Dissertations / Theses on the topic 'Phase flow'
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Al-Yarubi, Qahtan. "Phase flow rate measurements of annular flows." Thesis, University of Huddersfield, 2010. http://eprints.hud.ac.uk/id/eprint/9104/.
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In the international oil and gas industry multiphase annular flow in pipelines and wells is extremely important, but not well understood. This thesis reports the development of an efficient and cheap method for measuring the phase flow rates in two phase annular and annular mist flow, in which the liquid phase is electrically conducting, using ultrasonic and conductance techniques. The method measures changes in the conductance of the liquid film formed during annular flow and uses these to calculate the volumetric and mass flow rates of the liquid film. The gas velocity in the core of the annular flow is measured using an ultrasonic technique. Combined with an entrainment model and the liquid film measurements described above, the ultrasonic technique enables the volumetric flow rate of the gas in the core and the volumetric and mass flow rates of entrained liquid droplets to be measured. This study was based on experimental work and the use of modelling techniques. The practical investigation comprised a series of experiments conducted on a purpose built flow loop in which the test section was a Perspex pipe of 50mm ID. The experimental work was limited to two-phase air-water flow. The flow loop was specifically designed to accommodate the different instruments and subsystems designed in this investigation including bespoke flow meters and a film extraction system. Most flow loop controls were automated using a MATLAB program. Reference measurement of the total water flow rate was made using a calibrated turbine flow meter and of the air flow rate using a calibrated rotameter. For the combined ultrasonic/conductance method investigated in this thesis, the velocity of the gas in the core was found using a novel Ultrasonic Flow Meter (USFM). The positioning and arrangement of the transducers have never been used previously. The flow velocity of the liquid film and the thickness of the film were measured using a novel Conductance Flow Meter (CFM). The CFM measured the liquid film thickness using novel wall conductance probes. By cross correlating the signals from a pair of such probes the film velocity was obtained. Good agreement of the experimental results obtained from the CFM and USFM with results published in the literature was found. Although not investigated experimentally in the work described in this thesis, annular flows encountered in the oil industry may contain a liquid phase comprising a mixture of oil and water. For such flows, the volume fractions of the oil and water can be measured using an automated bypass system developed during this project. The bypass system periodically extracts part of the liquid film, measures its density and then releases the sample back into the pipeline. The liquid phase volume fractions are determined from this density measurement which can be performed more than once per minute. An entrainment model was developed, which is required by the ultrasonic/conductance flow metering technique described in this thesis, in which the mass fraction of the liquid flowing as entrained droplets in the core can be determined from the liquid film thickness and velocity measurements. A mathematical model was also developed to describe the properties of the liquid film, such as liquid velocity profile within the film, and the model’s results were found to agree with the experimental results obtained during the project and also with previous work cited in the literature. The complexity of this latter model was reduced by making a number of simplifying assumptions, which are presented and discussed in the thesis, including the assumption that in annular flow there is a dynamic balance liquid entrainment and droplets being deposited back onto the film. The combination of the designed CFM and USFM with the bypass tube and the entrainment model offer the opportunity for a ‘wet gas’ flow meter to be developed to measure two and three phase annular flows at relatively low cost and with enhanced accuracy. Such a device would have the advantage that it would by substantially smaller than systems using separators and it could even be retrofitted onto off-shore platforms. The integration of the subsystems developed in this project into a single system capable of giving on-line measurements of annular flow would be a major benefit to the author’s sponsor, Petroleum Development of Oman.
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Kunda, Wilkinson. "Two phase problems and two phase flow." Thesis, University of Hull, 1986. http://hydra.hull.ac.uk/resources/hull:5902.
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In section 1 of this thesis a two-dimensional mathematical model is used to investigate the circulation in a gas-bubble agitation system of a cylindrical vessel for the case of an orifice located at the centre of the base. The two-phase (liquid/gas) region is assumed to be confined to a cone-shaped region and is investigated using Wallis' Drift Flux Model. In the single-phase (liquid) region the turbulent Navier-Stokes equations, written in terms of the stream function, are used for the mathematical model. The analysis in the two-phase region yields the boundary conditions on the two-phase/single-phase boundary. The velocity field in the two-phase region is solved analytically giving results in closed form. A numerical algorithm is developed for calculating liquid flow in the single phase region, and numerical results are presented graphically in terms of the stream function. In section 2 two moving interface problems are investigated. Small time analytic solutions are found for three-dimensional inward solidification of a half space initially at fusion temperature in the first problem. In the second problem, perturbation solutions for melting of a cylindrical annulus with constant heat flux on inner surface are given. In both problems the interface immobilization technique is used. Interface locations at various times are calculated for the inward solidification problem and the results shown in three-dimensional graphs. First and second perturbation terms for the interface location are given for the second problem and graphs of each are presented for a particular case.
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Ariyoshi, Gen. "Flow Characteristics of Lead-Bismuth Two-phase Flow." Kyoto University, 2019. http://hdl.handle.net/2433/242325.
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Whitaker, T. S. "Measurement of two-phase flows by phase separation." Thesis, University of Liverpool, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240831.
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Kazeem, Akintunde. "Flow induced phase inversion emulsification." Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267627.
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Wong, Wai-Lid. "Flow development and mixing in three phase slug flow." Thesis, Imperial College London, 2003. http://hdl.handle.net/10044/1/7780.
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Neuweiler, Insa. "Macroscopic parameters for two-phase flow." [S.l.] : [s.n.], 1999. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=13490.
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Dillon, Chad Michael. "Two-Phase Flow Within Narrow Annuli." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5097.
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A study of two-phase flow in annular channels with annular gaps of less than 1 mm is useful for the design and safety analysis of high power density systems such as accelerator targets and nuclear reactor cores. Though much work has been done on pressure drop in two-phase flow, designers rely mostly on empirical models and correlations; hence, it is valuable to study their applicability for different channel sizes, geometries, and gas qualities.
The pressure drop along a concentric annular test section was measured for cases of either constant quality or variable quality along its length (such as in sub-cooled and flow boiling). A porous tube was used to inject gas along the inner surface of the annular channel, thereby simulating the case of flow boiling along the inner surface. The data were compared to predictions of various models and correlations. Additionally, the effect of wall vibrations on the pressure drop was examined. Experiments were conducted by imposing vibrations of known amplitudes and frequencies on the outer tube of the annulus. Wall vibrations were thought to be important for flow in microchannels where the vibration amplitudes may be significant compared to the channel hydraulic diameter.
The results obtained in this investigation indicate that the pressure drop correlation given by Beattie and Whalley provides the best agreement with the data for both porous tube gas injection (i.e. variable quality) and constant quality two-phase flow within the narrow annulus. Furthermore, the results show that there is a minimal effect of vibrations on two-phase pressure drop over the range of frequencies and amplitudes studied.
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Srichai, Somprasong. "High pressure separated two-phase flow." Thesis, Imperial College London, 1994. http://hdl.handle.net/10044/1/8656.
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Shaha, Jonathan. "Phase interactions in transient stratified flow." Thesis, Imperial College London, 2000. http://hdl.handle.net/10044/1/8653.
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Sharma, Yugdutt. "Modeling transient two-phase slug flow /." Access abstract and link to full text, 1985. http://0-wwwlib.umi.com.library.utulsa.edu/dissertations/fullcit/8605319.
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Lillibridge, Kris Hamilton. "Buoyancy-driven two-phase countercurrent flow." Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/16027.
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McQuillan, K. W. "Flooding in annular two-phase flow." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354843.
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Willetts, I. P. "Non-aqueous annular two-phase flow." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393120.
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Klidonas, G. "Void fraction in two phase flow." Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235032.
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Stewart, Colin. "Metering of two-phase slug flow." Thesis, University of Strathclyde, 2002. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21158.
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This thesis describes the development of a novel system, for metering of two-phase (gaswater) slug flows. The approach combines a model for stable slug flow, a non-intrusive set of conductance sensors, and appropriate closure relationships. This system allows each of the parameters in the model to be determined. The slug flow model is analysed, to determine the sensitivity of the phase flowrates to each measurement parameter. A metering system is then proposed which combines ring-shaped electrodes, electronic instrumentation, and processing software. The ring electrodes are optimised, for the measurement of the phase fraction and the translation velocity. New instrumentation is developed to activate the electrodes, with high measurement accuracy and a wide bandwidth. Analysis software is developed, to process the sensor data, provide suitable closure relations, and deliver the flowrates. A unique feature of this software is its ability to calculate uncertainty margins in the predicted flowrates. The NEL multiphase facility is used, to obtain data for developed, horizontal, gas-water slug flow in a 4-inch pipe. The data span the range of liquid phase superficial velocities 0.1 m s⁻¹ to 1.0 m s⁻¹, and gas phase superficial velocities 0.6 m s⁻¹ to 6.0 m s⁻¹. The analysis software is used to obtain the flowrate predictions and estimates for the uncertainty margins. The stable slug flow model does not give good results. The relative error in the gas phase prediction is between 10% and 100%, and for the liquid phase prediction, between 50% and 500%. The uncertainty margins are also of comparable magnitude. Proposals for improving the accuracy of the translation velocity measurement, and for directly measuring the local velocities in the slug body (using a pressure transducer) are presented. These proposals aim to reduce the uncertainty that is caused by the use of the empirical closure relationships in the model.
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Roberts, Paul Anthony. "Two-phase flow at T-junctions." Thesis, University of Nottingham, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240490.
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Teixeira, Jose Carlos Fernandes. "Turbulence in annular two phase flow." Thesis, University of Birmingham, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.570318.
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The structure of turbulent flow in vertical upwards annular air water two-phase flow was examined. Experiments were carried out in a 32 mm internal diameter tube using laser Doppler anemometry. Simultaneous measurements of the two velocity components and the Reynolds stress were obtained by the use of two colours (blue and green) of a 50 mW argon ion laser. The gas core was seeded by polystyrene particles of 1 um diameter which were believed to follow the gas turbulent fluctuations. The characteristics of the signal were used to discriminate these tracer particles from the water droplets. The gas velocity profiles were shown to be more peaked at the centre of the tube than those observed in turbulent single phase flow. Comparative analysis with other data suggested that both interfacial roughness and, particularly, the momentum interchange between the droplets and the gas core, are the most important factors affecting the gas velocity profile in annular flow. Turbulent fluctuations of the gas velocity were found to be significantly higher than those typical of single phase flow, for similar gas Reynolds numbers. The interfacial shear, droplet size and concentration and the presence of disturbance waves at the interface were identified as being the most important factors affecting the gas turbulence in annular flow. A model was developed to predict the axial component of the turbulent fluctuations at the centre of the tube. The turbulence transport properties were observed to differ from those typical of single phase flow: i.e., higher production of turbulent energy (associated with higher anisotropy ratios), higher turbulence length scales and comparativelly lower dissipation ratios. Extrapolation of the mixing length theory to annular flow appeared to be inappropriate. Droplet size measurements showed that the gas velocity and the droplet concentration are the most important parameters affecting droplet size. At low droplet concentrations (where the gas-droplet interaction is more important than that between the droplets), a modified Weber number based on the homogeneous gas core momentum describes the maximum droplet diameter. At high droplet concentrations, the data suggests that coalescence is the dominant factor. Droplet velocity was found to be related to the size of the droplets: i.e., large droplets travel slower than small ones. The difference in velocity between large and small droplets was found to depend on the liquid and gas flow rates. This observation is related to conditions where droplet coalescence occurs. The effect of inserts on droplet size and the entrained fraction was examined. Disturbances in the channel geometry were found to affect the mean droplet size due to the creation of a new droplet population. The entrained fraction of liquid downstream of the insert was also affected. A model was formulated to describe the liquid interchange in the presence of a vertical plate.
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Velat, Christopher James. "Experiments in cryogenic two phase flow." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0006941.
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Doup, Benjamin. "Experimental Investigation of Flow Structure Development in Air-water Two-phase Flows." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1332514704.
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Galambos, Paul C. "Two-phase dispersion in micro-channels /." Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/7100.
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Lei, Siu Long. "Phase-field simulations of two-phase flows /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?MATH%202009%20LEI.
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Chen, Lejun. "Flow patterns in upward two-phase flow in small diameter tubes." Thesis, Brunel University, 2006. http://bura.brunel.ac.uk/handle/2438/5104.
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Two-phase flow in small tubes and channels is becoming a common phenomenon in industrial processes. However, the study of two-phase flow regimes in small tubes is still at its infancy. The previous studies are reviewed and discussed in the literature section. The problems and inconsistencies encountered in the earlier studies are presented and discussed. The experimental facility is introduced in the chapters that follow. They include a section on the design of the experimental system and the test sections, the selection of the experimental parameters and the introduction of the purposely-developed programs to control the experiments and collect and process the data. The methodology of the calibration and the uncertainty analysis, the problems encountered and their solutions and the single-phase validation experiments are also described. In this project we studied the effect of tube diameter and fluid flow parameters on flow patterns in small tubes using R134a as the working fluid. The tested tube diameters were 1.10, 2.01, 2.88 and 4.26 mm; the fluid pressures were 6, 10 and 14 bar; the liquid and gas superficial velocities covered a range of 0.04-5.0 m/s and 0.01-10.0 m/s respectively. The observed flow patterns included bubbly, dispersed bubble, confined bubble, slug, chum, annular and mist flow. Twelve integrated flow maps are sketched in this report. The obtained results were compared with earlier experiments by other workers and with existing models, with obvious differences in the prediction of the transition boundaries. A set of new models and correlations were developed, based on the new data for boiling R134a presented in this thesis, to predict the effect of tube diameter and fluid properties on the transition boundaries. Some also agreed with the limited data available from earlier studies for adiabatic air-water flow in small to normal size tubes.
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Abrishami-Savjublagh, Yoseph. "Numerical computations of dispersed flow and gravity stratified two-phase flow." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/47736.
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Özdemir, Mehmed Rafet. "Single-phase flow and flow boiling of water in rectangular metallic microchannels." Thesis, Brunel University, 2016. http://bura.brunel.ac.uk/handle/2438/13254.
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This experimental research aims at investigating the single-phase flow heat transfer and friction factor, flow boiling heat transfer and pressure drop, and flow visualisation in microchannels using de-ionized water. In the literature, many studies failed to explain the effect of aspect ratio on the single-phase and two-phase flow heat transfer rate and pressure drop. Because the channel aspect ratios and hydraulic diameters were varied together in those studies. Also, there is a discrepancy between past studies and the conventional theory for the flow boiling heat transfer characteristics. Accordingly, the objectives of this research can be listed as follows: (i) modifying the existing experimental facility to perform single-phase and two-phase flow heat transfer and pressure drop and two-phase flow pattern visualization experiments in microchannels, (ii) clarifying the fundamental aspects of flow boiling in micro passages, (iii) investigating the aspect ratio, heat flux, mass flux and vapour quality effects on flow patterns, heat transfer rate and pressure drop in single-phase and two-phase flow, (iv) comparing the obtained results with heat transfer and pressure drop correlations and flow pattern maps available in the literature. Consequently, the pre-existing experimental facility was modified in the current research by changing the pre-heaters, flowmeter and piping in order to achieve the goals of this study. Four copper rectangular microchannels were designed and manufactured. Three microchannel test sections having the same hydraulic diameter and length but different aspect ratios were investigated to reveal the effect of aspect ratio on the single-phase and two-phase flow heat transfer rate and pressure drop. The surface roughness of each microchannel was also examined. It was found that the surface roughnesses of all microchannels are similar. Moreover, an additional microchannel test section was used to examine the effect of heated length on the flow boiling heat transfer coefficient and pressure drop. The single-phase flow results demonstrated that the channel aspect ratio has no influence on the friction factor and heat transfer rate for the tested microchannels and experimental range. In the flow boiling experiments, bubbly, bubbly/slug, slug, churn and annular flow regimes were observed in the tested microchannels. The channel aspect ratio effect was found to be small on the observed flow patterns. The experimental flow patterns were predicted well by the flow pattern map proposed by Galvis and Culham (2012) except for the slug flow regime. The flow pattern maps of Sobierska et al. (2006) and Harirchian and Garimella (2009) reasonably predicted the experimental flow pattern data. The flow boiling heat transfer results showed that the prevailing heat transfer mechanism is nucleate boiling for the low and medium heat flux inputs. On the other hand, the dominant heat transfer mechanism is unclear at the high heat flux inputs while smaller aspect ratio microchannel has better heat transfer performance for low and medium heat flux inputs. However, at high heat flux inputs the channel aspect ratio effect was found to be insignificant on the flow boiling heat transfer coefficient. The experimental flow boiling heat transfer coefficient data were reasonably predicted by the correlations of Sun and Mishima (2009), Li and Wu (2010) and Mahmoud and Karayiannis (2011) from the literature. The flow boiling pressure drop characteristics were also examined in the tested microchannels. Outcome of the experiments consistently indicated a highly linear trend between the increasing flow boiling pressure drop and the heat and mass flux. Also, the flow boiling pressure drop increased with the increase in vapour quality. The effect of channel aspect ratio on the flow boiling pressure drop was also assessed. It was found that when the channel aspect ratio decreased, the flow boiling pressure drop increased. The experimental flow boiling pressure drop data were compared to correlations from the literature. Mishima and Hibiki (1996), Yu et al. (2002) and Zhang et al. (2010) correlations reasonably predicted the experimental flow boiling pressure drop results.
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Zschuppe, Robert. "Pulse Flow Enhancement in Two-Phase Media." Thesis, University of Waterloo, 2001. http://hdl.handle.net/10012/1267.
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This laboratory project has been done to evaluate pressure pulsing as an Enhanced Oil Recovery (EOR) technique. To perform the study, a consistent laboratory methodology was developed, including the construction of a Consistent Pulsing Source (CPS). Tests compared pulsed and non-pulsed waterfloods in a paraffin or crude oil saturated medium, which also contained connate water (an irreducible water saturation). Results revealed that pulsed tests had maximum flow rates 2. 5--3 times higher, greater oil recovery rates, and final sweep efficiencies that were more than 10% greater than non-pulsed tests. The CPS design has proven very successful, and has since been copied by a major oil corporation. However, there are two limitations, both caused by fluctuating water reservoir levels. Longer pulsed tests (reservoir-depletion tests) were periodically paused to refill the water reservoir, resulting in reservoir depressurization and lower flow rates. The final effect of this was impossible to quantify without correcting the problem. The second CPS limitation was the change in pulse shape with time. However, it is not expected that this had any major effect on the results. The pulse pressure and period studies were limited by early tests, which did not have the necessary time duration. Both increasing pulse pressure and decreasing pulse period were found to increase the final sweep efficiency. Slightly decreasing porosity (0. 4% lower) was found to lower sweep efficiencies. However, the 34. 9% porosity results were not done until reservoir depletion, so it is difficult to quantitatively compare results. An emulsion appeared after water breakthrough when using the CPS on light oils (mineral oil). This may have been the result of isolated oil ganglia being torn apart by the sharp pulses. Although it is difficult to apply laboratory results to the field, this study indicates that pressure pulsing as an EOR technique would be beneficial. Doubled or tripled oil recovery rates and 10% more oil recovery than waterflooding would be significant numbers in a field operation. A valuable application would be in pulsing excitation wells to both pressurize the reservoir and enhance the conformance of the displacing fluid over a long-term period. It would also be valuable for short-term chemical injections, where mixing with the largest volume possible is desirable.
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Tahmasbi, Nowtarki Koroush. "Two phase hydrodynamics in cross-flow distillation." Thesis, Imperial College London, 1997. http://hdl.handle.net/10044/1/8424.
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Odozi, Utomi Ayodele. "Three-phase gas/liquid/liquid slug flow." Thesis, Imperial College London, 2000. http://hdl.handle.net/10044/1/8444.
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Djatmiko, Wahju. "Well testing in multi-phase flow reservoirs." Thesis, Imperial College London, 1996. http://hdl.handle.net/10044/1/8128.
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Pan, Xuefeng. "Immiscible two-phase flow in a fracture." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0025/NQ47907.pdf.
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Olsson, Elin. "Mass Conserving Simulations of Two Phase Flow." Licentiate thesis, Stockholm, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3851.
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Sachdeva, Rajesh. "Two-phase flow through electric submersible pumps /." Access abstract and link to full text, 1988. http://0-wwwlib.umi.com.library.utulsa.edu/dissertations/fullcit/9021070.
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Malik, Amer. "Phase change with stress effects and flow." Doctoral thesis, KTH, Fysiokemisk strömningsmekanik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-118451.
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In this thesis two kinds of phase change i.e., solid state phase transformation in steels and solid-to-liquid phase transformation in paraffin, have been modeled and numerically simulated. The solid state phase transformation is modeled using the phase field theory while the solid-to-liquid phase transformation is modeled using the Stokes equation and exploiting the viscous nature of the paraffin, by treating it as a liquid in both states.The theoretical base of the solid state, diffusionless phase transformation or the martensitic transformation comes from the Khachaturyan's phase field microelasticity theory. The time evolution of the variable describing the phase transformation is computed using the time dependent Ginzburg-Landau equation. Plasticity is also incorporated into the model by solving another time dependent equation. Simulations are performed both in 2D and 3D, for a single crystal and a polycrystal. Although the model is valid for most iron-carbon alloys, in this research an Fe-0.3\%C alloy is chosen.In order to simulate martensitic transformation in a polycrystal, it is necessary to include the effect of the grain boundary to correctly capture the morphology of the microstructure. One of the important achievements of this research is the incorporation of the grain boundary effect in the Khachaturyan's phase field model. The developed model is also employed to analyze the effect of external stresses on the martensitic transformation, both in 2D and 3D. Results obtained from the numerical simulations show good qualitative agreement with the empirical observations found in the literature.The microactuators are generally used as a micropump or microvalve in various miniaturized industrial and engineering applications. The phase transformation in a paraffin based thermohydraulic membrane microactuator is modeled by treating paraffin as a highly viscous liquid, instead of a solid, below its melting point. The fluid-solid interaction between paraffin and the enclosing membrane is governed by the ALE technique. The thing which sets apart the presented model from the previous models, is the use of geometry independent and realistic thermal and mechanical properties. Numerical results obtained by treating paraffin as a liquid in both states show better conformity with the experiments, performed on a similar microactuator. The developed model is further employed to analyze the time response of the system, for different input powers and geometries of the microactuator.QC 20130219
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Ekberg, Nathanial Paul. "Two-phase flow in horizontal thin annuli." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/17250.
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Du, Xiaoju. "Numerical Solvers for Transient Two-Phase Flow." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-23608.
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Certain numerical methods have been well developed for solving one-dimensional two-phase flow (e.g. gas and liquid) problems in the literatures during the last two decades. Based on the existing methods, the present work compares the computational efficiency, accuracy, and robustness of various numerical schemes by predicting the numerical solutions of fluid properties for a specific case to find the proper numerical method. One of the numerical schemes introduced in this work is a practical, semi-implicit upwind method used for fluid flow simulations in different flow patterns,stratified flow and slug flow. This method implements the iterative and non-iterative schemes using a two-fluid model that consists of sets of non-hyperbolic equations. A numerical error term is applied in the pressure equation to maintain the volume balance of the two-phase flow model. If the temperature varies, the discretised energy equations use similar error terms as in the pressure equation. In some cases, the small values of the numerical errors are negligible and do not influence the numerical results. These errors are, however, important factors to consider when maintaining the stability and robustness of the above numerical schemes for strong non-linear cases. The computational efficiency ofthe non-iterative scheme, where the inner iterations are deactivated, is better than the iterative scheme. Different grid arrangements are compared with respect to computational accuracy and efficiency. A staggered structured grid implements the same semi-implicit upwind method as in the non-iterative scheme; the non-staggered grid arrangement uses an existing flux-splitting scheme (Evje and Flåtten, 2003) as a reference. All the above schemes produce numerical solutions with a single precision that normally satisfy the requirements of computational accuracy of industrial two-phase pipe flows. However, if one pursues a higher-order accuracy scheme, e.g. a Roe-averaged algorithm, the governing equations should be strictly a hyperbolic system of partial differential equations, which is achieved by introducing the nonviscous force terms in the two-fluid model (LeVeque, 2002).By properly incorporating the non-conservative terms in the formulation of the numerical fluxes, the capability of the Roe-averaged algorithm is demonstrated by capturing shock waves. Results from the present research include the following. A one-dimensional scheme that solves a system of discretised equations with the staggered semi-implicit upwind method is presented and validated for its computational efficiencyand robustness. This scheme can be widely used in the industry with sufficient accuracy. The other first-order semi-implicit numerical schemes producestable numerical results, especially in the dynamic cases of two-phase flow, except when the gas phase nearly disappears or appears in pipes. The Roe-averaged algorithm is recommended due to the high-resolution numerical results obtained, but at the costs of computational time and effort.
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Brown, Ian Stuart. "The compositional consequences of two phase flow." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293611.
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Valle, Arne. "Three phase gas-oil-water pipe flow." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248608.
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Suicmez, Vural Sander. "Pore scale simulation of three-phase flow." Thesis, Imperial College London, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441972.
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Piri, Mohammad. "Pore scale modelling of three-phase flow." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.407699.
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Rahbari, Ahmadreza. "Dynamic two phase flow models for flushing." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-26320.
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This thesis aims at modeling the separated liquid-liquid flows with application for flushing. In the beginning, there will be a short review of the governing equations and the fundamental concepts used in this thesis. Two models are introduced and developed based on two previous PhD dissertations from NTNU(Trygve Wangensteen and Tor Kindsbekken Kjeldby). The properties of the fluids in these models are based on Oil, Exxsol D80, mu_o=1.79 [cP] and tapped water, mu_w=1.11 [cP]. These models will be numerically developed for both dynamic and stationary flows. The numerical scheme used for these models is explicit. A complete explanation about discretization is given in chapter 4.After developing the dynamic and stationary solutions for both models, there will be two major case studies. The first one is to understand when the dynamic and stationary solutions depart from one another as the mixture velocity varies between low velocities to high velocities. It turns out that The solutions look quite similar until the mixture velocity reaches the value of around U_M=1 [m/s]. Then the solutions become more and more different especially at the oil front. The second case study is about keeping the mixture velocity constant and varying the pipe angle. The pipe angle variation range lies between -2.5 and +5 degrees. For negative inclinations, the dynamic and stationary solutions agree quite well. However when the positive slope is put to the test and gravity is acting against the flow, the dynamic and stationary solutions differ more.\\Finally there will be a discussion on where this different behavior stems from. The two fluid model introduced at the beginning of this report is studied closely, term by term. These terms represent the frictional forces that balance the pressure gradient in the pipe. These forces are plotted for four different cases with mixture velocities varying from U_M=0.25 [m/s] to U_M=5 [m/s]. These figures reveal which forces dominate the solution for relatively low and high mixture velocities. The dominating forces are the ones that balance the pressure gradient. It turns out that the level gradient is quite significant and a dominant term in almost all cases. However as the mixture velocity increases, the acceleration terms grow to the same order of magnitude as the level gradient. But for the most part, the spatial and the temporal acceleration act symmetrically, and in effect cancel each other out. There will be a thorough discussion about this in the final chapter.
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Dai, Yunfeng. "Integration of tomographic two-phase flow measurements." Thesis, University of Leeds, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421439.
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Summers, Paul Eugene. "Quantitative flow by magnetic resonance phase mapping." Thesis, King's College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267482.
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Bacon, Roger Philip. "Large bubbles in downwards two-phase flow." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388824.
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Yang, Xiaogang. "Two-phase flow dynamical simulations and modelling." Thesis, University of Birmingham, 1996. http://etheses.bham.ac.uk//id/eprint/1417/.
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Considerable progress in understanding and predicting two-phase flow phenomena has been advanced over the past 10 years or so using a combination of model development, computational techniques and well-designed experiments. However, there remain many modelling uncertainties mainly associated with inadequate physical prescriptions rather than with limitations of the numerical schemes. The present project addresses some of these questions, in particular in relation to dispersive transport by transient large eddies in free shear flows.
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Sweeney, Edmund J. "Water hammer transients in two-phase flow." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/14518.
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Texin, Cheryl (Cheryl A. ). "Optical flow using phase information for deblurring." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/41673.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 121-123).
This thesis presents a method for reconstructing motion-degraded images by using velocity information generated with a phase-based optical flow calculation. The optical flow method applies a set of frequency-tuned Gabor filters to an image sequence in order to determine the component velocities for each pixel by tracking temporally separated phase contours. The resulting set of component velocities is normalized and averaged to generate a single 2D velocity at each pixel in the image. The 2D optical flow velocity is used to estimate the motion-blur PSF for the image reconstruction process, which applies a regularization filter to each pixel. The 2D velocities generally had small angular and magnitude errors. Image sequences where the motion varied from frame to frame had poorer results than image sequences where the motion was constant across all frames. The quality of the deblurred image is directly affected by the quality of the velocity vectors generated with the optical flow calculations. When accurate 2D velocities are provided, the deblurring process generates sharp results for most types of motion. The magnitude error proved to be a larger problem than the angular error, due to the averaging process involved in creating the 2D velocity vectors from the component velocities. Both the optical flow and deblurring components had difficulty handling rotational motion, where the linearized model of the motion vector is inappropriate. Retaining the component velocities may solve the problem of linearization.
by Cheryl Texin.
M.Eng.
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Quintana, Michael Steven. "Two phase flow splitting in piping branches." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/50127.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1998.Includes bibliographical references (leaf 36).
The objectives of this research are to evaluate the performance of a flow-splitting tripod, discover the factors which most affect the flow distribution; and quantify the effects of geometry, quality and flow rate on the distribution. Knowing all this allows one to predict the distribution for given conditions. An R-22 test apparatus was constructed for carrying out the experiments. The factors examined were tripod orientation, Froude number, void fraction, and swirl induced by helical grooves in the tube supplying the two-phase flow to the tripod. The flow regime of concern is primarily annular. Experiments were run and data was collected and analyzed. The two piece tripods were generally found to have manufacturing defects which made their performance unpredictable. The hole through which the flow was provided was often off center. This defect greatly affected the distribution and masked other geometric factors. To eliminate this variable a number of tripods were tested, using an air-water rig, to find a tripod that was not defective. Tests using R-22 were then run on this tripod and it was found that inlet swirl had little or no affect on the flow distribution. The factors that had the greatest effect on the flow distribution were the tripod's orientation, the Froude number of the flow, and the void fraction. An empirical correlation for flow splitting was derived including these factors.
by Michael Steven Quintana.
S.M.
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Martinez, Cora E. "Eulerian-Lagrangian Two Phase Debris Flow Model." FIU Digital Commons, 2009. http://digitalcommons.fiu.edu/etd/138.
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The main objective of this work is to develop a quasi three-dimensional numerical model to simulate stony debris flows, considering a continuum fluid phase, composed by water and fine sediments, and a non-continuum phase including large particles, such as pebbles and boulders. Large particles are treated in a Lagrangian frame of reference using the Discrete Element Method, the fluid phase is based on the Eulerian approach, using the Finite Element Method to solve the depth-averaged Navier–Stokes equations in two horizontal dimensions. The particle’s equations of motion are in three dimensions. The model simulates particle-particle collisions and wall-particle collisions, taking into account that particles are immersed in a fluid. Bingham and Cross rheological models are used for the continuum phase. Both formulations provide very stable results, even in the range of very low shear rates. Bingham formulation is better able to simulate the stopping stage of the fluid when applied shear stresses are low. Results of numerical simulations have been compared with data from laboratory experiments on a flume-fan prototype. Results show that the model is capable of simulating the motion of big particles moving in the fluid flow, handling dense particulate flows and avoiding overlap among particles. An application to simulate debris flow events that occurred in Northern Venezuela in 1999 shows that the model could replicate the main boulder accumulation areas that were surveyed by the USGS. Uniqueness of this research is the integration of mud flow and stony debris movement in a single modeling tool that can be used for planning and management of debris flow prone areas.
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Lucas, G. P. "The measurement of two-phase flow parameters in vertical and deviated flows." Thesis, University of Manchester, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292554.
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Sukarno, Pudjo. "Inflow performance relationship curves in two-phase and three-phase flow conditions /." Access abstract and link to full text, 1986. http://0-wwwlib.umi.com.library.utulsa.edu/dissertations/fullcit/8614191.
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