Dissertations / Theses on the topic 'Liquid-liquid flows'
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Hasan, Norpa'iza Mohamad. "Stratifying liquid-liquid flows." Thesis, University of Nottingham, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.440994.
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Simmons, Mark John Harry. "Liquid-liquid flows and separation." Thesis, University of Nottingham, 1998. http://eprints.nottingham.ac.uk/27793/.
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The transport and separation of oil and water is a vital process to the oil and chemical industries. Fluids exiting from oil wells usually consist of gas, oil and water and these three phases need to be transported and separated before they can be processed further. Operation of the primary separators has often proved to be problematic due to the change in composition of the fluids as the well matures, often accompanied by the build up of sand or asphaltenes. These vessels are very expensive to install so there is motivation to improve their design and performance. One major factor affecting separator performance is the phase distribution of the inlet flow, as reflected in the flow pattern and droplet size. In this work, flow pattern boundaries and drop sizes of liquid-liquid dispersions were measured for vertical and horizontal flow of a kerosene and water mixture in a 0.063m tube. Drop size was investigated by using two different laser optical techniques. A laser backscatter technique was employed for concentrated dispersions and a diffraction technique was used at low concentrations. In order to develop a greater understanding of separator performance, a 1/5th-scale model was constructed of diameter 0.6m and length 205m. Residence Time Distributions were obtained for a range of different internal configurations and flow rates using a colorimetric tracer technique. Flow rates of 1.5-4 kg/s oil and 1-4 kg/s water were used and the vessel was equipped with a perforated flow-spreading baffle at the inlet and an overflow weir. Experiments were performed with no internals and with dip or side baffles. The side baffles acted to create quiescent zones within the vessel while the dip baffle caused a local acceleration of both phases. These situations are similar to those that can be caused by blocked internals or existing baffling or structured packing within field separators. A Residence Time Distribution model of a primary separator, the Alternative Path Model, was developed using transfer functions. This model has the ability to reproduce features of the experimental data by representing the flow as a series of continuous stirred tanks in series or in parallel. The model was used to develop parameters that could be used to obtain information about the performance of the separator. This model was also applied to Residence Time Distribution data obtained from field separators by BP Exploration, to relate features of the pilot scale separator to the field vessels.
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Angeli, Panagiota. "Liquid-liquid dispersed flows in horizontal pipes." Thesis, Boston Spa, U.K. : British Library Document Supply Centre, 1996. http://ethos.bl.uk/OrderDetails.do?did=1&uin=uk.bl.ethos.321543.
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Liu, Lan. "Optical and computational studies of liquid-liquid flows." Thesis, Imperial College London, 2005. http://hdl.handle.net/10044/1/7937.
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Hussain, Siti Aslina. "Experimental and computational studies of liquid-liquid dispersed flows." Thesis, Imperial College London, 2004. http://hdl.handle.net/10044/1/7998.
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Yusoff, Nazrul Hizam. "Stratifying of liquid-liquid two phase flows through sudden expansion." Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/12939/.
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The transport and separation of oil and water is an essential process to the oil and chemical industries. Although transporting the mixtures is often necessary due to few reasons, it is generally beneficial to separate out the phases in order to reduce installation and maintenance costs, at the same time, avoiding safety problems. Thus, separation of liquid-liquid flows is a necessary part of many industrial processes. Hence, knowledge of two-phase flow dynamics is important for the design optimisation of separators. Therefore, the aim of this research is to investigate the feasibility of a sudden pipe expansion to be used as phase separator because it compact in design and capable for converting dispersed flow to stratified flow. In the test section, spatial distribution of the liquid-liquid phases in a dynamics flow system was visualised for the first time for by means of capacitance Wire Mesh Sensor (CapWMS), providing instantaneous information about the interface shapes, waves and phase layer evolution of oil-water flow. Visual assessment and analysis of the WMS data showed three distinct layers: an oil layer at the pipe top; a water layer at the pipe bottom and a mixed layer between them. The interfaces that form between the separated phases (oil or water) and the mixed layer were classified as oil interface or water interface. Results showed interface shapes were initially concave or convex near to the inlet of the test section and became flat further downstream the expansion, especially for water interfaces. There were no waves observed for horizontal and downward pipe orientations at all flow conditions and axial position downstream of the expansion. As for the upward inclined pipe orientation, waves were found, and they formed at position close to the inlet at all input oil volume fraction except at 0.2 OVF. The amplitude of the waves was: ~ 0.29D for 0.8 OVF; ~ 0.22D for 0.6 OVF and ~ 0.26D for 0.4 OVF. The higher the input oil volume fraction, the larger the waves become. In conclusion, the WMS results demonstrated that spatial distributions are strongly dependent on the mixture velocity, input oil fraction and inclination angles for the far position. In this present work, droplets were found to be larger near the interface. Drops were large nearer to the interface at the near position (10D) for all pipe orientations and throughout the test section for horizontal flow. The drops size decreased when the distance from the interface increased for these pipe configurations. As for the furthest position from the expansion for upward and downward inclined pipe orientation, larger droplets could also be seen at distance away from the interface and vice versa. The gravity or buoyant force is one of the contributing factors to the settling of the droplets. These forces are acting simultaneously on the droplets i.e. if the buoyant force which tends to spread the droplets throughout the pipe cross-section, is not large enough to overcome the settling tendency of gravity settling of the droplets occurs. Hence, the droplets that are non-uniformly scattered within the continuous phase begin to coalesce as they flow further downstream the pipe, producing larger drops. In addition, as the distance from expansion increased, the mixed layer becomes narrow and more drops begin to coalescence to form large drop due to increased droplet-droplet collision. Owing to these factors, results indicate that the mechanisms of coalescence occurred faster at the bottom, for water droplets and at the top, for oil droplets than the other locations in a pipe cross-section. For a better separation design, the coalescence process should occur at the aforementioned (bottom for water and top for oil) locations within the expansion pipe. However, at higher mixture velocities the mixed layer would be responsible for the smaller droplet size for horizontal and both inclinations of pipe orientation. The mixed layer dominated almost entirely in the pipe cross-section.
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Costigan, G. "Flow pattern transitions in vertical gas - liquid flows." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361925.
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Yang, Limin. "Liquid-liquid two-phase flows at T-junctions and through expansions." Thesis, University of Nottingham, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404047.
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Morgan, Rhys Gareth. "Studies of liquid-liquid two-phase flows using laser-based methods." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/10145.
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The research described in this thesis has been focused on the detailed investigation of horizontal co-current liquid-liquid two-phase flows. The experiments were carried out in channels of square and circular cross section and involved the use of two immiscible liquids of matched refractive index; namely an oil (Exxol™D80) and a 81.7 wt% glycerol-water solution. The experiments were carried out in a refurbished liquid-liquid flow facility (TOWER) and the focus was on examining the flows using high-speed laser-based visualisation methods which allowed both qualitative evaluation of the nature of the flows (i.e. the flow patterns) and quantitative measurements of parameters such as drop size and velocity distribution. The laser-based techniques used included Planar Laser Induced Fluorescence (PLIF), Particle Tracking Velocimetry (PTV) and Particle Image Velocimetry (PIV). Using these techniques, it was possible to obtain high spatial and temporal resolution measurements of velocity and phase distribution of liquid-liquid flows which enabled the detailed diagnostic inspection to an extent that has not been previously possible. 144 experiments were carried out in three experimental campaigns. In the first campaign, a square cross section channel was used in order to avoid image distortion by the channel walls. In the second and third campaigns, a circular tube was employed and a graticule correction method was used to correct the distortion to the PLIF and PTV/PIV images which occurs when the circular cross-section visualisation cell is used. In the two circular tube experiments, two methods of injection of the phases were used: (1) the heavier (glycerol solution) phase was injected in its natural location at the bottom of the channel, and (2) in the second case the heavier phase was injected at the top of the channel. The PLIF images gave a clear indication of the distribution of the phases at the channel centre line and have been used qualitatively in obtaining information about the flow patterns occurring. The PLIF images have also been used quantitatively in generating data on phase distribution, insitu phase fraction, interface level and drop size distribution. Much of the data on in-situ phase fraction and interface level fits well with a simple laminar-laminar stratified flow model. The PTV/PIV method provided extensive data on velocity profiles; in the lower (aqueous glycerol solution) phase, the profile usually showed the curved shape characteristic of laminar flow and in the upper (Exxol™D80) phase, the velocity profile often showed the flattened form characteristic of turbulent flow.
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Badeau, Allen E. "A droplet formation and entrainment model for stratified liquid-liquid flows." Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1737.
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Thesis (M.S.)--West Virginia University, 2000.Title from document title page. Document formatted into pages; contains xiii, 150 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 140-144).
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Zhao, Liqiang. "Liquid film flows over complex surfaces /." Access abstract and link to full text, 1991. http://0-wwwlib.umi.com.library.utulsa.edu/dissertations/fullcit/9123415.
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Moore, Bryce Kirk. "Gas-liquid flows in adsorbent microchannels." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47519.
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A study of two the sequential displacement of gas and liquid phases in microchannels for eventual application in temperature swing adsorption (TSA) methane purification systems was performed. A model for bulk fluid displacement in 200 m channels was developed and validated using data from an air-water flow visualization study performed on glass microchannel test sections with a hydraulic diameter of 203 m. High-speed video recording was used to observe displacement samples at two separate channel locations for both the displacement of gas by liquid and liquid by gas, and for driving pressure gradients ranging from 19 to 450 kPa m-1. Interface velocities, void fractions, and film thicknesses were determined using image analysis software for each of the 63 sample videos obtained.
Coupled 2-D heat and mass transfer models were developed to simulate a TSA gas separation process in which impurities in the gas supply were removed through adsorption into adsorbent coated microchannel walls. These models were used to evaluate the impact of residual liquid films on system mass transfer during the adsorption process. It was determined that for a TSA methane purification system to be effective, it is necessary to purge liquid from the adsorbent channel. This intermediate purge phase will benefit the mass transfer performance of the adsorption system by removing significant amounts of residual liquid from the channel and by causing the onset of rivulet flow in the channel. The existence of the remaining dry wall area, which is characteristic of the rivulet flow regime, improves system mass transfer performance in the presence of residual liquid.
The commercial viability of microchannel TSA gas separation systems depends strongly on the ability to mitigate the presence and effects of residual liquid in the adsorbent channels. While the use of liquid heat transfer fluids in the microchannel structure provides rapid heating and cooling of the adsorbent mass, the management of residual liquid remains a significant hurdle. In addition, such systems will require reliable prevention of interaction between the adsorbent and the liquid heat transfer fluid, whether through the development and fabrication of highly selective polymer matrix materials or the use of non-interacting large-molecule liquid heat transfer fluids. If these hurdles can be successfully addressed, microchannel TSA systems may have the potential to become a competitive technology in large-scale gas separation.
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Zenit, Camacho José Roberto Hunt Melany L. "Collisional mechanics in solid-liquid flows /." Diss., Pasadena, Calif. : California Institute of Technology, 1998. http://resolver.caltech.edu/CaltechETD:etd-08122005-140811.
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Koos, Erin Crystal Hunt Melany L. Hunt Melany L. "Rheological measurements in liquid-solid flows /." Diss., Pasadena, Calif. : Caltech, 2009. http://resolver.caltech.edu/CaltechETD:etd-03032009-092653.
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Abdulahi, Abolore. "Investigating the effect of liquid viscosity on two-phase gas-liquid flows." Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/30935/.
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Simultaneous flow of gas-liquid in pipes presents considerable challenges and difficulties due to the complexity of the two-flow mixture. Oil-gas industries need to handle highly viscous liquids, hence studying the effect of changing the fluid viscosity becomes imperative as this is typically encountered in deeper offshore exploration. This work looks at the effect of liquid viscosity on gas-liquid flows. The work was carried out using two different pipes of 67mm and 127mm internal diameter. For the experiments carried out on the 67mm diameter pipe, air and three different liquids were used with viscosities 1, 42 and 152cp. With these experiments, the effect of viscosity on the entrainment process from the Taylor bubble in a vertical tube was investigated with the Taylor bubble being held stationary in a downward liquid flow with the use of three different gas injection methods. Taylor bubble length, the gas flow rate and the liquid flow rate approaching the stationary bubble were varied. In addition, the wake length below the stationary bubble was measured at different conditions of gas and liquid superficial velocities and comparison was made with the work by previous authors. Videos were taken with high speed camera to validate the measurement taken on wake lengths. A Wire Mesh Sensor system was placed at two different positions below the air injection point on the 67mm diameter pipe of the stationary bubble facility whose data acquisition provided time and cross-sectionally resolved information about spatial distribution. This information was used to generate time averaged void fraction, bubble size distribution and contour plots of the two-phase flow structure. A Probability Density Function (PDF) of void fraction can be obtained from the former, with PDFs of the wake section of the stationary bubbles showing that the flows are in the bubbly region while the PDF for the entire slug unit assumed that for a typical twin-peaked slug flow. The interpretation of this is that holding a bubble stationary can simulate real slug flow. Results on the bubble length measurement and gas loss into a bubble wake have shown good agreement with existing work by other authors. Experiments on the 127 mm diameter pipe were carried out because most published work on gas/liquid flow were on smaller diameter pipes with air and water, yet many of the industrial applications of such flows in vertical pipes are in larger diameter pipes and with liquids which are much more viscous than water. Another important parameter considered in the study is pressure because of its effect on gas density. This part of the research goes some way to rectify this lack and presents void fraction and pressure gradient data for sulphur hexafluoride with gas densities of 28 and 45 kg/m3 and oil (viscosity 35 times water). The gas and liquid superficial velocities were varied in the ranges 0.1-3 and 0.1-1 m/s respectively. The void fraction was also measured with a Wire Mesh Sensor system. Flow patterns were identified from the signatures of the Probability Density Function of cross-sectionally averaged void fraction. These showed the single peak shapes associated with bubbly and churn flow but not the twin-peaked shape usually seen in slug flow. This confirms previous work in larger diameter pipes but with less viscous liquids. For the bubble to churn flows investigated, the pressure gradients decreased with increasing superficial gas velocity. The change in pressure ultimately affects the density of gas in the two-phase flow mixture. Though there was little effect of pressure on void fraction below certain transitional flow rates, the effect became significant beyond these values. Different statistical analysis techniques such as power spectral density, probability density function, mean, standard deviation and time series of the acquired data have been used which also show the significant effect of pressure on void fraction at high gas density which have not been measured previously.
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Schmidt, Patrick. "Interfacial dynamics in counter-current gas-liquid flows." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/23474.
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This dissertation considers the genesis and dynamics of interfacial instability in vertical laminar gas-liquid flows, using as a model the two-dimensional channel flow of a thin falling film sheared by counter-current gas. The methodology is linear stability theory by means of Orr-Sommerfeld analysis together with direct numerical simulation of the two-phase flow in the case of nonlinear disturbances. The influence of two main flow parameters on the interfacial dynamics, namely the film thickness and pressure drop applied to drive the gas stream, is investigated. To make contact with existing studies in the literature, the effect of various density and viscosity contrasts as well as surface tension is also examined. Energy budget analyses based on the Orr-Sommerfeld theory reveal various coexisting unstable modes (interfacial, shear, internal) in the case of high density contrasts, which results in mode coalescence and mode competition, but only one dynamically relevant unstable interfacial mode for low and intermediate density contrast. Furthermore, high viscosity contrast and increases in surface tension lead to some amount of mode competition for thin film. A study of absolute and convective instability for low density contrast shows that the system is absolutely unstable for all but two narrow regions of the investigated parameter space. These regions are extended at intermediate density contrast and exhibit only small changes with increased viscosity contrast or surface tension. Direct numerical simulations of the system with low density contrast show that linear theory holds up remarkably well upon the onset of large-amplitude waves as well as the existence of weakly nonlinear waves. For high density contrasts corresponding more closely to an air-water-type system, linear stability theory is also successful at determining the most-dominant features in the interfacial wave dynamics at early-to-intermediate times. Nevertheless, the short waves selected by the linear theory undergo secondary instability and the wave train is no longer regular but rather exhibits chaotic motion. Furthermore, linear stability theory also predicts when the direction of travel of the waves changes - from downwards to upwards. The practical implications of this change in terms of loading and flooding is discussed. The change in direction of the wave propagation is represented graphically for each investigated system in terms of a flow map based on the liquid and gas flow rates and the prediction carries over to the nonlinear regime with only a small deviation. Besides the semi-analytical and numerical analyses, experiments with an practically relevant setup and flow system have been carried out to benchmark and validate the models developed in this work.
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VARGES, PRISCILLA RIBEIRO. "LIQUID-LIQUID DISPLACEMENT FLOWS IN A HELE-SHAW CELL INCLUDING NON-NEWTONIAN EFFECTS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2010. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=16992@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOEstudou-se neste trabalho o deslocamento de fluidos em meios porosos utilizando células de Hele-Shaw. Especificamente, investigou-se experimentalmente o deslocamento de um fluido não newtoniano por um newtoniano em uma célula retangular de Hele-Shaw. A instabilidade de Saffman-Taylor ou viscous fingering é um fenômeno observado quando um fluido de menor viscosidade desloca um de maior viscosidade, e a célula de Hele-Shaw é uma ferramenta conveniente para a sua observação. Esse fenômeno é muito importante em diversas aplicações, como por exemplo: recuperação secundária e terciária de petróleo, invasão de fluidos de perfuração em meios porosos, fraturamento hidráulico, processamento de polímeros, hidrologia e filtração. É vasta a literatura relativa ao estudo de fluidos newtonianos e não newtonianos deslocados por ar em células de Hele-Shaw. Entretanto, existem poucos trabalhos envolvendo deslocamentos de líquidos com viscosidades comparáveis, ou seja, razão de viscosidade diferente de zero. Apresentou-se o detalhamento do projeto de construção de uma célula de Hele-Shaw aplicável ao deslocamento de um líquido por outro líquido. A evolução da forma da interface foi analisada, através de uma câmera fotográfica, em função dos parâmetros geométricos, dinâmicos e reológicos. A partir da vetorização da forma da interface, determinou-se a eficiência do deslocamento. Sendo assim, foi definido o espectro de situações em que há formação de fingers e plugs relativos ao deslocamento de goma xantana por um óleo mineral. Não há na literatura uma convenção universal para apresentação dos resultados, logo uma contribuição original refere-se à adimensionalização proposta onde os principais parâmetros governantes são a velocidade adimensional, o número de capilaridade reológico e o índice de comportamento da goma xantana. Observou-se que para um valor constante do índice de comportamento e para um valor do número de capilaridade reológico da ordem de 10-1, a eficiência de deslocamento aumenta com a velocidade adimensional, porque a razão de viscosidade diminui.
This work studied the displacement of fluids in porous media using a Hele-Shaw cell. Specifically, was investigated experimentally the displacement of a non-Newtonian fluid by a Newtonian in a rectangular Hele-Shaw cell. The Saffman-Taylor or viscous fingering instability occurs when one fluid pushes a more viscous one, and a Hele-Shaw is a convenient tool to the phenomenon observation. Applications include displacement of heavy crude oil in reservoirs, drilling fluid invasion through porous media, fracture conductivity, polymer processing, hydrology and filtration. The Saffman-Taylor instability has been extensively studied for Newtonian and non-Newtonian liquids displaced by air in a Hele-Shaw cell. However displacement flows involving two liquids of comparable viscosity (nonzero viscosity ratio) have received very little attention. It was presented the details of construction of a Hele-Shaw applicable to a liquid-liquid displacement. The evolution of the shape of the interface was analyzed through a digital camera, as a function of the geometric, dynamic and rheological parameters. From tracing the shape of the interface, was determined the displacement efficiency. Thus, it was defined the spectrum of situations in which there is formation of fingers and plugs relating to displacement of xanthan gum by a mineral oil. There is no universal convention in the literature for presenting the results so a original contribution concerns the proposed dimensionless parameters. The main parameters that govern this flow are the dimensionless flow rate, the rheological capillary number and the behavior index of xanthan gum. It was observed that for a constant value of the behavior index and for a rheological capillary number of magnitude of 10-1, the displacement efficiency increases with the dimensionless flow rate, because the viscosity ratio decreases.
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AZEVEDO, PATRICIA EMIDIO DE. "LIQUID-LIQUID DISPLACEMENT FLOWS IN A HELE-SHAW CELL INCLUDING NON-NEWTONIAN EFFECTS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2015. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=26868@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
A perfuração de poços de petróleo, principalmente em ambientes offshore, é uma operação que demanda um custo muito elevado, portanto a minimização de problemas e danos ao reservatório produtor é muito importante. O projeto de um fluido de perfuração que garanta a mínima invasão na rocha reservatório é um tópico fundamental, como consequência a indústria petrolífera tem investido em estudos com o intuito de evitar que este problema ocorra. Sendo assim, nesse trabalho estudou-se o escoamento de fluidos em um meio poroso ideal, a célula de Hele-Shaw. Para realizar esse trabalho foram utilizados dois fluidos não newtonianos: uma solução aquosa de um polímero flexível, a poliacrilamida; e uma solução aquosa de um polímero rígido, a goma xantana. Esses fluidos não newtonianos representaram o fluido de perfuração, já o papel do petróleo presente na rocha reservatório foi desempenhado pelo óleo mineral. A partir desse experimento é possível observar a instabilidade de Saffman-Taylor ou viscous fingers, que é um fenômeno observado quando um fluido de menor viscosidade desloca outro de maior viscosidade. Esse fenômeno é muito importante em diversas aplicações, tais como: invasão de fluido de perfuração em meios porosos (caso que será estudado), recuperação secundária e terciária de petróleo, fraturamento hidráulico, processamento de polímeros, hidrologia e filtração. O experimento consiste em analisar a evolução da interface entre os dois fluidos através de uma câmera filmadora. A partir das imagens é determinada qualitativamente a eficiência do deslocamento. Com o conjunto de imagens é possível observar também em quais parâmetros dinâmicos e reológicos ocorre a transição fingers (interface instável) para plug (interface estável), e viceversa. Também foram realizados testes reológicos nos quais foi possível conhecer o comportamento dos fluidos não newtonianos utilizados. Com base nos dados coletados observou-se que tanto para a poliacrilamida quanto para a goma xantana a transição ocorre a uma taxa de cisalhamento adimensional próxima de 3.
The drilling of oil wells, particularly in offshore environments, is an operation which demands a high cost, thus, the minimization of problems and damage to the producing reservoir is very important. The design of a drilling fluid that ensures minimum invasion into the reservoir rock is a major topic, consequently the oil industry has invested in research in order to prevent this problem from occurring. Therefore, this research studied the displacement of fluids in an ideal porous medium, a Hele-Shaw cell. To accomplish this task, the following two non-Newtonian fluids were used: an aqueous solution of a flexible polymer, polyacrylamide; and the other an aqueous solution of a rigid polymer, xanthan gum. Such non-Newtonian fluids represent the drilling fluid, while the function of oil present in the reservoir rock was represented by mineral oil. From this experiment it is possible to observe the Saffman-Taylor instability or viscous fingers, which is a phenomenon observed when a low viscosity fluid displaces a higher viscosity fluid. This phenomenon is very important in many applications, such as drilling fluid invasion in porous media, secondary and tertiary oil recovery, hydraulic fracturing, polymer processing, hydrology and filtration. The experiment consists in analyzing the evolution of the interface between two fluids through a digital camera, and determining the displacement efficiency qualitatively from the imagens. With the set of images is possible to observe in which dynamic and rheological parameters the transition from fingers (unstable interface) to plug (stable interface) occurs, and vice versa. Also, rheological tests were performed in which it was possible to know the behavior of non-Newtonian fluids used in the study. From the data collected it was observed that both the polyacrylamide and for xanthan gum transition occurs near the dimensionless shear rate of 3.
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Hardwick, Robert Carlton. "Experimental studies of solid/liquid pipe flows." Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/33430.
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Brotherton-Ratcliffe, Rupert Victor. "Boundary-layer effects in liquid-layer flows." Thesis, University College London (University of London), 1987. http://discovery.ucl.ac.uk/1317966/.
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In this thesis we describe various regimes of practical and theoretical significance that arise in the laminar two-dimensional flow of a layer of an incompressible viscous fluid over a solid surface at high Reynolds number. In Part I we consider steady flows over a distorted rigid surface. Almost uniform flows are considered first, when the distortion is sufficient to provoke a viscous-inviscid interaction, and therefore boundary-layer separation. The two cases of supercritical and subcritical flow have quite distinct features, and are discussed separately. The governing equations in each case require a numerical treatment in general, but analytical progress has been made in certain important regimes e. g. when the distortion is relatively small and linearisation of the problem is possible. Next, the grossly separated motion of fully-developed flows over large obstacles, with dimensions of the order of the depth of the liquid layer, is studied on the basis of inviscid Kirchhoff free-streamline theory. Some comparisons of the theory with recent experiments are also given. In Part II we discuss unsteady and instability aspects of two-dimensional flow over a flat surface. It is shown that viscous and mean flow effects can combine to give instability in some cases, whereas previous studies have only found viscous effects to be stabilising. Unsteadiness of a two-layer fluid flow, with fluids of different viscosity and density, and incorporating surface tension effects, is also discussed. In Part III, deviating from the above theme slightly, we discuss briefly the steady, high-Reynolds-number flow in an asymmetric branching channel, again in the context of viscous-inviscid interactions. The asymmetry is found to force a large-scale response both up- and downstream of the start of the bifurcation. The aim is to find the pressure distributions on the channel walls and on the dividing body. This requires the use of a Wiener-Hopf technique in view of the mixed boundary conditions.
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Schuricht, Paul Hans. "Liquid crystal thermography in high speed flows." Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310549.
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Kenny, Richard Gerrard. "Liquid metal flows through non-uniform magnetic fields." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358643.
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Geraci, Giorgio. "Gas-liquid flows in inclined pipes and venturis." Thesis, University of Nottingham, 2006. http://eprints.nottingham.ac.uk/14313/.
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In oil industrial applications, the modem practice in the drilling of oil wells, deviated drilling, results in inclinations from the vertical to the horizontal being present in such wells. Their design requires an accurate knowledge of the pressure drop/flowrates/physical-properties relationships. The measurement of wet-gas streams can be improved significantly by the use of a Venturi flow meter with an "overreading" correction. Moreover, at high gas mass fractions, knowledge of the liquid distribution about the well tubing cross section is required to inform policy on the use of inhibitors to protect the tubing from corrosion. Therefore, the aims of this study are to address aspects of two-phase gas/liquid flow in the pipe upstream the Venturi and in the Venturi. The main thrust of the project is to examine the effects of stratification that occur in annular flow when the pipe inclination is from horizontal to much higher inclinations. The study of annular flow includes the prediction of the three principal dependent variables – film flowrate, film thickness and pressure drop - as a function of position along the channel. All experiments were carried out with air and water in an inclinable rig. It consisted of a 5 m long stainless steel pipe of 38 mm internal diameter. The pipe could be positioned at any angle between horizontal and vertical in intervals of 5 degrees. The Venturi, located downstream the pipe, had a 19 mm i.d. throat and angles of convergent and diffuser respectively of 32° and 4°. Measurements on liquid film flowrate and liquid film thickness were carried on with two conductance probe techniques and sintered porous wall units. Measurements on pressure drop were conducted with the use of two differential pressure cells. In all experiments described, gas and liquid flowrates and pipe orientation were varied. Another aim of the study was to develop computer modelling for the prediction of air-water pressure gradient and liquid film thickness along the Venturi. The models of Azzopardi et al. (1991) regarding pressure drop and the models of Fukano and Ousaka (1988) for film thickness circumferential variations have been analysed and modified according to the characteristics of the system.
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Mankad, Sunil. "Heat transfer in two phase solid-liquid flows." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307988.
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Badie, Shahrokh. "Horizontal stratifying annular gas liquid flow." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249385.
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Wilson, Wesley M. "The development of a droplet formation and entrainment model for simulations of immiscible liquid-liquid flows." Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=1161.
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Thesis (M.S.)--West Virginia University, 1999.Title from document title page. Document formatted into pages; contains xvi, 219 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 166-169).
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Sanna, Francesco. "Interaction between Flow Induced Pulsations and Multiphase Flows in Gas Liquid Systems." Thesis, Le Mans, 2016. http://www.theses.fr/2016LEMA1008/document.
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Le couplage entre un écoulement instable et des résonances acoustiques dans des systèmes de conduites peut conduire à des phénomènes d’oscillations auto-induites. Ce type de phénomènes trouve principalement place dans des conduites latérales fermées, par exemple dans des systèmes de transport ou de compression de gaz. L’objectif de ce travail est d’étudier les oscillations auto-induites dans le cas où le fluide transporté ne se limite pas à un gaz, mais est un mélange de gaz et de liquide. Les pulsations sont mesurées dans des conduites latérales fermées, pour deux types de configurations (en tandem et en croix), avec écoulement d’un mélange variable d’air et d’eau. La position de l’injection d’eau est variable afin d’obtenir plusieurs régimes d’écoulement diphasique. Les résultats indiquent que la présence d’eau a un effet important sur les niveaux de pulsations dans les conduites. Cet effet a pu être attribué à deux mécanismes dus à la présence d’eau : les instabilités de couches de mélange sont modifiées et l’amortissement des ondes acoustiques est amplifié.Le deuxième mécanisme a été quantifié à l’aide de mesures sur un montage expérimental dédié conçu pour avoir un écoulement stratifié. On a observé que, dans tous les cas, la présence d’eau augmente l’amortissement. Cette augmentation a pu être attribuée à la réduction de la section effective de la conduite (due au remplissage partiel par l’eau) et à l’augmentation de la friction turbulente à l’interface entre les phases liquide et gazeuseCoupling between flow instabilities and acoustic resonances in ducts with closed side branches leads to Flow Induced Pulsations (FIPs). This is a typical phenomenon in engineering applications (gas transport systems, compressor installations, and chemical plants). The objective of this work is to extend the knowledge about FIPs when the transported medium is not uniquely gas but a combination of gas and (a small quantity of) liquid. For two configurations of double side branches (in tandem and in quasi-cross), the amplitude of pressure pulsations in the side branches was measured for different liquid injection rates. This was repeated with the liquid injection point located at different places to allow different flow regimes at the pipe connections. The results show a strong effect of the water content on the pulsations. On basis of these results and additional measurements, the following hypotheses for the effect of liquid were made: (1) interaction of the liquid with the flow instability and (2) increase of the acoustical damping in the ducts in presence of liquid.The effect of liquid on damping was measured with a dedicated test setup designed to have a stratified flow. It was found that the liquid always increases the acoustical damping, mainly due to the reduction of the effective cross section by the liquid, and because of the increased turbulent friction at the interface between gas and liquid
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Miller, Ryan Michael. "Continuum Modeling of Liquid-Solid Suspensions for Nonviscometric Flows." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4864.
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A suspension flow model based on the "suspension balance" approach has been developed. This work modifies the model to allow the solution of suspension flows under general flow conditions. This requires the development of a frame-invariant constitutive model for the particle stress which can take into account the spatially-varying local kinematic conditions. The mass and momentum balances for the bulk suspension
and particle phase are solved numerically using a finite volume method. The particle stress is based upon the computed rate of strain and the local kinematic conditions. A nonlocal stress
contribution corrects the continuum approximation of the particle phase for finite particle size effects. Local kinematic conditions are accounted through the local ratio of rotation to extension in the flow field. The coordinates for the stress definition are the local principal axes of the rate of strain field.
The developed model is applied to a range of problems. (i) Axially-developing conduit flows are computed using both the full two-dimensional solution and the more computationally
efficient "marching" method. The model predictions are compared to experimental results for cross-stream particle concentration profiles and axial development lengths. (ii) Model
predictions are compared to experiments for wide-gap circular Couette flow of a concentrated suspension in a shear-thinning liquid. With minor modification, the suspension flow model predicts the major trends and results observed in this flow. (iii) Comparisons are made to experiments for an axisymmetric contraction-expansion. Model predictions for a two-dimensional planar contraction flow test the influence of model formulation. The variation of the magnitude of an isotropic particle normal stress with local kinematic conditions and anisotropy in the
in-plane normal stresses are both explored. The formulation of the particle phase stress is found to have significant effects on the solid fraction and velocity. (iv) Finally, for a rectangular
piston-driven flow and an obstructed channel flow, a "computational suspension dynamics" study explores the effect of particle migration on the bulk flow field, system pressure drop
and particle phase composition.
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Hale, Colin Paul. "Slug formation, growth and decay in gas-liquid flows." Thesis, Imperial College London, 2000. http://hdl.handle.net/10044/1/8550.
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Choate, Eric P. Forest M. Gregory. "Small amplitude oscillatory flows of nematic liquid crystal polymers." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2007. http://dc.lib.unc.edu/u?/etd,835.
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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2007.Title from electronic title page (viewed Dec. 18, 2007). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Mathematics." Discipline: Mathematics; Department/School: Mathematics.
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Shetty, Sanat Achanna. "Liquid spreading and thin film flows over complex surfaces /." Access abstract and link to full text, 1995. http://0-wwwlib.umi.com.library.utulsa.edu/dissertations/fullcit/9610610.
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Roy, Ajoy Krishna. "Application of smooth particle hydrodynamics to solid-liquid flows." Thesis, University of Surrey, 2002. http://epubs.surrey.ac.uk/2108/.
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Oddie, G. M. "The characterisation of multicomponent (liquid) flows using scattered ultrasound." Thesis, Cranfield University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333538.
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Williams, Harvey Alec Rodney. "Two-dimensional surfactant-driven flows of thin liquid films." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.625029.
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Menghini, Filippo <1989>. "Advanced Computational Fluid Dynamics models for liquid metal flows." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amsdottorato.unibo.it/7505/.
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In this thesis it is shown the development, implementation and numerical solution of several computational fluid dynamics models for the study of liquid metal flows. The work is organized in two main parts in which different modeling techniques are analyzed. These two parts are introduced by a brief chapter on the finite element methods and on the computational platform developed during the Ph.D. studies which have been the basis for the implementation and numerical solution of all the developed mathematical models.
In the first part, turbulence modeling based on Reynolds Averaged Navier Stokes equations is considered for the study of turbulent heat transfer in liquid metal flows. A new four parameter turbulence model is introduced and validated in two different k-e and k-w formulations. Several results in four geometries interesting for the fast nuclear reactor field are reported in order to assess and prove the feasibility of this model for the study of turbulent heat transfer in liquid metal flows.
In the second part the adjoint optimal control theory is introduced. Some numerical cases are presented by solving the optimality system with state and adjoint variables. The first application is a temperature boundary optimal control in which an improved way of setting boundary conditions in weak form has been developed. The second application is a distributed optimal control problem for the RANS system. Numerical simulations in two and three dimensions have been carried on for this type of applications and are reported in the final chapter.
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Escrig, Josep. "Influence of geometrical parameters on gas-liquid intermittent flows." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/47085/.
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The influence of geometrical parameters on the development of intermittent flow is studied in this thesis. The geometrical parameters considered are the diameter of the pipe, the angle of inclination of the pipe, and the distribution of the area of the gas injection. Intermittent flow in gas-liquid two-phase flows occurs when, from a fixed point, a gas dominated structure followed by a liquid dominated structure seems to repeat at a certain mean frequency. It is mainly slug flow but churn and cap bubble flow also fall into this broad category. Intermittent gas-liquid two-phase flow was investigated in a 67 mm diameter, 6 m long rig and also in a 127 mm diameter, 12 m long rig. The test section of the 67 mm rig was mounted in a steel frame supported by a pivot that allowed changing the inclination of the pipe from vertical to horizontal in steps of 15°. The 127 mm rig can only be operated in the upwards vertical position. The fluids utilised were air and silicon oil of viscosity = 5 cP and density = 0.912 kg/m3. The interfacial surface tension was measured at 0.02 N/m. The facilities were both operated at atmospheric pressure. The gas superficial velocity (Ugs) was varied from 0.17 to 2.9 m/s and liquid superficial velocity (Uls) from 0.023 to 0.47 m/s. The void fraction generated by each set of conditions was captured for 60 seconds using a Wire Mesh Sensor and a twin plane Electrical Capacitance Tomography probe. The effect of the diameter and the angle of inclination of the pipe under different gas and liquid superficial velocities was reported. The main findings can be summarised as that the velocity of the periodic structures was found to be higher in large diameter pipes and increases with increasing the angle of inclination reaching a maximum around 50° then decreases. In addition, the frequency of the gas structures was found to be higher in small diameter pipes and increases with increasing the inclination of the pipe for all the gas and liquid superficial velocities investigated. Additionally, two correlations to predict the velocity and the frequency of the periodic gas structures as a function of the diameter, the inclination of the pipe, the gas superficial velocity and the liquid superficial velocity were developed. The proposed correlations were found to not only be in excellent agreement with the present experimental results (less than 20% difference), but also in good agreement with data published by other researchers. This include data produced using different fluids, different diameters of pipe and different gas and liquid superficial velocities to the ones investigated in this work. It was also found that the gas injection area, modified using different gas-liquid mixers, do not have an influence on the development of the intermittent two-phase flows at 75 diameters axial length from the mixing point.
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Bühler, Leo. "Three-dimensional liquid metal flows in strong magnetic fields." Karlsruhe Forschungszentrum Karlsruhe, 2008. http://d-nb.info/991370600/34.
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Burt, Andrew C. "A computational study of mixing in stratified liquid-liquid flows using analogy between heat and mass transfer." Morgantown, W. Va. : [West Virginia University Libraries], 2001. http://etd.wvu.edu/templates/showETD.cfm?recnum=1948.
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Thesis (M.S.)--West Virginia University, 2001.Title from document title page. Document formatted into pages; contains x, 76 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 71-72).
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Hau, Lap Wing. "Electrokinetically-driven liquid flows in microchannels using surface-chemistry technology /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?MECH%202005%20HAU.
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Monsen, Gisle Otto Tviberg. "Modeling of a centrifugal separator for dispersed gas-liquid flows." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18678.
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Natural gas is a vital component of the worlds’ supply of energy. In Norway all the gas can be found offshore where it needs to processed before transport. A vital part of the processing is gas and liquid separation. Current gas-liquid separators are big and expensive, and the offshore industry is looking for more compact separators. One of the more prominent technologies is the NNNGLseparator developed at NTNU. To further identify its possibilities, a thorough research program has been startedIn this thesis one-dimensional models describing pressure drop and separation performance of the NTNU Natural Gas Liquid Separator (NNGLseparator) for dispersed gas-liquid flows has been studied. Here modeling of separation performance was divided into cyclonic separation and droplet capture by the meshpad, and then combined in sequence. The droplet capture is assumed to occur before cyclonic separation.To analyze the impact of centrifugal force on droplet capture, the force was included in a previous proposed model describing droplet capture by a single fiber in the meshpad. With this as basis, modeling of total droplet capture for the meshpad was analyzed. Through this analysis we proposed an extension on the existing model for the case of the flow not following the rotation of the meshpad. The droplets that are not captured are then separated through cyclonic separation. To model this separation mechanism, a modified time of flight model was developed. The modification includes the mesh porosity, and a - factor describing the droplet’s reduced radial velocity due to the obstructing meshpad.Existing models for pressure drop across fixed porous media were compared to experimental data to identify which model best applies to the meshpad used in the NNGLseparator. How this model performs in describing a rotating porous media was then analyzed for the two scenarios; fully developed flow before mesh entry and developing flow inside a rotating meshpad. Through this analysis an extension to the pressure drop model was proposed, which includes the tangential velocity difference between rotating mesh and gas flow. A previous proposed model for pressure drop across wet mesh pad was reviewed. This led to a discussion on how liquid hold up differs in the NNGLseparator from conventional fixed meshpads. The proposed one-dimensional models were then analyzed through a parametric study of the separator performance in terms of pressure drop and efficiency of droplet separation for different flow conditions and geometries.
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Lee, Betty. "Dynamic response of small turbine flowmeters in pulsating liquid flows." Thesis, Brunel University, 2002. http://bura.brunel.ac.uk/handle/2438/4971.
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The dynamic response of turbine flowmeters in low pressure gas flows (i. e. where the rotational inertia of the fluid is negligible) is well understood and methods for correcting meter signals for a lack of response are available. For liquid flows there has been a limited amount of experimental work on the response of meters to step changes but no reports have been found of the response of meters to sinusoidally pulsating flows. "Small" turbine meters are expected to behave differently from "large" meters for a number of reasons: a smaller meter would generally have: (1) a larger percentage of tip clearance leakage flow; (2) less fluid momentum between the meter blading; and, (3) less fluid friction forces on the effective surface area. In this research, arbitrarily, meters up to size 25 mm were defined as small; and within this study, meters of size 6 mm to 25 mm were investigated. The aim of the research was to investigate and to understand the response of small turbine meters to pulsating liquid flows and to provide methods for correction. Three approaches were used: (1) application of an existing theoretical model of turbine meter behaviour; (2) an experimental investigation of meter performance in pulsating flows; and (3) simulation of flow behaviour through one selected meter using CFD and extending the simulation to predict the rotor dynamics and, hence, the response of this meter to specified cases of pulsating flow. A theoretical model developed by Dijstelbergen (1966) assumes frictionless behaviour and that flow is perfectly guided by meter blading through the rotor and that fluid within the rotor envelope rotates as a "solid body". Results from this theoretical model applied for pulsating flows showed that there was likely to be positive error in predicted mean flow rate (over-registration) and negative error for predicted values of the amplitude of the pulsations (amplitude attenuation). This behaviour is due to the fundamental asymmetry between flows with increasing and decreasing angle of attack relative to the meter blades, throughout a pulsation cycle. This qualitative behaviour was confirmed by experimental work with meters up to size 25mm working with pulsation frequencies up to 300 Hz. For low frequency pulsations (below 10 Hz), the over-registration errors were within the limits of specified meter accuracy. At higher frequencies and larger pulsation amplitudes, the largest over-registration observed was 5.5 % and amplitude attenuation could be as large as 90 %. The dependence of these errors on both the flow pulsation amplitude and frequency were investigated. The theoretical model was also used as a basis for generating correction procedures, to be applied to both the mean flow and the pulsation amplitude measurements. The results from the CFD simulation showed qualitative good agreement with the experimental data. The same kind of meter error trends were observed and it was shown to provide a better correlation with the experimental trends than the theoretical model derived from Dijstelbergen. From the CFD simulation, the causes of over-registration and amplitude attenuation in turbine flowmetering were understood through the investigation of rotor dynamics coupled with fluid behaviour around meter blading within the pulsation cycle. The CFD results were used to evaluate fluid angular momentum flux and to review the validity of the assumption that fluid within the rotor "envelope" rotated as a solid body. For the case investigated, whilst the assumption that flow is perfectly guided is not inappropriate, the volume of fluid assumed to rotate as a "solid body" was found to be significantly less than the rotor envelope volume.
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Sultan, Khaled M. "The propagation of pressure waves in two-phasegas/liquid flows." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0004/MQ42100.pdf.
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Laforgia, Antonio. "Modelling of gas-liquid annular flows at high mass fluxes." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415910.
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Adechy, Didier. "Phase separation in annular gas-liquid flows at t-junctions." Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251963.
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Van, der Meulen Gerrit Pieter. "Churn-annular gas-liquid flows in large diameter vertical pipes." Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/12581/.
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This thesis presents an investigation on the churn to annular flow pattern boundary in an 11 m tall, 127 mm id vertical riser. Experimental data on film thickness, pressure drop and drop size and velocity was analysed and interpreted. Entrained fraction, interfacial and wall shear stresses and the interfacial friction were calculated from the experimental data. A new churn-annular flow transition boundary was derived based on trends, and in particular changes of slopes, observed in film thickness, pressure drop and structure velocity data. This is supported by observations made using high speed photography. Minima in slopes are found in plots of film thickness and pressure gradient with gas superficial velocity at low liquid flow rates. These minima are however not clearly visible at higher liquid flow rates in the data obtained. Dimensional analysis of this transition boundary and those proposed by other workers, using Froude and Weber numbers, resulted in a closer agreement between transition boundaries then was achieved till present. The correlation found, which describes the boundary, performs well for different pipe diameters, fluid properties and experimental flow conditions. It was observed that existing models for the calculation of interfacial and wall shear stresses, including the interfacial friction factor, do not perform well in churn type flows. Their performance and agreement with the present data at high gas flow rates, thus annular flow, was however better. This indicated that these models do not take some of the characteristics of the flow into account, e.g., gas core density. It was found that the latter parameter plays an important role in churn flow since the gas core density increases steeply with decreasing gas flow rate. New relationships for these parameters are suggested for a more accurate prediction in large diameter pipes. The diameter, velocity, and entrained fraction of drops show similar trends to that of the liquid film thickness and pressure drop. The velocity and the entrained fractions show most profound information. The entrained fraction increases in churn flow with gas flow rate. It then shows a steep decrease in a transitional area. In this area it may be that the entrained fraction is more contained in large waves and wisps than in drops. At higher gas flow rates, the entrained fraction increases again, as is well reported by other researchers. Here the breakup and atomisation of large waves and wisps play an important role. From comparison between drop fractions deposited by diffusion and direct impaction in the CFD and experimental results, there is evidence that in large diameter pipes a third deposition mechanism applies: Transitional deposition. Analysis shows that transitional impaction occurs at medium sized drops at medium gas flow rates. Around these conditions, large waves are present in the flow as described above. The third deposition mechanism probably occurs when the majority of entrained liquid is carried in large waves and wisps as reported above. Therefore, at the transition from churn to annular flow in large diameter vertical pipes, the behaviour of the flow is not typical to that observed in smaller diameter pipes.
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Kolb, Kelly Jean. "Modeling Bright Gully Deposits' Formation in Hale Crater, Mars: Implications for Recent Liquid Water." Thesis, The University of Arizona, 2008. http://hdl.handle.net/10150/193349.
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This study aims at uncovering the formation mechanism of the recent bright gully deposits observed on Mars in order to assess the viability of liquid water involvement. I use a high resolution topography model as input into a kinematic model to assess whether or not a dry granular flow could form the bright gully deposits seen in Hale Crater. I investigate a dry mechanism due to the difficulty of producing water on the martian surface under present-day pressure and temperature conditions. I examine a range of particle sizes, flow thicknesses, and upslope initiation points to examine how these parameters affect the run-out distances of flows. The results show that multiple combinations of parameters could produce flows that travel to within the observed deposits' boundaries. The results suggest that the recent bright gully deposits are not evidence of recent liquid water on the surface of Mars.
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Ceballos, Castillo Carlos Alberto. "Multidisciplinary design approach and safety analysis of ADSR cooled by buoyancy driven flows." Delft : Delft University Press, 2007. http://www.loc.gov/catdir/toc/fy0712/2007276538.html.
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Thesis (doctoral)--Delft University of Technology, 2007."Proefschrift ter verkrijging van de graad van doctor aan de Technische Universiteit Delft." Includes bibliographical references (p.120-128) and index.
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Omgba-Essama, C. "Numerical modelling of transient gas-liquid flows (application to stratified & slug flow regimes)." Thesis, Cranfield University, 2004. http://hdl.handle.net/1826/1057.
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A new methodology was developed for the numerical simulation of transient two-phase
flow in pipes. The method combines high-resolution numerical solvers and adaptive mesh
refinement (AMR) techniques, and can achieve an order of magnitude improvement in
computational time compared to solvers using conventional uniform grids.
After a thorough analysis of the mathematical models used to describe the complex
behaviour of two-phase flows, the methodology was used with three specific models in
order to evaluate the robustness and accuracy of the numerical schemes developed, and to
assess the ability of these models to predict two physical flow regimes, namely stratified
and slug flows.
The first stage of the validation work was to examine the physical correlations required for
an accurate modelling of the stratified smooth and wavy flow patterns, and a new
combination of existing correlations for the wall and interfacial friction factors was
suggested in order to properly predict the flow features of the experimental transient case
investigated.
The second and final phase of the work dealt with the complex and multi-dimensional
nature of slug flow. This flow regime remains a major and expensive headache for oil
producers, due to its unsteady nature and high-pressure drop. The irregular flow results in
poor oil/water separation, limits production and can cause flaring. The modelling
approached that was adopted here is based on the two-fluid model, which can theoretically
follows each formed slug and predicts its evolution, growth and decay, as it moves along
the pipe.
However, the slug flow study, performed here through a test case above the Inviscid
Kelvin-Helmholtz transition from stratified to slug flow, showed that the incompressible
two-fluid model used is unable to accurately predict most of the features of this complex
flow. Mechanisms such as the interfacial wave formation, the slug growth and propagation,
although observed from the simulations, cannot be accurately determined by the model.
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Renault, Fabien. "A Lagrangian Slug Capturing Scheme for Gas-Liquid Flows in Pipes." Doctoral thesis, Norwegian University of Science and Technology, Department of Energy and Process Engineering, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1754.
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In this thesis a new Lagrangian numerical scheme for the simulation of gas-liquid flows in pipelines is presented. Based on an approximate two-fluid model, this new scheme, called LASSI (Lagrangian Approximate Scheme for Slug Initiation) is dedicated to the modelling of the transition between stratified and slug flow. It is able to capture directly the slug initiation process and to track the motion of every single slug in the pipe without numerical diffusion. It can thus be qualified as a slug capturing and slug tracking scheme.
The scheme is based on the decoupling between the fast pressure dynamics governing the motion of the slugs and the much slower liquid transport in the bubbles. The liquid motion in the bubbles is then approximately modelled by a modified version of the shallow water equations, in which the influence of the Bernoulli suction force is subtracted from the traditional hydrodynamical term. The fully Lagrangian structure of the scheme makes it possible to accurately capture the transport of the fast interfacial waves whose growth can eventually result in a slug initiation.
The model predictions are compared with some experimental results obtained in the NTNU multiphase flow laboratory or taken from the literature. Several flow conditions are considered, in particular the case of hydrodynamic slugging in near-horizontal flows, slugging in an upwards pipe, severe slugging, and slugging triggered by fast transients. Numerical predictions are also compared with theoretical considerations regarding the stability of stratified flow.
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Gomaa, Hassan [Verfasser]. "Modeling of Liquid Dynamics in Spray Laden Compressor Flows / Hassan Gomaa." München : Verlag Dr. Hut, 2014. http://d-nb.info/1064560040/34.
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