Tesi: "Multiphase flow"

1

Ibrahim, Abba A. "Intelligent Multiphase Flow Measurement." Thesis, Cranfield University, 2009. http://hdl.handle.net/1826/4082.

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The oil and gas industry’s goal of developing high performing multiphase flow metering systems capable of reducing costs in the exploitation of marginal oil and gas reserves, especially in remote environments, cannot be over emphasised. Development of a cost-effective multiphase flow meter to determine the individual phase flow rates of oil, water and gas was experimentally investigated by means of low cost, simple and non-intrusive commercially available sensors. Features from absolute pressure, differential pressure (axial), gamma densitometer, conductivity and capacitance meters, in combination with pattern recognition techniques were used to detect shifts in flow conditions, such as flow structure, pressure and salinity changes and measured multiphase flow parameters simultaneously without the need for preconditioning or prior knowledge of either phase. The experiments were carried out at the National Engineering Laboratory (NEL) Multiphase facility. Data was sampled at 250 Hz across a wide spectrum of flow conditions. Fluids used were nitrogen gas, oil (Forties and Beryl crude oil – D80, 33o API gravity) and water (salinity levels of 50 and 100 g/l MgSO4). The sensor spool piece was horizontally mounted on a 4-inch (102mm) pipe, and the database was obtained from two different locations on the flow loop. The ability to learn from ‘experience’ is a feature of neural networks. The use of neural networks allows re-calibration of the measuring system on line through a retraining process when new information becomes available. Some benefits and capabilities of intelligent multiphase flow systems include:  Reduction in the physical size of installations.  Sensor fusion by merging the operating envelopes of different sensors employed provided even better results.  Monitoring of flow conditions, not just flow rate but also composition of components.  Using conventional sensors within the system will present the industry with a much lower cost multiphase meter, and better reliability. Comment [HS1]: I think this word should be measured to make the sentence read correctly.

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2

Nikhar, Hemant G. "Flow assurance and multiphase pumping." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1180.

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3

Carlson, Johan. "Multiphase flow measurements using ultrasound." Licentiate thesis, Luleå tekniska universitet, Signaler och system, 1999. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-17175.

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In process industries such as for example the oil and gas industry, the paper pulp industry, and the mining industry, multiphase flows are common. It is often of interest to measure the mass fractions of the different phases. In for example the mining industry, iron ore powder is transported using water, and there is a need of measurement techniques to monitor the particle mass fraction. Most existing techniques are either invasive, inaccurate, or too slow to be used in an on-line manner. The long-term goal of this research project is to develop a method for measuring mass fractions and mass fraction velocities, using ultrasound. The first two papers in this thesis consider how scattering of sound can be measured, and how this can be used to measure mass fractions. The ideas are verified with experiments. The third paper is on optimal experimental design. The problem is selecting suitable experiments from a large candidate set. We present a new algorithm for generating optimal designs. The methods in the first two papers can be extended to incorporate more of the underlying physics, as well as using more sophisticated multi-dimensional signal processing techniques. Godkänd; 1999; 20070320 (ysko)

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4

Little, Sylvia Bandy. "Multiphase flow through porous media." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/11779.

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5

Ogazi, Anayo Isaac. "Multiphase severe slug flow control." Thesis, Cranfield University, 2011. http://dspace.lib.cranfield.ac.uk/handle/1826/8345.

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Severe slug flow is one of the most undesired multiphase flow regimes, due to the associated instability, which imposes major challenges to flow assurance in the oil and gas industry. This thesis presents a comprehensive analysis of the systematic approach to achieving stability and maximum production from an unstable riser-pipeline system. The development of a plant-wide model which comprises an improved simplified riser model (ISRM) required for severe slug controller design and control performance analysis is achieved. The ability of the ISRM to predict nonlinear stability of the unstable riser-pipeline is investi¬gated using an industrial riser and a 4 inch laboratory riser system. Its predic¬tion of the nonlinear stability showed close agreement with experimental and simulation results. Through controllability analysis of the unstable riser-pipeline system, which is focused on achieving the core operational targets of the riser-pipeline produc¬tion system, the maximum stable valve opening achievable with each controlled variable considered is predicted and confirmed through the simulation results. The potential to increase oil production through feedback control is presented by analysing the pressure production relationship using a pressure dependent dimensionless variable known as Production Gain Index (PGI). The performance analyses of three active slug controllers are presented to show that the ability of a slug controller to achieve closed loop stability at large valve opening can be assessed by the analysis of the H∞ norm of the comple¬mentary sensitivity function of the closed loop system, T(s) ∞. A slug controller which achieves the lowest value of the T(s) ∞, will achieve closed loop stability at a larger valve opening. Finally, the development of a new improved relay auto-tuned slug controller algorithm based on a perturbed first-order-plus dead-time (FOPDT) model of the riser system is achieved. Its performance showed that it has the ability to stabilise the riser system at a valve opening that is larger than that achieved with the original (conventional) algorithm with about 4% increase in production.

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6

Woods, George Stephen. "Studies in vertical multiphase flow." Thesis, Queen's University Belfast, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247344.

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7

Ben, Mahmud Hisham. "Multiphase Transient Flow in Pipes." Thesis, Curtin University, 2012. http://hdl.handle.net/20.500.11937/1669.

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The development of oil and gas fields in offshore deep waters (more than 1000 m) will become more common in the future. Inevitably, production systems will operate under multiphase flow conditions. The two–phase flow of gas–liquid in pipes with different inclinations has been studied intensively for many years. The reliable prediction of flow pattern, pressure drop, and liquid holdup in a two–phase flow is thereby important.With the increase of computer power and development of modelling software, the investigation of two–phase flows of gas–liquid problems using computational fluid dynamics (CFD) approaches is gradually becoming attractive in the various engineering disciplines. The use of CFD as a modelling tool in multiphase flow simulation has enormously increased in the last decades and is the focus of this thesis. Two basic CFD techniques are utilized to simulate the gas–liquid flow, the Volume of Fluid (VOF) model, and the Eulerian–Eulerian (E–E) model.The purpose of this thesis is to investigate the risk of hydrate formation in a low–spot flowline by assessing the flow pattern and droplet hydrodynamics in gas– dominated restarts using the VOF method, and also to develop and validate a model for gas–liquid two–phase flow in horizontal pipelines using the Eulerian– Eulerian method; the purpose of this is to predict the pressure drop and liquid holdup encountered during two–phase (i.e. gas–oil, gas–water) production at different flow conditions, such as fluid properties, volume fractions of liquid, superficial velocities, and mass fluxes.In the first part of this thesis, the VOF approach was used to simulate the droplet formation and flow pattern at various levels of liquid patched and restart gas superficial velocities. The effect of restart gas superficial velocity on the liquid displacement from the low section of the pipe showed a decrease in the remaining liquid with an increase in gas superficial velocity, and the amount of liquid depends on the fluid properties, such as density and viscosity. Moreover, the flow pattern is also strongly dependent on the restart gas superficial velocity as well as the patched liquid in the low section. A low gas superficial velocity with different patched liquids illustrated no risk of hydrate formation due to the observed flow pattern that is often a stratified flow. However, as the restart gas superficial velocity is increased, regardless of initial liquid patching, hydrate formation is more likely to be observed due to the observed flow pattern, such as annular, churn or dispersed flow.In the second part, the E–E model was employed to establish a computational model to predict the pressure drop and liquid holdup in a horizontal pipeline. Due to the complicated process phenomena of two–phase flow, a new drag coefficient was implemented to model the pressure drop and liquid holdup in the 3D pipe. Different simulations were performed with various superficial velocities of two–phase and liquid volume fractions, and were carried out using RNG k-ε model to account for turbulence. Based on the results from the numerical model and previous experimental study, the currently used E–E model is improved to get more accurate prediction for the pressure drop and liquid holdup in horizontal pipes compared with the existing models of Hart et al. (1989) and Chen et al. (1997).The improved model is validated by previously reported experimental data (Badie et al., 2000). The deviation of pressure drop and liquid holdup obtained throughout the CFD simulation with regard to the experimental data was found to be relatively small at low superficial gas velocities. It was observed that the pressure gradient increased with the system parameters, such as the drop size, liquid and gas superficial velocity and the liquid volume fraction, where the liquid holdup decreased.The developed model provided a basis for studying the pressure drop and liquid holdup in a horizontal pipe. Different parameters have been examined, such as gas and liquid mass flux and liquid volume fraction. Two empirical correlations have been examined (Beggs and Brill (1973), and Mukherjee and Brill (1985)) against the CFD simulation results of pressure drop and liquid holdup, it was noted that they gave better agreement with the air–oil system rather than the air–water system, but shows reasonable agreement over the entire gas mass fluxIn the third part, the coupling of Eulerian–Eulerian multiphase model with the population balance equation (PBE), accounting for droplet coalescence and breakage, is considered. Strengths and weaknesses of each numerical approach for solving PBE have been given in details. The Quadrature Method of Moments (QMOM) is used and particular coalescence and breakup kernels were utilized to demonstrate the droplet size distribution behaviour. Numerical simulations on a two–phase flow in a horizontal pipe, including coalescence and breakage are performed. The QMOM is shown to give the solution of the PBE with reasonable agreement. The numerical data are compared with the experiment data of Simmons and Henratty (2001). The flow variables, such as liquid volume fractions, gas and liquid superficial velocities are employed to examine the droplet size distribution and the potential of the multiphase k–ε with population balance model for predicting the two–phase pressure drop and liquid holdup.The significance of this work is to assist in understanding the risk of hydrate formation in bend pipes at gas–dominated restarts with different patched liquid values. The knowledge gained from this work can be utilized to avoid the hydrate formation operating conditions. The developed of multiphase flow E–E model will provide an accurate prediction for two–phase pressure drop and liquid holdup in a horizontal pipe which will be of benefit to the design of tubing and surface facilities.

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8

Zhao, Yujie. "Wave behaviour in vertical multiphase flow." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/26588.

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The work described in this thesis was aimed at developing the understanding of two regimes in vertical gas-liquid flow in tubes, namely annular flow and churn flow. In annular flow, there is a continuous gas passage at the centre of the pipe with a film of liquid travelling upwards at the wall. Part of the liquid phase in annular flow may be entrained as droplets in the core gas flow. In churn flow there is also a gas core (which the present work has shown to be continuous) and a liquid film; however, the flow direction of the liquid in this film varies with time. Thus, the liquid flows upwards in large waves on the surface of the film; between the waves, the film may change direction and flow downwards towards the next wave. Such flows are extremely complex and there are aspects of their behaviour which are poorly understood. In the work described in this thesis, several areas have been studied. Disturbance waves are of central importance in annular flows. Such waves are characterised by their large amplitudes relative to the mean film thickness, their high translation velocities relative to the mean film speed, and their circumferential coherence (i.e. their 'ring-like' structure when fully developed). An important part of the present work was concerned with the existence, development and translation of disturbance waves in upwards, gas-liquid annular flows. At very low liquid flow rates, disturbance waves are not formed (and, as other work has shown, the entrainment of droplets from the liquid film is negligible). In the present work, multiple conductance probe units have been employed to study the growth and development of disturbance waves. From the results, it is found that disturbance waves begin to appear and to start to achieve their circumferential coherence from lengths as short as 5-10 pipe diameters downstream of the liquid injection location; this coherence gradually strengthens with increasing distance from the inlet. It is further shown that the spectral content of the entire interfacial wave activity shifts to lower frequencies with increasing axial 3 distance from the inlet, with the peak frequency levelling off after approximately 20 pipe diameters. Interestingly, on the other hand, the frequency of occurrence of the disturbance waves first increases away from the inlet as these waves form, reaches a maximum at a length between 7.5 and 15 pipe diameters depending on the flow conditions, and then decreases again. This trend becomes increasingly evident at higher gas and/or liquid flow-rates. Both wave frequency measures increase monotonically at higher gas and/or liquid flowrates. Important evidence regarding the mechanisms of disturbance waves and the associated droplet entrainment can be obtained by the axial view photography technique. This technique is described in Chapters 3 and 6. The technique was used to visualise the wave characteristics, in particular of the two entrainment mechanisms (bag break up and ligament break up mechanisms) proposed previously by Azzopardi (1983). The axial view photography technique provided visual evidence for the existence of the two mechanisms, although in contrast to Azzopardi's findings, both break up mechanisms were observed to occur simultaneously. The axial view photography technique was also used in the present work to provide further insights into the inception of disturbance waves. It was found that the initiation mechanism for disturbance waves was the occurrence of a disturbance at a given location around the tube periphery. This is consistent with the idea of a link between turbulent burst phenomena and disturbance waves first proposed by Azzopardi and Martin (1986). The initial disturbance links up with similar disturbances to ultimately form the characteristic ring-like structure characteristic of fully developed disturbance waves. In churn flow the present work concentrated on three aspects: The use of axial view photography to explore the continuity of the gas core in churn flow. The development (in collaboration with two other research students - Deng Peng and Masroor Ahmad) of a correlation for entrainment rate and hence entrained fraction in churn flow. Measurements of 4 pressure gradient and holdup in churn flow, from which an average wall shear stress can be deduced. In the first task, it was shown (it is believed for the first time) that there is a continuous path for the gas phase near the tube axis. In churn flow the behaviour of entrained fraction is extremely complex and conventional methods for measuring it are no longer valid. Barbosa etal (2002) studied entrainment in churn flow using iso-kinetic sampling probes and the correlation referred to above was based on this data. The correlation has been widely used in predicting the entrained fraction at the transition between churn and annular flow. Since the direction of flow of the liquid film near the channel wall fluctuates, it is difficult to estimate the instantaneous value of wall shear stress. However, if measurements are made of total pressure gradient and liquid holdup, then the mean value of wall shear stress can be estimated. This procedure was pursued by Govan (1990) who used mechanically operated quick-closing valves to measure holdup. In the current work, a new measurement technique was utilised, namely quick closing pinch valve which offer a great accuracy and are easy to install. Pressure gradient and hold up data were collected over a wide range of gas and liquid flowrate. An averaged wall shear stress was then calculated based on these measurements. At higher liquid mass flow rates, the results were in good qualitative agreement with those of Govan (1990) but (at lower mass fluxes) anomalies occur which need further investigation.

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9

Sheng, Jopan. "Multiphase immiscible flow through porous media." Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/53630.

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A finite element model is developed for multiphase flow through soil involving three immiscible fluids: namely air, water, and an organic fluid. A variational method is employed for the finite element formulation corresponding to the coupled differential equations governing the flow of the three fluid phase porous medium system with constant air phase pressure. Constitutive relationships for fluid conductivities and saturations as functions of fluid pressures which may be calibrated from two-phase laboratory measurements, are employed in the finite element program. The solution procedure uses iteration by a modified Picard method to handle the nonlinear properties and the backward method for a stable time integration. Laboratory experiments involving soil columns initially saturated with water and displaced by p-cymene (benzene-derivative hydrocarbon) under constant pressure were simulated by the finite element model to validate the numerical model and formulation for constitutive properties. Transient water outflow predicted using independently measured capillary head-saturation data agreed well with observed outflow data. Two-dimensional simulations are presented for eleven hypothetical field cases involving introduction of an organic fluid near the soil surface due to leakage from an underground storage tank. The subsequent transport of the organic fluid in the variably saturated vadose and ground water zones is analysed. Ph. D.

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10

Kanshio, Sunday. "Multiphase flow in pipe cyclonic separator." Thesis, Cranfield University, 2015. http://dspace.lib.cranfield.ac.uk/handle/1826/9847.

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In the petroleum industry, cyclonic separators are acceptable as hydrocyclone, mist eliminators, separator internal device and compact metering package. Weight and small footprint requirements for applications such as subsea separation, downhole separation, and compact gas monetization systems is driving interest in using cyclonic separator for bulk gas-liquid separation. Unfortunately, the challenge of coping with the effect of unsteady inlet flow behaviour on the separator performance limit it acceptance for bulk gas-liquid separation. Fundamental understanding of the flow behaviour inside the separator under various inlet flow conditions is required to deal with the challenge. While most published work have addressed flow behaviour in the lower half of cyclonic separator, this thesis concentrated on the upper half. A gas-liquid pipe cyclonic separator was setup at Cranfield University for bulk gas-liquid separation. Large amount of data at the inlet and upper part of the separator were acquired using electrical resistance tomography (ERT), wire meshes sensor (WMS), conductivity hold up probe and pressure transducers. The acquired data were used in analysing flow regimes, upward swirling liquid film (USLF), zero-net liquid flow (ZNLF), liquid holdup and, general separator performance. It was found from analysis of USLF data that a maximum USLF height exists for every constant superficial liquid velocity. A correlation based on dimensionless numbers was proposed for predicting this height. Experimental results on ZNLF showed that a critical ZNLF also exist above which liquid carryover can take place. The liquid holdup for this critical ZNLF was measured under separator operating condition using ERT and a correlation for predicting the liquid holdup was proposed. Four flow regimes were identified as swirling annular, light-mist heavy-mist and churn using visual observations, ERT, WMS and pressure transducer. A flow regime map was proposed based on gas and liquid Froude number. The performance based on the operating envelope for liquid carryover and pressure drop for horizontal and 270 downward inclined tangential inlet was compared. It was concluded that the separation performance was marginally improved by using an inclined tangential inlet. The pressure drop for the inclined inlet was far greater than that of horizontal inlet. Two inlet nozzles with D–shape were used for separation enhancement. The nozzle that reduces the diameter of full pipe bore by 25% gave slight improvement but also gave the greatest pressure drop. The nozzle that reduced the full pipe bore diameter by 50% performed poorly.

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Gorasia, A. K. "Multiphase flow and mixing in microreactors." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2009. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/2795.

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12

Dhanabalan, Dinesh. "Multiphase corrosion in wet gas pipelines." Ohio : Ohio University, 2001. http://www.ohiolink.edu/etd/view.cgi?ohiou1173812563.

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13

Xu, Wenyuan. "A multiphase harmonic load flow solution technique." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/31035.

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This thesis presents a comprehensive solution technique for power system harmonic analysis with unbalanced load flow conditions. It is based on multiphase modelling of the system in phase quantities. Two of the most important features of this technique are the multiphase approach to the harmonic load flow problem, and the capability to add component nonlinearities easily. The first feature allows the technique to be used for either single-phase or three-phase, and for either balanced or unbalanced harmonic analysis. The second feature allows the later addition of power electronic device models. The technique is simple in concept. The nonlinear elements are first modelled as harmonic Norton equivalent circuits based on the network load flow conditions. These linear circuits are then included in the network solution with multiphase load flow constraints and network unbalances. Once the new load flow solutions are obtained, improved Norton equivalent circuits can be calculated, which in turn are used for improved network solutions. The entire solution scheme is therefore iterative, and stops when certain convergence criteria are met. The unbalanced harmonics from nonlinear inductors, synchronous machines and static compensators with thyristor-controlled reactors are studied in this thesis. The convergence properties of the technique are investigated with test cases and theoretical analysis. In addition to the harmonic load flow analysis, this technique can also be used as an improved initialization procedure for the Electromagnetic Transient Program (EMTP). Applied Science, Faculty of Electrical and Computer Engineering, Department of Graduate

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14

Duque, Carlos A. "Critical evaluation of multiphase flow in pipes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0010/MQ35013.pdf.

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15

Olsen, Robert. "Time-dependent boundary conditions for multiphase flow." Doctoral thesis, [Trondheim : Norges teknisk-naturvitenskapelige universitet, 2004. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-237.

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16

Valvatne, Per Henrik. "Predictive pore-scale modelling of multiphase flow." Thesis, Imperial College London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.405885.

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17

Arubi, Isaac Marcus Tesi. "Multiphase flow measurement using gamma-based techniques." Thesis, Cranfield University, 2011. http://dspace.lib.cranfield.ac.uk/handle/1826/8347.

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The oil and gas industry need for high performing and low cost multiphase meters is ever more justified given the rapid depletion of conventional oil reserves. This has led oil companies to develop smaller/marginal fields and reservoirs in remote locations and deep offshore, thereby placing great demands for compact and more cost effective soluti8ons of on-line continuous multiphase flow measurement. The pattern recognition approach for clamp-on multiphase measurement employed in this research study provides one means for meeting this need. Cont/d.

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18

Donnelly, G. F. "An analytical evaluation of horizontal multiphase flow." Thesis, Queen's University Belfast, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361244.

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Albusaidi, Khamis H. "An investigation of multiphase flow metering techniques." Thesis, University of Huddersfield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338602.

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20

GOMES, DALILA DE SOUSA. "MULTIPHASE FLOW SIMULATOR FOR OIL PRODUCTION WELLS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2015. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=26315@1.

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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO Sistemas de escoamento multifásico se formam ao longo de um poço de produção de petróleo. A análise do comportamento do escoamento através da coluna de produção é realizada com o apoio de ferramentas computacionais e é essencial para o projeto e operação de um sistema de produção de petróleo. Os simuladores comerciais disponíveis para esse tipo de análise exigem aquisição de licença, cujo custo é elevado, restringindo seu uso às grandes companhias petrolíferas e aos renomados institutos de pesquisa. Além disso, esses programas não permitem a visualização da metodologia utilizada para o tratamento do problema físico e para a solução numérica empregada, e nem a alteração de parâmetros internos, tornando seu uso restrito a certas classes de problemas. Apesar da grande demanda e utilidade desse tipo de software ainda há poucos trabalhos desenvolvidos nessa área. Esta pesquisa tem como objetivo apresentar o desenvolvimento de um simulador de escoamento multifásico simplificado e aberto, com aplicação na otimização da produção de óleo e gás. Dentre as aplicações do programa podemos citar a obtenção das curvas de gradiente de pressão e a otimização de gás-lift. Um estudo paramétrico foi conduzido, mostrando a influência de parâmetros como, por exemplo, o diâmetro da tubulação. Os resultados obtidos foram comparados com a literatura e são fisicamente coerentes. Sendo assim, o programa desenvolvido mostra-se promissor. Multiphase flow systems are formed along an oil production well. The analysis of the flow behavior through the production column is performed with the aid of computational tools, and is very important to the design and optimization of the oil well production operation. In general, the commercial softwares available to analyze this process are very expensive, which restrict its use to some particular companies. In addition, the methodology used to analyze the physical problem, and the numerical solution are fixed and closed, which restrict its use to certain classes of problems, since it is not possible to change or improve the numerical solution. Despite the great demand and use of this kind of software, there are few researches in this area. This research aims to present the development of a simplified multiphase flow simulator open to public, with application to the optimization of oil and gas production wells. Among the applications are the plot of pressure-distribution curves and the optimization of gas-lift. A parametric study is performed, showing the influence of some governing parameters, such as tubing diameter, in the production flow rate. The results obtained were compared with pertinent literature and are physically reasonable, showing that the software developed is promising.

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Suo, Si. "Modelling Multiphase Flow in Heterogeneous Porous Media." Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/27362.

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Multiphase flows in porous media, featured by distributed fluid-fluid interfaces, are commonly seen in nature and daily life. In this dissertation, we focus on effects of the heterogeneity in porous media on multiphase flow processes with the purpose of obtaining further knowledge regarding flow patterns to benefit a range of engineering applications, such as enhanced oil recovery, CO2 sequestration, and transfer printing. Followed by the background introduction and related literature review in Chapters 1 and 2, the main body of this dissertation is composed of three parallel parts investigating multiphase flow processes in porous media with different types of heterogenous structures. Chapter 3 focuses on continuum modelling of spontaneous imbibition in porous media containing heterogeneous features. We firstly develop a numerical framework aiming to handle porous material heterogeneity at continuum scale by combining a new interface integral method and the classical Richard’s equation. After validating against some experimental results, the spontaneous imbibition processes in various heterogeneous porous media, e.g., layered and mixed one, are investigated and we emphasise the movement of the liquid front when crossing the material interfaces. In Chapter 4, we study fluid displacement and fingering instability in hierarchical porous media. We provide a further understanding on how geometric heterogeneity influences the fluid-fluid displacement processes in porous media at pore scale, and moreover indicate a possible way to suppress the interfacial instability by adjusting the hierarchical geometry. Through numerical and theoretical analysis, we demonstrate and quantify the combined effects of wettability and hierarchical geometry highlighting the crossover of displacement patterns from fingering to compact mode. In Chapter 5, we focus on the spreading and imbibition of droplets adhered on porous surfaces, as a typical scenario coupling free surface flow and porous media flow. Both flows are dominated by capillary effects and thus strongly depend on the characteristic length of the respective domain. In this study, we characterise the droplet spreading on and imbibition into fixing or moving porous tips, with special focus on such interaction between two flows with distinct physical lengths. In summary, this dissertation provides a fundamental research on the multiphase flows in porous media highlighting the heterogeneity effects across various length scales. The acquired results can shed light on the design of microfluidic devices of high flow controllability and optimising configuration of geothermal energy systems.

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Butler, Jason Edward. "Tomographic imaging for the visualization of multiphase flows /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.

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23

Mandolesi, Pierpaolo. "Analysis of subcritical multiphase flow through wellhead chokes." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.

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This work presents the evaluation of the theoretical models and empirical correlations for the prediction of multiphase flow rate through wellhead chokes in subcritical conditions. First, literature review was conducted to have a comprehensive understanding of problem and areas that needed to be improved. Then selected existing models, correlations and slip correlations are studied to determine which of them gives the best prediction relative stability and accuracy, evaluating and comparing the flow data tests with three different errors parameters: absolute errors, relative errors and standard deviation. Before generating results, all selected models and correlations are tested by using the same database. Models and correlations were compared with three different errors parameters: absolute errors, relative errors and standard deviations. Before generating results, all selected model and correlations are tested by using the same flow data base. The database that we have built is considered very representative with wide ranges of oil rates, pressures, GOR, choke size and fluid characteristics. The flow tests are manily from Norway, Angola, Italy and Nigeria fields. This thesis work evaluates Sachdeva et al. and Perkins model, Gilbert equation and two semi-analytical models chosen after an accurate analysis of the literature (Kargarpour model). Additionally, this study proposes a new empirical correlation (De ghetto Equation) and modifications conducted on Sachdeva model and Gilbert equation. This is the added value of this work.

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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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25

Reynolds, David A. "Multiphase flow and transport in fractured geologic environments." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ63448.pdf.

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26

Stevens, Nia Eleri. "Multiphase modelling methods for dry powder inhaler flow." Thesis, Imperial College London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429946.

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27

McBride, William James. "Division of multiphase flow at a horizontal bifurcation." Thesis, Queen's University Belfast, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324829.

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28

CRUZ, SAMUEL RODRIGUES. "WAX DEPOSITION STUDY IN A MULTIPHASE PIPE FLOW." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2011. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=18475@1.

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O Petróleo é formado por um conjunto de hidrocarbonetos. No reservatório, devido à altas pressões e temperaturas, encontra-se na forma de líquido. Conforme o petróleo escoa, a pressão cai assim como a temperatura, devido a perda de calor para o ambiente marinho, causando a liberação do gás dissolvido no petróleo tornando o escoamento bifásico. Adicionalmente, caso a temperatura caia abaixo da temperatura inicial de cristalização (TIAC), ocorre precipitação dos cristais, formando uma fase sólida que se deposita na parede interna das tubulações. Deposição de parafinas é um dos mais críticos problemas operacionais na produção e transporte de petróleo em linhas submarinas. O presente trabalho analisa numericamente a deposição de parafina em escoamento multifásico no interior de dutos para diversos padrões de fluxo. Investiga-se ainda a influência da presença da água e dos ângulos de inclinação da tubulação com a horizontal nas taxas de deposição. Para prever o escoamento multifásico utilizou-se o modelo de deslizamento e a deposição da parafina foi determinada baseada no modelo de difusão molecular. A modelagem desenvolvida foi validada com a simulação do escoamento ao longo de um duto curto, reproduzindo condições experimentais de laboratório. Os resultados obtidos para a espessura do depósito apresentaram excelente concordância com os dados experimentais e com os dados obtidos com o simulador comercial OLGA. Analisou-se o escoamento entre um poço produtor e uma plataforma na Bacia de Campos, onde determinou-se o impacto na perda de carga devido a diminuição do diâmetro interno da tubulação causada pelo aumento da espessura dos depósitos. Os resultados obtidos destes estudos apresentaram boa coerência física e razoável concordância com relação aos dados experimentais. Crude oil is formed by several hydrocarbons. At the reservoir, due to high pressures and temperatures, it is found in the liquid form. As the oil flows, its pressure drops as well as its temperature, due to a heat loss to the ambient, causing liberation of the gas dissolved in the oil and it becomes a two-phase flow. Further, if the temperature drops below the initial crystallization temperature, crystals precipitation occurs, forming a solid phase deposit at the inner pipeline walls. Wax deposition is one of the most critical operational problems regarding oil flow through subsea pipelines. This work, wax deposition in a multiphase flow is numerically predicted. The influence of a water phase and pipe inclination angle in the deposition rate is investigated. The Drift Flux Model was employed to predict the multiphase flow and the wax deposition was determined based on a Molecular Diffusion Model. The methodology was validated by investigating the flow in a short pipe, reproducing laboratory experimental conditions. The wax deposit thickness presented a excellent agreement with the experimental data and against results of commercial code OLGA. An existing oil production well in Campos Basin was modeled, and the impact in pressure drop due to cross section area reduction caused by progressive wax deposition on the pipe wall. The results obtained in this study demonstrated good physical consistency and a reasonable agreement with the compared experimental database.

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Snyder, Kevin P. "Multiphase flow and mass transport through porous media." Thesis, Virginia Tech, 1993. http://hdl.handle.net/10919/40658.

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30

Lebon, Gerard Serge Bruno. "Unstructured finite volume algorithms for compressible multiphase flow." Thesis, University of Greenwich, 2011. http://gala.gre.ac.uk/8077/.

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This research presents novel algorithms for computing flow within an unstructured, collocated, finite volume solver in the presence of non-orthogonality and compressibility in order to extend the range of problems which can be modelled with the University's in-house CFD code: PHYSICA. A new non-orthogonality diffusion correction relaxation parameter has been successfully introduced and tested with benchmarks from the literature. Cases involving geometries meshed with commercial packages have been successfully run with the diffusion correction methods, variable bounding and proper under-relaxation practices. The applicability of a pressure interpolation method has also been tested with these cases. A procedure for solving compressible flow within a finite volume, pressure correction type scheme, has been devised and successfully implemented in different test cases. This method is however prone to numerical diffusion in the presence of shocks, but does work even in the presence of skewed meshes. The method was then tested with the case of an oxygen jet entering a heated furnace, for which experimental data is available for comparison. The method was successful in predicting the axial variables of the jet, and used to develop a turbulence modification model for such jets. The method was finally used to model the deformation of a free surface impinged by a compressible jet, using a novel zonal method called zonal Gas And Liquid Analyser (GALA). Convergence was achieved with the method developed in this research, together with the application of the counter diffusion method to model the moving interface.

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31

Goater, Aaron Lewis. "Multiphase flow simulation with applications for CO₂ storage." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9538.

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Geological storage of carbon dioxide (CO2) has potential to significantly reduce atmospheric emissions of greenhouse gases. However, challenges exist to the successful establishment of this process. These include estimating and understanding storage capacity as well as its economic viability. A large proportion of Europe’s potential storage capacity is to be found in large open aquifers. However, in times when the European carbon price is low, storage in depleted oil reservoirs may be required to make early commercial projects economically viable. Regulation will require that storage in these sites is well understood and it currently requires conformity of actual with modelled behaviour. In this thesis we consider two areas with direct implication for these issues. Firstly, we consider the effect of top-surface structure and heterogeneity upon the storage capacity of open aquifers. It is found that top-surface structure is more likely to decrease storage efficiency in models with low average reservoir dip and/or permeability. Heterogeneity is seen to reduce injectivity and reduce capacity in low permeability models but increase lateral spread of CO2 and storage efficiency in higher permeability cases. Both features can change storage capacity by more than a factor of two. Secondly, we undertake investigation into 1D solutions for three-phase flow problems representative of CO2 storage in depleted oil reservoirs. We begin by trying to determine rigorously the physical solution to three-phase flow problems that may have non-unique solutions using the third-order essentially non-oscillatory (ENO) numerical method. However, we demonstrate that ENO only produces first-order convergence in discontinuous solutions, which means rigorous analysis using our proposed methodology is not possible. We do, however, benchmark compositional three-phase, three-component ENO simulations against analytic solutions for the first time and demonstrate that ENO is still preferable to low-order numerical methods. Finally, we demonstrate the convergence of three-phase numerical solutions by comparing solutions with water-wet and oil-wet capillary pressure functions as the magnitude of the capillary pressure functions become small.

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Blaney, S. "Gamma radiation methods for clamp-on multiphase flow metering." Thesis, Cranfield University, 2008. http://dspace.lib.cranfield.ac.uk/handle/1826/5655.

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The development of a cost-effective multiphase flow meter to determine the individual phase flow rates of oil, water and gas was investigated through the exploitation of a single clamp-on gamma densitometer and signal processing techniques. A fast-sampling (250 Hz) gamma densitometer was installed at the top of the 10.5 m high, 108.2 mm internal diameter, stainless steel catenary riser in the Cranfield University multiphase flow test facility. Gamma radiation attenuation data was collected for two photon energy ranges of the caesium-137 radioisotope based densitometer for a range of air, water and oil flow mixtures, spanning the facility’s delivery range. Signal analysis of the gamma densitometer data revealed the presence of quasi-periodic waveforms in the time-varying multiphase flow densities and discriminatory correlations between statistical features of the gamma count data and key multiphase flow parameters. The development of a mechanistic approach to infer the multiphase flow rates from the gamma attenuation information was investigated. A model for the determination of the individual phase flow rates was proposed based on the gamma attenuation levels; while quasi-periodic waveforms identified in the multiphase fluid density were observed to exhibit a strong correlation with the gas and liquid superficial phase velocity parameters at fixed water cuts. Analysis of the use of pattern recognition techniques to correlate the gamma densitometer data with the individual phase superficial velocities and the water cut was undertaken. Two neural network models were developed for comparison: a single multilayer-perceptron and a multilayer hierarchical flow regime dependent model. The pattern recognition systems were trained to map the temporal fluctuations in the multiphase mixture density with the individual phase flow rates using statistical features extracted from the gamma count signals as their inputs. Initial results yielded individual phase flow rate predictions to within ±10% based on flow regime specific correlations.

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33

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 gazeuse Coupling 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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Soundararajan, Krishna Kumar. "Multi-scale multiphase modelling of granular flows." Thesis, University of Cambridge, 2015. https://www.repository.cam.ac.uk/handle/1810/252953.

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Geophysical hazards usually involve multiphase flow of dense granular solids and water. Understanding the mechanics of granular flow is of particular importance in predicting the run-out behaviour of debris flows. The dynamics of a homogeneous granular flow involve three distinct scales: the microscopic scale, the meso-scale, and the macroscopic scale. Conventionally, granular flows are modelled as a continuum because they exhibit many collective phenomena. Recent studies, however, suggest that a continuum law may be unable to capture the effect of inhomogeneities at the grain scale level, such as orientation of force chains, which are micro-structural effects. Discrete element methods (DEM) are capable of simulating these micro-structural effects, however they are computationally expensive. In the present study, a multi-scale approach is adopted, using both DEM and continuum techniques, to better understand the rheology of granular flows and the limitations of continuum models. The collapse of a granular column on a horizontal surface is a simple case of granular flow; however, a proper model that describes the flow dynamics is still lacking. In the present study, the generalised interpolation material point method (GIMPM), a hybrid Eulerian ? Lagrangian approach, is implemented with the Mohr-Coloumb failure criterion to describe the continuum behaviour of granular flows. The granular column collapse is also simulated using DEM to understand the micro-mechanics of the flow. The limitations of MPM in modelling the flow dynamics are studied by inspecting the energy dissipation mechanisms. The lack of collisional dissipation in the Mohr-Coloumb model results in longer run-out distances for granular flows in dilute regimes (where the mean pressure is low). However, the model is able to capture the rheology of dense granular flows, such as the run-out evolution of slopes subjected to lateral excitation, where the inertial number I < 0.1. The initiation and propagation of submarine flows depend mainly on the slope, density, and quantity of the material destabilised. Certain macroscopic models are able to capture simple mechanical behaviours, however the complex physical mechanisms that occur at the grain scale, such as hydrodynamic instabilities and formation of clusters, have largely been ignored. In order to describe the mechanism of submarine granular flows, it is important to consider both the dynamics of the solid phase and the role of the ambient fluid. In the present study, a two-dimensional coupled Lattice Boltzmann LBM ? DEM technique is developed to understand the micro-scale rheology of granular flows in fluid. Parametric analyses are performed to assess the influence of initial configuration, permeability, and slope of the inclined plane on the flow. The effect of hydrodynamic forces on the run-out evolution is analysed by comparing the energy dissipation and flow evolution between dry and immersed conditions.

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Al-Awadi, Hameed. "Multiphase characteristics of high viscosity oil." Thesis, Cranfield University, 2011. http://dspace.lib.cranfield.ac.uk/handle/1826/13902.

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Heavy oil production has drawn more and more attention in petroleum industry. The amount of heavy oil in the world is twice more than the conventional oil (low viscosity), which has been consumed rapidly from the past. The understanding of flow patterns and pressure losses in multiphase flow with high viscosity oil are vital to assist the design of transportation pipeline. This thesis involves experimental investigation of two phase and three phase flows under high oil viscosity conditions (up to 17000cP) in horizontal pipelines. The multiphase (oil/water/solid/gas) facility was designed and constructed at Cranfield University and consists of 6m long horizontal pipeline of 0.026m diameter along with instrumentations. The principal objectives of the work were to study the effect of viscosity, water cut, temperature variance, and flow conditions on flow patterns and pressure drops for (oil/gas and oil/water) two phase flows; to compare the measured flow parameters and phase distribution with those predicted from models found in the literature for two phase flows; and to conduct an experimental study of gas injection effect on pressure gradient in (oil/water/gas) three phase flow. Due to the nature of heavy oil reservoirs, sand is associated with oil/water mixture when extracted; therefore sand concentration effect on pressure drop in (oil/water/sand) three phase flow is also examined. For oil-air flow, a smooth oil coating was observed in the film region of slug flow, while a ripple structure of oil coating film was found at higher superficial air velocity for slug flow regime and annular flow regime. The ripple structure was believed to increase the effective roughness of the pipe wall, which resulted in higher pressure gradients. The pressure drop correlations from Beggs and Brill (1973) and Dukler et al. (1964) were used to compare with experimental pressure gradients for oil/air flow. It was found that these correlations failed to predict the pressure gradients for heavy oil/air flows in this work. Several new heavy oil/water flow patterns were named and categorized based on observations. Though the heavy oil viscosity is an essential parameter for oil continuous phase flow on pressure drop, it had no significant effect beyond Water Assist Flow (WAF) condition, as a threshold was found for water cut with fixed superficial oil velocity. The transition criterion by McKibben et al. (2000b) for WAF was found to be able to predict this threshold reasonably well. Core Annular Flow (CAF) models were found to greatly under predict the pressure gradients mainly due to the coating (oil fouling) effect associated with this study. A new coating coefficient was introduced to models presented by Bannwart (2001) and Rodriguez et al (2009). The addition of solid in the mixed flow led to minor increase in the pressure gradient when the particles were moving with the flow. However, higher sand concentration in the system led to higher pressure gradient values. The addition of gaseous phase to the oil/water flow was more complex. The gaseous injection was beneficial toward reducing the pressure gradient when introduced in oil continuous phase only at very low water cuts.

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Jofre, Cruanyes Lluís. "Numerical simulation of multiphase immiscible flow on unstructured meshes." Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/277545.

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The present thesis aims at developing a basis for the numerical simulation of multiphase flows of immiscible fluids. This approach, although limited by the computational power of the present computers, is potentially very important, since most of the physical phenomena of these flows often happen on space and time scales where experimental techniques are impossible to be utilized in practice. In particular, this research is focused on developing numerical discretizations suitable for three-dimensional (3-D) unstructured meshes. In detail, the first chapter delimits the considered multiphase flows to the case in which the components are immiscible fluids. In particular, the focus is placed on those cases where two or more continuous streams of different fluids are separated by interfaces, and hence, correspondingly named separated flows. Additionally, once the type of flow is determined, the chapter introduces the physical characteristics and the models available to predict its behavior, as well as the mathematical formulation that sustains the numerical techniques developed within this thesis. The second chapter introduces and analyzes a new geometrical Volume-of-Fluid (VOF) method for capturing interfaces on 3-D Cartesian and unstructured meshes. The method reconstructs interfaces as first- and second-order piecewise planar approximations (PLIC), and advects volumes in a single unsplit Lagrangian-Eulerian (LE) geometrical algorithm based on constructing flux polyhedrons by tracing back the Lagrangian trajectories of the cell-vertex velocities. In this way, the situations of overlapping between flux polyhedrons are minimized. Complementing the previous chapter, the third one proposes a parallelization strategy for the VOF method. The main obstacle is that the computing costs are concentrated in the interface between fluids. Consequently, if the interface is not homogeneously distributed, standard domain decomposition (DD) strategies lead to imbalanced workload distributions. Hence, the new strategy is based on a load balancing process complementary to the underlying domain decomposition. Its parallel efficiency has been analyzed using up to 1024 CPU-cores, and the results obtained show a gain with respect to the standard DD strategy up to 12x, depending on the size of the interface and the initial distribution. The fourth chapter describes the discretization of the single-phase Navier-Stokes equations to later extend it to the case of multiphase immiscible flow. One of the most important characteristics of the discretization schemes, aside from accuracy, is their capacity to discretely conserve kinetic energy, specially when solving turbulent flow. Hence, this chapter analyzes the accuracy and conservation properties of two particular collocated and staggered mesh schemes. The extension of the numerical schemes suitable for the single-phase Navier-Stokes equations to the case of multiphase immiscible flow is developed in the fifth chapter. Particularly, while the numerical techniques for the simulation of turbulent flow have evolved to discretely preserve mass, momentum and, specially, kinetic energy, the mesh schemes for the discretization of multiphase immiscible flow have evolved to improve their stability and robustness. Therefore, this chapter presents and analyzes two particular collocated and staggered mesh discretizations, able to simulate multiphase immiscible flow, which favor the discrete conservation of mass, momentum and kinetic energy. Finally, the sixth chapter numerically simulates the Richtmyer-Meshkov (RM) instability of two incompressible immiscible liquids. This chapter is a general assessment of the numerical methods developed along this thesis. In particular, the instability has been simulated by means of a VOF method and a staggered mesh scheme. The corresponding numerical results have shown the capacity of the discrete system to obtain accurate results for the RM instability. Aquesta tesi té com a objectiu desenvolupar una base per a la simulació numèrica de fluids multi-fase immiscibles. Aquesta estratègia, encara que limitada per la potència computacional dels computadors actuals, és potencialment molt important, ja que la majoria de la fenomenologia d'aquests fluids sovint passa en escales temporals i especials on les tècniques experimentals no poden ser utilitzades. En particular, aquest treball es centra en desenvolupar discretitzacions numèriques aptes per a malles no-estructurades en tres dimensions (3-D). En detall, el primer capítol delimita els casos multifásics considerats al cas en que els components són fluids immiscibles. En particular, la tesi es centra en aquells casos en que dos o més fluids diferents són separats per interfases, i per tant, corresponentment anomenats fluxos separats. A més a més, un cop el tipus de flux es determinat, el capítol introdueix les característiques físiques i els models disponibles per predir el seu comportament, així com també la formulació matemàtica i les tècniques numèriques desenvolupades en aquesta tesi. El segon capítol introdueix i analitza un nou mètode "Volume-of-Fluid" (VOF) apte per a capturar interfases en malles Cartesianes i no-estructurades 3-D. El mètode reconstrueix les interfases com aproximacions "piecewise planar approximations" (PLIC) de primer i segon ordre, i advecciona els volums amb un algoritme geomètric "unsplit Lagrangian-Eulerian" (LE) basat en construïr els poliedres a partir de les velocitats dels vèrtexs de les celdes. D'aquesta manera, les situacions de sobre-solapament entre poliedres són minimitzades. Complementant el capítol anterior, el tercer proposa una estratègia de paral·lelització pel mètode VOF. L'obstacle principal és que els costos computacionals estan concentrats en les celdes de l'interfase entre fluids. En conseqüència, si la interfase no està ben distribuïda, les estratègies de "domain decomposition" (DD) resulten en distribucions de càrrega desequilibrades. Per tant, la nova estratègia està basada en un procés de balanceig de càrrega complementària a la DD. La seva eficiència en paral·lel ha sigut analitzada utilitzant fins a 1024 CPU-cores, i els resultats obtinguts mostren uns guanys respecte l'estratègia DD de fins a 12x, depenent del tamany de la interfase i de la distribució inicial. El quart capítol descriu la discretització de les equacions de Navier-Stokes per a una sola fase, per després estendre-ho al cas multi-fase. Una de les característiques més importants dels esquemes de discretització, a part de la precisió, és la seva capacitat per conservar discretament l'energia cinètica, específicament en el cas de fluxos turbulents. Per tant, aquest capítol analitza la precisió i propietats de conservació de dos esquemes de malla diferents: "collocated" i "staggered". L'extensió dels esquemes de malla aptes per els casos de una sola fase als casos multi-fase es desenvolupa en el cinquè capítol. En particular, així com en el cas de la simulació de la turbulència les tècniques numèriques han evolucionat per a preservar discretament massa, moment i energia cinètica, els esquemes de malla per a la discretització de fluxos multi-fase han evolucionat per millorar la seva estabilitat i robustesa. Per lo tant, aquest capítol presenta i analitza dos discretitzacions de malla "collocated" i "staggered" particulars, aptes per simular fluxos multi-fase, que afavoreixen la conservació discreta de massa, moment i energia cinètica. Finalment, el capítol sis simula numèricament la inestabilitat de Richtmyer-Meshkov (RM) de dos fluids immiscibles i incompressibles. Aquest capítol es una prova general dels mètodes numèrics desenvolupats al llarg de la tesi. En particular, la inestabilitat ha sigut simulada mitjançant un mètode VOF i un esquema de malla "staggered". Els resultats numèrics corresponents han demostrat la capacitat del sistema discret en obtenir bons resultats per la inestabilitat RM.

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Reichenberger, Volker. "Numerical simulation of multiphase flow in fractured porous media." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=970266049.

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38

Da, Silva Marco Jose. "Impedance Sensors for Fast Multiphase Flow Measurement and Imaging." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1228836406821-31677.

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Multiphase flow denotes the simultaneous flow of two or more physically distinct and immiscible substances and it can be widely found in several engineering applications, for instance, power generation, chemical engineering and crude oil extraction and processing. In many of those applications, multiphase flows determine safety and efficiency aspects of processes and plants where they occur. Therefore, the measurement and imaging of multiphase flows has received much attention in recent years, largely driven by a need of many industry branches to accurately quantify, predict and control the flow of multiphase mixtures. Moreover, multiphase flow measurements also form the basis in which models and simulations can be developed and validated. In this work, the use of electrical impedance techniques for multiphase flow measurement has been investigated. Three different impedance sensor systems to quantify and monitor multiphase flows have been developed, implemented and metrologically evaluated. The first one is a complex permittivity needle probe which can detect the phases of a multiphase flow at its probe tip by simultaneous measurement of the electrical conductivity and permittivity at up to 20 kHz repetition rate. Two-dimensional images of the phase distribution in pipe cross section can be obtained by the newly developed capacitance wire-mesh sensor. The sensor is able to discriminate fluids with different relative permittivity (dielectric constant) values in a multiphase flow and achieves frame frequencies of up to 10 000 frames per second. The third sensor introduced in this thesis is a planar array sensor which can be employed to visualize fluid distributions along the surface of objects and near-wall flows. The planar sensor can be mounted onto the wall of pipes or vessels and thus has a minimal influence on the flow. It can be operated by a conductivity-based as well as permittivity-based electronics at imaging speeds of up to 10 000 frames/s. All three sensor modalities have been employed in different flow applications which are discussed in this thesis. The main contribution of this research work to the field of multiphase flow measurement technology is therefore the development, characterization and application of new sensors based on electrical impedance measurement. All sensors present high-speed capability and two of them allow for imaging phase fraction distributions. The sensors are furthermore very robust and can thus easily be employed in a number of multiphase flow applications in research and industry.

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Machadao, Ricardo Tavora Heitmann. "Multiphase flow in Venturi : an experimental and theoretical study." Thesis, Imperial College London, 1997. http://hdl.handle.net/10044/1/8069.

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Kéchavarzi, Cédric. "Physical modelling of immiscible multiphase flow in porous media." Thesis, University of Cambridge, 2001. https://www.repository.cam.ac.uk/handle/1810/251766.

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41

Gopal, Madan. "Visualization and mathematical modelling of horizontal multiphase slug flow." Ohio : Ohio University, 1994. http://www.ohiolink.edu/etd/view.cgi?ohiou1173979842.

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42

Malcolm, Lorna Taryn. "Multiphase flow in porous media at low interfacial tension." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362036.

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43

Nieves, Remacha María José. "Microreactor technology : scale-up of multiphase continuous flow chemistries." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/91068.

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Thesis: Sc. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2014. Cataloged from PDF version of thesis. Includes bibliographical references. Microreactors have been demonstrated to provide many advantages over conventional process technologies for the synthesis of chemical compounds and kinetic studies at the laboratory scale. High heat and mass transfer rates, rapid mixing, and higher selectivities and conversions can be achieved in these microdevices thanks to the small characteristic dimensions, enabling the synthesis of compounds that cannot be synthesized in conventional reactors. In the past years, efforts have been directed towards the application of microreactor technology for production purposes, especially in the pharmaceutical and fine chemicals industry. The challenge is how to get benefit of the transport rates inherent to microreactors while increasing the throughput for production applications. Two approaches to increase production rate are possible: a) scale-out by parallelization of units; b) scale-up by increase in channel size and flow rates. Scale-out would require thousands of units to achieve kg/min of production rates and development of very expensive and complex control systems to ensure identical operating conditions in each unit for a perfect and predictable overall reactor performance. On the other hand, scale-up by increase in channel size risks losing mass and heat transfer performance. The Advanced-Flow Reactor (AFR) manufactured by Corning Inc. combines both approaches being able to yield production rates of 10 - 300 g/min per module. If the AFR is demonstrated to perform efficiently and to be easily scalable, it may become an alternative for process intensification and transition from batch to continuous in the pharmaceutical and fine chemicals industry. Additional advantages include shorter process development times thanks to the scalability of the reactor modules, higher selectivities and yields, greener production processes, and possibility of introducing new chemistries. In this context, fundamental understanding of the hydrodynamics for multiphase systems is essential and critical for process development and scale-up purposes. The objective of this thesis is to study both experimentally and through computational fluid dynamic simulations the hydrodynamic characteristics of the AFR to demonstrate the capabilities of this technology using non-reactive (hexane/water) and reactive systems (carbon dioxide/water, ozone/alkene) at ambient conditions. by María José Nieves Remacha. Sc. D.

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Jacobs, Bruce Lee. "Effective properties of multiphase flow in heterogeneous porous media." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/9697.

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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, February 1999. Includes bibliographical references (leaves 218-224). The impact of heterogeneity on multiphase fl.ow is explored using a spectral perturbation technique employing a stationary, stochastic representation of the spatial variability of soil properties. A derivation of the system's effective properties - nonwetting phase moisture content, capillary pressure, normalized saturation and permeability - was developed which is not specific as to the form of the permeability dependence on saturation or capillary pressure. This lack of specificity enables evaluation and comparison of effective properties with differing characterization forms. Conventional characterization techniques are employed to parameterize the saturation, capillary pressure, relative permeability relationships and applied to the Cape Cod and Borden aquifers. An approximate solution for the characteristic width of a dense nonaqueous phase liquid (DNAPL) plume or air sparging contributing area is derived to evaluate the sensitivity of system behavior to properties of input processes. Anisotropy is predicted for uniform, vertical flow in the Borden Aquifer consistent with both prior experimental observations and Monte Carlo simulations. Increases of the mean capillary pressure (increasing nonwetting phase saturation) is accompanied by reductions in nonwetting phase anisotropy. Similar levels of anisotropy are not found in the case of the Cape Cod aquifer; the difference is attributed largely to the mean value of the log of the characteristic pressure which is shown to control the rate of return to asymptotic permeability and hence system uniformity. A positive relation between anisotropy and interfacial tension was observed, consistent with prior numerical simulations. Positive dependence of lateral spreading on input fl.ow rate is predicted for Cape Cod Aquifer with reverse response at Borden Aquifer due to capillary pressure dependent anisotropy of Borden Aquifer. The effective permeability for horizontal fl.ow with core scale heterogeneity was found to be velocity dependent with features qualitatively similar to experimental observations and numerical experiments. Application of Leverett scaling as generally implemented in Monte Carlo simulations under represents aquifer hetero geneity and for the Borden Aquifer, van Genuchten characterization reduces system anisotropy by several orders of magnitude. Anisotropy of the effective properties proved to be less sensitive to Leverett scaling if the Brooks-Corey characterization was used due to insensitivity in this case to the variance of the slope parameter. by Bruce L. Jacobs. Ph.D.

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45

Nitsche, Ludwig C. (Ludwig Carlos). "Multiphase flow through spatially periodic models of porous media." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/111043.

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46

Jhunjhunwala, Manish. "Multiphase flow and control of fluid path in microsystems." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/37456.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, February 2005. Includes bibliographical references. Miniaturized chemical-systems are expected to have advantages of handling, portability, cost, speed, reproducibility and safety. Control of fluid path in small channels between processes in a chemical/biological network is crucial for connecting process elements. We show complete separation of individual phases (phase routing) from two-phase gas-liquid and liquid-liquid (aqueous-organic) mixtures on microscale. To provide for robust interfacing of operations in a network, we demonstrate this ability over a wide range of two-phase flow conditions, including transient ones. Enabled by the technique for complete separation of individual phases from two-phase mixtures, we show mixing of liquids by introduction of a passive gas-phase and demonstrate integration of mixing, reaction and phase separation on a single platform. Additionally, we use the principles developed for phase routing to design microfluidic valves that do not rely on elastic deformation of material. Such valves can be used in a variety of chemical environments, where polymer-based deformable materials would fail. (cont.) We show a concept for realization of logic-gates on microscale using appropriate connections for these valves, paving the way for design of automation and computational control directly into microfluidic analysis without use of electronics. Further, we use the phase separation concept for sampling liquid from gas-liquid and liquid-liquid mixtures. Such sampling ability, when coupled with a suitable analysis system, can be used for retrieving process information (example mass-transfer coefficients, chemical kinetics) from multiphase-processes. We provide evidence of this through estimation of mass-transfer coefficients in a model oxygen-water system and show at least an order-of-magnitude improvement over macroscale systems. Controlled definition of fluid path enabled by laminar flow on microscale is used in a large number of applications. We examine the role of gravity in determining flow path of fluids in a microchannel. We demonstrate density-gradient-driven flows leading to complete reorientation of fluids in the gravitational field. (cont.) We provide estimates of the time and velocity scales for different parameter ranges through two-dimensional and three-dimensional finite-element models, in agreement with experimental observations. We believe this thesis addresses a number of both: system and fundamental issues, advancing applications and understanding of microfluidic networks. by Manish Jhunjhunwala. Ph.D.

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Gunstensen, Andrew K. (Andrew Knut). "Lattice-Boltzmann studies of multiphase flow through porous media." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/13168.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1992. Includes bibliographical references (p. 115-122). by Andrew K. Gunstensen. Ph.D.

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48

Silva, Marco Jose da. "Impedance Sensors for Fast Multiphase Flow Measurement and Imaging." Dresden : TUDpress, 2008. http://deposit.d-nb.de/cgi-bin/dokserv?id=3200883&prov=M&dok_var=1&dok_ext=htm.

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49

Zhang, Jiazuo. "Self-potential during multiphase flow in complex porous media." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/48479.

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The rock pore space in many subsurface settings is saturated with water and one or more immiscible fluid phases; examples include non-aqueous-phase liquids (NAPLs) in contaminated aquifers, supercritical CO2 during sequestration in deep saline aquifers, the vadose zone, and hydrocarbon reservoirs. Self-potential (SP) methods have been proposed to monitor multiphase flow in such settings. However, to properly interpret and model these data requires an understanding of the saturation dependence of the streaming potential. This study presents a methodology to determine the saturation dependence of the streaming potential coupling coefficient and streaming current charge density in unsteady-state drainage and imbibition experiments and applies the method to published experimental data. Unsteady-state experiments do not yield representative values of coupling coefficient and streaming current density (or other transport properties such as relative permeability and electrical conductivity) at partial saturation because water saturation within the sample is not uniform. An interpretation method is required to determine the saturation dependence of coupling coefficient and streaming current density within a representative elementary volume with uniform saturation. The method makes no assumptions about the pore-space geometry. We also applied pore network models that can capture the distribution of fluids and electrical charge in real complex porous media to investigate and quantify streaming potential signals during multiphase flow at the pore level. The network modelling results were tested against the interpreted data and experimental data of Estaillades carbonate and St. Bees sandstone, which provided reliable pore-scale explanations of the experimental observations. The results presented here can be used to help interpret SP measurements obtained in partially-saturated subsurface settings.

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Grieb, Neal Phillip. "Multiresolution analysis for adaptive refinement of multiphase flow computations." Thesis, University of Iowa, 2010. https://ir.uiowa.edu/etd/677.

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Flows around immersed boundaries exhibit many complex, well defined and active dynamical structures. In fact, features such as shock waves, strong vorticity concentrations in shear layers, wakes, or boundary layer regions are critical elements in representing the dynamics of a flow field. In order to capture the correct kinematic and dynamic quantities associated with the fluid flows, one must be able to efficiently refine the computational mesh around areas containing high gradients of pressure, density, velocity, or other suitable flowfield variables that characterize distinct structures. Although there are techniques which utilize simple gradient-based Local Mesh Refinement (LMR) to adapt resolution selectively to capture structures in the flow, such methods lack the ability to refine structures based on the relative strengths and scales of structures that are presented in the flow. The inability to adequately define the strength and scale of structures typically results in the mesh being over-refined in regions of little consequence to the physical definition of the problem, under-refined in certain regions resulting in the loss of important features, or even the emergence of false features due to perturbations in the flowfield caused by unnecessary mesh refinement. On the other hand, significant user judgment is required to develop a "good enough" mesh for a given flow problem, so that important structures in the flowfield can be resolved. In order to overcome this problem, multiresolution techniques based on the wavelet transform are explored for feature identification and refinement. Properties and current uses of these functional transforms in fluid flow computations will be briefly discussed. A Multiresolution Transform (MRT) scheme is chosen for identifying coherent structures because of its ability to capture the scale and relative intensity of a structure, and its easy application on non-uniform meshes. The procedure used for implementation of the MRT on an octree/quadtree LMR mesh is discussed in detail, and techniques used for the identification and capture of jump discontinuities and scale information are also presented. High speed compressible flow simulations are presented for a number of cases using the described MRT LMR scheme. MRT based mesh refinement performance is analyzed and further suggestions are made for refinement parameters based on resulting refinement. The key contribution of this thesis is the identification of methods that lead to a robust, general (i.e. not requiring user-defined parameters) methodology to identify structures in compressible flows (shocks, slip lines, vertical patterns) and to direct refinement to adequately refine these structures. The ENO-MRT LMR scheme is shown to be a robust, automatic, and relatively inexpensive way of gaining accurate refinement of the major features contained in the flowfield.

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Tesi sul tema "Multiphase flow"

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