Thèses sur le sujet « Multi phase flow measurements »
Pour voir les autres types de publications sur ce sujet consultez le lien suivant : Multi phase flow measurements.
Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres
Consultez les 50 meilleures thèses pour votre recherche sur le sujet « Multi phase flow measurements ».
À côté de chaque source dans la liste de références il y a un bouton « Ajouter à la bibliographie ». Cliquez sur ce bouton, et nous générerons automatiquement la référence bibliographique pour la source choisie selon votre style de citation préféré : APA, MLA, Harvard, Vancouver, Chicago, etc.
Vous pouvez aussi télécharger le texte intégral de la publication scolaire au format pdf et consulter son résumé en ligne lorsque ces informations sont inclues dans les métadonnées.
Parcourez les thèses sur diverses disciplines et organisez correctement votre bibliographie.
1
Teague, Gavin. « Mass flow measurement of multi-phase mixtures by means of tomographic techniques ». Doctoral thesis, University of Cape Town, 2002. http://hdl.handle.net/11427/5097.
Texte intégralRésumé :
Includes bibliographical references.This thesis investigates the use of a dual-plane impedance tomography system to calculate the individual mass flow rates of the components in an air-gravel-seawater mixture. The long-term goal of this research is to develop a multi-phase flowmeter for the on-line monitoring of an airlift used in an offshore mining application. This requires the measurement of both the individual component volume fractions and their velocities. Tomography provides a convenient non-intrusive technique to obtain this information. Capacitance tomography is used to reconstruct the dielectric distribution of the material within a pipeline. It is based on the concept that the capacitance of a pair of electrodes depends on the dielectric distribution of the material between the electrodes. By mounting a number of electrodes around the periphery of the pipeline, and measuring the capacitances of the different electrode combinations, it is possible to reconstruct the distribution of the phases within the pipeline, provided the phases have different dielectric constants. Resistance tomography is used to reconstruct the resistivity distribution within the cross-section of the pipeline and operates in a similar way to capacitance tomography. Impedance tomography can be described as a dual-modal approach since both the capacitance and conductance of the different electrode combinations are measured to reconstruct the omplex impedance of the material distribution. Previous research has shown that impedance tomography can be used to reconstruct a three-phase air-gravelwater mixture [3,4]. In addition, it has been shown that neural networks can be used to perform this reconstruction task [3,4]. In particular, a single-layer feed-forward neural network with a 1-of-C output encoding can be trained to perform a three-phase image reconstruction. Further, a double-layer feed-forward neural network can be trained to predict the volume fractions of the three phases within the flow directly, based on the capacitance and conductance readings obtained from the data acquisition system. However, these tests were only for static configurations. This thesis will readdress this problem from the dynamic viewpoint. In addition, the individual component velocities will be calculated using the cross-correlation of the volume fraction predictions from two impedance tomography systems spaced a certain distance apart.
2
Hastings, Robert. « Use of multi-scale phase-based methods to determine optical flow in dynamic scene analysis ». Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2003. https://ro.ecu.edu.au/theses/1487.
Texte intégralRésumé :
Estimates of optical flow in images can be made by applying a complex periodic transform to the images and tracking the movement of points of constant phase in the complex output. This approach however suffers from the problem that filters of large width give information only about broad scale image features, whilst those of small spatial extent (high resolution) cannot track fast motion, which causes a feature to move a distance that is large compared to the filter-size. A method is presented in which the flow is measured at different scales, using a series of complex filters of decreasing width. The largest filter is used to give a large scale flow estimate at each image point. Estimates at smaller scales are then carried out by using the previous result as an a priori estimate. Rather than comparing the same region in different images in order to estimate flow, the regions to be compared are displaced from one another by an amount given by the most recent previous flow estimate. This results in an estimate of flow relative to the earlier estimate. The two estimates are then added together to give a new estimate of the absolute displacement. The process is repeated at successively smaller scales. The method can therefore detect small local velocity variations superimposed on the broad scale flow, even where the magnitude of the absolute displacement is larger than the scope of the smaller filters. Without the assistance of the earlier estimates in ‘tuning' the smaller filters in this manner, a smaller filter could fail to capture these velocity variations, because the absolute displacement carry the feature out of range of-the filter during successive frames. The output of the method is a series of scale-dependent flow fields corresponding to different scales, reflecting the fact that motion in the real world is a scale-dependent quantity. Application of the method to some 1 dimensional test images gives good results, with realistic flow values that could be used as an aid to segmentation. Some synthetic 2-dimentional images containing only a small number of well defined features aIso yield good-results but the method performs poorly on a random-dot stereogram and on a real-world test image pair selected from the Hamburg Taxi sequence.
3
Al-Yarubi, Qahtan. « Phase flow rate measurements of annular flows ». Thesis, University of Huddersfield, 2010. http://eprints.hud.ac.uk/id/eprint/9104/.
Texte intégralRésumé :
In the international oil and gas industry multiphase annular flow in pipelines and wells is extremely important, but not well understood. This thesis reports the development of an efficient and cheap method for measuring the phase flow rates in two phase annular and annular mist flow, in which the liquid phase is electrically conducting, using ultrasonic and conductance techniques. The method measures changes in the conductance of the liquid film formed during annular flow and uses these to calculate the volumetric and mass flow rates of the liquid film. The gas velocity in the core of the annular flow is measured using an ultrasonic technique. Combined with an entrainment model and the liquid film measurements described above, the ultrasonic technique enables the volumetric flow rate of the gas in the core and the volumetric and mass flow rates of entrained liquid droplets to be measured. This study was based on experimental work and the use of modelling techniques. The practical investigation comprised a series of experiments conducted on a purpose built flow loop in which the test section was a Perspex pipe of 50mm ID. The experimental work was limited to two-phase air-water flow. The flow loop was specifically designed to accommodate the different instruments and subsystems designed in this investigation including bespoke flow meters and a film extraction system. Most flow loop controls were automated using a MATLAB program. Reference measurement of the total water flow rate was made using a calibrated turbine flow meter and of the air flow rate using a calibrated rotameter. For the combined ultrasonic/conductance method investigated in this thesis, the velocity of the gas in the core was found using a novel Ultrasonic Flow Meter (USFM). The positioning and arrangement of the transducers have never been used previously. The flow velocity of the liquid film and the thickness of the film were measured using a novel Conductance Flow Meter (CFM). The CFM measured the liquid film thickness using novel wall conductance probes. By cross correlating the signals from a pair of such probes the film velocity was obtained. Good agreement of the experimental results obtained from the CFM and USFM with results published in the literature was found. Although not investigated experimentally in the work described in this thesis, annular flows encountered in the oil industry may contain a liquid phase comprising a mixture of oil and water. For such flows, the volume fractions of the oil and water can be measured using an automated bypass system developed during this project. The bypass system periodically extracts part of the liquid film, measures its density and then releases the sample back into the pipeline. The liquid phase volume fractions are determined from this density measurement which can be performed more than once per minute. An entrainment model was developed, which is required by the ultrasonic/conductance flow metering technique described in this thesis, in which the mass fraction of the liquid flowing as entrained droplets in the core can be determined from the liquid film thickness and velocity measurements. A mathematical model was also developed to describe the properties of the liquid film, such as liquid velocity profile within the film, and the model’s results were found to agree with the experimental results obtained during the project and also with previous work cited in the literature. The complexity of this latter model was reduced by making a number of simplifying assumptions, which are presented and discussed in the thesis, including the assumption that in annular flow there is a dynamic balance liquid entrainment and droplets being deposited back onto the film. The combination of the designed CFM and USFM with the bypass tube and the entrainment model offer the opportunity for a ‘wet gas’ flow meter to be developed to measure two and three phase annular flows at relatively low cost and with enhanced accuracy. Such a device would have the advantage that it would by substantially smaller than systems using separators and it could even be retrofitted onto off-shore platforms. The integration of the subsystems developed in this project into a single system capable of giving on-line measurements of annular flow would be a major benefit to the author’s sponsor, Petroleum Development of Oman.
4
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.
Texte intégral
5
Carlson, Johan E. « Ultrasound measurements in moving multi-phase supsensions ». Thesis, Luleå tekniska universitet, Signaler och system, 1998. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-24689.
Texte intégral
6
Lakkadi, Navneeth Sagar Reddy. « Flow Measurements in Turbulent Flow Fields with Magnetic Resonance Phase Velovity Mapping ». Cleveland State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=csu1251412647.
Texte intégral
7
Lakkadi, Navneeth Sagar Reddy. « Flow measurements in turbulent flow fields with magnetic resonance phase velocity mapping ». Cleveland, Ohio : Cleveland State University, 2009. http://etd.ohiolink.edu/view.cgi?acc_num=csu1251412647.
Texte intégralRésumé :
Thesis (M.S.)--Cleveland State University, 2009.Abstract. Title from PDF t.p. (viewed on Sept. 8, 2009). Includes bibliographical references (p. 129-135). Available online via the OhioLINK ETD Center and also available in print.
8
Djatmiko, Wahju. « Well testing in multi-phase flow reservoirs ». Thesis, Imperial College London, 1996. http://hdl.handle.net/10044/1/8128.
Texte intégral
9
Bunch, Thomas K. « Performance measurements of a flashing flow nozzle ». Thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-03042009-041255/.
Texte intégral
10
Petersson, Sven. « Simulation of Phase Contrast MRI Measurements from Numerical Flow Data ». Thesis, Linköping University, Department of Biomedical Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-14871.
Texte intégralRésumé :
Phase-contrast magnetic resonance imaging (PC-MRI) is a powerful tool for measuring blood flow and has a wide range of cardiovascular applications. Simulation of PC-MRI from numerical flow data would be useful for addressing the data quality of PC-MRI measurements and to study and understand different artifacts. It would also make it possible to optimize imaging parameters prior to the PC-MRI measurements and to evaluate different methods for measuring wall shear stress.
Based on previous studies a PC-MRI simulation tool was developed. An Eulerian-Lagrangian approach was used to solve the problem. Computational fluid dynamics (CFD) data calculated on a fix structured mesh (Eulerian point of view) were used as input. From the CFD data spin particle trajectories were computed. The magnetization of the spin particle is then evaluated as the particle travels along its trajectory (Lagrangian point of view).
The simulated PC-MRI data were evaluated by comparison with PC-MRI measurements on an in vitro phantom. Results indicate that the PC-MRI simulation tool functions well. However, further development is required to include some of the artifacts. Decreasing the computation time will make more accurate and powerful simulations possible. Several suggestions for improvements are presented in this report.
11
Czarske, J. W., N. Koukourakis, J. Koenig, B. Fregin et L. Büttner. « Wavefront shaping for flow-field measurements through varying phase boundaries ». SPIE, 2016. https://tud.qucosa.de/id/qucosa%3A35104.
Texte intégralRésumé :
We propose the usage of wavefront shaping approaches for image correlation based flow-field measurements. Aberrations introduced by a single phase boundary in the detection beam path were explored. Variations of the optical path-length result in strong errors in position allocation and thus to an enhancement of the measurement uncertainty of the velocity. Our results show that the usage of wavefront shaping enables to reduce these errors and to strongly improve the quality of image correlation based flow-field measurements. First experimental and simulated results underline the importance of these approaches
12
Perret, Matias Nicholas. « Experimental measurements of a two phase surface jet ». Thesis, University of Iowa, 2013. https://ir.uiowa.edu/etd/5041.
Texte intégralRésumé :
The effects of bubbles on a jet issued below and parallel to a free surface are experimentally studied. The jet under study is isothermal and in fresh water, with air injectors that allow variation of the inlet air volume fraction for 0% to 13%. Measurements of the jet exit conditions, water velocity, water entrainment, Reynolds stresses and surface currents have been performed using LDV, PIV and surface PIV. Air volume fraction, bubble velocity, chord length and free surface elevation and RMS have been obtained using local phase detection probes. Visualization was performed using laser-induced fluorescence. Measurements show that water entrainment decreases up to 22% with the presence of bubbles, but surface current strength increases up to 60% with 0.4 l/min of air injection. The mean free surface elevation and turbulent fluctuation significantly increase with the injection of air. The water normal Reynolds stresses are damped by the presence of bubbles in the bulk of the liquid, but very close to the free surface the effect is reversed and the normal Reynolds stresses increase slightly for the bubbly flow. Flow visualizations show that the two-phase jet is lifted with the presence of bubbles and attaches to the free surface sooner. Significant bubble coalescence is observed, leading to an increase of 20% in mean bubble size as the jet develops. The coalescence near the free surface is particularly strong, due to the time it takes the bubbles to pierce the free surface, resulting in a considerable increase in the local air volume fraction.
13
Lu, Qin. « A parallel multi-block/multi-physics approach for multi-phase flow in porous media / ». Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
Texte intégral
14
Cunningham, Michael (Michael Ian) Carleton University Dissertation Engineering Civil and Environmental. « Relative permeability measurements for two phase flow through low permeability soils ». Ottawa, 1994.
Trouver le texte intégral
15
Kraczek, Jeffrey Read. « Piston Phase Measurements to Accelerate Image Reconstruction in Multi-Aperture Systems ». University of Dayton / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1323284036.
Texte intégral
16
Tahmasbi, Nowtarki Koroush. « Two phase hydrodynamics in cross-flow distillation ». Thesis, Imperial College London, 1997. http://hdl.handle.net/10044/1/8424.
Texte intégral
17
Svanholm, Ulrika. « Evaluation of measurements of pulsating flow under controlled conditions using phase contrast MRI ». Thesis, Stockholm University, Medical Radiation Physics (together with KI), 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-7222.
Texte intégralRésumé :
The accuracy and precision of measurements of pulsating flow obtained with phase contrast magnetic resonance imaging (PC MRI) was studied. Measurements were carried out using known flow rates through a phantom connected to a pump that created pulsation in the flow. Repeated measurements were made in both the negative and positive encoding direction, using both breath-hold and non breath hold sequences. The obtained data was analyzed using code written in MATLAB and also using the FLOW software that is offered by the manufacturer of the MRI system.
A range of different flow velocities was scanned, and results show that the overall accuracy of the measurements is relatively good, with an average error of between 1.2% to 5.7% using the clinically employed flow calculation software. There is however indication of a systematic phase offset in the data that influences the measurements. The effect of the offset on the results depends on the direction of flow and the sequence used. The results also show the importance of properly selecting the area over which the flow rate is calculated.
18
SHI, WENJIANG. « Surface mapping by polarization and Multi-Wavelength synthesis measurements ». Thesis, Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-20053.
Texte intégralRésumé :
Modern optical measurement techniques have developed rapidly in recent years. One of the measurement technologies is polarization interferometry that can be used for roughness evaluation, deformation measurement, and vibration analysis of objects. based on LabVIEW and MATLAB, this project introduces the technique of virtual instruments into the field of modern optical measurements. The optical phase images have been captured by LabVIEW and processed by MATLAB to acquire the surface structures. The main research work in the project involves: (1) Introduction of the virtual instrument technique to capture and process optical phase images; (2) Processing of phase images acquired with different wavelengths using MATLAB to reveal show the 2D and 3D surface structures.
19
Dunbar, Oliver. « A diffuse interface model of surfactants in multi-phase flow ». Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/99133/.
Texte intégralRésumé :
We investigate a free boundary problem arising in fluid dynamics, by modelling multiple incompressible fluids over subdomains with different material quantities, and in the presence of surface tension reducing chemicals known as surfactants. We construct a free energy for this system, and we require it obey the second law of thermodynamics, leading to the formulation of an energy minimisation problem (the sharp problem). This problem is degenerate, so we regularise it by constructing a new energy of Ginzburg-Landau type, parametrised by a (small) constant ε > 0 and when ε → 0 the sharp problem is recovered in the sense of Γ-convergence. This multi-phase energy is formed from a multiwell potential and gradient term, and the minimisers are known as phase field variables. The phase field variables approximate characteristic functions of the subdomains, and the model is rewritten as functions of them. Beneficially, the energy analysis can be repeated as before to obtain a diffuse interface model. We construct and perform numerical analysis of a novel discretisation scheme for a Cahn-Hilliard Navier-Stokes system. Here we create a fractional-theta coupling scheme which is importantly proved to be of second order in time. The key property of this scheme is that it uses weighted operator splitting to separate the different nonlinearities that appear in a Cahn-Hilliard Navier-Stokes system. That is, the Cahn-Hilliard multiwell potential, the incompressibility condition and the convection. We discuss stability and the extension to surfactants. We implement the novel scheme in DUNE (Distributed Unified Numerics Environment), a finite element package and use simulation to run tests to validate the stability and consistency of the schemes, convergence of the diffuse interface model with respect to its parametrisation, and flexibility for the code development.
20
Hashemi, Mohammad Reza. « Direct numerical simulation of multi-phase flow in complex media ». Doctoral thesis, Universitat Politècnica de Catalunya, 2022. http://hdl.handle.net/10803/673617.
Texte intégralRésumé :
In numerous applications, two-phase liquid-gas transport at sub-millimeter length scales plays a substantial role in the determination of the behavior of the system at hand. As its main application, the present work focuses on the polymer electrolyte membrane (PEM) fuel cells. Desirable performance and operational life-time of this class of high-throughput energy conversion devices requires an effective water management, which per se relies on proper prediction of the water-air transport mechanisms. Such two-phase flow involves interfacial forces and phenomena, like hysteresis, that are associated with the physicochemical properties the liquid, gas, and if present, the solid substrate. In this context, numerical modeling is a viable means to obtain valuable predictive understanding of the transport mechanisms, specially for cases that experimental analyses are complicated and/or prohibitively expensive.
In this work, an efficient finite element/level-set framework is developed for three-dimensional simulation of two-phase flow. In order to achieve a robust solver for practical applications, the physical complexities are consistently included and the involved numerical issues are properly tackled; the pressure discontinuity at the liquid-gas interface is consistently captured by utilizing an enriched finite element space. The method is stabilized within the framework of variational multiscale stabilization technique. A novel treatment is further proposed for the small-cut instability problem. It is shown that the proposed model can provide accurate results minimizing the spurious currents. A robust technique is also developed in order to filter out the possible noises in the level-set field. It is shown that it is a key to prevent irregularities caused by the persistent remnant of the spurious currents. It is shown how the well-established contact-line models can be incorporated into the variational formulation. The importance of the inclusion of the sub-elemental hydrodynamics is also elaborated. The results presented in the present work rely on the combination of the linearized molecular kinetic and the hydrodynamic theories. Recalling the realistic behavior of liquids in contact with solid substrates, the contact--angle hysteresis phenomenon is taken into account by imposing a consistent pinning/unpinning mechanism developed within the framework of the level-set method.
Aside from the main developments, a novel technique is also proposed to significantly improve the accuracy and minimize the the loss in the geometrical features of the interface during the level-set convection based on the back and forth error compensation correction (BFECC) algorithm.
Within the context of this thesis, the numerical model is validated for various cases of gas bubble in a liquid and liquid droplets in a gas. For the latter scenario, besides free droplets, the accuracy of the proposed numerical method is assessed for capturing the dynamics droplets spreading on solid substrates. The performance of the model is then analyzed for the capturing the configuration of a water droplet on an inclined substrate in the presence the contact--angle hysteresis. The proposed method is finally employed to simulate the dynamics of a water droplet confined in a gas channel and exposed to air-flow.Existen numerosas aplicaciones industriales en las que transporte bifásico (líquido-gas) a escalas submilimétricas resulta crucial para la determinación del comportamiento del sistema en cuestión. Entre todas ellas, el presente trabajo se centra en las pilas de combustible con membrana de electrolito polimérico (PEMFC). El rendimiento deseable y la vida útil operativa de esta clase de dispositivos de conversión de energía de alto rendimiento requieren una gestión eficaz del agua (conocida como “water management”), que per se depende de la predicción adecuada de los mecanismos de transporte de agua y aire. Así pues, el análisis del flujo microfluídico de dos fases obliga considerar fuerzas y fenómenos interfaciales, tales como la histéresis, que están asociados con las propiedades fisicoquímicas del líquido, el gas y, si está presente, el sustrato sólido. En este contexto, la modelización numérica es una alternativa viable para obtener una predicción precisa de los mecanismos de transporte, especialmente en aquellos casos en los que los análisis experimentales son prohibitivos, ya sea por su complejidad o coste económico. En este trabajo, se desarrolla un marco eficiente, basado en la combinación del método de elementos finitos y el método de “level-set”, para la simulación tridimensional de flujos bifásicos. Con el fin de lograr una herramienta numérica robusta para aplicaciones prácticas, las complejidades físicas se incluyen consistentemente y los problemas numéricos involucrados se abordan adecuadamente. Concretamente, la discontinuidad de la presión en la interfaz líquido-gas se captura consistentemente utilizando un espacio de elementos finitos enriquecido. La estabilización del método se consigue mediante la introducción de la técnica de multiescalas variacionales. Asimismo, se propone también un tratamiento novedoso para el problema de la inestabilidad de tipo “small-cut”. Se muestra que el modelo propuesto puede proporcionar resultados precisos minimizando las corrientes espurias en la interfaz liquido-gas. Complementariamente, se presenta una nueva metodología para filtrar el ruido en el campo de “level-set”. Esta metodología resulta ser crucial para prevenir las irregularidades provocadas por el remanente persistente de las corrientes espurias. El comportamiento de la línea de contacto es considerado a través de la inclusión los modelos correspondientes en la formulación variacional. A este respecto, el presente trabajo aborda la importancia de la inclusión de la hidrodinámica subelemental. Los resultados presentados se basan en la combinación de la cinética molecular linealizada y las teorías hidrodinámicas. Para representación del comportamiento realista de los líquidos en contacto con sustratos sólidos, el fenómeno de histéresis del ángulo de contacto se tiene en cuenta imponiendo un mecanismo de anclado / desanclado consistente desarrollado en el marco del método de level-set. Aparte de los desarrollos principales, también se propone una técnica novedosa para la convección de la función ”level-set”. Ésta permite mejorar significativamente la precisión, minimizando a su vez la pérdida en las características geométricas de la interfaz asociadas al transporte. Esta nueva metodología está basada en el algoritmo de corrección de compensación de errores (BFECC). La herramienta numérica desarrollada en esta tesis es validada para varios casos que involucran burbujas de gas en un líquido y pequeñas gotas de líquido en un gas. Para el último escenario, además de las gotas libres, se evalúa la precisión de la herramienta propuesta para capturar la dinámica de las gotas sobre sustratos sólidos. A continuación, se analiza el rendimiento del modelo para capturar la configuración de una gota de agua sobre un sustrato inclinado en presencia de la histéresis del ángulo de contacto. El método propuesto finalmente se aplica
Enginyeria civil
21
Yang, Yihong. « Experimental Study of Multi-phase Flow Hydrodynamics in Stirring Tanks ». Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/77056.
Texte intégralRésumé :
Stirring tanks are very important equipments used for mixing, separating, chemical reaction, etc. A typical stirring tank is a cylindrical vessel with an agitator driving the fluid and generating turbulence to promote mixing. Flotation cells are widely used stirring tanks in phase separation where multiphase flow is involved. Flotation refers to the process in which air bubbles selectively pick up hydrophobic particles and separate them from hydrophilic solids. This technology is used throughout the mining industry as well as the chemical and petroleum industries.
In this research, efforts were made to investigate the multi-phase flow hydrodynamic problems of some flotation cells at different geometrical scales. Pitot-static and five-hope probes were employed to lab- pilot- and commercial-scale tanks for velocity measurements. It was found that the tanks with different scales have similar flow patterns over a range of Reynolds numbers. Based on the velocity measurement results, flotation tanks' performance was evaluated by checking the active volume in the bulk. A fast-response five-hole probe was designed and fabricated to study the turbulence characteristics in flotation cells under single- and multi-phase flow conditions. The jet stream in the rotor-stator domain has much higher turbulence intensity compared with other locations. The turbulent dissipation rate (TDR) in the rotor-stator domain is around 20 times higher than that near tank's wall. The TDR could be used to calculate the bubble and particle slip velocities. An isokinetic sampling probe system was developed to obtain true samples inthe multi-phase flow and then measure the local void fraction. It was found that the air bubbles are carried out by the stream and dispersed to the whole bulk. However, some of the bubbles accumulate in the inactive regions, where higher void fractions were detected. The isokinetic sampling probe was then extended to be an isokinetic borescope system, which was used to detect the bubble-particle aggregates in the tank. Aggregates were found in the high-turbulence level zones. The isokinetic sampling probe and the isokinetic borescope provide new methods for flotation tank tests. An experiment was also set up to study the dynamics of bubble particle impact. Four different modes were found for the collision. The criterion is that if the fluid drainage time is less than the residence time, the attachment will occur, otherwise, the particle will bounce back.Ph. D.
22
Ben, Dhia Zakaria. « Novel Treatments for Multi-phase Flow Prediction Inspired By Kinetic Theory ». Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34924.
Texte intégralRésumé :
This study entails an investigation of a novel moment closure, originally constructed for rarefied-gas prediction, to the modelling of inert, dilute, disperse, particle flows. Such flows are important in many engineering situations. As one example, in internal-combustion engines, fuel is often injected as a spray of tiny droplets and, during combustion, a cloud of tiny soot particles can be formed. These particle phases are often difficult to model, especially when particles display a range of velocities at each location in space. Lagrangian methods are often too costly and many Eulerian field-based methods suffer from model deficiencies and mathematical artifacts. Often, Eulerian formulations assume that all particles at a location and time have the same velocity. This assumption leads to nonphysical
results, including an inability to predict particle paths crossing and a limited number of boundary conditions that can be applied.
The typical multi-phase situation of many particles is, in many ways, similar to that
of a gas compressed of a huge number of atoms or molecules. It is therefore expected that powerful techniques from the kinetic theory of gases could be applied. This work explores the advantages of using a modern fourteen-moment model, originally derived for rarefied gases, to predict multi-phase flows. Details regarding the derivation, the mathematical structure, and physical behaviour of the resulting model are explained. Finally, a numerical implementation is presented and results for several flow problems that are designed to demonstrate the fundamental behaviour of the models are presented. Comparisons are made with other classical models.
23
Maru, Wessenu-Abegaz. « Modelling two-phase flow and transport effects of multi-component fuels ». Thesis, Cranfield University, 2005. http://hdl.handle.net/1826/3936.
Texte intégralRésumé :
Three novel multicomponent fuel spray droplet evaporation models are developed by employing the theory of continuous thermodynamics(CT) with the aim of applying them in the design and analysis of various energy conversion devices such as, aircraft jet engines, liquid-fuel rocket engines, diesel engines, and industrial
furnaces. The CT methodology seeks to represent complex mixtures - for example,aviation kerosene or JP8 that typically comprise blends of a large number of chemical compounds by using probability distribution functions (PDFs). The components of JP8, which is constituted by the homologous series of paraffin, naphthene, and aromatic hydrocarbons; are each represented by the Pearson-Shultz type three-parameter gamma PDF, where the three (shape, scale, and origin) parameters characterise changes in the mixture composition. The phase transition of the liquid droplet due to evaporation is modelled using both low-pressure (LP) and high-pressure (HP) vapour-liquid equilibrium (VLE) models employing various mixing and combining rules by applying a general cubic equation of state (CEOS). Interestingly enough, the phase transition of the liquid fuel into vapour mixture is characterised by a change in the PDF scale parameter alone. Once the description of the fuel mixture is complete, the traditional species and energy transport equations
both for the liquid and vapour phases respectively, are re-written using the composition PDF moments under
Lagrangian and Eulerian frameworks. In order to solve the governing equations for the three droplet evaporation models, which characteristically involve phase change and a moving interface, a novel fully
Adaptive Method Of Lines using B-Spline Collocation (AMOLBSC) is developed. The models are tested at various pressures, temperatures and convective conditions, including at a lean, premixed, prevaporised (LPP) combustor operating condition. In general, the computational results at an ambient pressure close to atmospheric showed good to excellent agreement against available experimental data in the literature.
However, for ambient conditions with elevated-high pressures and temperatures only models that employ the HP formulation gave reliable results. In particular, when the liquid is at or near its critical pressure and temperature it is characterised by faster vaporisation and shorter droplet lifetime, including some evidence of
liquid mass diffusion. The liquid model that incorporates the effects of liquid core circulation using semiempirical
approximation and adaptive mesh refinement (AMR) technique is the most accurate and
computationally efficient, although further work is required to establish its ranges of applicability.
24
Sederman, Andrew John. « MRI studies of single and multi-phase flow in porous media ». Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624232.
Texte intégral
25
Ito, Kei. « Study on high-precision numerical algorithms for multi-phase flow analyses ». 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/126506.
Texte intégral
26
Nadim, Nima. « Fluid and thermal behaviour of multi-phase flow through curved ducts ». Thesis, Curtin University, 2012. http://hdl.handle.net/20.500.11937/794.
Texte intégralRésumé :
Fluid flow through curved ducts is influenced by the centrifugal action arising from duct curvature and has behaviour uniquely different to fluid flow through straight ducts. In such flows, centrifugal forces induce secondary flow vortices and produce spiralling fluid motion within curved ducts. Secondary flow promotes fluid mixing with intrinsic potential for thermal enhancement and, exhibits possibility of fluid instability and additional secondary vortices under certain flow conditions. Reviewing published numerical and experimental work, this thesis discusses the current knowledge-base on secondary flow in curved ducts and, identifies the deficiencies in analyses and fundamental understanding. It then presents an extensive research study capturing advanced aspects of secondary flow behaviour in single and two-phase fluid flow through curved channels of several practical geometries and the associated wall heat transfer processes.As a key contribution to the field and overcoming current limitations, this research study develops a new three-dimensional numerical model for single-phase fluid flow in curved ducts incorporating vortex structure (helicity) approach and a curvilinear mesh system. The model is validated against the published data to ascertain modelling accuracy. Considering rectangular, elliptical and circular ducts, the flow patterns and thermal characteristics are obtained for a range of duct aspect ratios, flow rates and wall heat fluxes. Results are analysed for parametric influences and construed for clearer physical understanding of the flow mechanics involved. The study formulates two analytical techniques whereby secondary vortex detection is integrated into the computational process with unprecedented accuracy and reliability. The vortex inception at flow instability is carefully examined with respect to the duct aspect ratio, duct geometry and flow rate. An entropy-based thermal optimisation technique is developed for fluid flow through curved ducts.Extending the single-phase model, novel simulations are developed to investigate the multiphase flow in heated curved ducts. The variants of these models are separately formulated to examine the immiscible fluid mixture flow and the two-phase flow boiling situations in heated curved ducts. These advanced curved duct flow simulation models are validated against the available data. Along with physical interpretations, the predicted results are used to appraise the parametric influences on phase and void fraction distribution, unique flow features and thermal characteristics. A channel flow optimisation method based on thermal and viscous fluid irreversibilities is proposed and tested with a view to develop a practical design tool.
27
Akartuna, Sevket Ersin. « Identification of phase flow rates in oil-gas-water flow from turbulent capacitance and pressure signals ». Thesis, Imperial College London, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321627.
Texte intégral
28
Hadded, O. « A packaged laser instrument for drop size and velocity measurements in two-phase flow ». Thesis, Bucks New University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372321.
Texte intégral
29
FERNANDES, LEONARDO SOARES. « STEREO-PIV LIQUID VELOCITY MEASUREMENTS IN TWO-PHASE, INTERMITENT FLOW IN A HORIZONTAL PIPE ». PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2017. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=31013@1.
Texte intégralRésumé :
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
FUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
BOLSA NOTA 10
Escoamentos intermitentes gás-líquido são encontrados em diversas aplicações de engenharia, como em linhas de produção de petróleo e em sistemas de refrigeração de reatores nucleares. O conhecimento detalhado deste padrão de escoamento é indispensável para a construção de modelos matemáticos representativos deste fenômeno físico complexo. No presente trabalho, foi desenvolvido um estudo experimental com o objetivo de fornecer informações que possibilitem a melhoria dos modelos existentes para o escoamento bifásico intermitente em duto horizontal. A técnica de velocimetria por imagem de partículas estereoscópica (SPIV) de alta frequência foi empregada, em conjunto com a técnica de fluorescência induzida por laser (LIF), permitindo a obtenção de campos de velocidade na região do pistão de líquido, a jusante da bolha alongada, e na região do filme líquido, a montante da bolha. O arranjo experimental possibilitou a medição das três componentes do vetor velocidade do escoamento bifásico água-glicerina e ar na seção transversal de uma tubulação horizontal de 40mm de diâmetro interno. Os resultados obtidos, originais na literatura, mostraram a evolução detalhada das três componentes dos campos médios do vetor velocidade ao longo da passagem da bolha alongada durante o escoamento intermitente.
Gas-liquid intermittent flows can be found in many engineering applications, such as oil production lines and nuclear reactors cooling systems. The detailed knowledge of this flow pattern is necessary for the development of accurate mathematical models of this complex phenomenon. In this work, an experimental study was developed with the goal to provide data that could be used to improve the existing models for two-phase intermittent flow in horizontal pipes. The high-frequency stereoscopic particle image velocimetry (SPIV) technique was employed along with the laser induced fluorescence (LIF) technique, allowing the measurement of velocity fields in the liquid slug, downstream of the elongated bubble, and in the liquid film, upstream of the elongated bubble. The experimental arrangement allowed the measurement of the three components of the velocity vector in an intermittent two-phase water-glycerine and air flow, in a transversal sections of a 40mm internal diameter horizontal pipe. The results obtained revealed original detailed information on the evolution of the three components of the averaged velocity field associated with the passage of the elongated bubble characteristic of the intermittent flow.
30
Johansen, James Paul. « Full-scale two-phase flow measurements using optical probes on Athena II research vessel ». Thesis, University of Iowa, 2010. https://ir.uiowa.edu/etd/523.
Texte intégralRésumé :
Measurements of gas volume fraction, bubble velocity, chord length and bubble size distributions were performed in the research vessel Athena II operating in Saint Andrew Bay in the gulf coast near Panama City, FL. Double tipped sapphire optical local phase-detection probes were used to acquire indicator functions downstream of the breaking bow wave, behind the masker and at the stern. These indicator functions were also taken at different depths, distances from the hull, operating speeds and headings respect to the waves. The data processing includes the computation of velocity of individual bubbles and chord lengths, resulting in chord length distributions. These chord length distributions are used to obtain bubble size distributions using a novel procedure described in detail. Uncertainty analysis is performed for gas volume fraction, average bubble velocity and chord length. The results indicate that air entrainment increases with ship speed and sailing against the waves at all positions. The bow wave exhibits unsteady breaking that creates bubble clouds, which were characterized and identified by signal processing. At the stern a very strong dependence of bubble size with depth was found, with evidence that bubbles smaller than 500 micrometers are transported through the bottom of the hull and reach the transom. The roller present at the transom, the associated strong unsteadiness and bubble entrainment are well captured, as indicated by the stern results, showing the frothy nature of the upper layer.
31
Biswas, Souvik. « Direct numerical simulation and two-fluid modeling of multi-phase bubbly flows ». Link to electronic thesis, 2007. http://www.wpi.edu/Pubs/ETD/Available/etd-050307-224407/.
Texte intégralRésumé :
Dissertation (Ph.D.) -- Worcester Polytechnic Institute.Keywords: Multiphase flow; Two-fluid modeling; Direct numerical simulation; Two fluid modeling. Includes bibliographical references (leaves 116-119).
32
Kronbichler, Martin. « Numerical methods for the Navier-Stokes equations applied to turbulent flow and to multi-phase flow / ». Licentiate thesis, Uppsala : Uppsala University, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-110246.
Texte intégral
33
Kleinberg, Michael R. Miu Karen Nan. « Distributed multi-phase distribution power flow : modeling, solution algorithm, and simulation results / ». Philadelphia, Pa. : Drexel University, 2007. http://hdl.handle.net/1860/1307.
Texte intégral
34
Johansson, Mats. « Simulation of a multi phase flow in a rotating-lid driven cylinder ». Thesis, Umeå universitet, Institutionen för fysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-82177.
Texte intégralRésumé :
This report describes the development of a software for computing viscous incompressiblemultiphase ows. The software does this with solving the coupled non-linear Navier-Stokes(Fluid) and the Cahn-Hilliard (Phase-Field) equations using a Finite Element Method. Thereason for the development is to produce a simulation tool, which eventually is capable ofsimulating the ow of uids inside the OptusAir aeronator manufactured by the Sorubincompany. The solving software developed is built on the ParMetis, PETSc and OpenMPIframeworks. Our primary benchmark has been a geometry resembling the OptusAir product,a cylinder with a rotating bottom. We have made comparisons between simulation resultsand the theory of a free surface in a uniform rotating ow.This thesis shows that the shape of the interface between two uids coincides with theoryto some extent, while the approximate boundary conditions prevent it from coinciding fully.
35
Ghafouri, H. R. « Finite element modelling of multi-phase flow through deformable fractured porous media ». Thesis, Swansea University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637047.
Texte intégralRésumé :
Based on the theory of 'Double-Porosity', three-phase fluid flow in a fractured porous media has been formulated using continuity and equilibrium equations where displacement is also a primary unknown. Unlike previous models used for fractured media, the pressure of each fluid phase within the fracture network and porous rock has been considered to be coupled with the deformation of porous media. Also coupling between the fracture network and the porous rock is carried out using 'Transfer Function' or 'Leakage Term'. The derived equations are then discretised using 'Finite Element Method' where the displacements as well as pressure of fluids within matrix and fracture are primary unknowns. The resulting set of equations, is an implicit, fully coupled formulation which is capable of modelling three phase (Oil, Gas and Water) flow in a fractured reservoir where the deformation and consequent surface subsidence is of particular interest i.e. a case frequently encountered in petroleum engineering. In its extreme case, the presented formulation turns to the conventional one-phase models for heterogeneous porous media and by further simplification, the governing equations for ordinary single porosity models could be obtained. A computer code based on the mathematical model is developed and validated. Important aspects of the developed code, based on the double porosity theory, are presented together with several example problems. The model is also employed to solve a field scale example where the results are compared to those of ten other uncoupled models. As a genuine application of the present model, it is employed to solve the real field problem of the subsidence at the Ekofisk oil field in the Norwegian sector of the North Sea. The impact of various parameters of the model are verified by conducting sensitivity analyses. The results illustrate a significantly different behaviour for the case of a reservoir where the impact of coupling is also considered.
36
Kollmeier, Jost M. [Verfasser]. « Multi-Directional Phase-Contrast Flow MRI in Real Time / Jost M. Kollmeier ». Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2021. http://d-nb.info/1225936535/34.
Texte intégral
37
Shahmohamadi, Hamed. « Multi-phase thermal cavitation flow in rough conforming and partially conforming conjunctions ». Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/18460.
Texte intégralRésumé :
The main aim of this research was to investigate the mechanism of cavitation in conforming and partially conforming tribological conjunctions. The effect of cavitation on load carrying capacity and frictional performance of is also investigated. This is important with regards to fuel efficiency in internal combustion (IC) engines. Friction accounts for 15–20% of IC engine losses. The piston–cylinder system contributes to 40–50% of these, with the compression ring(s) being responsible for most of this. This is because the primary function of the ring is to seal the combustion chamber, thus small emerging gaps lead to increased friction. In fact, compression ring(s) expend 3–5% of engine input fuel energy. The share of frictional losses of engine bearings is approximately 20–25%. Traditionally, prediction of performance of tribological conjunctions has been studied using Reynolds equation. When the effect of cavitation is considered, various cavitation algorithms with associated boundary conditions for lubricant rupture and reformation are proposed. These include Elrod, and Elrod and Coyne algorithms, as well as boundary conditions such as Swift-Stieber, JFO and Prandtl-Hopkins. There are a number of assumptions embodied in these approaches, as well as the use of Reynolds equation itself. These approaches do not uphold the continuity of mass and momentum in multi-phase flow, in cavitation beyond the lubricant film rupture. A detailed methodology for multi-phase flow, comprising simultaneous solution of Navier-Stokes, energy and lubricant rheological state equations is developed.
38
He, Xin. « Robust preconditioning methods for algebraic problems, arising in multi-phase flow models ». Licentiate thesis, Uppsala universitet, Avdelningen för teknisk databehandling, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-151683.
Texte intégralRésumé :
The aim of the project is to construct, analyse and implement fast and reliable numerical solution methods to simulate multi-phase flow, modeled by a coupled system consisting of the time-dependent Cahn-Hilliard and incompressible Navier-Stokes equations with variable viscosity and variable density. This thesis mainly discusses the efficient solution methods for the latter equations aiming at constructing preconditioners, which are numerically and computationally efficient, and robust with respect to various problem, discretization and method parameters. In this work we start by considering the stationary Navier-Stokes problem with constant viscosity. The system matrix arising from the finite element discretization of the linearized Navier-Stokes problem is nonsymmetric of saddle point form, and solving systems with it is the inner kernel of the simulations of numerous physical processes, modeled by the Navier-Stokes equations. Aiming at reducing the simulation time, in this thesis we consider iterative solution methods with efficient preconditioners. When discretized with the finite element method, both the Cahn-Hilliard equations and the stationary Navier-Stokes equations with constant viscosity give raise to linear algebraic systems with nonsymmetric matrices of two-by-two block form. In Paper I we study both problems and apply a common general framework to construct a preconditioner, based on the matrix structure. As a part of the general framework, we use the so-called element-by-element Schur complement approximation. The implementation of this approximation is rather cheap. However, the numerical experiments, provided in the paper, show that the preconditioner is not fully robust with respect to the problem and discretization parameters, in this case the viscosity and the mesh size. On the other hand, for not very convection-dominated flows, i.e., when the viscosity is not very small, this approximation does not depend on the mesh size and works efficiently. Considering the stationary Navier-Stokes equations with constant viscosity, aiming at finding a preconditioner which is fully robust to the problem and discretization parameters, in Paper II we turn to the so-called augmented Lagrangian (AL) approach, where the linear system is transformed into an equivalent one and then the transformed system is iteratively solved with the AL type preconditioner. The analysis in Paper II focuses on two issues, (1) the influence of a scalar method parameter (a stabilization constant in the AL method) on the convergence rate of the preconditioned method and (2) the choice of a matrix parameter for the AL method, which involves an approximation of the inverse of the finite element mass matrix. In Paper III we consider the stationary Navier-Stokes problem with variable viscosity. We show that the known efficient preconditioning techniques in particular, those for the AL method, derived for constant viscosity, can be straightforwardly applicable also in this case. One often used technique to solve the incompressible Navier-Stokes problem with variable density is via operator splitting, i.e., decoupling of the solutions for density, velocity and pressure. The operator splitting technique introduces an additional error, namely the splitting error, which should be also considered, together with discretization errors in space and time. Insuring the accuracy of the splitting scheme usually induces additional constrains on the size of the time-step. Aiming at fast numerical simulations and using large time-steps may require to use higher order time-discretization methods. The latter issue and its impact on the preconditioned iterative solution methods for the arising linear systems are envisioned as possible directions for future research. When modeling multi-phase flows, the Navier-Stokes equations should be considered in their full complexity, namely, the time-dependence, variable viscosity and variable density formulation. Up to the knowledge of the author, there are not many studies considering all aspects simultaneously. Issues on this topic, in particular on the construction of efficient preconditioners of the arising matrices need to be further studied.
39
Siegel, John Mather Jr. « Magnetic resonance imaging of flow through a stenosis : accuracy of angiography and phase velocity measurements ». Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/17626.
Texte intégral
40
JUNIOR, ROBERTO DA FONSECA. « INSTANTANEOUS LIQUID VELOCITY FIELD MEASUREMENTS IN TWO-PHASE INTERMITTENT FLOW THROUGH HORIZONTAL AND INCLINED PIPES ». PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2009. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=15406@1.
Texte intégralRésumé :
No presente trabalho foi realizado um estudo experimental sobre
escoamento bifásico em regime intermitente através de tubos horizontais e de
pequena inclinação, com o objetivo de determinação dos campos de
velocidade instantâneos nas regiões a montante do nariz, a jusante da cauda
das bolhas de gás, assim como na região do filme de líquido sob as bolhas. Foi
implementada uma combinação de três técnicas ópticas não invasivas.
Velocimetria por Imagem de Partículas bi-dimensional (Particle Image
Velocimetry – PIV) foi utilizada para determinar os campos de velocidade
instantâneos nas regiões de interesse, enquanto luz de fundo pulsada e
sincronizada proveniente de uma matriz de LED’s vermelhos iluminava os
contornos das bolhas aumentando o contraste das interfaces líquido-gás
(Pulsed Shadow Technique – PST). Uma técnica baseada na fluorescência
induzida por laser foi utilizada (Laser Induced Fluorescence - LIF) para separar
a luz verde intensa proveniente do laser associado à técnica PIV. Os testes
foram conduzidos em seção transparente tendo água e ar como fluidos de
trabalho. Os resultados obtidos revelaram informações detalhadas sobre o
escoamento de líquido no escoamento intermitente. Foram produzidos também
resultados estatísticos de algumas variáveis globais do escoamento como, a
velocidade e os comprimentos das bolhas e pistões de líquido, além da
frequência de passagem desta estruturas do escoamento.instantaneous liquid velocity fields at the film, nose and tail regions of slugs in horizontal and inclined two phase flow. To this end, a combination of three nonintrusive optical techniques was employed. Two-dimensional particle image velocimetry (PIV) was used to measure the instantaneous liquid velocity field at a meridional plane of the horizontal pipe test section, while a synchronized pulsed back lighting, provided by a matrix of red LED s, illuminated the bubble contours thereby enhancing contrast of the interfaces (Pulsed Shadow Technique - PST). A laser-induced fluorescence technique (LIF) was employed to separate the strong reflections coming from the gas-liquid interfaces produced by the green PIV laser, The tests were conducted on a specially built transparent pipe test section, using air and water as the working fluids. The velocity fields were obtained for flow regimes where the slugs were lightly aerated. The velocity field results in the nose, tail and film regions revealed valuable detailed information that helped to better understand the physics of the flow, besides contributing to the formation of a data bank for supporting the development of two-phase, horizontal slug flow simulations. The work conducted also provided statistical information on the main global variables that characterize the flow, such as, speed and length of gas bubbles and liquid slugs, and the frequency of passage of these structures.
41
Silas, Kevin Alexander. « Phase Transform Time Delay Estimation to Counteract Spectral Haystacking Effects in Jet Exhaust Flow Measurements ». Thesis, Virginia Tech, 2021. http://hdl.handle.net/10919/104892.
Texte intégralRésumé :
This study determined a superior data processing technique for correlating an acoustic signal passing through a subsonic jet engine exhaust in order to estimate the traversal time of the signal. Thrust measurement is possible with enough time delay estimates across different portions of the exhaust. This preliminary study did not take the full array of data necessary to measure thrust, but did validate key aspects of the measurement process. The turbulent shear layers of the exhaust spectrally broaden the signal, creating the appearance of spectral "haystacks", making traditional correlation methods unworkable. An experiment was performed to evaluate the ability of a novel sound source to produce a signal from which a reliable and precise time delay estimate could be found. The test apparatus was installed on either side of a Honeywell TFE731-2 turbofan research engine exhaust cone, with the source and receivers placed near the jet exit plane. The signal was then directed across the jet exhaust. This flow environment is considered an extreme challenge for accurate acoustic signal propagation. A key contribution of this paper is the determination that the Phase Transform processor of the Generalized Cross-Correlation (GCC) method produces the most reliable time delay estimates, for the given signal and flow conditions. Several alternative time delay estimators and GCC processors were examined and evaluated on this data. A proposed explanation is provided for why this time delay estimation technique produces the most accurate results, as well as explanations for why the technique became less reliable as the flow environment became more challenging, with an observed 22% anomalous TDE selection rate for the N1Corr = 60% and N1Corr = 70% conditions combined, versus only 6% for the idle and N1Corr = 50% conditions combined. This paper also details the development and first use of a novel acoustic source that produces a two-tone narrowband signal emanating from a single point – the dual Hartmann generator.Master of Science
This study builds on a Computational Tomography (CT) technique that uses an acoustic signal and an array of receivers to measure the velocity and temperature of a gas flow field. In particular, the velocity and temperature field tested involves multiple turbulent and disruptive elements, requiring a loud and specifically designed signal. As such, a novel acoustic signal generator, the dual Hartmann generator, was designed that is both loud and produces a specific two-toned signal. The key contribution of the study was to process the data, comparing the sets of transmitted and received signals, in order to estimate the time delay amongst receiver pairs – a key input in the CT method. Traditional cross-correlation methods were inadequate, and multiple alternatives were evaluated. The Phase Transform (PHAT) technique showed the most promise, and an explanation is given for why this technique is most suitable for this type of signal.
42
Shimizu, Yuma. « Enhanced Particle Methods with Highly-Resolved Phase Boundaries for Incompressible Fluid Flow ». Kyoto University, 2019. http://hdl.handle.net/2433/244528.
Texte intégral
43
Hron, Pavel [Verfasser], et Peter [Akademischer Betreuer] Bastian. « Numerical Simulation of Multi-Phase Multi-Component Reactive Flow in Porous Media / Pavel Hron ; Betreuer : Peter Bastian ». Heidelberg : Universitätsbibliothek Heidelberg, 2015. http://d-nb.info/1180500148/34.
Texte intégral
44
Wang, Qiang. « A data fusion and visualisation platform for multi-phase flow by electrical tomography ». Thesis, University of Leeds, 2017. http://etheses.whiterose.ac.uk/18436/.
Texte intégralRésumé :
Electrical tomography, e.g. electrical resistance tomography (ERT) and electrical capacitance tomography (ECT), has been successfully applied to many industries for measuring and visualising multiphase flow. This research aims to investigate the data fusion and visualisation technologies with electrical tomography as the key data processing tools of a platform for multiphase flow characterisation. Gas-oil-water flow is a common flow in the gas and oil industries but still presents challenges in understanding its complex dynamics. This research systematically studied the data fusion and visualisation technologies using dual-modality electrical tomography (ERT-ECT). Based on a general framework, two data fusion methods, namely threshold and fuzzy logic with decision tree, were developed to quantify and qualify the flow. The experimental results illustrated the feasibility of the methods integrated with the framework to visualise and measure flows in six typical common flow regimes, including stratified, wavy stratified, slug, plug, annular, and bubble flow. In addition, the performance of ERT-ECT was also evaluated. A 3D visualisation approach, namely Bubble Mapping, was proposed to transform concentration distribution to individual bubbles. With a bubble-based lookup table and enhanced isosurface algorithms, the approach overcomes the limits of the conventional concentration tomograms in visualisation of bubbles with sharp boundaries between gas and liquid, providing sophisticated flow dynamic information. The experiments proved that Bubble Mapping is able to visualise typical flow regimes in different pipeline orientations. Two sensing methods were proposed, namely asymmetrical sensing and imaging (ASI) and regional imaging with limited measurement (RILM), to improve the precision of the velocity profile derived from the cross-correlation method by enhancing ERT sensing speed, which is particularly helpful for industrial flows that their disperse phase velocity is very high, e.g. 20 m/s of the gas phase. It is expected that the outcome of this study will significantly move electrical tomography for multiphase flow applications beyond its current challenges in both quantification and qualification.
45
Al-Hinai, Suleiman Mohammed. « Multi-phase fluid flow properties of fault rocks : implication for production simulation models ». Thesis, University of Leeds, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.581870.
Texte intégralRésumé :
It is becoming increasingly common practise to model the impact of faults on fluid flow within petroleum reservoirs by applying transmissibility multipliers, calculated from the single-phase permeability of fault rocks, to the grid-blocks adjacent to faults in produc- tion simulations. The multi-phase flow properties (e.g. relative permeability and capillary pressure) of fault rocks are not considered because special core analysis has never previ- ously been conducted on fault rock samples. The principle aim of this thesis is to fill this knowledge gap. Two distinct approaches have been adopted. First, a considerable num- ber of experiments have been conducted to measure the multi-phase flow properties of faults. The measurements represent different type of fault rocks: cataclastic fault rocks, and fault rocks in impure sandstone; significant amount of effort was needed to evaluate and design new experimental methods. Second, an attempt has also been made to numer- ically model the multi-phase flow behaviour of fault rocks; several numerical techniques (lattice Boltzmann method, pore scale network modelling) have been used. In addition, production simulation modelling has been conducted to investigate the implications of the results. The relative permeability measurements were made using a gas pulse-decay technique on samples whose water saturation was varied using vapour chambers. The measurements indicate that if the same cataclastic fault rocks were present in gas reservoirs from the southern Permian Basin they would have k,.g values of < 0.02. Such large reduction in gas effective permeability was also seen for tight gas sandstones and siltstones. However, the steady-state oil relative permeability measurements for a kaolin rich sample which represents an analogue to fault in impure sandstone was found to be higher then those for the cataclastic fault rocks. The samples studied show also different sensitivity to effective stress. The gas relative permeability measurements proved far more stress sensitive than the single phase permeability values. Pore scale network models have a strong capability in modelling the relative permeability and capillary pressure curves for such low permeability rocks. The predicted results by the model were in good agreement with the experimental data presented in this work. Similarly, lattice Boltzmann method found to have a strong capability for modelling the multi-phase fluid flow in a variety of situation.
46
Marashdeh, Qussai. « Validation of Electrical Capacitance Volume Tomography with Applications to Multi-Phase Flow Systems ». The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1244652779.
Texte intégral
47
Hansen, Laura C. « Phase Locked Flow Measurements of Steady and Unsteady Vortex Generator Jets in a Separating Boundary Layer ». Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd763.pdf.
Texte intégral
48
Bonuccelli, Courtney Leigh Herring. « A theoretical and experimental investigation of multi-phase interactions in pure and multicomponent droplet evaporation ». Online access for everyone, 2006. http://www.dissertations.wsu.edu/Thesis/Fall2006/C_Bonuccelli_012907.pdf.
Texte intégral
49
Lu, Yong. « Investigation of the particle dynamics of a multi-component solid phase in a dilute phase pneumatic conveying system ». Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/3894.
Texte intégralRésumé :
In order to mitigate the risk of global warming by reducing CO2 emissions, the co-firing technique, burning pulverized coal and granular biomass together in conventional pulverised fuel power station boilers, has been advocated to generate “greener” electricity to satisfy energy demand while continuing to utilize existing rich coal resources. A major problem is controllably distributing fuel mixtures of pulverized coal and granular biomass in a common pipeline, thus saving much investment. This is still under development in many co-firing studies. This research into particle dynamics in pipe flow was undertaken in order to address the problem of controllable distribution in co-firing techniques and gain an improved understanding of pneumatic conveying mechanisms. The objectives of this research were, firstly, to numerically evaluate the influence of various factors on the behaviour of particles of the different materials in a horizontal pipe gas-solid flow, secondly, to develop an extended technique of Laser Doppler Anemometry in order to determine cross-sectional characteristics of the solid phase flow in the horizontal and vertical legs of a pneumatic conveying system, and, thirdly, to develop a novel imaging system for visualizing particle trajectories by using a high definition camcorder on a cross-section illuminated by a white halogen light sheet. Finally, a comparison was made of cross-sectional flow characteristics established by experiments and those simulated by using a commercial Computational Fluid Dynamics code (Fluent) and the coupling calculations of Fluent & EDEM (a commercial code of Discrete Element Method) respectively. Particle dynamic behaviour of the solid phase in a dilute horizontal pipe flow was investigated numerically by using the Discrete Phase Model (DPM) in Fluent 6.2.16. The numerical results indicate that the Saffman force plays an important role in re-suspending particles at the lower pipe boundary and that three critical parameters of the critical air: conveying velocity, the critical particle size and the critical pipe roughness, exist in pneumatic conveying systems. The Stokes number can be used as a similarity criterion to classify the dimensionless mean particle velocity of the different materials in the fully developed region. An extended Laser Doppler Anemometry (LDA) technique has been developed to measure the distributions of particle velocities and particle number over a whole pipe cross section in a dilute pneumatic conveying system. The first extension concentrates on a transform matrix for predicting the refracted laser beams’ crossing point in a pipe according to the shift coordinate of the 3D computer-controlled traverse system on which the probes of the LDA system were mounted. Another part focussed on the proper sampling rate of LDA for measurements on the gas-solid pipe flow with polydispersing particles. A suitable LDA sampling rate should ensure that enough data is recorded in the measurement interval to precisely calculate the particle mean velocity or other statistical values at every sample point. The present study explores the methodology as well as fundamentals of measurements of the local instantaneous density of particles as a primary standard using a laser facility. The extended LDA technique has also been applied to quantitatively investigate particle dynamic behaviour in the horizontal and vertical pipes of a dilute pneumatic conveying system. Three kinds of glass beads were selected to simulate the pulverized coal and biomass pellets transported in a dilute pneumatic conveying system. Detailed information on the cross-sectional spatial distributions of the axial particle velocity and particle number rate is reported. In the horizontal pipe section, experimental data on a series of cross-sections clearly illustrate two uniform fluid patterns of solid phase: an annular structure describing the cross-sectional distribution of the axial particle velocity and a stratified configuration describing particle number rate. In the vertical pipe downstream of an elbow R/D=1.3, a horseshoe-shaped feature, which shows that the axial particle velocity is highest in wall regions of the pipe on the outside of the bend for all three types of glass beads on the section 0D close to the elbow outlet. The developments of cross-sectional distributions of particle number rate indicate that the horseshoe-shaped feature of particle flow pattern is rapidly dispersed for particles with high inertia. A video & image processing system has been built using a high definition camcorder and a light sheet from a source consisting of a halogen lamp. A set of video and image processing algorithms has been developed to extract particle information from each frame in a video. The experimental results suggest that the gas-solid flow in a dilute pneumatic conveying system is always heterogeneous and unsteady. The parameter of particle mass mean size is superior to particle number mean size for statistically describing the unsteady properties of gas-solid pipe flow. It is also demonstrated that the local data of particle number rate or concentration are represented by a stratified structure of the flow pattern over a horizontal pipe cross-section. Finally, comparisons of numerically predicated flow patterns and experimental ones show that there is reasonable agreement at pipe cross-sections located at horizontal positions less than half the product of particle mean velocity and mean free fall time in the pipe from the particle inlet. Further away from the inlet, the numerical results show flow patterns which are increasingly divergent from the experimental results along the pipe in the direction of flow. This discrepancy indicates that particles’ spatial distribution in the pipe is not accurately predicted by the Discrete Phase Model or Fluent coupled with EDEM.
50
Xie, Tao. « Hydrodynamic characteristics of gas/liquid/fiber three-phase flows based on objective and minimally-intrusive pressure fluctuation measurements ». Diss., Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-09192004-033703/unrestricted/xie%5Ftao%5F200412%5Fphd.pdf.
Texte intégralRésumé :
Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2005.D. William Tedder, Committee Member ; Minami Yoda, Committee Member ; Tom McDonough, Committee Member ; Andrei G. Fedorov, Committee Member ; S. Mostafa Ghiaasiaan, Committee Chair ; Seppo Karrila, Committee Member. Includes bibliographical references.