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Hydrodynamic characteristics of gas/liquid/fiber three-phase flows based on objective and minimally-intrusive pressure fluctuation measurementsXie, Tao 27 September 2004 (has links)
Flow regime identification in industrial systems that rely on complex multi-phase flows is crucial for their safety, control, diagnostics, and operation. The objective of this investigation was to develop and demonstrate objective and minimally-intrusive flow regime classification methods for gas/water/paper pulp three-phase slurries, based on artificial neural network-assisted recognition of patterns in the statistical characteristics of pressure fluctuations.
Experiments were performed in an instrumented three-phase bubble column featuring vertical, upward flow. The hydrodynamics of low consistency (LC) gas-liquid-fiber mixtures, over a wide range of superficial phase velocities, were investigated. Flow regimes were identified, gas holdup (void fraction) was measured, and near-wall pressure fluctuations were recorded using high-sensitivity pressure sensors. Artificial neural networks of various configurations were designed, trained and tested for the classification of flow regimes based on the recorded pressure fluctuation statistics. The feasibility of flow regime identification based on statistical properties of signals recorded by a single sensor was thereby demonstrated. The transportability of the developed method, whereby an artificial neural network trained and tested with a set of data is manipulated and used for the characterization of an unseen and different but plausibly similar data set, was also examined. An artificial neural network-based method was developed that used the power spectral characteristics of the normal pressure fluctuations as input, and its transportability between separate but in principle similar sensors was successfully demonstrated. An artificial neural network-based method was furthermore developed that enhances the transportability of the aforementioned artificial neural networks that were trained for flow pattern recognition. While a redundant system with multiple sensors is an obvious target application, such robustness of algorithms that provides transportability will also contribute to performance with a single sensor, shielding effects of calibration changes or sensor replacements.
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Simulador de escoamento multif?sico em po?os de petr?leo (SEMPP)Nascimento, Julio Cesar Santos 07 February 2013 (has links)
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Previous issue date: 2013-02-07 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The multiphase flow occurrence in the oil and gas industry is common throughout fluid
path, production, transportation and refining. The multiphase flow is defined as flow
simultaneously composed of two or more phases with different properties and
immiscible. An important computational tool for the design, planning and optimization
production systems is multiphase flow simulation in pipelines and porous media,
usually made by multiphase flow commercial simulators. The main purpose of the
multiphase flow simulators is predicting pressure and temperature at any point at the
production system. This work proposes the development of a multiphase flow simulator
able to predict the dynamic pressure and temperature gradient in vertical, directional
and horizontal wells. The prediction of pressure and temperature profiles was made by
numerical integration using marching algorithm with empirical correlations and
mechanistic model to predict pressure gradient. The development of this tool involved
set of routines implemented through software programming Embarcadero C++
Builder? 2010 version, which allowed the creation of executable file compatible with
Microsoft Windows? operating systems. The simulator validation was conduct by
computational experiments and comparison the results with the PIPESIM?. In general,
the developed simulator achieved excellent results compared with those obtained by
PIPESIM and can be used as a tool to assist production systems development / Na ind?stria do petr?leo a ocorr?ncia de escoamento multif?sico ? comum em todo o
percurso dos fluidos, durante a produ??o, transporte e refino. O escoamento multif?sico
? definido como o escoamento simult?neo composto por duas ou mais fases com
propriedades diferentes e imisc?veis. Uma importante ferramenta computacional para o
dimensionamento, planejamento e otimiza??o de sistemas de produ??o ? a simula??o de
escoamento multif?sico em dutos e meios porosos, normalmente, feita por simuladores
comerciais. O objetivo b?sico desses simuladores ? prever a press?o e temperatura em
diferentes pontos do sistema de produ??o. Este trabalho prop?e o desenvolvimento de
um simulador de escoamento multif?sico em po?os verticais, direcionais e horizontais,
capaz de determinar o gradiente din?mico de press?o e temperatura. A determina??o dos
perfis de press?o e de temperatura foi feita por meio de integra??o num?rica utilizando o
algoritmo de marcha com correla??es emp?ricas e modelo mecanicista para determinar o
gradiente de press?o. O desenvolvimento do simulador envolveu o conjunto de rotinas
implementadas atrav?s do software de programa??o Embarcadero C++ Builder? vers?o
2010, que permitiu a cria??o de arquivo execut?vel compat?vel com os sistemas
operacionais da Microsoft Windows?. A valida??o do simulador foi conduzida por
experimentos computacionais e compara??o dos resultados com o simulador de uso
comercial PIPESIM?. De modo geral, o simulador desenvolvido alcan?ou excelentes
resultados quando comparado com os obtidos pelo PIPESIM, podendo ser utilizado
como ferramenta para auxiliar no desenvolvimento de sistemas de produ??o
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Multiphase fluid hammer: modeling, experiments and simulationsLema Rodríguez, Marcos 10 October 2013 (has links)
This thesis deals with the experimental and numerical analysis of the water hammer phenomenon generated by the discharge of a pressurized liquid into a pipeline kept under vacuum conditions. This flow configuration induces several multiphase phenomena such as cavitation and gas desorption that cannot be ignored in the water hammer behavior.<p><p>The motivation of this research work comes from the liquid propulsion systems used in spacecrafts, which can undergo fluid hammer effects threatening the system integrity. Fluid hammer can be particularly adverse during the priming phase, which involves the fast opening of an isolation valve to fill the system with liquid propellant. Due to the initial vacuum conditions in the pipeline system, the water hammer taking place during priming may involve multiphase phenomena, such as cavitation and desorption of a non-<p>condensable gas, which may affect the pressure surges produced in the lines. Even though this flow behavior is known, only few studies model the spacecraft hardware configuration, and a proper characterization of the two-phase flow is still missing. The creation of a reliable database and the physical understanding of the water hammer behavior in propulsion systems are mandatory to improve the physical models implemented in the numerical codes used to simulate this flow configuration.<p><p>For that purpose, an experimental facility modeling a spacecraft propulsion system has been designed, in which the physical phenomena taking place during priming are generated under controlled conditions in the laboratory using inert fluids. An extended experimental campaign was performed on the installation, aiming at analyzing the effect of various working parameters on the fluid hammer behavior, such as the initial pressure in the line, liquid saturation with the pressurant gas, liquid properties and pipe configuration. The influence of the desorbed gas during water hammer occurrence is found to have a great importance on the whole process, due to the added compressibility and lower speed of sound by an increasing amount of non-condensable gas in the liquid + gas mixture. This results in lower pressure levels and faster pressure peaks attenuation, compared to fluids without desorption. The two-phase flow was characterized by means of flow visualization of the liquid front at the location where the fluid hammer is generated. The front arrival was found to be preceded by a foamy mixture of liquid, vapor and non-condensable gas, and the pressure wave reflected at the tank may induce the liquid column separation at the bottom end. While column separation takes place, the successive pressure peaks are generated by the impact of the column back against the bottom end.<p><p>The resulting experimental database is then confronted to the predictions of the 1D numerical code EcosimPro/ESPSS used to assess the propulsion system designs. Simulations are performed with the flow configuration described before, modeling the experimental facility. The comparison of the numerical results against the experimental data shows that aspects such as speed of sound computation with a dissolved gas and friction modeling need to be improved. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished
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Effect of Wall Shear Stress on Corrosion Inhibitor Film PerformanceCanto Maya, Christian M. January 2015 (has links)
No description available.
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Experimental and computational study of multiphase flow in dry powder inhalersFouda, Yahia M. January 2014 (has links)
Dry Powder Inhalers (DPIs) have great potential in pulmonary drug delivery; the granular powder, used as active ingredient in DPIs, is ozone friendly and the operation of DPIs ensures coordination between dose release and patient inhalation. However, the powder fluidisation mechanisms are poorly understood which leads to low efficiency of DPIs with 10-35 % of the dose reaching the site of action. The main aim of this thesis is to study the hydrodynamics of powder fluidisation in DPIs, using experimental and computational approaches. An experimental test rig was developed to replicate the process of transient powder fluidisation in an impinging air jet configuration. The powder fluidisation chamber was scaled up resulting in a two dimensional particle flow prototype, which encloses 3.85 mm glass beads. Using optical image processing techniques, individual particles were detected and tracked throughout the experimental time and domain. By varying the air flow rate to the test section, two particle fluidisation regimes were studied. In the first fluidisation regime, the particle bed was fully fluidised in less than 0.25 s due to the strong air jet. Particle velocity vectors showed strong convective flow with no evidence of diffusive motion triggered by inter-particle collisions. In the second fluidisation regime, the particle flow experienced two stages. The first stage showed strong convective flow similar to the first fluidisation regime, while the second stage showed more complex particle flow with collisional and convective flow taking place on the same time and length scales. The continuum Two Fluid Model (TFM) was used to solve the governing equations of the coupled granular and gas phases for the same experimental conditions. Sub-models for particle-gas and particle-particle interactions were used to complete the model description. Inter-particle interactions were resolved using models based on the kinetic theory of granular flow for the rapid flow regime and models based on soil mechanics for the frictional regime. Numerical predictions of the first fluidisation regime showed that the model should incorporate particle-wall friction and minimise diffusion, simultaneously. Ignoring friction resulted in fluidisation timing mismatch, while increasing the diffusion resulted in homogenous particle fluidisation in contrast to the aggregative convective fluidisation noticed in the experiments. Numerical predictions of the second fluidisation regime agreed well with the experiments for the convection dominated first stage of flow up to 0.3 s. However, later stages of complex particle flow showed qualitative discrepancies between the experimental and the computational approaches suggesting that current continuum granular models need further development. The findings of the present thesis have contributed towards better understanding of the mechanics of particle fluidisation and dense multiphase flow in DPI in particular, and particle bed fluidisation using impinging air jet in general. The use of TFM for predicting high speed convective granular flows, such as those in DPIs, is promising. Further studies are needed to investigate the form of particle-particle interactions within continuum granular flow models.
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Multiphase flow measurement using gamma-based techniquesArubi, Isaac Marcus Tesi January 2011 (has links)
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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Modelling of the motion of a mixture of particles and a Newtonian fluidWilms, Josefine Maryna 03 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: See full text for abstract / AFRIKAANSE OPSOMMING: Sien volteks vir opsomming
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On some problems in the simulation of flow and transport through porous mediaThomas, Sunil George 20 October 2009 (has links)
The dynamic solution of multiphase flow through porous media is of
special interest to several fields of science and engineering, such as petroleum,
geology and geophysics, bio-medical, civil and environmental, chemical engineering
and many other disciplines. A natural application is the modeling of
the flow of two immiscible fluids (phases) in a reservoir. Others, that are broadly
based and considered in this work include the hydrodynamic dispersion (as in
reactive transport) of a solute or tracer chemical through a fluid phase. Reservoir
properties like permeability and porosity greatly influence the flow of these
phases. Often, these vary across several orders of magnitude and can be discontinuous
functions. Furthermore, they are generally not known to a desired level
of accuracy or detail and special inverse problems need to be solved in order
to obtain their estimates. Based on the physics dominating a given sub-region
of the porous medium, numerical solutions to such flow problems may require
different discretization schemes or different governing equations in adjacent regions.
The need to couple solutions to such schemes gives rise to challenging
domain decomposition problems. Finally, on an application level, present day
environment concerns have resulted in a widespread increase in CO₂capture and
storage experiments across the globe. This presents a huge modeling challenge
for the future. This research work is divided into sections that aim to study various
inter-connected problems that are of significance in sub-surface porous media
applications. The first section studies an application of mortar (as well as nonmortar,
i.e., enhanced velocity) mixed finite element methods (MMFEM and
EV-MFEM) to problems in porous media flow. The mortar spaces are first
used to develop a multiscale approach for parabolic problems in porous media
applications. The implementation of the mortar mixed method is presented for
two-phase immiscible flow and some a priori error estimates are then derived
for the case of slightly compressible single-phase Darcy flow. Following this,
the problem of modeling flow coupled to reactive transport is studied. Applications
of such problems include modeling bio-remediation of oil spills and other
subsurface hazardous wastes, angiogenesis in the transition of tumors from a
dormant to a malignant state, contaminant transport in groundwater flow and
acid injection around well bores to increase the permeability of the surrounding
rock. Several numerical results are presented that demonstrate the efficiency
of the method when compared to traditional approaches. The section following
this examines (non-mortar) enhanced velocity finite element methods for solving
multiphase flow coupled to species transport on non-matching multiblock grids.
The results from this section indicate that this is the recommended method of
choice for such problems.
Next, a mortar finite element method is formulated and implemented
that extends the scope of the classical mortar mixed finite element method
developed by Arbogast et al [12] for elliptic problems and Girault et al [62] for
coupling different numerical discretization schemes. Some significant areas of
application include the coupling of pore-scale network models with the classical
continuum models for steady single-phase Darcy flow as well as the coupling
of different numerical methods such as discontinuous Galerkin and mixed finite
element methods in different sub-domains for the case of single phase flow [21,
109]. These hold promise for applications where a high level of detail and
accuracy is desired in one part of the domain (often associated with very small
length scales as in pore-scale network models) and a much lower level of detail at other parts of the domain (at much larger length scales). Examples include
modeling of the flow around well bores or through faulted reservoirs.
The next section presents a parallel stochastic approximation method
[68, 76] applied to inverse modeling and gives several promising results that
address the problem of uncertainty associated with the parameters governing
multiphase flow partial differential equations. For example, medium properties
such as absolute permeability and porosity greatly influence the flow behavior,
but are rarely known to even a reasonable level of accuracy and are very often
upscaled to large areas or volumes based on seismic measurements at discrete
points. The results in this section show that by using a few measurements of
the primary unknowns in multiphase flow such as fluid pressures and concentrations
as well as well-log data, one can define an objective function of the
medium properties to be determined, which is then minimized to determine the
properties using (as in this case) a stochastic analog of Newton’s method. The
last section is devoted to a significant and current application area. It presents a
parallel and efficient iteratively coupled implicit pressure, explicit concentration
formulation (IMPEC) [52–54] for non-isothermal compositional flow problems.
The goal is to perform predictive modeling simulations for CO₂sequestration
experiments.
While the sections presented in this work cover a broad range of topics
they are actually tied to each other and serve to achieve the unifying, ultimate
goal of developing a complete and robust reservoir simulator. The major results
of this work, particularly in the application of MMFEM and EV-MFEM
to multiphysics couplings of multiphase flow and transport as well as in the
modeling of EOS non-isothermal compositional flow applied to CO₂sequestration,
suggest that multiblock/multimodel methods applied in a robust parallel
computational framework is invaluable when attempting to solve problems as
described in Chapter 7. As an example, one may consider a closed loop control
system for managing oil production or CO₂sequestration experiments in huge
formations (the “instrumented oil field”). Most of the computationally costly activity occurs around a few wells. Thus one has to be able to seamlessly connect
the above components while running many forward simulations on parallel
clusters in a multiblock and multimodel setting where most domains employ an
isothermal single-phase flow model except a few around well bores that employ,
say, a non-isothermal compositional model. Simultaneously, cheap and efficient
stochastic methods as in Chapter 8, may be used to generate history matches of
well and/or sensor-measured solution data, to arrive at better estimates of the
medium properties on the fly. This is obviously beyond the scope of the current
work but represents the over-arching goal of this research. / text
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Experimental study of turbulent flow with dispersed rod-like particles through optical measurementsAbbasi Hoseini, Afshin January 2014 (has links)
The knowledge of the behavior of non-spherical particles suspended in turbulent flows covers a wide range of applications in engineering and science. Dispersed two-phase flows and turbulence are the most challenging subjects in engineering, and when combined it gives rise to more complexities as the result of the inherent stochastic nature of the turbulence of the carrier-phase together with the random distribution of the dispersed phase. Moreover, for anisotropic particles the coupling between the translation and rotation of particle increases the complication. Because of the practical importance of prolate particleladen turbulent flows, the plenty of numerical and experimental works have been conducted to study such suspensions. Numerical approaches have given valuable insight of turbulent suspension flows, although the computation has been only carried out at the macro scale and models, not including flow distortion around the particle, comprise the detail of the flow in the order of a particle size. In addition, the model of the forces imposed on the particle by the fluid and mass point treatment are strictly valid for infinitely small particle having size less than all scales of the fluid turbulence. Fully resolved solution at the scale of the dispersed phase in turbulent flows for high Reynolds number has been recently performed but is still a challenge. On the other hand, the presence of particle as the dispersed phase makes experimental measurements much more complicated than those with single phase as a result of particles interference. The area of considerable difficulty with this type of experiments is the measurement of the fluid-phase velocity remarkably close to the particle surface. Generally, experimental researches have been concentrated on measuring the mean velocity and Reynolds stresses of the carrier-phase, and the mean velocity, fluctuations, orientation and accumulation of the non-spherical particles. Higher-order quantities, including Lagrangian particle velocity correlations, the carrier-phase turbulence modulation, and two-particle and particlefluid velocity correlations are also of interest. It has been found that the rotational and translational movements of the fibershaped particle depend on the nature of carrier-phase field and fiber characteristics such as aspect ratio, fiber Stokes number, fiber Reynolds number, and the ratio of fiber to flow length scale. With the development of PIV (Particle Image Velocimetry) and PTV (Particle Tracking Velocimetry) techniques, it has been appeared that combined PIV/PTV will be the best available choice for the experimental study of dispersed two-phase flows. The purpose of combined PIV/PTV measurement of two-phase systems is simultaneous measurements of fluid and suspended objects, where the PIV measurement of the fluid phase are combined with PTV measurement of the dispersed phase. The objective of this doctoral thesis is to study the behavior of rod-like particles suspended in wall-bounded turbulent flow through simultaneous PIV/PTV measurements of the velocity of the flow field and particle motion. As a representative of rod-like particles, I have employed cellulose acetate fibers with the length to diameter ratio (aspect ratio) larger than one. Here, It has been considered only dilute suspensions with no flocculation; thus fiber-fiber interaction is negligible. The measurements have been conducted within the parallel planes (2D view) illuminated by laser in the streamwise direction in thin film suspension flowing on the water table setup at Linné FLOW Centre, KTH Mechanics Lab. It is shown that this setup is a well-behaved experimental model of half channel flows often used in Direct Numerical Simulation (DNS) investigations. Therefore, the experimental results are comparable to their DNS counterpart where it is convenient. A single camera PIV technique has been used to measure flowing suspension. Therefore, it has been needed to preprocess images using a spatial median filter to separate images of two phases, tracer particles as representative of fluid and fibers suspended. The well-known PIV processing algorithms have been applied to the phase of fluid. I have also introduced a novel algorithm to recognize and match fibers in consecutive images to track fibers and estimate their velocity. It is not feasible to study all relevant aspects of particle-laden turbulent flows in a single study. In this study, I present the statistics of the rotational and translational motion of fiber-like particles and the surrounding fluid velocity. To the author’s knowledge, remarkably little experimental work has been published to date on simultaneous measurement of fiber motion and turbulence field in a turbulent fiber suspension flow to reveal dynamics of fibers in this regime. Therefore, the results of this work will be profitable in better understanding of such multiphase flows. The statistical analysis of the translational motion of fibers shows that the size of fiber is a significant factor for the dynamical behavior of the fiber near the wall. It has been observed that, in the region near the wall, the probability of presence of the long fibers is high in both the high-speed and low-speed streaks of flow, and the mean velocity of fibers almost conforms to the mean velocity of flow; whereas the short fibers are mostly present in the low-speed areas, and the fiber mean velocity obey the dominant flow velocity in these areas. In the far-wall regions, the translation of fibers is practically unaffected by the aspect ratio, whereas it depends crucially on the wall-normal distance. Moreover, it was found that in the case of long fibers near the wall, the low speed fibers mostly are orientated in streamwise direction. On the other hand, there is no preferential orientation for fast long fibers. Although wall-normal velocities were not measured in this study, it is hypothesized that this behavior is a result of fibers being affected by the sweep and ejection events known to occur in wall-bounded turbulent flow. The fast fibers are in sweep environment and comes from the upper layer. The low speed fibers are into ejection areas in the vicinity of the wall, and the wall has a stabilizing effect on them. The short fibers are still oriented mostly in streamwise direction for a certain range of low velocity. Furthermore, since a considerable change of the fiber behavior is observed in a certain ratio of the fiber length to the fiber distance from the solid wall, it is supposed that this ratio is also a prominent parameter for the behavior of fiber near the wall. The results presented are in terms of viscous wall units wherever are denoted by superscript “+”.
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Microfluidic cells as a model 2D granular materialFantinel, Paolo 25 January 2017 (has links)
No description available.
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