PMM testing is a method used to identify the added mass and damping coefficients used in the equations of motion of a vehicle by attempting to decouple the forces on a body due to velocity and acceleration as a result of creating "hydrodynamically pure" velocities and accelerations. This makes it possible to use quasi-steady state models with terms independent of both velocity and acceleration. This paper explores the ability of simple damping models (solely a function of velocity) with added mass terms (solely a function of acceleration) to simulate the heave force of an 8:1 ellipsoid undergoing PMM testing. In order to help explain the complexity of the flow during PMM tests, a flow analysis of the 8:1 spheroid is provided, which discusses the flow topology of spheroids at steady angle of attack, validity of quasi-steady models, and some other basic flow features seen in PMM testing. In this paper, a simple proportionality relationship between a linear and quadratic damping model is revealed. It is also shown that variations in the heave force response during PMM tests are most heavily influenced by viscous effects, especially cross flow separation. Finally, it is shown where these models break down, owing to the increasing nonlinearity of the flow induced by the harsher motions of large amplitude and/or large frequency tests. / Master of Science

La clarification des vins par procédés membranaires en particulier la microfiltration tangentielle a toujours été limitée par le colmatage, générant des flux de perméation faibles incompatibles avec la rentabilité économique. La compréhension, la maîtrise, ainsi que l'anticipation des phénomènes de colmatage font l'objet de ce travail. Dans un premier temps, la contribution individuelle puis en mélange des composés du vin (tannins, pectines, mannoprotéines et levures) au colmatage d'une membrane céramique multicanaux a été évaluée. Une approche fondamentale a permis de proposer des mécanismes de colmatage : la présence des pectines induit les flux de perméation les plus faibles en formant un gel à la surface de la membrane tandis que les levures semblent au contraire avoir un effet protecteur dans le cas d'un vin brut. Parce qu'il représente le flux au-delà duquel un colmatage irréversible apparaît à la surface de la membrane, le flux critique pour l'irréversibilité est un paramètre clef pour contrôler le colmatage. Dans le cas de la filtration de vin, aucun flux critique n'a pu être déterminé ce qui a conduit à définir un critère identifiant une zone de travail où le degré de colmatage reste acceptable. La dernière partie de cette thèse est consacrée à l'étude de la filtration dynamique (RVF) pour une éventuelle application dans le secteur vinicole. Cette technique est testée en présence de deux membranes organiques différentes: PES (hydrophile) et PTFE (hydrophobe). Les observations ont permis de mettre en évidence l'efficacité du système contre le colmatage des membranes PES induite par l'action de l'agitateur. Le colmatage des membranes PTFE est énormément affecté par les interactions molécules/membrane rendant la filtration dynamique inefficace pour lutter contre le colmatage de ces membranes. / Wine clarification by membrane processes mainly cross-flow microfiltration has been limited by membrane fouling generating low permeate fluxes with economic efficiency. Understanding, controlling and anticipation of fouling are the main goals of this work. In a first time, the individual contribution of wine compounds (tannins, pectins, mannoproteins and yeasts) to a multichannel ceramic membrane fouling was evaluated. The fouling mechanisms were analyzed using a fundamental approach. The presence of pectins induce the lowest fluxes by a gel-type formation at the membrane surface while yeasts presence tends to reduce fouling in the case of crude wine (case of mixed components). Because it represents the flux beyond which irreversible fouling appears on the membrane surface, the critical flux for irreversibility is a key parameter to control fouling. No critical flux for irreversibility could be measured, hence a criterion that identifies a range of operating conditions where the degree of fouling remains acceptable was proposed. The last part of this work was devoted to the study of dynamic filtration (RVF) for further application in wine sector. This technique was tested with two different membranes: hydrophilic PES and hydrophobic PTFE. Results have allowed to demonstrate the efficiency of the system to reduce fouling in the case of PES membrane. Fouling of PTFE membrane is greatly influenced by molecules / membrane interaction making dynamic filtration ineffective in reducing of membrane fouling.

This thesis presents some new techniques that were developedfor continuous chemical analysis of a paper furnish. First, ageneral background is presented, covering topics from theorigins of papermaking to present day. A short introduction topapermaking chemistry and a variety of presently availableon-line chemical analysers and measurement strategies are alsodiscussed. A method is described for the continuous fractionation of apaper furnish containing coarse fibres (&gt;10µm) in orderto obtain a sample for analytical purposes (Paper I). Aconsistent sample, containing a representative fraction of thedissolved and colloidal substances (DCS) present in the bulkfurnish, was achieved by preventing cake formation on a filtersurface. A combination of turbulent flow above a membranefilter, while continuously withdrawing a relatively low samplevolume, were key factors in the prevention of filterfouling. For the continuous flow-extraction of DCS, a technique isdescribed whereby the extracting solvent was injected at a highvelocity into a continuous flow of analyte (Paper II).Comparison with conventional flow extraction showed anextraction enhancement of up to 9 times for colloidaltriglycerides. To achieve a continuous determination of chemicalsubstances, a real-time fully automated colorimetric titrationapparatus was developed (Paper III&amp;IV). This was achievedby using a series of micro-machined mixing channels for thecontinuous flow of analyte, with a sequence of detection unitsand titrant addition points along the flowpath (Paper III). Afuzzy logiccontroller was implemented to continuously adaptfor changes in the sample concentration, providing thepossibility of titrating over two orders of magnitude in sampleconcentration with minimal loss of accuracy (Paper IV). Also, a system is presented whereby the filtration apparatus(Paper I) is combined with the titration device (Paper III&amp;IV) in order to continuously determine total charge (orcolloidal charge) of a paper furnish in real-time (Paper V).This was achieved by utilising a back-titration approach andselected examples are presented showing the dynamicinteractions between wood fibres and polyelectrolyte adsorptionat various conditions of pH and polyelectrolyte molecularweight. Finally, some suggestions for a more comprehensive wet-endchemical monitoring platform are discussed and the role of thepresent work in evaluated in this context. <b>Keywords:</b>Chemical monitoring, continuous flowextraction, cross-flow filtration, dissolved and colloidalcomponents, fuzzy-logic control, on-line system, pitchanalysis, polyelectrolyte titration, process control, samplework-up, titrimetric analysis.

For flights beyond Mach 6 ramjets are inefficient engines due to huge total pressure loss in the normal shock systems, combustion conditions that lose a large fraction of the available chemical energy due to dissociation and high structural loads. However if the flow remains supersonic inside the combustion chamber, the above problems could be alleviated and here the concept of SCRAMJET(supersonic combustion ramjet) comes into existence. The scramjets could reduce launching cost of satellites by carrying only fuel and ingesting oxygen from atmospheric air. Further applications could involve defense and transcontinental hypersonic transport. In the current study an effort is made to achieve supersonic combustion in a ground based short duration test facility(combustion driven shock-tunnel), which in addition to flight Mach number can simulate flight Reynolds number as well. In this study a simple method of injection i.e. wall injection of the fuel into the combustion chamber is used. The work starts with threedimensional numerical simulation of a non-reacting gas(air) injection into a hypersonic cross-flow of air to determine the conditions in which air penetrates reasonably well into the cross-flow. Care is taken so that the process does not induce huge pressure loss due to the bow shock which appears in front of the jet column. The code is developed in-house and parallelized using OpenMp model. This is followed by experiments on air injection into a hypersonic cross-flow of air in a conventional shock-tunnel HST2 existing in IISc. The most tricky part is synchronization of injection with start of test-flow in such a short duration(test time 1 millisecond) facility. Next part focuses on numerical simulations to determine the free-stream conditions, mainly the temperature and pressure of air, so that combustion takes place when hydrogen is injected into a supersonic cross-flow of air. The simulations are two-dimensional and includes species conservation equations and source terms due to chemical reactions in addition to the Navier-Stokes equations. This code is also built in-house and parallelized because of more number of operations with the inclusion of species conservation equations and chemical non-equilibrium. However, the predicted conditions were not achievable by HST2 due to low stagnation conditions of HST2. Therefore, a new shock-tunnel which could produce the required conditions is built. The new tunnel is a combustion driven shock-tunnel in which the driver gas is at higher temperature than conventional shock-tunnel. The driver gas is basically a mixture of hydrogen, oxygen and helium at a mole ratio of 2:1:10 initially. The mixture is ignited by spark plugs and the hydrogen and oxygen reacts releasing heat. The heat released raises the temperature of the mixture which is now predominantly helium and small fractions of water vapour and some radicals. The composition of the driver gas and initial pressure are determined through numerical simulations. Experiments follow in the new tunnel on hydrogen injection into a region of supersonic cross-flow between two parallel plates with a wedge attached to the bottom plate. The wedge reduces the hypersonic free-stream to Mach 2. A high-speed camera monitors the flow domain around injection point and sharp rise in luminosity is observed. To ascertain whether the luminosity is due to combustion or not, two more driven gases namely nitrogen and oxygen-rich air are used and the luminosity is compared. In the first case, the free-stream contains no oxygen and luminosity is not observed whereas in the second case higher luminosity than air driver case is visible. Additionally heat-transfer rates are measured at the downstream end of the model and at a height midway between the plates. Similar trend is observed in the relative heat-transfer rates. Wall static pressure at a location downstream of injection port is also measured and compared with numerical simulations. Results of numerical simulations which are carried out at the same conditions as of experiments confirm combustion at supersonic speed. Experiments and numerical simulations show presence of supersonic combustion in the setup. However, further study is necessary to optimize the parameters so that thrust force could be generated efficiently.

<p>This thesis presents some new techniques that were developedfor continuous chemical analysis of a paper furnish. First, ageneral background is presented, covering topics from theorigins of papermaking to present day. A short introduction topapermaking chemistry and a variety of presently availableon-line chemical analysers and measurement strategies are alsodiscussed.</p><p>A method is described for the continuous fractionation of apaper furnish containing coarse fibres (>10µm) in orderto obtain a sample for analytical purposes (Paper I). Aconsistent sample, containing a representative fraction of thedissolved and colloidal substances (DCS) present in the bulkfurnish, was achieved by preventing cake formation on a filtersurface. A combination of turbulent flow above a membranefilter, while continuously withdrawing a relatively low samplevolume, were key factors in the prevention of filterfouling.</p><p>For the continuous flow-extraction of DCS, a technique isdescribed whereby the extracting solvent was injected at a highvelocity into a continuous flow of analyte (Paper II).Comparison with conventional flow extraction showed anextraction enhancement of up to 9 times for colloidaltriglycerides.</p><p>To achieve a continuous determination of chemicalsubstances, a real-time fully automated colorimetric titrationapparatus was developed (Paper III&IV). This was achievedby using a series of micro-machined mixing channels for thecontinuous flow of analyte, with a sequence of detection unitsand titrant addition points along the flowpath (Paper III). Afuzzy logiccontroller was implemented to continuously adaptfor changes in the sample concentration, providing thepossibility of titrating over two orders of magnitude in sampleconcentration with minimal loss of accuracy (Paper IV).</p><p>Also, a system is presented whereby the filtration apparatus(Paper I) is combined with the titration device (Paper III&IV) in order to continuously determine total charge (orcolloidal charge) of a paper furnish in real-time (Paper V).This was achieved by utilising a back-titration approach andselected examples are presented showing the dynamicinteractions between wood fibres and polyelectrolyte adsorptionat various conditions of pH and polyelectrolyte molecularweight.</p><p>Finally, some suggestions for a more comprehensive wet-endchemical monitoring platform are discussed and the role of thepresent work in evaluated in this context.</p><p><b>Keywords:</b>Chemical monitoring, continuous flowextraction, cross-flow filtration, dissolved and colloidalcomponents, fuzzy-logic control, on-line system, pitchanalysis, polyelectrolyte titration, process control, samplework-up, titrimetric analysis.</p>

The application of non-thermal processes pulsed electric fields (PEF) and cross-flow micro-filtration (CFMF) continuous to be studied with the purpose of controlling microorganisms in milk. Trends suggesting increased adoption include the study of Food Safety Objectives as a safety criterion, the promotion of sustainable processing, and the implementation of hurdle strategies. While the advance of gentle processing is counteracted by the risk of enhanced resistance due to microbial stress response, several techniques can be applied to quantitatively assess its impact. The objective of this project was to evaluate the effectiveness of microbial inactivation by PEF and CFMF at various steps of milk processing including shelf-life, its comparison with high temperature short time (HTST) pasteurization, and the quantitative assessment of the cross protection resistance to PEF of Escherichia coli O157:H7. Some differences in mesophilics inactivation were observed in milks (fat contents between 1.1% and 3.1%). Increasing the PEF inlet temperature decreased the treatment time by three or two-fold. The combination of CFMF/PEF yielded similar microbial reductions as CFMF/HTST. Higher inactivation of the coliforms was achieved in homogenized cream (12% fat) compared to non-homogenized. The linear relation between electrical conductivity and nutrient content (fat and solids content) was established. In a parallel study the PEF/CFMF sequence resulted in higher inactivation of mesophilics compared to CFMF/PEF and HTST. The shelf life was acceptable for CFMF/PEF and HTST after 7 days, while enterics and psychrotrophs grew more after PEF/CFMF, thermodurics did after HTST. The growth and stress of Escherichia coli O157:H7 in lactose containing broths was monitored by absorbance and fluorescence expression of stress reporters. Growth was explained using a secondary model, and stress response using mechanistic and probabilistic models. PEF inactivation was evaluated following the Weibull distribution after the cells reached stationary phase or maximum fluorescence expression. Similar resistances were observed within the cells grown in lactose broth at 10, 25 or 40°C, as within stressed cells (starved or cold shocked). Cells grown at 45 °C were more resistant compared to the cells grown in acid, high salt concentration while the ones grown at cold temperatures were the weakest. / Dairy Farmers of Ontario, Natural Sciences and Engineering Research Council.

Des méthodes numériques sont présentées qui permettent la simulation de jets chauds débouchants dans un écoulement transverse aux grands nombres de Reynolds et aux rapports des vitesses faibles. Différentes approches pour la modélisation de turbulence, c'est-à-dire URANS, SAS, DDES et ELES, sont validées par comparaison à des données expérimentales pour une configuration générique, soulignant la nécessité de résoudre les différentes échelles turbulentes pour une prévision correcte du mélange thermique. L'analyse de la solution instationnaire permet l'identification de processus dynamiques intrinsèques ainsi que des phénomènes de mélange et l'application de l'analyse en composantes principales révèle l'ondulation latérale du sillage de jet. Du fait du caractère multi-échelles qui se manifeste dans la simulation d'un jet débouchant sur une configuration avion, l'approche séquentielle basée sur le modèle SAS est mise en place. Comme les résultats pour la sortie d'un système de dégivrage de nacelle sont en bon accord avec les données d'essai en vol, cette approche est finalement appliquée à la sortie complexe d'un système de pre-cooler, mettant en valeur sa capacité à être appliquée dans un processus industriel. / Numerical methods for the simulation of hot jets in cross flow at high Reynolds numbers and small momentum ratios are presented. Different turbulence modeling strategies, i.e. URANS, SAS, DDES and ELES, are validated against experimental data on a generic configuration, highlighting the necessity of scale-resolution for a correct prediction ofthermal mixing. The analysis of transient flow simulations allows the identification of inherent flow dynamics as well as mixing phenomena and the application of the Proper Orthogonal Decomposition revealed the lateral wake meandering as being one of them. Due to the multi-scale problem which arises when simulating jets in cross flow on real aircraft configurations, the sequential approach based on the SAS turbulence model is introduced. As results for the exhaust of a nacelle anti-icing system comprising multiple jets in cross flow agree well with flight test data, the approach is applied in a last step to the complex exhaust of a pre-cooling system, emphasizing the capabilities of this methodology in an industrial environment.

L'étude développée dans cette thèse concerne le contrôle des performances et des lâchers tourbillonnaires au cours du cycle de rotation d'une hydrolienne à axe vertical de type Darrieus. L'élaboration d'une famille de lois de commande d'incidence de pales exploitant le principe de conservation de la circulation autour de profils en mouvement permet ici le contrôle du fonctionnement de l'hydrolienne ainsi que la maîtrise de son sillage tourbillonnaire afin de préserver l'environnement.L'écoulement 2D est simulé à l'aide du solveur incompressible de Star CCM+ afin de mettre en évidence l'effet de ce type de contrôle sur le rendement de la turbine pour différents points de fonctionnement. Ce modèle CFD a été utilisé pour améliorer l'analyse analytique en ce qui concerne l'extraction de l'énergie, la compréhension de l'écoulement autour de l'hydrolienne et le contrôle des tourbillons générés. La nouveauté de cette étude est l'élaboration de lois de commande de pales d'hydrolienne, basées sur des valeurs constantes et transitoires de la circulation, afin d'augmenter la puissance de la turbine tout en garantissant un contrôle efficace de la vorticité et ainsi prévenir de l'interaction entre les tourbillons et les pales. Une bonne comparaison est réalisée entre les résultats analytiques et numériques concernant les forces hydrodynamiques.En outre, une campagne d'essais a été menée afin d'acquérir des mesures quantitatives sur une hydrolienne de type Darrieus à pales fixes en terme de puissance, mais aussi des résultats qualitatifs pertinents comme la visualisation de l'écoulement autour des pales à différentes positions et pour différents points de fonctionnement. La mise en place complète d'un système PTV pour les mesures qualitatives et les étapes de traitement sont discutées et les divers paramètres obtenus à partir des études CFD sont validées en utilisant ces résultats PIV.L'étude expérimentale dans la présente recherche appo11e des informations détaillées sur les gradients de pression et de vitesse, les contours de vorticité et le critère Q qui ont servi à valider les visualisations obtenues numériquement. / With key applications in marine renewable energy. the vertical axis water turbine can use current or tidal energy in an eco-friendly manner. However, it is difficult to reconcile optimal performance of hydrokinetic turbines and compliance wilh the aquatic environment as the main drawback of the turbines is the formation of non-linear flow structures caused by the unsteady movement of the blades. Eddies in the flow are advected and can interact with other blades, which leads to a reduction in power output. To limit this phenomenon, the turbines operate at high speeds, which are likely to reduce the shaft power. High speeds of rotational so forbid the passage of aquatic animais, and are the cause of a suction effect on the sediments.The objective of this thesis work is twofold. First, it aims to develop a blade pitch control to get the flow adjusted around the blade profile at any given flow configuration by incorporatin.g the profile's motion with respect to incident flow. Such a system intends to achieve the objective of operating at reduced speeds without vortical releases, which should allow achieving a high torque without causing damage to the environment.This thesis work is mainly carried out in three phases. ln the first phase, the irrotational flow over an arbitrary profile is formulated using conforma] mapping. Prospective potential flow application on the basis of Couchet theory (1976) is involved in the development of a control law that decides the blade pitching in a constant circulation framework. In the second phase, a numerical validation of the developed analytical work is presented using CFD to examine how the theoretical fomulation can be effectively applied to Darricus turbines. In the final phase, two prototypes are developed, one is classical Darrieus turbine with fixed blades, and other is the turbine with pitching blades for experimental measurements of performance as well as flow fields(by PIV) in order to validate the computational results.

A lot of research effort is spent worldwide in order to reduce the environmental impact of the transportation and power generation sector. To minimize the environmental pollution the role of hydrogen fuelled gas turbines is intensively discussed in several research scenarios, like the IGCC-technology or the application of hydrogen as large scale storage for renewable energy sources. The adaptation of the applied gas turbine combustion chamber technology and control technology is mandatory for a stable and secure low NOx operation of a hydrogen fuelled gas turbine.<p>The micromix combustion principle was invented at Aachen University of Applied Sciences and achieves a significant reduction of the NOx-emissions by the application of multi miniaturized diffusion-type flamelets. Based on the research experiences, gained during the two European hydrogen research programs EQHHPP and Cryoplane at Aachen University of Applied Sciences, the intention of this thesis was to continue the scientific research work on low NOx hydrogen fuelled gas turbines. This included the experimental characterization of the micromix combustion principle, the design of an improved combustion chamber, based on the micromix combustion principle, for industrial gas turbine applications and the improvement of the gas turbine’s control and metering technology.<p>The experimental characterization of the micromix combustion principle investigated the impact of several key parameters, which influence the formation of the NOx-emissions, and allows therefore the definition of boundary conditions and design laws, in which a low NOx operation of the micromix combustion principle is practicable. In addition the ability of the micromix combustion principle to operate at elevated energy densities up to 15 MW/(m2bar) was successfully demonstrated. The improved combustion chamber design concept includes the experiences gained during the experimental characterization and covers the industrial needs regarding scalability and manufacturability.<p>The optimization and testing is done with an Auxiliary Power Unit GTCP 36-300. The original kerosene fuelled gas turbine was modified for the hydrogen application. Therefore several hardware and software modifications were realized. The improved gas turbine’s control and metering technology enables stable and comparable operational characteristics as in kerosene reference. An improved hydrogen metering unit, which is controlled by the industrial Versatile Engine Control Box, was successfully implemented. <p>The combination of the micromix combustion technology and of the optimized control and metering technology allows a stable, secure and low NOx hydrogen fuelled gas turbine operation.<p> / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

Vortex shedding is an important mechanism, by which the flow around bluff bodies create forces that excite vibratory motion. Vortex-induced vibration (VIV) is studied for a single circular cylinder by means of Computational Fluid Dynamics (CFD) simulations. An arbitrary Lagrangian Eulerian (ALE) formulation is used to achieve the grid deformation needed for VIV. In this thesis, a multifaceted approach is undertaken by which response dynamics and wake interaction are addressed. Four major aspects are considered in the study: the Reynolds number (Re); the mass and damping; the degree-of-freedom for VIV; and the mutual effect between VIV and heat transfer.As attention is paid towards high pre-critical Re flow, the turbulent flow around the cylinder is treated by two turbulence modelling approaches: unsteady Reynolds Averaged Navier Stokes (uRANS), and Large Eddy Simulation (LES). The wake-VIV interaction is analyzed by looking at mean velocities and Reynolds stresses, where decomposition of flow scales is undertaken to explore the evolution of coherent eddy structures, downstream of the cylinder. Conversely, the VIV response is analyzed by considering oscillation amplitude and frequency, in addition to the excitation and inertial dynamics.High turbulence in the separated shear layers disorders the cylinder's VIV response and induces higher amplitudes. The sensitivity for Re is found more pronounced in cylinders with low mass and damping. Meanwhile, VIV is found to enhance wake mixing, and to significantly change the near wake Reynolds stresses. It is suggested that the increase in Re brings a change to the wake patterns, which are known in VIV at lower Re. The kinetic energy production, of near wake eddy structures, is qualitatively altered with the presence of VIV. Furthermore, the surface heat flux is found to cause a noticeable increase in VIV amplitude, as long as it does not disorder the wake correlation. The cylinder's oscillation increases the average value of the Nusselt number (Nu), while the local variance of Nu rises markedly post-separation.