distribuição da fração de fase (por exemplo fração de gás ou líquido) e visualizar escoamentos multifásicos com alta resolução temporal e espacial. Sendo portanto, uma ferramenta importante para investigações de escoamentos mais detalhadas. No entanto, seu princípio de medição é baseado em eletrodos intrusivos posicionados dentro do tubo onde o escoamento flui. A resolução da imagem gerada pelo sensor é dada pelo número de cruzamentos entre os fios transmissores e receptores. Em muitos processos, no entanto, efeitos de intrusividade de tal sensor pode ser uma limitação no seu uso. Por isso, um número reduzido de fios poderia permitir uma expansão do campo de aplicações do sensor wire-mesh. Por essa razão, o presente trabalho sugere um método de reconstrução de imagem para aumentar a resolução dos dados de um sensor wire-mesh com um número de eletrodos menor que o ótimo. Desta forma, os efeitos de intrusividade no processo investigado poderiam ser reduzidos. O método de reconstrução é baseado em uma abordagem estatística de regularização e é conhecido como Maximum a Posteriori (MAP). Dados de escoamento de um WMS 16x16 são usados para determinar um modelo gaussiano multivariável do escoamento, o qual são empregados como regularização na reconstrução. Uma matriz de sensitividade é estimada pelo método de elementos finitos (FEM) para incorporar o algoritmo MAP. Dados experimentais são usados para validar o método proposto, sendo comparado com interpolação do tipo spline. Resultados experimentais mostram que a reconstrução por MAP possui um desempenho melhor do que interpolação do tipo spline, alcançando desvios de fração de vazio dentro de uma faixa de ± 10% na grande maioria dos pontos de operação. A validação foi executada em um loop de escoamento horizontal água/gás em regime intermitente (golfada). / Wire-mesh sensors (WMS) are able to generate cross-sectional images of multiphase flow and have been widely used to investigate flow phenomena in pilot plant studies. Such devices are able to measure flow parameters such as phase fraction (e.g. gas/liquid fraction) distribution and visualize multiphase flows with high temporal and spatial resolution. Hence, being important tool for detailed flow investigation. However, its sensing principle is based on intrusive electrodes placed inside the pipe where a multiphase flow streams. The image resolution generated by the sensor is given by the number of crossing points formed by the transmitter and receptor wires. In many processes, however, the intrusive effect of such sensor might be a limitation on its use. Therefore, a reduced number of wires could possibly increase the application field of wire-mesh sensors. For this reason, the present work presents an image reconstruction method to increase resolution of WMS data with less than optimal number of electrode wires. In this way, a reduction of intrusive effects on the process under investigation may be achieved. The reconstruction method is based on statistical view of regularization and is known as Maximum a Posterior (MAP). 16x16 WMS flow data are used to determine a Multivariate Gaussian flow model, which in turn is used as regularization in the reconstruction. A sensitive matrix is estimated by finite element method (FEM) to incorporate MAP algorithm. Experimental data are used to validate the proposed method, which is compared with spline interpolation. Experimental results show that the MAP reconstruction performs better than interpolation and achieves deviation in gas void fraction estimation in the range of ±10% in the vast majority of operating points. The tests were performed in a horizontal water-gas flow loop operating at intermittent (slug) flow regime.

Aujourd’hui, plus de 65% des sites pollués en France le sont par des COVs (BASOL), considérés comme étant très dangereux et toxiques pour l’homme et l’environnement. Cela nécessite d’utiliser des techniques de traitement pour restaurer les sites et limiter les risques de propagation vers les eaux souterraines. L’extraction multiphasique MPE est une méthode physique de traitement des COVs. Elle a plusieurs avantages : essentiellement économique, le fait de pouvoir être utilisée in-situ et le fait de permettre la remédiation simultanée de deux zones saturée et non saturée du sous-sol. L’objectif de cette thèse est d’étudier cette technique en développant un modèle mathématique qui permet de décrire l’écoulement multiphasiques des différentes phases, le transport et le transfert de masse entre ces phases. Deux sols sableux et un polluant modèles sont choisis et caractérisés. Des dispositifs expérimentaux sont utilisés pour l’étude de l’écoulement diphasique et multiphasique ainsi que l’étude de transfert de masse. Un modèle numérique est développé, il se compose de trois EDPs pour l’écoulement (gazeuse, aqueuse et PLNA) et quatre EDPs pour le transport/transfert de masse pour chaque composé. La validation du modèle MPE est réalisée par la vérification de différentes parties qui le constituent séparément. La partie de l’écoulement diphasique est vérifiée à travers les résultats d’expérience de drainage sur colonne 1D et sur des résultats issus de la littérature d’une cellule type Hele-show 2D. L’importance du choix des conditions aux limites est mise en évidence. La partie de l’écoulement triphasique est vérifiée à travers les résultats d’expériences d’infiltration sur cellule 2D, l’une réalisée au laboratoire et l’autre issue de la littérature. L’étude porte sur l’effet du choix des dimensions d’expériences de laboratoire sur l’extrapolation des résultats à l’échelle du terrain. La partie transport/transfert de polluant est vérifiée à travers des expériences d’extraction sous vide/Venting. Le coefficient de transfert est déterminé avec une meilleure précision que celle des modèles issus de la littérature. Enfin une simulation à l’échelle de terrain est effectuée avec le modèle MPE pour simuler la dépollution d’un site pollué selon un scénario supposé et développé par la MPE. Les limites de la méthode pour la dépollution de la frange capillaire sont mises en évidence. / Today, over 65% of polluted sites in France are by VOCs (BASOL), considered to be very dangerous and toxic to humans and the environment. This requires using treatment techniques to restore the sites and limit the risk of spread to groundwater. The multiphase extraction MPE is a physical method of soil VOCs treatment. It has several advantages: essentially economic, being able to be used in site and permitting the simultaneous remediation of both saturated and unsaturated zones. The objective of this thesis is to study this technique by developing a mathematical model to describe the multiphase flow of different phases, transport and mass transfer between these phases. Two sandy soils and a pollutant models are selected and characterized. Experimental devices are used to study the two-phase, multiphase flow and mass transfer. A numerical model is developed; it consists of three PDEs for the flow (gas, water and NAPL) and four PDEs to pollution transport/mass transfer for each compound. MPE Model validation is performed by the verification of different constituent parts separately. The two-phase flow is confirmed by the drainage experiment results of 1D column and of the results of the literature of a 2D Hele-show tank. The importance of the choice of boundary conditions is highlighted. The part of the three-phase flow is verified through the results of infiltration experiments on 2D tank, one conducted in the laboratory and the other of the literature. The study focuses on the effect of the choice of laboratory experiments dimensions on the extrapolation of results across the field. The transport/mass transfer part is verified by SVE/Venting experiments. The transfer coefficient is determined with a precision better than models from the literature. Finally a simulation at the field scale is carried out with the MPE model to simulate the remediation of polluted sites by MPE for a supposed scenario. The limitations of the method for remedying the capillary fringe are highlighted.

This paper covers information research of basic design rules of industrial wet sumps. It describes mathematical models of vortices and method for their identification and visualization. Then the author focuses on CFD modeling of surface vortices with single phase and multiphase approach with Volume of Fluid method. Basic principles of multiphase CFD modelling in OpenFOAM and ANSYS Fluent are given. Description and benchmarking of suitable turbulence models is also present. The single phase and multiphase approach were successfully validated for a simple test case of bathtub surface vortex. Satisfactory agreement with experimental data was achieved. The accuracy and behavior of both solvers were compared between each other. This gives us useful tool for evaluation of inflow condition and danger of surface vortex occurrence in wet sumps. The acquired knowledges were used to design an experimental test case with geometry similar to industrial wet sump. A map of surface vortex occurrence has been created for different operating points. One of the operating point has been used for numerical simulation (both single phase and multiphase). Partial agreement with experimental observation has been achieved.