Thesis (Ph. D.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 116-124). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 95-99). Also available on the World Wide Web.

Flow distribution chambers are devices commonly used by the water industry to distribute flows in water and sewage treatment plants. These have simple designs, and are required to operate over a range of volumetric flowrates. Many chambers surveyed (Herbath and Wong, 1997b) were found to perform poorly. They suffered from flow mal-distribution, where the flow was not distributed according to design. The most common cause of flow mal-distribution was hypothesised to be due to the presence of a pipe bend below the chamber (Herbath and Wong, 1997a, 1997b). Therefore, an experimental and numerical study of the flow within a distribution chamber was conducted in this thesis to prove this hypothesis. A novel large-scale model (1: 13) of a typical distribution chamber was constructed. This allowed the collection of high quality and novel velocity and turbulence measurements near the free surface using hot film anemometry. The free surface location was measured using a vernier point gauge while the flow distribution between the outlets was metered by orifice plates. Records of the flow patterns were also kept. The experimental results showed that flow mal-distribution did not occur as expected since the model distribution chamber was designed with a long length of straight inlet pipe, to eliminate the suspected cause of flow mal-distribution. Novel velocity and water surface data were also collected in the experiments, which contributed towards the small body of knowledge in this area of research into flow distribution. CFD models of the physical model were created and solved using a commercial CFD code, CFX 4.1, developed by CFX International of AEA Technology. Steady state and transient two- and three-dimensional calculations of the symmetrical chamber were carried out in the course of the study. A novel adaptation of the existing code was made in obtaining solutions to the numerical models. A new solution strategy was made and refined in this stage of the research using the two-dimensional representation of the distribution chamber, for reasons of reduced computational time. Differencing schemes, surface sharpening, mass residuals, mesh refinement and different turbulence models were investigated during model refinement. The accuracies of the calculated results were determined by comparison with experimental results. It was found that the 3D model, incorporating the RNG k-c model, without surface sharpening, and using the Van Leer differencing scheme, gave good quantitative agreement with the experimental velocities, free surface location and flow distribution. The 2D results gave qualitatively good predictions. Quantitatively, the results were over-predicted which was due, to dimensional effects. The volume of the 2D model was reduced from the 3D model, while the inlet velocity was made the same. This replicated the momentum effects near the free surface that were the governing causes of flow mal-distribution. Nevertheless, this approach was much more practical in terms of computational effort. More importantly, the correct trends for flow mal-distribution could be predicted accurately. Therefore, the next stage of the research used the 2D model developed and validated here. This part of the research involved the novel adaptation of the existing symmetrical 2D results for investigating the asymmetric effects of pipe bends. Three different approaches for modelling the asymmetric effects of a pipe bend were investigated. The first, and the most simplistic, was to incline the incoming flow at an angle to the vertical. The second was to calculate the velocities and turbulence at the outlet of a simple 2D pipe bend, separate from the chamber. These calculated variables were then input into the chamber, to build up a picture of the asymmetric flow, iteratively. The third, and the most accurate method, was to couple the bend to the chamber. It was found that only the third method was capable of accurately representing the conditions within the chamber. Two different pipe bend. lengths were examined using the third approach. The distances chosen were typical of the bend distances found in some treatment plants. The results . from both simulations produced large flow mal-distribution and asymmetric flows within the chamber. A value of 10% difference between the flows from the two outlets was taken to be the maximum limit for mal-distribution. However, values of 44.5 % and 22.8 % were obtained for the larger pipe distance and short pipe distance respectively. Novel remediation strategies using numerical techniques were used to determine the most effective means of improving the flow distribution. The first, used a vertical flow splitter, placed directly above the chamber inlet. Although it altered the path of the jet, it was felt that it would be ineffective for all situations. Although the magnitude of the asymmetry was improved with the use of the splitter, the improvement was insufficient to warrant its recommendation. The other device tested was a horizontal plate located at a certain distance from the chamber inlet. For the longer bend case, a separation distance equivalent to two inlet hydraulic diameters was sufficient to deflect the jet, and reduced the magnitude of the flow asymmetry to around 2%. When the same plate location was used for the shorter bend case, the efficiency of the plate was reduced. Although there was an improvement in the distribution, the magnitude of the asymmetry was greater than 10%. The plate was subsequently lowered by half a hydraulic diameter. This gave a large improvement to the effectiveness of the plate, and the resulting asymmetry was reduced to 7.31 %. The horizontal plate was considered more promising since its function was to deflect and reduce the peak velocities of the jet. With the reduction in velocities, the magnitudes of the nonlinear terms in the Navier-Stokes equations are reduced. The solution to the equations would be more likely to be symmetrical.

More and more transient gas-liquid operations in pipes are being successfully applied in the oil and gas industry. Pigging in two-phase pipelines, to remove liquid accumulation or for cleaning purposes, is an important transient operation. Another important operation is the injection of (-)-as to transport the accumulated liquid in the pipeline to process facilities. Analysis of such transient two-phase flow in a pipeline is necessary not only for designing the liquid and gas handling facilities, but also for safe operating procedure. In pipeline-fiser system such operations cause even more severe changes in flow conditions. A two-fluid model has been developed to determine the transient behaviour of fluids during these operations. The derived one-dimensional set of equations for each flow pattern describe the flow of fluids in all regions. Semi-implicit finite difference schemes were used to solve the initial and boundary value problem for each phase of the process - gas/pig injection, gas shut-in, slug production and gas flow out of the system. An extensive experimental program has been carried out to acquire two-phase transient flow and pigging data on a 67m long, 0.0525m diameter, 9.9m high pipeline-riser system. A computer based data acquisition system has been utilised to obtain rapidly changing and detailed information of the flow behaviour during the transient tests. The model results compare well with the experimental data for characteristics such as inlet pressure, hold-up and pig velocity.

Solid propellant is the highly energetic fuel burnt in the combustion chamber of ballistic weapons. It is manufactured, for this purpose, in either granular or stick form. Internal ballistics describes the behavior within the combustion chamber throughout the ballistic cycle upto projectile exit from the muzzle of the gun barrel. Over the last twenty years this has been achieved by modelling the process using two-phase flow equations. The solid granules or sticks constitute the first phase, which can be assumed to be incompressible over typical pressure ranges within the chamber. The gas-phase is composed of both the original ambient gas contained around the propellant and additional gas produced by the propellant gasifying on heating. Equations can be derived that describe the conservation of mass, momentum and energy in terms of average flow variables. The equations are a highly non-linear system of partial-differential- equations. High-speed flow features are observed in internal ballistics and ordinary fini te- difference methods are unsuitable numerical methods due to inaccurate prediction of discontinuous flow features. Modern shock-capturing methods are employed, which solve the system of equations in conservation form, with the ability to capture shocks and contact discontinuities. However, although the numerical solutions compare well with experiment over the bulk of the combustion chamber, the ignition models used in internal ballistics are unreliable. These are based on either gas or solid-surface temperature achieving some empirically measured 'ignition temperature' after which the propellant burns according to an empirical pressure dependent burning law. Observations indicate that this is not an adequate representation of ignition. Time differences between first solid gasification and ignition imply two distinct processes occurring. ]Further, ignition occurring in gas-only regions indicates that ignition is controlled by a gas-phase reaction. This thesis develops simple ideas to describe possible mechanisms for these physical observations. The aim is to provide an improved model of the ignition of solid propellant. A two stage reaction process is described involving endothermic gasification of the solid, to produce a source of reactant gas, followed by a very exothermic gas-phase ignition reaction. Firstly the gas-phase ignition is considered. A very simple reaction is suggested which is assumed to control the combustion of reactant gas, produced by solid gasification. Ignition is, by definition, the initiation of this exothermic reaction. Chemical kinetics are included in the gas-phase flow equations to explore the evolution of the reactant gas that is subject to changes in temperature and pressure. By assuming spatial uniformity, analytical solutions of the problem are deduced. The physical interpretation of the solution is discussed, in particular, the relationship between temperature, reactant concentration and ignition is explored. Numerical methods are required to solve the one-dimensional flow equations. Development of suitable CFD methods provides a method of solution. Finite-volume schemes, based on the original work by Godunov, are used to solve the conservation form of the equations. A simple test problem is considered whereby reactant gas is injected into a cylindrical combustion chamber. By examining the resulting flow histories, valuable information is gathered about the complicated coupling of chemistry and flow. Chemistry is included into a system of two-phase flow equations. By using standard averaging methods along with an equation for gas-phase species, equations are derived that describe the rate of change of average flo%v variables for both gas and particle phases. Numerical schemes are developed and some of the difficulties involved in two-phase flow systems, that are not an issue in single-phase flow, are presented. An internal ballistics application is considered as a test case and the solution discussed. The other important reaction involved in the combustion cycle, solid gasification, is explored. The model is based on detailed description of interphase mass and energy transfer at the solid-gas interface. This involves the solution of the heat conduction equation with a moving boundary that divides the solid and gas regions. Similar numerical schemes are constructed to solve the equations. Finally, this model is coupled with the equations of gas-phase reaction. This describes the complete cycle whereby increases in gas temperature cause the solid to increase in temperature and gasify. Subsequent gas-phase combustion of the reactant gases produces heat-transfer between the solid and gas and continues to accelerate gasification. Eventually this results in selfsustained combustion of the solid propellant.

Orientador: Antonio Carlos Bannwart / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica e Instituto de Geociências / Made available in DSpace on 2018-08-16T18:25:07Z (GMT). No. of bitstreams: 1 Santos_CynthiaAmaliaCardoso_M.pdf: 19031885 bytes, checksum: d7f4ccde723c3be25530db56830f68d3 (MD5) Previous issue date: 2010 / Resumo: Para que todo o potencial das reservas de óleo pesado existentes seja explorado são necessários o desenvolvimento de novas tecnologias e o aprimoramento de tecnologias já existentes. A produção e transporte deste tipo de óleo carregam consigo um conjunto de novos desafios devidos principalmente a sua alta viscosidade e densidade. A técnica de coreflow e uma das tecnologias ainda em desenvolvimento que busca uma resposta a estes desafios. Ela consiste na injeção de uma fina camada de água nas laterais do tubo, formando um filme ao redor do núcleo de óleo, evitando o contato direto entre o óleo e a parede do tubo. Nestas condições a perda de carga por atrito torna-se comparável a do escoamento monofásico de água. Algumas questões importantes sobre escoamento de óleos viscosos assistidos com água permanecem sem resposta, tal como o procedimento de repartida de uma linha apos uma parada súbita imprevista das bombas de óleo e de água. Este trabalho apresenta diversos experimentos de repartida de escoamento assistido com água. A repartida de uma linha parcialmente bloqueada com óleo viscoso, apos uma parada inesperada das bombas de água e óleo, foi realizada utilizando se somente água. Diversas configurações iniciais em termos de holdup de óleo, tempo em que o óleo permanece parado antes da repartida e vazão de água usada na repartida foram testadas / Abstract: In order to explore thoroughly the potential of existing heavy oil reserves it is necessary to develop new technologies and improve existing technologies. Heavy oil production and transport carry a set of new challenges due mainly its high viscosity and density. The core flow method is one of the new technologies in development that may provide an answer to those challenges. It consists in the lateral injection of a thin water layer that forms a film around de oil core, thereby avoiding direct oil-wall contact. In such conditions, frictional pressure drop becomes comparable to that observed in single phase water flow at mixture flow rate. Some important questions about the water-assisted flow of heavy oils remain unanswered, such as the possibility of re-starting the pipeline after an unexpected stop of the water and oil pumps. This work presents the results of several water assisted re-starting experiments. The re-start of a pipe partly blocked with viscous oil, after an unexpected stop of the water and oil pumps, was performed using a water flow only (i.e. a cleaning operation). Several initial configurations in terms of oil holdups, time in which the oil remain stopped before the re-start and water flow rate used in the re-start were tested / Mestrado / Explotação / Mestre em Ciências e Engenharia de Petróleo

Orientadores: Fernando de Almeida França, Eugenio Spano Rosa / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-04T03:18:43Z (GMT). No. of bitstreams: 1 Matos_Arlindode_D.pdf: 9963992 bytes, checksum: 98b022ae27ddb93d77b9a1df576b04af (MD5) Previous issue date: 2004 / Resumo: A distribuição das fases de um escoamento a bolhas ocorrendo no interior de um duto de seção quadrada em uma curva de 180º é o tema deste trabalho. Utilizou-se, para tanto, de abordagens experimental e numérica. Assim, aspectos como a influência da intensidade do campo centrífugo na segregação das fases, detalhes do processo de migração das bolhas de gás da seção externa para a interna da curva e o papel desempenhado pela turbulência neste fenômeno, são apresentados e discutidos. A experimentação ocorreu em um circuito devidamente preparado para o escoamento de misturas de ar e água no padrão em bolhas, ocorreu em pressões próximas da atmosfera e à temperatura ambiente (= 23°C). A filtração de vazio local foi medida sobre cada um de quatro planos transversais ao escoamento ao longo da curva. Para medir a distribuição de fração de vazio nestes quatro planos utilizou-se de sondas elétricas condutivas de fio único. As velocidades superficiais de líquido e gás e, conseqüentemente, as respectivas vazões, aplicadas no experimento variaram de 0,9 m/s a 3,0 m/s e 0,04 m/s a 0,5 m/s, respectivamente. Os resultados experimentais de distribuição de &ação de vazio foram comparados com cálculos numéricos realizados pelo CFD Phoenics. Uma implementação Euleriana-Euleriana do Modelo de Dois Fluidos, representado por suas equações locais médio-temporais, foi utilizada para representar matematicamente o escoamento. As equações de conservação da massa e da quantidade de movimento foram escritas em termos de coordenadas generalizadas para um sistema 3D cartesiano. Termos fontes adicionais simularam a ação do campo centrifugo que surge no escoamento ao longo da curva. O fechamento do sistema de equações diferenciais foi obtido com a utilização de termos interfaciais. Dois modelos foram empregados para representar o tensor turbulento (Algébrico, e k-e padrão), ambos com termo complementar que considerava a turbulência adicional induzida pelo movimento relativo das bolhas. Os resultados experimentais e numéricos da distribuição de fração de vazio nos quatro diferentes planos ao longo da curva, da seção de entrada até sua seção de saída, para as várias condições operacionais, foram comparados em termos de gráficos de iso-superficies, que deram uma visão geral, mas aproximada, das distribuições, e também em termos de gráficos lineares, em termos do valor local da fração de vazio. A comparação entre resultados indicou detalhes do processo de migração das fases. Adicionalmente, gráficos de escoamento secundário, distribuição de velocidades, distribuição de energia cinética turbulenta e de viscosidade turbulenta foram apresentados para que o papel da turbulência na segregação das fases se tomasse passível de análise / Abstract: The phase segregation in gas-liquid bubbly flow taking place inside a 180 degree plane curve, i.e., with null torsion, is the subject of this work. Both experimental and numerical approaches have been performed. Thus, aspects as the influence of intensity of centrifugal field on phase segregation, the role played by turbulence on phase segregation and details of the gas bubbles migration from the outer to inner curve section have been disclosed. The experimentation was carried on in a set-up prepared to run air-water flows, and the flow happened at near atmospheric pressure and ambient temperature (23°C). The local void fraction was measured four transversal planes along the curve. To measure the void fraction distribution one used a single wire conductive probe. The liquid and the gas superficial velocities varied from 0.9 m/s to 3.0 m/s and 0.04 m/s to 0.5 m/s, respectively. The experimental results for the void fraction distribution were compared with numerical calculations performed by the CFD Phoenics. An Eulerian-Eulerian implementation of the Two-Fluid Model, expressed by time-averaged variables, was used to give a mathematical representation of the flow. The mass and momentum conservation equations were written in terms of generalized coordinates for a 3D Cartesian coordinate system. Additional source terms simulated the centrifugal field that arises along the curve. The closure of the system of differential equations was achieved by the use of interfacial terms. Two models were used to express the turbulent tensor, (Algebraic and k-8 model) with complimentary terms accounting the bubble-induced turbulence. The numerical results for the void fraction distribution in different transversal planes were compared with the experimental ones, in terms of surface and linear plots, providing both a qualitative overview and a fine inspection of the gas segregation. The comparisons between the void distribution on the four planes along the curve, for different operational conditions, revealed the influence of the centrifugal field intensity on the phase segregation and gave an overview of the phase migration ITom the outer to the inner section of the curve. Additionally, plots of secondary flow, velocity distribution, turbulent kinetic energy and turbulent viscosity were also presented in order to turn on the light over the role played by the turbulence on the phase segregation process / Doutorado / Termica e Fluidos / Doutor Engenharia Mecânica

The major challenge associated with saving energy in the pumping stations of the fluid transportation in the pipeline networks, especially the crude oil transportation for long-distance is drag forces. In other words, this grossly increases the drag form force and friction losses making fluids transport inside pipeline taken a long time to pass, that increases energy consumption and costs. Therefore, the effective solution to overcome these problems is added drag reduction materials (DRMs) with the main fluid using the drag reduction technique (DR). One of the most important drag reduction technique to enhance flow in the pipeline is an active drag reduction using DRMs. Where the DRMs can reduce drag forces in relatively small amounts part per million (ppm), as well as environment friendly. Thereby, the drag reduction enhancement is highly important in terms of fluid transportation in the many industrial applications. An experimental and mathematical study have been performed in the fully development flow to measure fluid characteristics and to evaluate %DR using various DRMs: polymers, surfactants, and nanoparticles in pipeline network. The active drag reduction experiments have been conducted in the rotational disk apparatus (RDA) and in the closed-loop recirculation system (CLRS) using different solutions of DRMs: individual, binary, and triple at different Reynolds numbers (Re) and at different concentrations. The morphological tests have been done employing XDR, TEM and SEM techniques. Mathematical model was presented to validate the experimental results using the statistic softwareV6.2. The results have been displayed with complete explanation, analysis, and conclusions. The results show that the %DR increases with increasing the velocity (Re) and concentration for the most of DRMs solutions. Also, the results confirm that the use of nanoparticle in complex solutions is more effective than using nanoparticle individually within the same work condition. further, the new complex solutions were formed in a manner that can contribute significantly to increase drag reduction performance and enhance shear resistance of the DRMs. Finally, all microscopy techniques confirm the fact that complex solutions were effectively formed and homogenized within the main fluid.

With existing numerical models for fluid particle systems in CHEM, the acoustic-particle interactions associated with two-phase dilute dispersed flow can be captured and the particle model can be validated using experimental and analytical data and verified using numerical techniques. The experimental and analytical data come from Zink and Delsasso and provides data for particles of diameters 5 to 15 microns for frequencies between 500Hz to 13600Hz. In the particle number density measurements by Zink and Delsasso there was a 10% estimated error range. Using the fourth order skew symmetric flux in CHEM and the built in Eulerian and Lagrangian particle models, the sound wave dissipation was captured and found to be within the margin of error. Two additional tests were conducted to measure the effect of nonlinear acoustics and increased bulk density on the dissipation. Nonlinear effects showed no significant effect and the linear increase in bulk density showed a linear increase in dissipation.

No description available.