Esse trabalho apresenta um modelo termodinâmico de uma bomba multifásica do tipo duplo parafuso. Para uma dada condição de operação, o modelo calcula a potência consumida, as condições do fluido na descarga e o perfil de pressão ao longo da bomba. Ao invés de simular diretamente o escoamento dentro da bomba, simulou-se os processos que ocorrem dentro das suas câmaras. Para tanto, dividiu-se o processo de bombeamento multifásico em uma seqüência de processos simples, facilitando-se a construção do modelo no simulador de processos Hysys.Process v2.1. Os resultados de potência e temperatura de descarga obtidos com a simulação mostram uma boa concordância com valores experimentais, principalmente para FVG’s baixos. Para FVG’s elevados, o modelo passa a superestimar a potência consumida indicando que as fendas, nesses casos, já não se encontram totalmente preenchidas com líqüido. Dos resultados obtidos para o refluxo, conclui-se que, das equações sugeridas na literatura, aquelas para escoamento turbulento liso são mais adequadas para os números de Reynolds envolvidos. O perfil de pressão e a vazão de refluxo quando o escoamento é multifásico aproxima-se qualitativamente das medições experimentais. Estudou-se a influência de diversos parâmetros na eficiência exergética da bomba. Os resultados mostram que a otimização da eficiência depende das condições de operação da bomba: FVG, tipo de líqüido, diferença de pressão, entre outros. / The goal of this project was to develop a thermodynamic model of a twin-screw multiphase pump. With given operation conditions the model can determine the absorbed power, discharge conditions and the pressure profile along the screw. An alternative approach was suggested to overcome the complex flow problem and the processes inside the pump were simulated instead of direct simulation of the flow. For this purpose, the multiphase pumping process was divided in a sequence of simple processes so the model could be developed in an easier way. The power and temperature values calculated by the model are in good agreement with experimental data, mainly when the gas fraction is low. With higher gas fractions, the model overestimates the absorbed power indicating that screw gaps are not completely filled with liquid anymore. Concerning about the backflow rate, the results show that the equations for turbulent flow in smooth ducts fits better the Reynolds number range in the gaps. The pressure profile and backflow rate for multiphase flow agree qualitatively with experimental results. The influence of several parameters in the exergetic eficiency of the pump were analysed and results show that the efficiency optimization depends on pump operation conditions: gas fraction, liquid type, pressure difference and others.

The focus of this study is the prediction of trajectories of solid particles injected into either a cylindrically- shaped solid rocket motor (SRM) or a bidirectional vortex chamber (BV). The Lagrangian particle trajectory is assumed to be governed by drag, virtual mass, Magnus, Saffman lift, and gravity forces in a Stokes flow regime. For the conditions in a solid rocket motor, it is determined that either the drag or gravity forces will dominate depending on whether the sidewall injection velocity is high (drag) or low (gravity). Using a one-way coupling paradigm in a solid rocket motor, the effects of particle size, sidewall injection velocity, and particle-to-gas density ratio are examined. The particle size and sidewall injection velocity are found to have a greater impact on particle trajectories than the density ratio. Similarly, for conditions associated with a bidirectional vortex engine, it is determined that the drag force dominates. Using a one-way particle tracking Lagrangian model, the effects of particle size, geometric inlet parameter, particle-to-gas density ratio, and initial particle velocity are examined. All but the initial particle velocity are found to have a significant impact on particle trajectories. The proposed models can assist in reducing slag retention and identifying fuel injection configurations that will ensure proper confinement of combusting droplets to the inner vortex in solid rocket motors and bidirectional vortex engines, respectively.

Worldwide demand for energy is increasing rapidly, partly driven by dramatic economic growth in developing countries. This growth has sparked concerns over the finite availability of fossil fuels and the impact of their combustion on climate change. Consequently, many recent research efforts have been devoted to the development of renewable fuels and sustainable energy systems. Interest in liquid biofuels, such as ethanol, has been particularly high because these fuels fit into the conventional infrastructure for the transportation sector. Ethanol is a renewable fuel produced through the anaerobic fermentation of sugars obtained from biomass. However, the relatively high energy demand of its production process is a major factor limiting the usefulness of ethanol as a fuel. Due to the dilute nature of the fermentation product stream and the presence of the ethanol-water azeotrope, the separation processes currently used to recover anhydrous ethanol are particularly inefficient. In fact, the ethanol separation processes account for a large fraction of the total process energy demand. In the conventional ethanol separation process, ethanol is recovered using several distillation steps combined with a dehydration process. In this dissertation, a new hybrid pervaporation-distillation system, named Membrane Dephlegmation, was proposed and investigated for use in ethanol recovery. In this process, countercurrent vapour-liquid contacting is carried out on the surface of a pervaporation membrane, leading to a combination of distillation and pervaporation effects. It was intended that this new process would lead to improved economics and energy efficiency for the entire ethanol production process. The Membrane Dephlegmation process was investigated using both numerical and experimental techniques. Multiphase Computational Fluid Dynamics (CFD) was used to study vapour-liquid contacting behaviour in narrow channels and to estimate heat and mass transfer rates. Results from the CFD studies were incorporated into a simplified design model and the Membrane Dephlegmation process was studied numerically. The results indicated that the Membrane Dephlegmation process was more efficient than simple distillation and that the ethanol-water azeotrope could be broken. Subsequently, a pilot-scale experimental system was constructed using commercially available, hydrophilic NaA zeolite membranes. Results obtained from the experimental system confirmed the accuracy of the simulations.

Multiphase flow and transport in fractured rock is of importance to many practical and engineering applications. In the field of groundwater hydrology an issue of significant environmental concern is the release of dense non-aqueous phase liquids (DNAPLs) which can cause long-term groundwater contamination in fractured aquifers. This study deals with two fundamental processes – fluid displacement and interphase mass transfer – concerning the behavior of the multiphase contaminants in fractured media. The focus of this work has been placed on improving the current understanding of small-scale (single fracture) physics by a combined effort of numerical modeling analysis, laboratory experiments and model development. This thesis contributes to the improved understanding through several aspects. Firstly, the effect of aperture variability, as characterized by geostatistical parameters such as standard deviation and correlation length, on the DNAPL entrapment, dissolution and source-depletion behaviors in single fractures was revealed. Secondly, a novel, generalized approach (adaptive circle fitting approach) to account for the effect of in-plane curvature of fluid-fluid interfaces on immiscible fluid displacement was developed; the new approach has demonstrated good performance when applied to simulate previously published experimental data. Thirdly, the performance of a continuum-based two-phase flow model and an invasion percolation model was compared for modeling fluid displacement in a variable-aperture fracture and the dependence of fracture-scale capillary pressure – saturation relationships on aperture variability was studied. Lastly, through experimental studies and mechanistic numerical modeling of DNAPL dissolution, kinetic mass transfer characteristics of two different entrapment configurations (residual blobs and dead-end pools) were investigated. The obtained understanding from this thesis will be useful for predictive modeling of multiphase contaminant behavior at a larger (fracture network) scale. / Flerfasflöde och ämnestransport i sprickigt berg är av betydelse för många praktiska och tekniska problem. Tunga, svårlösliga organiska vätskor (engelska: dense non-aqueous phase liquids: DNAPLs; t.ex. klorerade lösningsmedel) kan orsaka långvarig förorening av vattenresurser, inklusive akviferer i sprickigt berg, och utgör ett viktigt miljöproblem inom grundvattenhydrologin. Denna studie behandlar två fundamentala processer för spridning av flerfasföroreningar i sprickiga medier – utbredning av den organiska vätskan och massöverföring mellan organisk vätska och vatten. Arbetet har fokuserat på att förbättra nuvarande kunskap om de fysikaliska processerna på liten skala (enskilda sprickor) genom en kombination av numerisk modellering, laboratorieexperiment och modellutveckling. Avhandlingen har bidragit till utökad processförståelse i flera avseenden. För det första har arbetet belyst effekterna av sprickaperturens variabilitet, uttryckt med geostatistiska parametrar som standardavvikelse och rumslig korrelationslängd, på fastläggning och lösning av organiska vätskor i enskilda sprickor, samt utmattningsbeteendet hos dessa källor till grundvattenförorening. För det andra har en ny, generell metod (adaptiva cirkelpassningsmetoden) för att ta hänsyn till effekten av krökningen av gränsytan mellan organisk vätska och vatten i sprickplanet utvecklats; denna metod har visats fungera väl i simuleringar av tidigare publicerade experimentella data. För det tredje, har en jämförelse gjorts mellan en kontinuumbaserad tvåfasflödesmodell och en invasions-perkolationsmodell med avseende på hur väl de kan simulera tvåfasflöde i en spricka med varierande apertur. Här studerades även hur relationen mellan kapillärtryck och mättnadsgrad på sprickplansskala beror av variabiliteten i sprickapertur. Till sist undersöktes lösning av den organiska vätskan i grundvatten för två fastläggningsscenarier (fastläggning i immobila droppar och ansamling i fällor – ”återvändssprickor”) både genom experiment och mekanistisk numerisk modellering. Kunskapen som tagits fram i denna avhandling bedöms vara användbar även för att modellera spridningen av flerfasföroreningar på större (spricknätverks-) skalor.

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Worldwide demand for energy is increasing rapidly, partly driven by dramatic economic growth in developing countries. This growth has sparked concerns over the finite availability of fossil fuels and the impact of their combustion on climate change. Consequently, many recent research efforts have been devoted to the development of renewable fuels and sustainable energy systems. Interest in liquid biofuels, such as ethanol, has been particularly high because these fuels fit into the conventional infrastructure for the transportation sector. Ethanol is a renewable fuel produced through the anaerobic fermentation of sugars obtained from biomass. However, the relatively high energy demand of its production process is a major factor limiting the usefulness of ethanol as a fuel. Due to the dilute nature of the fermentation product stream and the presence of the ethanol-water azeotrope, the separation processes currently used to recover anhydrous ethanol are particularly inefficient. In fact, the ethanol separation processes account for a large fraction of the total process energy demand. In the conventional ethanol separation process, ethanol is recovered using several distillation steps combined with a dehydration process. In this dissertation, a new hybrid pervaporation-distillation system, named Membrane Dephlegmation, was proposed and investigated for use in ethanol recovery. In this process, countercurrent vapour-liquid contacting is carried out on the surface of a pervaporation membrane, leading to a combination of distillation and pervaporation effects. It was intended that this new process would lead to improved economics and energy efficiency for the entire ethanol production process. The Membrane Dephlegmation process was investigated using both numerical and experimental techniques. Multiphase Computational Fluid Dynamics (CFD) was used to study vapour-liquid contacting behaviour in narrow channels and to estimate heat and mass transfer rates. Results from the CFD studies were incorporated into a simplified design model and the Membrane Dephlegmation process was studied numerically. The results indicated that the Membrane Dephlegmation process was more efficient than simple distillation and that the ethanol-water azeotrope could be broken. Subsequently, a pilot-scale experimental system was constructed using commercially available, hydrophilic NaA zeolite membranes. Results obtained from the experimental system confirmed the accuracy of the simulations.

A new measurement technique called fiber optic reflectometer (FOR) was developed to investigate multiphase flows. The principle and setup of the FOR technique were introduced and applied to various experiments. Based on the coherently mixed signal between the Fresnel reflection off the fiber-liquid interface and the scattered signal off the object, such as a gas bubble, and a solid particle, this single probe technique is capable of simultaneously measuring the velocity of the object with a high accuracy and the phase of the fluid. In addition, bubble diameter, velocity, and void fraction were measured directly. By means of a simple modification of the FOR technique, solute concentration and refractive index change were measured with a greatly improved accuracy. This modified technique was used for measuring of a NaCl concentration in deionized water to validate a new normalization technique. In the second part of this thesis, a plunging breaking wave in deep water has been studied. Using the wave focusing method, a strong plunging breaker was generated with accuracy in the deep water condition in a two-dimensional wave tank. It was possible to describe the breaking process in detail using a high speed camera with a frame rate of 500 or 1000 fps. Four kinds of experimental techniques were employed or developed to investigate the plunging breaker. Bubble image velocimetry (BIV) and particle image velocimetry (PIV) were used to measure the velocity fields. The velocity fields of the highly aerated region were obtained from the BIV measurements. In addition, the modified PIV technique is capable of measuring the velocities in the entire flow field including the aerated region. Mean and turbulent properties were obtained by the ensemble average. The mean velocity, mean vorticity, and mean kinetic energy were examined over the entire flow field. In addition, the Reynolds stresses and turbulent kinetic energy were calculated with high temporal and spatial resolutions. Free surface elevation was obtained from wave gauge measurements. BIV and PIV images were also used to obtain the free surface elevation and the boundary of the aerated region for more accurate results. The FOR technique was used to obtain the void ratio at each splash-up region. Compressibility of the plunging breaker was considered. Mass flux, momentum flux, kinetic energy, and Reynolds stresses at each FOR station were recalculated using the void ratio obtained from the FOR measurements. All terms at the first splash-up region were highly overestimated more than 100 percent unless the void ratio was applied to the calculation of fluxes and energies. Compared with the fully developed first splash-up region, the overestimation at the second and third splash-up was less significant. However, most terms were overestimated by 20~30 percent when the void ratio was not considered.

High explosive charges when detonated ensue in a flow field characterized by several physical phenomena that include blast wave propagation, hydrodynamic instabilities, real gas effects, fluid mixing and afterburn effects. Solid metal particles are often added to explosives to augment the total impulsive loading, either through direct bombardment if inert, or through afterburn energy release if reactive. These multiphase explosive charges, termed as heterogeneous explosives, are of interest from a scientific perspective as they involve the confluence and interplay of various additional physical phenomena such as shock-particle interaction, particle dispersion, ignition, and inter-phase mass, momentum and energy transfer. In the current research effort, chemical explosions in multiphase environments are investigated using a robust, state-of-the-art Eulerian-gas, Lagrangian-solid methodology that can handle both the dense and dilute particle regimes. Explosions into ambient air as well as into aluminum particle clouds are investigated, and hydrodynamic instabilities such as Rayleigh- Taylor and Richtmyer-Meshkov result in a mixing layer where the detonation products mix with the air and afterburn. The particles in the ambient cloud, when present, are observed to pick up significant amounts of momentum and heat from the gas, and thereafter disperse, ignite and burn. The amount of mixing and afterburn are observed to be independent of particle size, but dependent on the particle mass loading and cloud dimensions. Due to fast response times, small particles are observed to cluster as they interact with the vortex rings in the mixing layer, which leads to their preferential ignition/ combustion. The total deliverable impulsive loading from heterogeneous explosive charges containing inert steel particles is estimated for a suite of operating parameters and compared, and it is demonstrated that heterogeneous explosive charges deliver a higher near-field impulse than homogeneous explosive charges containing the same mass of the high explosive. Furthermore, particles are observed to introduce significant amounts of hydrodynamic instabilities in the mixing layer, resulting in augmented fluctuation intensities and fireball size, and different growth rates for heterogeneous explosions compared to homogeneous explosions. For aluminized explosions, the particles are observed to burn in two regimes, and the average particle velocities at late times are observed to be independent of the initial solid volume fraction in the explosive charge. Overall, this thesis provides useful insights on the role played by solid particles in chemical explosions.

An understanding of the motion of soft capsules in microchannels is useful for a number applications. This knowledge can be used to develop devices to sort biological cells based on their size and stiffness. For example, cancer cells have a different stiffness from healthy cells and thus can be readily identified. Additionally, devices can be developed to detect flaws in synthetic particles. Using a 3D hybrid lattice Boltzmann and lattice spring method, the motion of rigid and soft capsules in a pressure-driven microfluidic flow was probed. The effect of inertial drift is evaluated in channels different Reynolds numbers. Other system parameters such as capsule elasticity and channel size are also varied to determine their effect. The equilibrium position of capsules in the channel is also obtained. The equilibrium position of rigid and soft capsules depends on the relative particle size. If the capsule is small, the equilibrium position is found to be closer to the channel wall. Conversely, for larger capsules, the equilibrium position is closer to the channel centerline. The capsule stiffness affects the magnitude of the cross-stream drift velocity. For a given Reynolds number, the equilibrium position of softer capsules is closer to the channel centerline. However, It is found that the equilibrium position of soft capsules is insensitive to the magnitude of the Reynolds number.

This thesis has developed an efficient methodology for automatic kinematic analysis of planar linkages using the concept of modular kinematics. Unlike conventional general purpose kinematic analysis packages where each joint in the mechanism is represented using a set of non-linear constraint equations which need to be solved by some iterative numerical procedure, modular kinematics is based on the original observation by Assur that kinematic state of a mechanism involving large number of links can be constructed out of the kinematic states of patterns of sub chains called modules taken in a given sequence called module sequence which in turn emulates the step by step construction procedure of traditional graphical methods. The position, velocity and acceleration analysis of modules are available in closed form. Kinematic analysis of modules later in the sequence is enabled by those of the ones earlier in the sequence, hence, the kinematic analysis of a mechanism is accomplished without any iterative endeavor by doing the kinematics of the modules as given in the module sequence. [102] classified all modules into three fundamental types namely input, dyad and transformation and also introduced the concept of constraint module for analyzing graphically non-constructible mechanisms within the paradigm of modular kinematics where a small step of numerical search was needed in an over all closed form kinematic formulation. Module sequence for a mechanism using the modules is not unique. Choice of a later module in the sequence depends upon the selection of modules earlier in the sequence. This thesis has presented a systematic approach of identifying all such methods for all the inversions of the mechanism and represented in the form of a module hierarchy or a module tree where each path from root to the leaf node represents a valid module sequence for the kinematic chain in hand. The work also extended the set of modules by adding eight new modules to what has already been used in literature to make it complete in the sense that all planar mechanisms involving revolute, prismatic and pin-in-slot (including circular slots) can be handled. The computational effort involved for analyzing these mechanisms thus depend on the number of constraint modules occurring in succession in the module sequence. However, maximum possible number of constraint modules in any mechanism with up to twelve links is only two. The derivative analysis also uses the same module sequence, but they are always devoid of any iterative steps. During the process of generation of a module sequence, at every stage multitude of modules could be identified for their potential placement in the sequence. But for every module sequence the difference between the number of input modules and that of constraint modules is constant and is equal to the kinematic degrees-of-freedom (d.o.f) of the mechanism. The algorithm presented in this thesis minimizes the number of generalized inputs (and hence extraneous constraints) and thus attempting to identify the simplest of the module sequences. In that sense the module sequences represented in the module tree are all optimal module sequences. The present work introduced the concept of multi phase modular kinematics which enables a large variety of mechanisms, conventionally identified as complex mechanisms, to be solved in closed form. This is achieved through the use of novel virtual link and virtual joints. Virtual link is slightly different from a normal rigid link in the sense that the joint locations on this are functions of some independent parameters. Since, the locations of joints are not fixed even in the local coordinate frame of the virtual link, the relative velocities between joints are not zero, they need to be appropriately accounted in kinematic analysis. The theory presented in the thesis is implemented in a computer program written in C++ on Windows platform and Graphics library (OpenGL) is used to display linkage configurations and simulations. The program takes the data of joints, input pairs, ground link in certain format through a file. Geometric models developed in any of the existing modeling softwares like ProE, Ideas, AutoCad etc. can be imported in VRML format to the links and in case of no geometric models a simple convex 2D geometry is created for each link for the purpose of visualization. Geometric import of links helps not only in understanding the simulations better but also in useful for dynamic analysis, dynamic motion analysis and interference analysis. A complete kinematic analysis (position, velocity and acceleration) is given for a four bar mechanism and illustrated the positional ( configuration) analysis using modular kinematics for several other examples like old-ham, quick-return mechanisms etc. in the current work. Multi-phase modular approach is illustrated using a five bar with floating input pairs, a back actor and a drafter mechanism and the Back actor configuration is shown with the imported link geometries. It is observed in practice that there are many apparently spatial Mechanisms, which are constructed out of symmetric dispositions of planar mechanisms in space. A pseudo spatial mechanism concept is proposed to solve this class of spatial mechanisms, which can actually be analyzed with the effort of solving only one such component. This concept is illustrated with Shaker and Umbrella mechanisms. Possible extensions of the concept for modeling and analysis of more general class of pseudo-spatial mechanisms are also indicated.