Dissertations / Theses: 'Two phase flow'

1

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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2

Ariyoshi, Gen. "Flow Characteristics of Lead-Bismuth Two-phase Flow." Kyoto University, 2019. http://hdl.handle.net/2433/242325.

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3

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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4

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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5

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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7

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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8

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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9

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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10

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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11

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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12

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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13

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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14

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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15

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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16

MONNI, GRAZIA. "Special Instrumentation for Two-Phase Flow." Doctoral thesis, Politecnico di Torino, 2014. http://hdl.handle.net/11583/2555139.

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The design of engineering systems, involving two-phase flow, such as nuclear water reactors, requires the ability to model and predict the detailed behavior of those flows and the phenomena that they manifest, with a required degree of accuracy. In the past a significant amount of effort has been addressed to the development of intrusive and nonintrusive measurement techniques of two-phase flows, with special application to the determination of mass flow rates. Many extensive experiments are being performed to investigate in detail loss of coolant accidents (LOCA). During these experiments the coolant is released as a two-phase mixture through a simulated break of a coolant pipe, and the measurement of the mass flow rate of the two phases was required to analyze the accident evolution and consequences. In this context, most flow meters have been designed to measure the single-phase flow of a Newtonian fluid, and then used to measure quantities in more complex fluids. The key to fundamental understanding of two-phase flow is still the careful development of specialized instrumentation, in particular for special and complex geometrical applications. Within the framework of an Italian R&D program on Nuclear Fission, supported by the Ministry of Economic Development, the SPES3 experimental facility, able to simulate the innovative small and medium size PWR nuclear reactors, is being built and will be operated at SIET Company laboratories. In such facility some design and beyond design basis accidents, like LOCAs, with and without the emergency heat removal systems, will be simulated. In most accident simulations, a two-phase flow mixture will occur in the lines, during the transient evolution, due to the simulated strong depressurization of the system. An accurate accident analysis requires the measurement of the mixture mass flow rate and for this reason, instruments and methodologies to evaluate different two-phase flow parameters need to be developed. Typically a set of instruments (Spool Piece - SP) must be installed in order to evaluate the mass flow rate of the phases in a large range of flow patterns, pressures and temperatures. An ideal SP is a control volume constituted by different measurement instruments, fed with a two-phase flow. In single-phase flow, each instrument is able to measure a well defined flow parameter, while the instrument signal interpretation, in two-phase flow, is not easy due to the different flow patterns and the to the large number of parameters that influence the flow, so that a model of the SP, depending on the geometry and on the SP orientation, is required. Moreover the selection of the instruments strongly depends on the experimental conditions: pressure, temperature and phases velocities. The thesis work consists in the development of special instrumentation and in the development of models, based on the analysis of experimental data, that are able to interpret the measurement signals for many possible two-phase conditions. The two different measurement fields, internal flow structure investigation and instrument modeling for phases mass flow rate reconstruction purposes, have been analyzed. In the first field the instrumentation must be able to characterize momentum, mass, energy balance with a resolution sufficient to investigate local phenomena and characteristic structure (interface evolution, void profiles, liquid film level, characteristic frequencies, etc..). The investigation of an horizontal two-phase flow has been performed by means of a Wire Mesh Sensor. Local, chordal, cross-section void fraction values are derived from the sensor data in a wide range of phases superficial velocities, and a new signal methodology, able to characterize the flow in terms of phases distribution (flow patterns) and time evolution, has been developed. Moreover the methodology allows the extraction of important flow information, such as the local and time average void fraction, the interface evolution, and characteristic frequencies. The evolution of the void fraction profiles has been related to the superficial velocity of the two-phases (Jg and Jl) and the flow evolution in time and space has been analyzed and discussed, showing that such methodology is useful to identify and characterize in detail the two-phase flow. Concerning the second measurement field, the analysis of the instruments used for two-phase flow measurement applications has been described. This bibliographic research allowed the definition of the candidate instruments suitable to be installed in a nuclear safety experimental facility, and their measurement characteristics. The selection of the candidate instruments has been made defining some fundamental criteria that should be satisfied: range of measurement, dynamic response, installation requirements, materials/electrical compatibility with pressure and temperature conditions, flow velocity compatibility. The selected instruments have been experimentally studied in different pipe configurations, and different models have been developed for each one. Different instrument combinations have been tested, and the performance of each one has been analyzed in terms of estimation of the mass flow rate of the two phases. The performed research allows the identification of the advantage and drawbacks of the different instrument combinations, and the identification of the phases mass flow rate measurement accuracy achievable for each SP configuration.

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17

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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18

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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19

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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20

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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21

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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22

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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23

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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24

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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25

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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26

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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27

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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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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30

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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31

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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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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33

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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34

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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35

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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37

Wälchli, Severin. "Two-phase flow characteristics in gas-liquid microreactors /." Zürich, 2005. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=16116.

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38

Gustafsson, Gabriella. "Multiphase Motion Estimation in a Two Phase Flow." Thesis, Linköping University, Department of Electrical Engineering, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-5424.

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To improve the control of a steel casting process ABB has developed an Electro Magnetic Brake (EMBR). This product is designed to improve steel quality, i.e. reduce non-metallic inclusions and blisters as well as risk of surface cracks. There is a demand of increasing the steel quality and in order to optimize the steel casting, simulations and experiments play an important role in achieving this. An advanced CFD simulation model has been created to carry out this task.

The validation of the simulation model is performed on a water model that has been built for this purpose. This water model also makes experiments possible. One step to the simulation model is to measure the velocity and motion pattern of the seeding particles and the air bubbles in the water model to see if it corresponds to the simulation results.

Since the water is transparent, seeding particles have been added to the liquid in order to observe the motion of the water. They have the same density as water. Hence the particles will follow the ﬂow accurately. The motions of the air bubbles that are added into the water model need also to be observed since they inﬂuence the ﬂow pattern.

An algorithm - ”Transparent motions” - is thoroughly inspected and implemented. ”Transparent motions” was originally designed to post process x-ray images. However in this thesis, it is investigated whether the algorithm might be applicable to the water model and the image sequences containing seeding particles and air bubbles that are going to be used for motion estimation.

The result show satisfying results for image sequences of particles only, however with a camera with a faster sampling interval, these results would improve. For image sequences with both bubbles and particles no results have been achieved.

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39

Vist, Sivert. "Two-phase Flow Distribution in Heat Exchanger Manifolds." Doctoral thesis, Norwegian University of Science and Technology, Department of Energy and Process Engineering, 2004. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-199.

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The current study has investigated two-phase refrigerant flow distribution in heat exchange manifolds. Experimental data have been acquired in a heat exchanger test rig specially made for measurement of mass flow rate and gas and liquid distribution in the manifolds of compact heat exchangers. Twelve different manifold designs were used in the experiments, and CO² and HFC-134a were used as refrigerants.

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40

Darwich, Tarek D. A. "A statistical technique for two-phase flow metering." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/7482.

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41

Davies, Stephen Roy. "Studies of two-phase intermittent flow in pipelines." Thesis, Imperial College London, 1992. http://hdl.handle.net/10044/1/7882.

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Hill, David Paul. "The computer simulation of dispersed two-phase flow." Thesis, Imperial College London, 1998. http://hdl.handle.net/10044/1/8733.

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Matko, T. I. R. "Two-phase flow in circular secondary sedimentation tanks." Thesis, Cranfield University, 1997. http://dspace.lib.cranfield.ac.uk/handle/1826/3920.

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The main objective of this work was to optimise a numerical model to predict the flow in circular secondary sedimentation tanks. The numerical models in the literature were reviewed and the new opportunities for research were identified. Single-phase flow characteristics of two circular sedimentation tanks were investigated using the CFD program, CFX-F3D. The flow in the circular clarifiers were modelled in two dimensions (axial and radial) and using the standard k-E turbulence model. Results indicated that a vertical inlet instead of a horizontal inlet did not improve the correlation with the experimental data in a pilot-scale tank. Modelling the diurnal variation in flow to a full-scale tank significantly improved the correlation with experimental data. The 'Eulerian multi-fluid' model in the program, CFX-F3D was modified to predict the flow in circular secondary sedimentation tanks. The model compared quite closely with the measured residence time of the effluent and return activated sludge (RAS) in a conventional secondary clarifier. The residence time of the effluent in another secondary clarifier with a turbulent jet, was over-predicted. The mean particle diameter in the model was found by comparing the numerical predictions with experimental data. The particle diameter was between 100 to 190 μm for the secondary clarifiers, which was in agreement with the experimental data in the literature. The flow patterns in the conventional secondary clarifier were affected by the particle density, particle diameter, axial slip velocity, colloids settling parameter, axial turbulent Prandtl number, inlet flow rate and inlet solids concentration. A 3-D simulation of the conventional secondary clarifier was in agreement with a 2-D simulation. Recommended values were given for all these parameters. However, the drag force between the phases was not formulated correctly and the water surface was modelled as a symmetry plane. Therefore, some more work is still required to make suitable modifications to the model.

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Lundberg, Matthew James. "Two-phase reactive flow within variable aperture fractures." Diss., Connect to online resource, 2005. http://wwwlib.umi.com/cr/colorado/fullcit?p1427766.

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Sarica, Cem. "Two-phase flow in low velocity terrain pipelines /." Access abstract and link to full text, 1990. http://0-wwwlib.umi.com.library.utulsa.edu/dissertations/fullcit/9030838.

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Zheng, Guohua. "Two-phase slug flow in hilly terrain pipelines /." Access abstract and link to full text, 1991. http://0-wwwlib.umi.com.library.utulsa.edu/dissertations/fullcit/9201599.

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47

Nygaard, Thor Isak. "Two phase swirling flow in a cylindrical reactor." Thesis, Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/10192.

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Wartell, Jason David. "Moisture fraction measurement for two-phase mist flow." Thesis, Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/16876.

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Al-Gharbi, Mohammed Saif Hilal. "Dynamic pore-scale modelling of two-phase flow." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409745.

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Carabateas, Nicolas. "Two phase flow and combustion in S.I. engines." Thesis, Imperial College London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265853.

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Dissertations / Theses on the topic 'Two phase flow'

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