A multiphase compressible model for the simulation of multiphase flows
International Nuclear Information System (INIS)
Caltagirone, J.P.; Vincent, St.; Caruyer, C.
2011-01-01
A compressible model able to manage incompressible two-phase flows as well as compressible motions is proposed. After a presentation of the multiphase compressible concept, the new model and related numerical methods are detailed on fixed structured grids. The presented model is a 1-fluid model with a reformulated mass conservation equation which takes into account the effects of compressibility. The coupling between pressure and flow velocity is ensured by introducing mass conservation terms in the momentum and energy equations. The numerical model is then validated with four test cases involving the compression of an air bubble by water, the liquid injection in a closed cavity filled with air, a bubble subjected to an ultrasound field and finally the oscillations of a deformed air bubble in melted steel. The numerical results are compared with analytical results and convergence orders in space are provided. (authors)
Modeling compressible multiphase flows with dispersed particles in both dense and dilute regimes
McGrath, T.; St. Clair, J.; Balachandar, S.
2017-06-01
Many important explosives and energetics applications involve multiphase formulations employing dispersed particles. While considerable progress has been made toward developing mathematical models and computational methodologies for these flows, significant challenges remain. In this work, we apply a mathematical model for compressible multiphase flows with dispersed particles to existing shock and explosive dispersal problems from the literature. The model is cast in an Eulerian framework, treats all phases as compressible, is hyperbolic, and satisfies the second law of thermodynamics. It directly applies the continuous-phase pressure gradient as a forcing function for particle acceleration and thereby retains relaxed characteristics for the dispersed particle phase that remove the constituent material sound velocity from the eigenvalues. This is consistent with the expected characteristics of dispersed particle phases and can significantly improve the stable time-step size for explicit methods. The model is applied to test cases involving the shock and explosive dispersal of solid particles and compared to data from the literature. Computed results compare well with experimental measurements, providing confidence in the model and computational methods applied.
International Nuclear Information System (INIS)
Petitpas, Fabien; Franquet, Erwin; Saurel, Richard; Le Metayer, Olivier
2007-01-01
The relaxation-projection method developed in Saurel et al. [R. Saurel, E. Franquet, E. Daniel, O. Le Metayer, A relaxation-projection method for compressible flows. Part I: The numerical equation of state for the Euler equations, J. Comput. Phys. (2007) 822-845] is extended to the non-conservative hyperbolic multiphase flow model of Kapila et al. [A.K. Kapila, Menikoff, J.B. Bdzil, S.F. Son, D.S. Stewart, Two-phase modeling of deflagration to detonation transition in granular materials: reduced equations, Physics of Fluids 13(10) (2001) 3002-3024]. This model has the ability to treat multi-temperatures mixtures evolving with a single pressure and velocity and is particularly interesting for the computation of interface problems with compressible materials as well as wave propagation in heterogeneous mixtures. The non-conservative character of this model poses however computational challenges in the presence of shocks. The first issue is related to the Riemann problem resolution that necessitates shock jump conditions. Thanks to the Rankine-Hugoniot relations proposed and validated in Saurel et al. [R. Saurel, O. Le Metayer, J. Massoni, S. Gavrilyuk, Shock jump conditions for multiphase mixtures with stiff mechanical relaxation, Shock Waves 16 (3) (2007) 209-232] exact and approximate 2-shocks Riemann solvers are derived. However, the Riemann solver is only a part of a numerical scheme and non-conservative variables pose extra difficulties for the projection or cell average of the solution. It is shown that conventional Godunov schemes are unable to converge to the exact solution for strong multiphase shocks. This is due to the incorrect partition of the energies or entropies in the cell averaged mixture. To circumvent this difficulty a specific Lagrangian scheme is developed. The correct partition of the energies is achieved by using an artificial heat exchange in the shock layer. With the help of an asymptotic analysis this heat exchange takes a similar form as
Petitpas, Fabien; Franquet, Erwin; Saurel, Richard; Le Metayer, Olivier
2007-08-01
The relaxation-projection method developed in Saurel et al. [R. Saurel, E. Franquet, E. Daniel, O. Le Metayer, A relaxation-projection method for compressible flows. Part I: The numerical equation of state for the Euler equations, J. Comput. Phys. (2007) 822-845] is extended to the non-conservative hyperbolic multiphase flow model of Kapila et al. [A.K. Kapila, Menikoff, J.B. Bdzil, S.F. Son, D.S. Stewart, Two-phase modeling of deflagration to detonation transition in granular materials: reduced equations, Physics of Fluids 13(10) (2001) 3002-3024]. This model has the ability to treat multi-temperatures mixtures evolving with a single pressure and velocity and is particularly interesting for the computation of interface problems with compressible materials as well as wave propagation in heterogeneous mixtures. The non-conservative character of this model poses however computational challenges in the presence of shocks. The first issue is related to the Riemann problem resolution that necessitates shock jump conditions. Thanks to the Rankine-Hugoniot relations proposed and validated in Saurel et al. [R. Saurel, O. Le Metayer, J. Massoni, S. Gavrilyuk, Shock jump conditions for multiphase mixtures with stiff mechanical relaxation, Shock Waves 16 (3) (2007) 209-232] exact and approximate 2-shocks Riemann solvers are derived. However, the Riemann solver is only a part of a numerical scheme and non-conservative variables pose extra difficulties for the projection or cell average of the solution. It is shown that conventional Godunov schemes are unable to converge to the exact solution for strong multiphase shocks. This is due to the incorrect partition of the energies or entropies in the cell averaged mixture. To circumvent this difficulty a specific Lagrangian scheme is developed. The correct partition of the energies is achieved by using an artificial heat exchange in the shock layer. With the help of an asymptotic analysis this heat exchange takes a similar form as
International Nuclear Information System (INIS)
Chang, Chih-Hao; Liou, Meng-Sing
2007-01-01
In this paper, we propose a new approach to compute compressible multifluid equations. Firstly, a single-pressure compressible multifluid model based on the stratified flow model is proposed. The stratified flow model, which defines different fluids in separated regions, is shown to be amenable to the finite volume method. We can apply the conservation law to each subregion and obtain a set of balance equations. Secondly, the AUSM + scheme, which is originally designed for the compressible gas flow, is extended to solve compressible liquid flows. By introducing additional dissipation terms into the numerical flux, the new scheme, called AUSM + -up, can be applied to both liquid and gas flows. Thirdly, the contribution to the numerical flux due to interactions between different phases is taken into account and solved by the exact Riemann solver. We will show that the proposed approach yields an accurate and robust method for computing compressible multiphase flows involving discontinuities, such as shock waves and fluid interfaces. Several one-dimensional test problems are used to demonstrate the capability of our method, including the Ransom's water faucet problem and the air-water shock tube problem. Finally, several two dimensional problems will show the capability to capture enormous details and complicated wave patterns in flows having large disparities in the fluid density and velocities, such as interactions between water shock wave and air bubble, between air shock wave and water column(s), and underwater explosion
Energy Technology Data Exchange (ETDEWEB)
R. A. Berry; R. Saurel; F. Petitpas; E. Daniel; O. Le Metayer; S. Gavrilyuk; N. Dovetta
2008-10-01
In nuclear reactor safety and optimization there are key issues that rely on in-depth understanding of basic two-phase flow phenomena with heat and mass transfer. Within the context of multiphase flows, two bubble-dynamic phenomena – boiling (heterogeneous) and flashing or cavitation (homogeneous boiling), with bubble collapse, are technologically very important to nuclear reactor systems. The main difference between boiling and flashing is that bubble growth (and collapse) in boiling is inhibited by limitations on the heat transfer at the interface, whereas bubble growth (and collapse) in flashing is limited primarily by inertial effects in the surrounding liquid. The flashing process tends to be far more explosive (and implosive), and is more violent and damaging (at least in the near term) than the bubble dynamics of boiling. However, other problematic phenomena, such as crud deposition, appear to be intimately connecting with the boiling process. In reality, these two processes share many details.
Dynamic relaxation processes in compressible multiphase flows. Application to evaporation phenomena
Directory of Open Access Journals (Sweden)
Le Métayer O.
2013-07-01
Full Text Available Phase changes and heat exchanges are examples of physical processes appearing in many industrial applications involving multiphase compressible flows. Their knowledge is of fundamental importance to reproduce correctly the resulting effects in simulation tools. A fine description of the flow topology is thus required to obtain the interfacial area between phases. This one is responsible for the dynamics and the kinetics of heat and mass transfer when evaporation or condensation occurs. Unfortunately this exchange area cannot be obtained easily and accurately especially when complex mixtures (drops, bubbles, pockets of very different sizes appear inside the transient medium. The natural way to solve this specific trouble consists in using a thin grid to capture interfaces at all spatial scales. But this possibility needs huge computing resources and can be hardly used when considering physical systems of large dimensions. A realistic method is to consider instantaneous exchanges between phases by the way of additional source terms in a full non-equilibrium multiphase flow model [2,15,17]. In this one each phase obeys its own equation of state and has its own set of equations and variables (pressure, temperature, velocity, energy, entropy,.... When enabling the relaxation source terms the multiphase mixture instantaneously tends towards a mechanical or thermodynamic equilibrium state at each point of the flow. This strategy allows to mark the boundaries of the real flow behavior and to magnify the dominant physical effects (heat exchanges, evaporation, drag,... inside the medium. A description of the various relaxation processes is given in the paper. Les changements de phase et les transferts de chaleur sont des exemples de phénomènes physiques présents dans de nombreuses applications industrielles faisant intervenir des écoulements compressibles multiphasiques. La connaissance des mécanismes associés est primordiale afin de reproduire
Directory of Open Access Journals (Sweden)
Coquel Frédéric
2013-07-01
Full Text Available We give in this paper a short review of some recent achievements within the framework of multiphase flow modeling. We focus first on a class of compressible two-phase flow models, detailing closure laws and their main properties. Next we briefly summarize some attempts to model two-phase flows in a porous region, and also a class of compressible three-phase flow models. Some of the main difficulties arising in the numerical simulation of solutions of these complex and highly non-linear systems of PDEs are then discussed, and we eventually show some numerical results when tackling two-phase flows with mass transfer. Nous présentons dans cet article quelques résultats récents concernant la modélisation et la simulation numérique des écoulements multiphasiques. Nous nous concentrons tout d’abord sur une classe de modèles diphasiques compressibles, en détaillant les lois de fermeture et les principales propriétés du sytème. Nous résumons ensuite brièvement les propositions de modélisation d’écoulements diphasiques en milieu poreux et d’écoulements triphasiques. Quelques difficultés apparaissant dans la simulation numérique de ces modèles sont présentées, et des résultats récents comportant un transfert de masse entre phases sont finalement décrits.
Tomographic multiphase flow measurement
International Nuclear Information System (INIS)
Sætre, C.; Johansen, G.A.; Tjugum, S.A.
2012-01-01
Measurement of multiphase flow of gas, oil and water is not at all trivial and in spite of considerable achievements over the past two decades, important challenges remain (). These are related to reducing measurement uncertainties arising from variations in the flow regime, improving long term stability and developing new means for calibration, adjustment and verification of the multiphase flow meters. This work focuses on the first two issues using multi gamma beam (MGB) measurements for identification of the type of flow regime. Further gamma ray tomographic measurements are used for reference of the gas/liquid distribution. For the MGB method one Am-241 source with principal emission at 59.5 keV is used because this relatively low energy enables efficient collimation and thereby shaping of the beams, as well as compact detectors. One detector is placed diametrically opposite the source whereas the second is positioned to the side so that this beam is close to the pipe wall. The principle is then straight forward to compare the measured intensities of these detectors and through that identify the flow pattern, i.e. the instantaneous cross-sectional gas-liquid distribution. The measurement setup also includes Compton scattering measurements, which can provide information about the changes in the water salinity for flow segments with high water liquid ratio and low gas fractions. By measuring the transmitted intensity in short time slots (<100ms), rapid regime variations are revealed. From this we can select the time sections suitable for salinity measurements. Since the salinity variations change at the time scale of hours, a running average can be performed to increase the accuracy of the measurements. Recent results of this work will be presented here. - Highlights: ► Multiphase flow gas-fraction and flow regime measurements by multi gamma ray beams. ► High-speed gamma ray tomograph as reference for the flow pattern and gas fraction. ► Dual modality
Mathematical modelling and numerical resolution of multi-phase compressible fluid flows problems
International Nuclear Information System (INIS)
Lagoutiere, Frederic
2000-01-01
This work deals with Eulerian compressible multi-species fluid dynamics, the species being either mixed or separated (with interfaces). The document is composed of three parts. The first parts devoted to the numerical resolution of model problems: advection equation, Burgers equation, and Euler equations, in dimensions one and two. The goal is to find a precise method, especially for discontinuous initial conditions, and we develop non dissipative algorithms. They are based on a downwind finite-volume discretization under some stability constraints. The second part treats of the mathematical modelling of fluids mixtures. We construct and analyse a set of multi-temperature and multi-pressure models that are entropy, symmetrizable, hyperbolic, not ever conservative. In the third part, we apply the ideas developed in the first part (downwind discretization) to the numerical resolution of the partial differential problems we have constructed for fluids mixtures in the second part. We present some numerical results in dimensions one and two. (author) [fr
Multiphase Flow Dynamics 1 Fundamentals
Kolev, Nikolay Ivanov
2012-01-01
Multi-phase flows are part of our natural environment such as tornadoes, typhoons, air and water pollution and volcanic activities as well as part of industrial technology such as power plants, combustion engines, propulsion systems, or chemical and biological industry. The industrial use of multi-phase systems requires analytical and numerical strategies for predicting their behavior. In its fourth extended edition the successful monograph package “Multiphase Flow Dynmics” contains theory, methods and practical experience for describing complex transient multi-phase processes in arbitrary geometrical configurations, providing a systematic presentation of the theory and practice of numerical multi-phase fluid dynamics. In the present first volume the local volume and time averaging is used to derive a complete set of conservation equations for three fluids each of them having multi components as constituents. Large parts of the book are devoted on the design of successful numerical methods for solving the...
Multiphase flow dynamics 1 fundamentals
Kolev, Nikolay Ivanov
2004-01-01
Multi-phase flows are part of our natural environment such as tornadoes, typhoons, air and water pollution and volcanic activities as well as part of industrial technology such as power plants, combustion engines, propulsion systems, or chemical and biological industry. The industrial use of multi-phase systems requires analytical and numerical strategies for predicting their behavior. In its third extended edition this monograph contains theory, methods and practical experience for describing complex transient multi-phase processes in arbitrary geometrical configurations, providing a systematic presentation of the theory and practice of numerical multi-phase fluid dynamics. In the present first volume the fundamentals of multiphase dynamics are provided. This third edition includes various updates, extensions and improvements in all book chapters.
Multiphase flow dynamics 1 fundamentals
Kolev, Nikolay Ivanov
2007-01-01
Multi-phase flows are part of our natural environment such as tornadoes, typhoons, air and water pollution and volcanic activities as well as part of industrial technology such as power plants, combustion engines, propulsion systems, or chemical and biological industry. The industrial use of multi-phase systems requires analytical and numerical strategies for predicting their behavior. In its third extended edition this monograph contains theory, methods and practical experience for describing complex transient multi-phase processes in arbitrary geometrical configurations, providing a systematic presentation of the theory and practice of numerical multi-phase fluid dynamics. In the present first volume the fundamentals of multiphase dynamics are provided. This third edition includes various updates, extensions and improvements in all book chapters.
Multiphase flow dynamics 1 fundamentals
Kolev, Nikolay Ivanov
2015-01-01
In its fifth extended edition the successful monograph package “Multiphase Flow Dynamics” contains theory, methods and practical experience for describing complex transient multi-phase processes in arbitrary geometrical configurations, providing a systematic presentation of the theory and practice of numerical multi-phase fluid dynamics. In the present first volume the local volume and time averaging is used to derive a complete set of conservation equations for three fluids each of them having multi components as constituents. Large parts of the book are devoted on the design of successful numerical methods for solving the obtained system of partial differential equations. Finally the analysis is repeated for boundary fitted curvilinear coordinate systems designing methods applicable for interconnected multi-blocks. This fifth edition includes various updates, extensions, improvements and corrections, as well as a completely new chapter containing the basic physics describing the multi-phase flow in tu...
International Nuclear Information System (INIS)
Uchibori, Akihiro; Ohshima, Hiroyuki; Watanabe, Akira
2010-01-01
SERAPHIM is a computer program for the simulation of the compressible multiphase flow involving the sodium-water chemical reaction under a tube failure accident in a steam generator of sodium cooled fast reactors. In this study, the numerical analysis of the highly underexpanded air jets into the air or into the water was performed as a part of validation of the SERAPHIM program. The multi-fluid model, the second-order TVD scheme and the HSMAC method considering a compressibility were used in this analysis. Combining these numerical methods makes it possible to calculate the multiphase flow including supersonic gaseous jets. In the case of the air jet into the air, the calculated pressure, the shape of the jet and the location of a Mach disk agreed with the existing experimental results. The effect of the difference scheme and the mesh resolution on the prediction accuracy was clarified through these analyses. The behavior of the air jet into the water was also reproduced successfully by the proposed numerical method. (author)
Multiphase flows with phase change
Indian Academy of Sciences (India)
Multiphase flows with phase change are ubiquitous in many industrial sectors ranging from energy and infra-structure to specialty chemicals and pharmaceuticals. My own interest in mul- tiphase flows with phase change started more than 15 years ago when I had initiated work on riser reactor for fluid catalytic cracking and ...
Multiphase Flow Dynamics 2 Mechanical Interactions
Kolev, Nikolay Ivanov
2012-01-01
Multi-phase flows are part of our natural environment such as tornadoes, typhoons, air and water pollution and volcanic activities as well as part of industrial technology such as power plants, combustion engines, propulsion systems, or chemical and biological industry. The industrial use of multi-phase systems requires analytical and numerical strategies for predicting their behavior. .In its fourth extended edition the successful monograph package “Multiphase Flow Daynmics” contains theory, methods and practical experience for describing complex transient multi-phase processes in arbitrary geometrical configurations, providing a systematic presentation of the theory and practice of numerical multi-phase fluid dynamics. In the present second volume the methods for describing the mechanical interactions in multiphase dynamics are provided. This fourth edition includes various updates, extensions, improvements and corrections. "The literature in the field of multiphase flows is numerous. Therefore, it i...
Multiphase Flow Dynamics 3 Thermal Interactions
Kolev, Nikolay Ivanov
2012-01-01
Multi-phase flows are part of our natural environment such as tornadoes, typhoons, air and water pollution and volcanic activities as well as part of industrial technology such as power plants, combustion engines, propulsion systems, or chemical and biological industry. The industrial use of multi-phase systems requires analytical and numerical strategies for predicting their behavior. .In its fourth extended edition the successful monograph package “Multiphase Flow Daynmics” contains theory, methods and practical experience for describing complex transient multi-phase processes in arbitrary geometrical configurations, providing a systematic presentation of the theory and practice of numerical multi-phase fluid dynamics. In the present third volume methods for describing of the thermal interactions in multiphase dynamics are provided. In addition a large number of valuable experiments is collected and predicted using the methods introduced in this monograph. In this way the accuracy of the methods is reve...
Frontiers and progress in multiphase flow
2014-01-01
This volume presents state-of-the-art of reviews in the field of multiphase flow. In focusses on nonlinear aspects of multiphase flow networks as well as visualization experiments. The first chapter presents nonlinear aspects or deterministic chaos issues in the systems of multi-phase reactors. The second chapter reviews two-phase flow dynamics in combination with complex network theory. The third chapter discusses evaporation mechanism in the wick of copper heat pipes. The last chapter investigates numerically the flow dynamics and heat and mass transfer in the laminar and turbulent boundary layer on the flat vertical plate.
Design of Multiphase Flow Experiments
Energy Technology Data Exchange (ETDEWEB)
Urkedal, Hege
1998-12-31
This thesis proposes an experimental design procedure for multiphase experiments. The two-phase functions can be determined using data from a single experiment, while the three-phase relative permeabilities must be determined using data from multiple experiments. Various three-phase experimental designs have been investigated and the accuracy with which the flow functions may be determined using the corresponding data have been computed. Analytical sensitivity coefficients were developed from two-phase to three-phase flow. Sensitivity coefficients are the derivative of the model output with respect to the model parameters. They are obtained by a direct method that takes advantage of the fact that the model equations are solved using the Newton-Raphson method, and some of the results from this solution can be used directly when solving the sensitivity equation. Numerical derivatives are avoided, which improves accuracy. The thesis uses an inverse methodology for determination of two- and three-phase relative permeability and capillary pressure functions. The main work has been the development of analytical sensitivity coefficients for two-and three-phase flow. This technical contribution has improved the accuracy both in parameter estimation and accuracy assessment of the estimates and reduced the computer time requirements. The proposed experimental design is also dependent on accurate sensitivity coefficients to give the right guidelines for how two- and three-phase experiments should be conducted. Following the proposed experimental design, three-phase relative permeability and capillary pressure functions have been estimated when multiple sets of experimental data have been reconciled by simulations. 74 refs., 69 figs., 18 tabs.
Accurate solution algorithms for incompressible multiphase flows
International Nuclear Information System (INIS)
Rider, W.J.; Kothe, D.B.; Mosso, S.J.; Cerutti, J.H.; Hochstein, J.I.
1994-01-01
A number of advances in modeling multiphase incompressible flow are described. These advances include high-order Godunov projection methods, piecewise linear interface reconstruction and tracking and the continuum surface force model. Examples are given
Measurement in multiphase reacting flows
Chigier, N. A.
1979-01-01
A survey is presented of diagnostic techniques and measurements made in multiphase reacting flows. The special problems encountered by the presence of liquid droplets, soot and solid particles in high temperature chemically reacting turbulent environments are outlined. The principal measurement techniques that have been tested in spray flames are spark photography, laser anemometry, thermocouples and suction probes. Spark photography provides measurement of drop size, drop size distribution, drop velocity, and angle of flight. Photographs are analysed automatically by image analysers. Photographic techniques are reliable, inexpensive and proved. Laser anemometers have been developed for simultaneous measurement of velocity and size of individual particles in sprays under conditions of vaporization and combustion. Particle/gas velocity differentials, particle Reynolds numbers, local drag coefficients and direct measurement of vaporization rates can be made by laser anemometry. Gas temperature in sprays is determined by direct in situ measurement of time constants immediately prior to measurement with compensation and signal analysis by micro-processors. Gas concentration is measured by suction probes and gas phase chromatography. Measurements of particle size, particle velocity, gas temperature, and gas concentration made in airblast and pressure atomised liquid spray flames are presented.
Simulation of multiphase flow in hydrocyclone
Directory of Open Access Journals (Sweden)
Rudolf P.
2013-04-01
Full Text Available Multiphase gas-liquid-solid swirling flow within hydrocyclone is simulated. Geometry and boundary conditions are based on Hsieh's 75 mm hydrocyclone. Extensive simulations point that standard mixture model with careful selection of interphase drag law is suitable for correct prediction of particle classification in case of dilute suspensions. However this approach fails for higher mass loading. It is also confirmed that Reynolds stress model is the best choice for multiphase modeling of the swirling flow on relatively coarse grids.
Energy Technology Data Exchange (ETDEWEB)
Perrier, V
2007-07-15
This work deals with the modelling and simulation of compressible flows. A seven equations model is obtained by homogenizing the Euler system. Fluctuation terms are modeled as relaxation terms. When the relaxation terms tend to infinity, which means that the phases are well mixed, a five equations model is obtained via an asymptotic expansion. This five equations model is strictly hyperbolic, but nonconservative. The discretization of this model is obtained by an asymptotic expansion of a scheme for the seven equations model. The numerical method is implemented, validated on analytic cases, and compared with experiments in the case of multiphase shocks. We are then interested in the modelling of phase transition with two equations of state. Optimization of the mixture entropy leads to the fact that three zones can be separated: one in which the pure liquid is the most stable, one in which the pure gas is the most stable, and one in which a mixture with equality of temperature, pressure and chemical potentials is the most stable. Conditions are given on the coupling of the two equations of state for ensuring that the mixture equation of state is convex, and that the system is strictly hyperbolic. In order to take into account phase transition, a vaporization wave is introduced in the solution of the Riemann problem, that is modeled as a deflagration wave. It is then proved that the usual closure, the Chapman-Jouguet closure, is wrong in general, and a correct closure in the case when both fluids have a perfect gas equation of state. Last, the solution of the Riemann problem is implemented in a multiphase code, and validated on analytic cases. In the same code, models of laser release and thermal conduction are implemented to simulate laser ablation. The results are comparable to the ones obtained with scale laws. The last chapter, fully independent, is concerned with correctors in stochastic homogenization in the case of heavy tails process. (author)
The simulation of multidimensional multiphase flows
International Nuclear Information System (INIS)
Lahey, Richard T.
2005-01-01
This paper presents an assessment of various models which can be used for the multidimensional simulation of multiphase flows, such as may occur in nuclear reactors. In particular, a model appropriate for the direct numerical simulation (DNS) of multiphase flows and a mechanistically based, three-dimensional, four-field, turbulent, two-fluid computational multiphase fluid dynamics (CMFD) model are discussed. A two-fluid bubbly flow model, which was derived using potential flow theory, can be extended to other flow regimes, but this will normally involve ensemble-averaging the results from direct numerical simulations (DNS) of various flow regimes to provide the detailed numerical data necessary for the development of flow-regime-specific interfacial and wall closure laws
Multiphase reacting flows modelling and simulation
Marchisio, Daniele L
2007-01-01
The papers in this book describe the most widely applicable modeling approaches and are organized in six groups covering from fundamentals to relevant applications. In the first part, some fundamentals of multiphase turbulent reacting flows are covered. In particular the introduction focuses on basic notions of turbulence theory in single-phase and multi-phase systems as well as on the interaction between turbulence and chemistry. In the second part, models for the physical and chemical processes involved are discussed. Among other things, particular emphasis is given to turbulence modeling strategies for multiphase flows based on the kinetic theory for granular flows. Next, the different numerical methods based on Lagrangian and/or Eulerian schemes are presented. In particular the most popular numerical approaches of computational fluid dynamics codes are described (i.e., Direct Numerical Simulation, Large Eddy Simulation, and Reynolds-Averaged Navier-Stokes approach). The book will cover particle-based meth...
EDITORIAL: Measurement techniques for multiphase flows Measurement techniques for multiphase flows
Okamoto, Koji; Murai, Yuichi
2009-11-01
Research on multiphase flows is very important for industrial applications, including power stations, vehicles, engines, food processing and so on. Multiphase flows originally have nonlinear features because of multiphase systems. The interaction between the phases plays a very interesting role in the flows. The nonlinear interaction causes the multiphase flows to be very complicated. Therefore techniques for measuring multiphase flows are very useful in helping to understand the nonlinear phenomena. The state-of-the-art measurement techniques were presented and discussed at the sixth International Symposium on Measurement Techniques for Multiphase Flows (ISMTMF2008) held in Okinawa, Japan, on 15-17 December 2008. This special feature of Measurement Science and Technology includes selected papers from ISMTMF2008. Okinawa has a long history as the Ryukyus Kingdom. China, Japan and many western Pacific countries have had cultural and economic exchanges through Okinawa for over 1000 years. Much technical and scientific information was exchanged at the symposium in Okinawa. The proceedings of ISMTMF2008 apart from these special featured papers were published in Journal of Physics: Conference Series vol. 147 (2009). We would like to express special thanks to all the contributors to the symposium and this special feature. This special feature will be a milestone in measurement techniques for multiphase flows.
Multiphase flow in porous media using CFD
DEFF Research Database (Denmark)
Hemmingsen, Casper Schytte; Walther, Jens Honore
We present results from a new Navier-Stokes model for multiphase flow in porous media implemented in Ansys Fluent 16.2 [1]. The model includes the Darcy-Forchheimer source terms in the momentum equations and proper account for relative permeability and capillary pressure in the porous media...
Visualization of multiphase flow by neutron radiography
International Nuclear Information System (INIS)
Mishima, Kaichiro; Takenaka, Nobuyuki.
1991-01-01
Neutron radiography (NRG) is a technique which produces images of the internal structure of a body, making use of the attenuation characteristics of neutrons in the materials being observed. Recently, attempts have been made to expand the application of this technique not only to non-destructive testing but also to a variety of industrial and basic research fields. The attenuation of neutrons is large in a light material like water and small in ordinary metals, which difference may make it possible to visualize a multiphase flow in a metallic container. Particularly, the neutron television, which is one of the applied techniques of NRG, is expected to be a useful tool for observing the behavior of two-phase flow, since it produces images in real time. In this paper the basic idea and the method of NRG are presented along with examples of visualization of multiphase flow by NRG. (author)
A development of multiphase flow facility
International Nuclear Information System (INIS)
Ismail Mustapha; Jaafar Abdullah
2004-01-01
Multiphase liquid flow facility shall be enabling to transport of oil/gas/water in pipelines. In horizontal pipelines, the different flow patterns that could be observed. The flow pattern will depend mainly on the gas and liquid velocities, and gas liquid ratio. For very high liquid velocities and low gas liquid ratios, the dispersed bubble flow is observed. For low flow rates of liquid and gas, a smooth or wavy stratified flow is expected. For intermediate liquid velocities, rolling waves of liquids are formed. The rolling waves increase to the point of forming a plug flow and a slug flow. For very high gas velocities, the annular flow is observed Also include a tillable test section allowing for testing at any angle between 0 0 degree from horizontal, lowering the measurement uncertainties and increased capabilities with respect to flow rates and gas fractions. (Author)
Non-Equilibrium Thermodynamics in Multiphase Flows
Mauri, Roberto
2013-01-01
Non-equilibrium thermodynamics is a general framework that allows the macroscopic description of irreversible processes. This book introduces non-equilibrium thermodynamics and its applications to the rheology of multiphase flows. The subject is relevant to graduate students in chemical and mechanical engineering, physics and material science. This book is divided into two parts. The first part presents the theory of non-equilibrium thermodynamics, reviewing its essential features and showing, when possible, some applications. The second part of this book deals with how the general theory can be applied to model multiphase flows and, in particular, how to determine their constitutive relations. Each chapter contains problems at the end, the solutions of which are given at the end of the book. No prior knowledge of statistical mechanics is required; the necessary prerequisites are elements of transport phenomena and on thermodynamics. “The style of the book is mathematical, but nonetheless it remains very re...
Modeling variability in porescale multiphase flow experiments
Energy Technology Data Exchange (ETDEWEB)
Ling, Bowen; Bao, Jie; Oostrom, Mart; Battiato, Ilenia; Tartakovsky, Alexandre M.
2017-07-01
Microfluidic devices and porescale numerical models are commonly used to study multiphase flow in biological, geological, and engineered porous materials. In this work, we perform a set of drainage and imbibition experiments in six identical microfluidic cells to study the reproducibility of multiphase flow experiments. We observe significant variations in the experimental results, which are smaller during the drainage stage and larger during the imbibition stage. We demonstrate that these variations are due to sub-porescale geometry differences in microcells (because of manufacturing defects) and variations in the boundary condition (i.e.,fluctuations in the injection rate inherent to syringe pumps). Computational simulations are conducted using commercial software STAR-CCM+, both with constant and randomly varying injection rate. Stochastic simulations are able to capture variability in the experiments associated with the varying pump injection rate.
Modeling variability in porescale multiphase flow experiments
Ling, Bowen; Bao, Jie; Oostrom, Mart; Battiato, Ilenia; Tartakovsky, Alexandre M.
2017-07-01
Microfluidic devices and porescale numerical models are commonly used to study multiphase flow in biological, geological, and engineered porous materials. In this work, we perform a set of drainage and imbibition experiments in six identical microfluidic cells to study the reproducibility of multiphase flow experiments. We observe significant variations in the experimental results, which are smaller during the drainage stage and larger during the imbibition stage. We demonstrate that these variations are due to sub-porescale geometry differences in microcells (because of manufacturing defects) and variations in the boundary condition (i.e., fluctuations in the injection rate inherent to syringe pumps). Computational simulations are conducted using commercial software STAR-CCM+, both with constant and randomly varying injection rates. Stochastic simulations are able to capture variability in the experiments associated with the varying pump injection rate.
Modeling reproducibility of porescale multiphase flow experiments
Ling, B.; Tartakovsky, A. M.; Bao, J.; Oostrom, M.; Battiato, I.
2017-12-01
Multi-phase flow in porous media is widely encountered in geological systems. Understanding immiscible fluid displacement is crucial for processes including, but not limited to, CO2 sequestration, non-aqueous phase liquid contamination and oil recovery. Microfluidic devices and porescale numerical models are commonly used to study multiphase flow in biological, geological, and engineered porous materials. In this work, we perform a set of drainage and imbibition experiments in six identical microfluidic cells to study the reproducibility of multiphase flow experiments. We observe significant variations in the experimental results, which are smaller during the drainage stage and larger during the imbibition stage. We demonstrate that these variations are due to sub-porescale geometry differences in microcells (because of manufacturing defects) and variations in the boundary condition (i.e.,fluctuations in the injection rate inherent to syringe pumps). Computational simulations are conducted using commercial software STAR-CCM+, both with constant and randomly varying injection rate. Stochastic simulations are able to capture variability in the experiments associated with the varying pump injection rate.
Multiphase flows with phase change
Indian Academy of Sciences (India)
odic dry-out/rewetting were observed. The presented data will be useful to provide insights into boiling in diverging micro-channels. ... discuss the development of a computational tool for simulating condensation processes. CFD models were used to understand flow and condensation as well as deposition of ice in the con-.
Soft-sensing, non-intrusive multiphase flow meter
Wrobel, K.; Schiferli, W.
2009-01-01
For single phase flow meters more and better non-intrusive or even clamp-on meters become available. This allows for a wider use of meters and for easier flow control. As the demand for multiphase meters is increasing, the current aim is to develop a non-intrusive multiphase flow meter. The
Multiphase flow dynamics 5 nuclear thermal hydraulics
Kolev, Nikolay Ivanov
2015-01-01
This Volume 5 of the successful book package "Multiphase Flow Dynamics" is devoted to nuclear thermal hydraulics which is a substantial part of nuclear reactor safety. It provides knowledge and mathematical tools for adequate description of the process of transferring the fission heat released in materials due to nuclear reactions into its environment. It step by step introduces into the heat release inside the fuel, temperature fields in the fuels, the "simple" boiling flow in a pipe described using ideas of different complexity like equilibrium, non equilibrium, homogeneity, non homogeneity. Then the "simple" three-fluid boiling flow in a pipe is described by gradually involving the mechanisms like entrainment and deposition, dynamic fragmentation, collisions, coalescence, turbulence. All heat transfer mechanisms are introduced gradually discussing their uncertainty. Different techniques are introduced like boundary layer treatments or integral methods. Comparisons with experimental data at each step demons...
Multiphase Flow Dynamics 5 Nuclear Thermal Hydraulics
Kolev, Nikolay Ivanov
2012-01-01
The present Volume 5 of the successful book package "Multiphase Flow Dynamics" is devoted to nuclear thermal hydraulics which is a substantial part of nuclear reactor safety. It provides knowledge and mathematical tools for adequate description of the process of transferring the fission heat released in materials due to nuclear reactions into its environment. It step by step introduces into the heat release inside the fuel, temperature fields in the fuels, the "simple" boiling flow in a pipe described using ideas of different complexity like equilibrium, non equilibrium, homogeneity, non homogeneity. Then the "simple" three-fluid boiling flow in a pipe is described by gradually involving the mechanisms like entrainment and deposition, dynamic fragmentation, collisions, coalescence, turbulence. All heat transfer mechanisms are introduced gradually discussing their uncertainty. Different techniques are introduced like boundary layer treatments or integral methods. Comparisons with experimental data at each step...
Quantitative tomographic measurements of opaque multiphase flows
Energy Technology Data Exchange (ETDEWEB)
GEORGE,DARIN L.; TORCZYNSKI,JOHN R.; SHOLLENBERGER,KIM ANN; O' HERN,TIMOTHY J.; CECCIO,STEVEN L.
2000-03-01
An electrical-impedance tomography (EIT) system has been developed for quantitative measurements of radial phase distribution profiles in two-phase and three-phase vertical column flows. The EIT system is described along with the computer algorithm used for reconstructing phase volume fraction profiles. EIT measurements were validated by comparison with a gamma-densitometry tomography (GDT) system. The EIT system was used to accurately measure average solid volume fractions up to 0.05 in solid-liquid flows, and radial gas volume fraction profiles in gas-liquid flows with gas volume fractions up to 0.15. In both flows, average phase volume fractions and radial volume fraction profiles from GDT and EIT were in good agreement. A minor modification to the formula used to relate conductivity data to phase volume fractions was found to improve agreement between the methods. GDT and EIT were then applied together to simultaneously measure the solid, liquid, and gas radial distributions within several vertical three-phase flows. For average solid volume fractions up to 0.30, the gas distribution for each gas flow rate was approximately independent of the amount of solids in the column. Measurements made with this EIT system demonstrate that EIT may be used successfully for noninvasive, quantitative measurements of dispersed multiphase flows.
Dan Joseph's contributions to disperse multiphase flow
Prosperetti, Andrea
2012-11-01
During his distinguished career, Dan Joseph worked on a vast array of problems. One of these, which occupied him off and on over the last two decades of his life, was that of flows with suspended finite-size particles at finite Reynolds numbers. He realized early on that progress in this field had to rely on the insight gained from numerical simulation, an area in which he was a pioneer. On the basis of the early numerical results he recognized the now famous ``drafting, kissing and tumbling'' mechanism of particle-particle interaction, the possibility of fluidization by lift and many others. With a number of colleagues and a series of gifted students he produced a significant body of work summarized in his on-line book Interrogations of Direct Numerical Simulation of Solid-Liquid Flows available from http://www.efluids.com/efluids/books/joseph.htm. This presentation will describe Joseph's contribution to the understanding of disperse multiphase flow and conclude with some examples from the author's recent work in this area. Supported by NSF.
Workshop on Scientific Issues in Multiphase Flow
Energy Technology Data Exchange (ETDEWEB)
Hanratty, Thomas J. [Univ. of Illinois, Urbana, IL (United States)
2003-01-02
This report outlines scientific issues whose resolution will help advance and define the field of multiphase flow. It presents the findings of four study groups and of a workshop sponsored by the Program on Engineering Physics of the Department of Energy. The reason why multiphase flows are much more difficult to analyze than single phase flows is that the phases assume a large number of complicated configurations. Therefore, it should not be surprising that the understanding of why the phases configure in a certain way is the principal scientific issue. Research is needed which identifies the microphysics controlling the organization of the phases, which develops physical models for the resultant multi-scale interactions and which tests their validity in integrative experiments/theories that look at the behavior of a system. New experimental techniques and recently developed direct numerical simulations will play important roles in this endeavor. In gas-liquid flows a top priority is to develop an understanding of why the liquid phase in quasi fully-developed pipe flow changes from one configuration to another. Mixing flows offer a more complicated situation in which several patterns can exist at the same time. They introduce new physical challenges. A second priority is to provide a quantitative description of the phase distribution for selected fully-developed flows and for simple mixing flows (that could include heat transfer and phase change). Microphysical problems of interest are identified – including the coupling of molecular and macroscopic behavior that can be observed in many situations and the formation/destruction of interfaces in the coalescence/breakup of drops and bubbles. Solid-fluid flows offer a simpler system in that interfaces are not changing. However, a variety of patterns exist, that depend on the properties of the particles, their concentration and the Reynolds number characterizing the relative velocity. A top priority is the
Introduction to compressible fluid flow
Oosthuizen, Patrick H
2013-01-01
IntroductionThe Equations of Steady One-Dimensional Compressible FlowSome Fundamental Aspects of Compressible FlowOne-Dimensional Isentropic FlowNormal Shock WavesOblique Shock WavesExpansion Waves - Prandtl-Meyer FlowVariable Area FlowsAdiabatic Flow with FrictionFlow with Heat TransferLinearized Analysis of Two-Dimensional Compressible FlowsHypersonic and High-Temperature FlowsHigh-Temperature Gas EffectsLow-Density FlowsBibliographyAppendices
2nd International Conference on Multiphase Flow - ICMF '95
Fukano, T; Bataille, Jean
1995-01-01
There is increasing world-wide interest in obtaining an understanding of various multiphase flow phenomena and problems in terms of a common language of multiphase flow. This volume contains state-of-the-art papers which have been contributed from all over the world by experts working on all aspects of multiphase flows. The volume also highlights international technology-sharing in the fields of energy, environment and public health, in order to create a brighter and sustainable future for man and for all life in the next century. It is intended that this volume will serve as a major source of
Multiphase Flow and Fluidization Continuum and Kinetic Theory Descriptions
Gidaspow, Dimitri
1994-01-01
Useful as a reference for engineers in industry and as an advanced level text for graduate engineering students, Multiphase Flow and Fluidization takes the reader beyond the theoretical to demonstrate how multiphase flow equations can be used to provide applied, practical, predictive solutions to industrial fluidization problems. Written to help advance progress in the emerging science of multiphase flow, this book begins with the development of the conservation laws and moves on through kinetic theory, clarifying many physical concepts (such as particulate viscosity and solids pressure) and i
Multiphase flow models for hydraulic fracturing technology
Osiptsov, Andrei A.
2017-10-01
drift-flux approaches. The derivation of the drift-flux model from conservation olaws is criticall revisited in order to define the list of underlying assumptions and to mark the applicability margins of the model. All these fundamental problems share the same technological application (hydraulic fracturing) and the same method of research, namely, the multi-fluid approach to multiphase flow modeling and the consistent use of asymptotic methods. Multi-fluid models are then discussed in comparison with semi-empirical (often postulated) models widely used in the industry.
Application of neutron radiography to visualization of multiphase flows
International Nuclear Information System (INIS)
Takenaka, N.; Fujii, T.; Nishizaki, K.; Asano, H.; Ono, A.; Sonoda, K.; Akagawa, K.
1990-01-01
Visualizations by real-time neutron radiography are demonstrated of various flow patterns of nitrogen gas-water two-phase flow in a stainless-steel tube, water inverted annular flow in a stainless-steel tube, flashing flow in an aluminium nozzle and fluidized bed in aluminium tube and vessels. Photographs every 1/60 s are presented by an image processing method to show the dynamic behaviours of the various flow patterns. It is shown that this visualization method can be applied efficiently to multiphase flow researches and will be applicable to multiphase flows in industrial machines. (author)
Multiphase flow metering: 4 years on
Energy Technology Data Exchange (ETDEWEB)
Falcone, G.; Hewitt, G.F.; Alimonti, C.; Harrison, B.
2005-07-01
Since the authors' last review in 2001 [1], the use of Multiphase Flow Metering (MFM) within the oil and gas industry continues to grow apace, being more popular in some parts of the world than others. Since the early 1990's, when the first commercial meters started to appear, there have been more than 1,600 field applications of MFM for field allocation, production optimisation and mobile well testing. As the authors predicted, wet gas metering technology has improved to such an extent that its use has rapidly increased worldwide. A ''who's who'' of the MFM sector is provided, which highlights the mergers in the sector and gives an insight into the meters and measurement principles available today. Cost estimates, potential benefits and reliability in the field of the current MFM technologies are revisited and brought up to date. Several measurements technologies have resurfaced, such as passive acoustic energy patterns, infrared wavelengths, Nuclear Magnetic Resonance (NMR) and Electrical Capacitance Tomography (ECT), and they are becoming commercial. The concept of ''virtual metering'', integrated with ''classical MFM'', is now widely accepted. However, sometimes the principles of the MFM measurements themselves are forgotten, submerged in the sales and marketing hype. (author) (tk)
A multi-phase flow model for electrospinning process
Directory of Open Access Journals (Sweden)
Xu Lan
2013-01-01
Full Text Available An electrospinning process is a multi-phase and multi-physicical process with flow, electric and magnetic fields coupled together. This paper deals with establishing a multi-phase model for numerical study and explains how to prepare for nanofibers and nanoporous materials. The model provides with a powerful tool to controlling over electrospinning parameters such as voltage, flow rate, and others.
International Symposium of Cavitation and Multiphase Flow (ISCM 2014)
International Nuclear Information System (INIS)
Wu, Yulin
2015-01-01
The International Symposium on Cavitation and Multiphase Flow (ISCM 2014) was held in Beijing, China during 18th-21st October, 2014, which was jointly organized by Tsinghua University, Beijing, China and Jiangsu University, Zhenjiang, China. The co-organizer was the State Key Laboratory of Hydroscience and Engineering, Beijing, China. Cavitation and multiphase flow is one of paramount topics of fluid mechanics with many engineering applications covering a broad range of topics, e.g. hydraulic machinery, biomedical engineering, chemical and process industry. In order to improve the performances of engineering facilities (e.g. hydraulic turbines) and to accelerate the development of techniques for medical treatment of serious diseases (e.g. tumors), it is essential to improve our understanding of cavitation and Multiphase Flow. For example, the present development towards the advanced hydrodynamic systems (e.g. space engine, propeller, hydraulic machinery system) often requires that the systems run under cavitating conditions and the risk of cavitation erosion needs to be controlled. The purpose of the ISCM 2014 was to discuss the state-of-the-art cavitation and multiphase flow research and their up-to-date applications, and to foster discussion and exchange of knowledge, and to provide an opportunity for the researchers, engineers and graduate students to report their latest outputs in these fields. Furthermore, the participants were also encouraged to present their work in progress with short lead time and discuss the encountered problems. ISCM 2014 covers all aspects of cavitation and Multiphase Flow, e.g. both fundamental and applied research with a focus on physical insights, numerical modelling and applications in engineering. Some specific topics are: Cavitating and Multiphase Flow in hydroturbines, pumps, propellers etc. Numerical simulation techniques Cavitation and multiphase flow erosion and anti-erosion techniques Measurement techniques for cavitation and
FOREWORD: International Symposium of Cavitation and Multiphase Flow (ISCM 2014)
Wu, Yulin
2015-01-01
The International Symposium on Cavitation and Multiphase Flow (ISCM 2014) was held in Beijing, China during 18th-21st October, 2014, which was jointly organized by Tsinghua University, Beijing, China and Jiangsu University, Zhenjiang, China. The co-organizer was the State Key Laboratory of Hydroscience and Engineering, Beijing, China. Cavitation and multiphase flow is one of paramount topics of fluid mechanics with many engineering applications covering a broad range of topics, e.g. hydraulic machinery, biomedical engineering, chemical and process industry. In order to improve the performances of engineering facilities (e.g. hydraulic turbines) and to accelerate the development of techniques for medical treatment of serious diseases (e.g. tumors), it is essential to improve our understanding of cavitation and Multiphase Flow. For example, the present development towards the advanced hydrodynamic systems (e.g. space engine, propeller, hydraulic machinery system) often requires that the systems run under cavitating conditions and the risk of cavitation erosion needs to be controlled. The purpose of the ISCM 2014 was to discuss the state-of-the-art cavitation and multiphase flow research and their up-to-date applications, and to foster discussion and exchange of knowledge, and to provide an opportunity for the researchers, engineers and graduate students to report their latest outputs in these fields. Furthermore, the participants were also encouraged to present their work in progress with short lead time and discuss the encountered problems. ISCM 2014 covers all aspects of cavitation and Multiphase Flow, e.g. both fundamental and applied research with a focus on physical insights, numerical modelling and applications in engineering. Some specific topics are: Cavitating and Multiphase Flow in hydroturbines, pumps, propellers etc. Numerical simulation techniques Cavitation and multiphase flow erosion and anti-erosion techniques Measurement techniques for cavitation and
Development of Next Generation Multiphase Pipe Flow Prediction Tools
Energy Technology Data Exchange (ETDEWEB)
Cem Sarica; Holden Zhang
2006-05-31
The developments of oil and gas fields in deep waters (5000 ft and more) will become more common in the future. It is inevitable that production systems will operate under multiphase flow conditions (simultaneous flow of gas, oil and water possibly along with sand, hydrates, and waxes). Multiphase flow prediction tools are essential for every phase of hydrocarbon recovery from design to operation. Recovery from deep-waters poses special challenges and requires accurate multiphase flow predictive tools for several applications, including the design and diagnostics of the production systems, separation of phases in horizontal wells, and multiphase separation (topside, seabed or bottom-hole). It is crucial for any multiphase separation technique, either at topside, seabed or bottom-hole, to know inlet conditions such as flow rates, flow patterns, and volume fractions of gas, oil and water coming into the separation devices. Therefore, the development of a new generation of multiphase flow predictive tools is needed. The overall objective of the proposed study is to develop a unified model for gas-oil-water three-phase flow in wells, flow lines, and pipelines to predict flow characteristics such as flow patterns, phase distributions, and pressure gradient encountered during petroleum production at different flow conditions (pipe diameter and inclination, fluid properties and flow rates). In the current multiphase modeling approach, flow pattern and flow behavior (pressure gradient and phase fractions) prediction modeling are separated. Thus, different models based on different physics are employed, causing inaccuracies and discontinuities. Moreover, oil and water are treated as a pseudo single phase, ignoring the distinct characteristics of both oil and water, and often resulting in inaccurate design that leads to operational problems. In this study, a new model is being developed through a theoretical and experimental study employing a revolutionary approach. The
On convergence of multigrid method in multiphase flow problems
Filatov, M.; Maksimov, D.
2013-12-01
Standard multigrid methods often become inefficient in multiphase flow problems because the coarse grid operators are constructed disregarding heterogeneous saturation distribution. This may lead to inefficient residual smoothing and significantly reduce convergence rate. Here we study the convergence behavior of geometric multigrid method in case when the upscaling methods (incl. multiphase) are employed in construction of coarse grid operators. The application for nonlinear multigrid method is also discussed.
Some Specific CASL Requirements for Advanced Multiphase Flow Simulation of Light Water Reactors
Energy Technology Data Exchange (ETDEWEB)
R. A. Berry
2010-11-01
Because of the diversity of physical phenomena occuring in boiling, flashing, and bubble collapse, and of the length and time scales of LWR systems, it is imperative that the models have the following features: • Both vapor and liquid phases (and noncondensible phases, if present) must be treated as compressible. • Models must be mathematically and numerically well-posed. • The models methodology must be multi-scale. A fundamental derivation of the multiphase governing equation system, that should be used as a basis for advanced multiphase modeling in LWR coolant systems, is given in the Appendix using the ensemble averaging method. The remainder of this work focuses specifically on the compressible, well-posed, and multi-scale requirements of advanced simulation methods for these LWR coolant systems, because without these are the most fundamental aspects, without which widespread advancement cannot be claimed. Because of the expense of developing multiple special-purpose codes and the inherent inability to couple information from the multiple, separate length- and time-scales, efforts within CASL should be focused toward development of a multi-scale approaches to solve those multiphase flow problems relevant to LWR design and safety analysis. Efforts should be aimed at developing well-designed unified physical/mathematical and high-resolution numerical models for compressible, all-speed multiphase flows spanning: (1) Well-posed general mixture level (true multiphase) models for fast transient situations and safety analysis, (2) DNS (Direct Numerical Simulation)-like models to resolve interface level phenmena like flashing and boiling flows, and critical heat flux determination (necessarily including conjugate heat transfer), and (3) Multi-scale methods to resolve both (1) and (2) automatically, depending upon specified mesh resolution, and to couple different flow models (single-phase, multiphase with several velocities and pressures, multiphase with single
Multiphase flow in micro- and nanochannels
Shui, Lingling; Eijkel, Jan C.T.; van den Berg, Albert
2007-01-01
Fluids that are of interest in nature, biotechnology and chemistry are rarely either simple single-phase or non-confined (open system) fluids. It is therefore not surprising that recently a surge of interest has arisen in multiphase confined fluid manipulation. This paper aims at reviewing
Multiscale Modeling of Multiphase Fluid Flow
2016-08-01
interactions within a molecular system are approximated by intramolecular (bonded) interactions: bond stretching, bond bending , and torsions , and...2, harmonic bond bending ( − )2, and the torsional energy for a dihedral angle defined by...many more. The combination of multiphase heat transfer and nano-technology, thus, opens up a wide range of possibilities for cooling technologies
Direct numerical simulations of gas-liquid multiphase flows
Tryggvason, Grétar; Zaleski, Stéphane
2011-01-01
Accurately predicting the behaviour of multiphase flows is a problem of immense industrial and scientific interest. Modern computers can now study the dynamics in great detail and these simulations yield unprecedented insight. This book provides a comprehensive introduction to direct numerical simulations of multiphase flows for researchers and graduate students. After a brief overview of the context and history the authors review the governing equations. A particular emphasis is placed on the 'one-fluid' formulation where a single set of equations is used to describe the entire flow field and
Multiphase Flow of Immiscible Fluids on Unstructured Moving Meshes
DEFF Research Database (Denmark)
Misztal, Marek Krzysztof; Erleben, Kenny; Bargteil, Adam
2013-01-01
In this paper, we present a method for animating multiphase flow of immiscible fluids using unstructured moving meshes. Our underlying discretization is an unstructured tetrahedral mesh, the deformable simplicial complex (DSC), that moves with the flow in a Lagrangian manner. Mesh optimization op...
Electrification of particulates in industrial and natural multiphase flows
Gu, Zhaolin
2017-01-01
This book introduces comprehensive fundamentals, numerical simulations and experimental methods of electrification of particulates entrained multiphase flows. The electrifications of two particulate forms, liquid droplets and solid particles, are firstly described together. Liquid droplets can be charged under preset or associated electric fields, while solid particles can be charged through contact. Different charging ways in gas (liquid)-liquid or gas-solid multiphase flows are summarized, including ones that are beneficial to industrial processes, such as electrostatic precipitation, electrostatic spraying, and electrostatic separation, etc., ones harmful for shipping and powder industry, and ones occurring in natural phenomenon, such as wind-blown sand and thunderstorm. This book offers theoretical references to the control and utilization of the charging or charged particulates in multiphase flows as well.
Multiphase flow parameter estimation based on laser scattering
International Nuclear Information System (INIS)
Vendruscolo, Tiago P; Fischer, Robert; Martelli, Cicero; Da Silva, Marco J; Rodrigues, Rômulo L P; Morales, Rigoberto E M
2015-01-01
The flow of multiple constituents inside a pipe or vessel, known as multiphase flow, is commonly found in many industry branches. The measurement of the individual flow rates in such flow is still a challenge, which usually requires a combination of several sensor types. However, in many applications, especially in industrial process control, it is not necessary to know the absolute flow rate of the respective phases, but rather to continuously monitor flow conditions in order to quickly detect deviations from the desired parameters. Here we show how a simple and low-cost sensor design can achieve this, by using machine-learning techniques to distinguishing the characteristic patterns of oblique laser light scattered at the phase interfaces. The sensor is capable of estimating individual phase fluxes (as well as their changes) in multiphase flows and may be applied to safety applications due to its quick response time. (paper)
Multiphase flow parameter estimation based on laser scattering
Vendruscolo, Tiago P.; Fischer, Robert; Martelli, Cicero; Rodrigues, Rômulo L. P.; Morales, Rigoberto E. M.; da Silva, Marco J.
2015-07-01
The flow of multiple constituents inside a pipe or vessel, known as multiphase flow, is commonly found in many industry branches. The measurement of the individual flow rates in such flow is still a challenge, which usually requires a combination of several sensor types. However, in many applications, especially in industrial process control, it is not necessary to know the absolute flow rate of the respective phases, but rather to continuously monitor flow conditions in order to quickly detect deviations from the desired parameters. Here we show how a simple and low-cost sensor design can achieve this, by using machine-learning techniques to distinguishing the characteristic patterns of oblique laser light scattered at the phase interfaces. The sensor is capable of estimating individual phase fluxes (as well as their changes) in multiphase flows and may be applied to safety applications due to its quick response time.
A mass-conserving multiphase lattice Boltzmann model for simulation of multiphase flows
Niu, Xiao-Dong; Li, You; Ma, Yi-Ren; Chen, Mu-Feng; Li, Xiang; Li, Qiao-Zhong
2018-01-01
In this study, a mass-conserving multiphase lattice Boltzmann (LB) model is proposed for simulating the multiphase flows. The proposed model developed in the present study is to improve the model of Shao et al. ["Free-energy-based lattice Boltzmann model for simulation of multiphase flows with density contrast," Phys. Rev. E 89, 033309 (2014)] by introducing a mass correction term in the lattice Boltzmann model for the interface. The model of Shao et al. [(the improved Zheng-Shu-Chew (Z-S-C model)] correctly considers the effect of the local density variation in momentum equation and has an obvious improvement over the Zheng-Shu-Chew (Z-S-C) model ["A lattice Boltzmann model for multiphase flows with large density ratio," J. Comput. Phys. 218(1), 353-371 (2006)] in terms of solution accuracy. However, due to the physical diffusion and numerical dissipation, the total mass of each fluid phase cannot be conserved correctly. To solve this problem, a mass correction term, which is similar to the one proposed by Wang et al. ["A mass-conserved diffuse interface method and its application for incompressible multiphase flows with large density ratio," J. Comput. Phys. 290, 336-351 (2015)], is introduced into the lattice Boltzmann equation for the interface to compensate the mass losses or offset the mass increase. Meanwhile, to implement the wetting boundary condition and the contact angle, a geometric formulation and a local force are incorporated into the present mass-conserving LB model. The proposed model is validated by verifying the Laplace law, simulating both one and two aligned droplets splashing onto a liquid film, droplets standing on an ideal wall, droplets with different wettability splashing onto smooth wax, and bubbles rising under buoyancy. Numerical results show that the proposed model can correctly simulate multiphase flows. It was found that the mass is well-conserved in all cases considered by the model developed in the present study. The developed
Dynamic effects in multiphase flow: A pore-scale network approach
Gielen, T.; Hassanizadeh, S.M.; Leijnse, A.; Nordhaug, H.F.
2005-01-01
Current theories of multiphase flow rely on capillary pressure and saturation relationships that are commonly measured under static conditions. To incorporate transient behaviour, new multiphase flow theories have been proposed. These include an extended capillary pressure-saturation relationship
New Turbulent Multiphase Flow Facilities for Simulation Benchmarking
Teoh, Chee Hau; Salibindla, Ashwanth; Masuk, Ashik Ullah Mohammad; Ni, Rui
2017-11-01
The Fluid Transport Lab at Penn State has devoted last few years on developing new experimental facilities to unveil the underlying physics of coupling between solid-gas and gas-liquid multiphase flow in a turbulent environment. In this poster, I will introduce one bubbly flow facility and one dusty flow facility for validating and verifying simulation results. Financial support for this project was provided by National Science Foundation under Grant Number: 1653389 and 1705246.
Ockendon, Hilary
2016-01-01
Now in its second edition, this book continues to give readers a broad mathematical basis for modelling and understanding the wide range of wave phenomena encountered in modern applications. New and expanded material includes topics such as elastoplastic waves and waves in plasmas, as well as new exercises. Comprehensive collections of models are used to illustrate the underpinning mathematical methodologies, which include the basic ideas of the relevant partial differential equations, characteristics, ray theory, asymptotic analysis, dispersion, shock waves, and weak solutions. Although the main focus is on compressible fluid flow, the authors show how intimately gasdynamic waves are related to wave phenomena in many other areas of physical science. Special emphasis is placed on the development of physical intuition to supplement and reinforce analytical thinking. Each chapter includes a complete set of carefully prepared exercises, making this a suitable textbook for students in applied mathematics, ...
Analytical modeling of pipeline failure in multiphase flow due to ...
African Journals Online (AJOL)
This research focuses on the development of a model that can predict pipeline failure due to corrosion in multiphase flows. The role that velocity, density, water cut and other parameters play in predicting corrosion is critically analyzed with Norsok Model. The result shows that velocity plays a key role in corrosion prediction.
Wettability control on multiphase flow in patterned microfluidics
Juanes, R.; Zhao, B.; MacMinn, C. W.
2016-12-01
Multiphase flow in porous media is important in many natural and industrial processes, including geologic CO2 sequestration, enhanced oil recovery, and water infiltration into soil. Although it is well known that the wetting properties of porous media can vary drastically depending on the type of media and pore fluids, the effect of wettability on multiphase flow continues to challenge our microscopic and macroscopic descriptions. Here, we study the impact of wettability on viscously unfavorable fluid-fluid displacement in disordered media by means of high-resolution imaging in microfluidic flow cells patterned with vertical posts. By systematically varying the wettability of the flow cell over a wide range of contact angles, we find that increasing the substrate's affinity to the injected fluid results in more efficient displacement of the defending fluid up to a critical wetting transition, beyond which the trend is reversed. We identify the pore-scale mechanisms—cooperative pore filling (increasing displacement efficiency) and corner flow (decreasing displacement efficiency)—responsible for this macroscale behavior, and show that they rely on the inherent 3D nature of interfacial flows, even in quasi-2D media. Our results demonstrate the powerful control of wettability on multiphase flow in porous media, and show that the markedly different invasion protocols that emerge—from pore-filling to post-bridging—are determined by physical mechanisms that are missing from current pore-scale and continuum-scale descriptions.
Development of Next Generation Multiphase Pipe Flow Prediction Tools
Energy Technology Data Exchange (ETDEWEB)
Tulsa Fluid Flow
2008-08-31
The developments of fields in deep waters (5000 ft and more) is a common occurrence. It is inevitable that production systems will operate under multiphase flow conditions (simultaneous flow of gas-oil-and water possibly along with sand, hydrates, and waxes). Multiphase flow prediction tools are essential for every phase of the hydrocarbon recovery from design to operation. The recovery from deep-waters poses special challenges and requires accurate multiphase flow predictive tools for several applications including the design and diagnostics of the production systems, separation of phases in horizontal wells, and multiphase separation (topside, seabed or bottom-hole). It is very crucial to any multiphase separation technique that is employed either at topside, seabed or bottom-hole to know inlet conditions such as the flow rates, flow patterns, and volume fractions of gas, oil and water coming into the separation devices. The overall objective was to develop a unified model for gas-oil-water three-phase flow in wells, flow lines, and pipelines to predict the flow characteristics such as flow patterns, phase distributions, and pressure gradient encountered during petroleum production at different flow conditions (pipe diameter and inclination, fluid properties and flow rates). The project was conducted in two periods. In Period 1 (four years), gas-oil-water flow in pipes were investigated to understand the fundamental physical mechanisms describing the interaction between the gas-oil-water phases under flowing conditions, and a unified model was developed utilizing a novel modeling approach. A gas-oil-water pipe flow database including field and laboratory data was formed in Period 2 (one year). The database was utilized in model performance demonstration. Period 1 primarily consisted of the development of a unified model and software to predict the gas-oil-water flow, and experimental studies of the gas-oil-water project, including flow behavior description and
Multiphase flow of immiscible fluids on unstructured moving meshes
DEFF Research Database (Denmark)
Misztal, Marek Krzysztof; Erleben, Kenny; Bargteil, Adam
2012-01-01
In this paper, we present a method for animating multiphase flow of immiscible fluids using unstructured moving meshes. Our underlying discretization is an unstructured tetrahedral mesh, the deformable simplicial complex (DSC), that moves with the flow in a Lagrangian manner. Mesh optimization...... operations improve element quality and avoid element inversion. In the context of multiphase flow, we guarantee that every element is occupied by a single fluid and, consequently, the interface between fluids is represented by a set of faces in the simplicial complex. This approach ensures...... that the underlying discretization matches the physics and avoids the additional book-keeping required in grid-based methods where multiple fluids may occupy the same cell. Our Lagrangian approach naturally leads us to adopt a finite element approach to simulation, in contrast to the finite volume approaches adopted...
Measurement Of Multiphase Flow Water Fraction And Water-cut
Xie, Cheng-gang
2007-06-01
This paper describes a microwave transmission multiphase flow water-cut meter that measures the amplitude attenuation and phase shift across a pipe diameter at multiple frequencies using cavity-backed antennas. The multiphase flow mixture permittivity and conductivity are derived from a unified microwave transmission model for both water- and oil-continuous flows over a wide water-conductivity range; this is far beyond the capability of microwave-resonance-based sensors currently on the market. The water fraction and water cut are derived from a three-component gas-oil-water mixing model using the mixture permittivity or the mixture conductivity and an independently measured mixture density. Water salinity variations caused, for example, by changing formation water or formation/injection water breakthrough can be detected and corrected using an online water-conductivity tracking technique based on the interpretation of the mixture permittivity and conductivity, simultaneously measured by a single-modality microwave sensor.
Multiphase flow in geometrically simple fracture intersections
Basagaoglu, H.; Meakin, P.; Green, C.T.; Mathew, M.; ,
2006-01-01
A two-dimensional lattice Boltzmann (LB) model with fluid-fluid and solid-fluid interaction potentials was used to study gravity-driven flow in geometrically simple fracture intersections. Simulated scenarios included fluid dripping from a fracture aperture, two-phase flow through intersecting fractures and thin-film flow on smooth and undulating solid surfaces. Qualitative comparisons with recently published experimental findings indicate that for these scenarios the LB model captured the underlying physics reasonably well.
Mixing and reactions in multiphase flow through porous media
Jimenez-Martinez, J.; Le Borgne, T.; Meheust, Y.; Porter, M. L.; De Anna, P.; Hyman, J.; Tabuteau, H.; Turuban, R.; Carey, J. W.; Viswanathan, H. S.
2016-12-01
The understanding and quantification of flow and transport processes in multiphase systems remains a grand scientific and engineering challenge in natural and industrial systems (e.g., soils and vadose zone, CO2 sequestration, unconventional oil and gas extraction, enhanced oil recovery). Beyond the kinetic of the chemical reactions, mixing processes in porous media play a key role in controlling both fluid-fluid and fluid-solid reactions. However, conventional continuum-scale models and theories oversimplify and/or ignore many important pore-scale processes. Multiphase flows, with the creation of highly heterogeneous fluid velocity fields (i.e., low velocities regions or stagnation zones, and high velocity regions or preferential paths), makes conservative and reactive transport more complex. We present recent multi-scale experimental developments and theoretical approaches to quantify transport, mixing, and reaction and their coupling with multiphase flows. We discuss our main findings: i) the sustained concentration gradients and enhanced reactivity in a two-phase system for a continuous injection, and the comparison with a pulse line injection; ii) the enhanced mixing by a third mobile-immiscible phase; and iii) the role that capillary forces play in the localization of the fluid-solid reactions. These experimental results are for highly-idealized geometries, however, the proposed models are related to basic porous media and unsaturated flow properties, and could be tested on more complex systems.
Multiphase flow modeling in centrifugal partition chromatography.
Adelmann, S; Schwienheer, C; Schembecker, G
2011-09-09
The separation efficiency in Centrifugal Partition Chromatography (CPC) depends on selection of a suitable biphasic solvent system (distribution ratio, selectivity factor, sample solubility) and is influenced by hydrodynamics in the chambers. Especially the stationary phase retention, the interfacial area for mass transfer and the flow pattern (backmixing) are important parameters. Their relationship with physical properties, operating parameters and chamber geometry is not completely understood and predictions are hardly possible. Experimental flow visualization is expensive and two-dimensional only. Therefore we simulated the flow pattern using a volume-of-fluid (VOF) method, which was implemented in OpenFOAM®. For the three-dimensional simulation of a rotating FCPC®-chamber, gravitational centrifugal and Coriolis forces were added to the conservation equation. For experimental validation the flow pattern of different solvent systems was visualized with an optical measurement system. The amount of mobile phase in a chamber was calculated from gray scale values of videos recorded by an image processing routine in ImageJ®. To visualize the flow of the stationary phase polyethylene particles were used to perform a qualitative particle image velocimetry (PIV) analysis. We found a good agreement between flow patterns and velocity profiles of experiments and simulations. By using the model we found that increasing the chamber depth leads to higher specific interfacial area. Additionally a circular flow in the stationary phase was identified that lowers the interfacial area because it pushes the jet of mobile phase to the chamber wall. The Coriolis force alone gives the impulse for this behavior. As a result the model is easier to handle than experiments and allows 3D prediction of hydrodynamics in the chamber. Additionally it can be used for optimizing geometry and operating parameters for given physical properties of solvent systems. Copyright © 2011 Elsevier B
Benchmark initiative on coupled multiphase flow and geomechanical processes during CO2 injection
Benisch, K.; Annewandter, R.; Olden, P.; Mackay, E.; Bauer, S.; Geiger, S.
2012-12-01
cap rock. For the second case, a fault is introduced to investigate the risk of fault reactivation and fracturing due to CO2 injection for a single and a multiple cap rock system, respectively. A multiple injector setting exposed to different tectonic stress regimes is proposed for the third case. Hereby, a 3D model is used compartmentalized by low permeability faults, which become permeable due to injection. Injection scenarios will be evaluated for extensional and compressive stress regimes. All model set-ups are based on already published simulation results of coupled multiphase flow and geomechanical processes during CO2 injection. To end with, a real site geometry including parameterization and realistic reservoir conditions is provided. The benchmark design and cases will be presented as well as some preliminary simulation results for the first cases. Interested institutions and researchers are invited to discuss and to participate in the study.
Impact of normal stress on multiphase flow through rough fractures
Alves da Silva Junior, J.; Kang, P. K.; Yang, Z.; Cueto-Felgueroso, L.; Juanes, R.
2015-12-01
Fluid flow and transport through geologic fractures plays a key role in several areas such as groundwater hydrology, geothermal energy, oil and gas production, CO2 sequestration and nuclear waste disposal. High-permeability zones associated with fracture corridors often serve as fast fluid conduits for both single and multiphase flow in otherwise low-permeability media. When multiphase flow occurs, the presence of one phase interferes with the flow of the other phase, resulting in complex displacement patterns through the fracture, and macroscopic descriptors (such as fracture-scale capillary pressure and relative permeability) that depend on the phase concentration of both phases. Here, we investigate the impact of normal stress on single and multiphase flow through rough-walled fractures: (1) we generate synthetic aperture fields that honor the fractal roughness structure observed in real fractures; (2) we model the effect of normal stress on the fracture aperture geometry by solving the contact problem between fracture walls; and (3) we use invasion percolation with trapping to model immiscible fluid displacement and then compute relative permeability numerically for each stress scenario. Our results indicate that normal stress increases the amount of contact area in the fracture wall, which results in an increase of the tortuosity of the available path for fluid displacement. Increasing normal stress results in low relative permeability for the wetting phase due to a decrease of the available path for fluid flow, and therefore a small amount of non-wetting fluid has a large impact on the flow of the wetting fluid. We find that the relative permeability of the non-wetting fluid shows less variation with stress than the wetting fluid, and that both fluids exhibit strong phase interference at intermediate saturations. Finally, we show early results from our experimental work currently underway to validate the modeling results.
CONTINOUS MULTI-PHASE FLOW REACTOR FOR SMALL AND LARGE FLOW CAPACITIES THAN L/MIN
Al-Rawashdeh, Ma'moun; Schouten, Jaap; Nijhuis, T. Alexander; Yue, Jun
2014-01-01
Multiphase flow processing in flow reactors holds great promises for diverse applications in fine chemicals and materials synthesis primarily due to its precise control over the flow, mixing and reaction inside or between each phase. Even though, flow reactors have shown superior performance, so far
Seeking simplicity for the understanding of multiphase flows
Stone, Howard A.
2017-10-01
Fluid mechanics is a discipline with rich phenomena, with motions occurring over an enormous range of length scales, and spanning a wide range of laminar and turbulent flows, instabilities, and applications in industry, nature, biology, and medicine. The subfield of complex fluids typically refers to those flows where the complexity is introduced, for example, by the presence of suspended particles, multiple phases, soft boundaries, and electrokinetic effects; several distinct multiphase flows of Newtonian fluids make up the examples in this article. Interfaces play a significant role and modify the flow with feedback that further changes the shapes of the interfaces. I will provide examples of our work highlighting (i) new features of classical instabilities triggered by changes in geometry, (ii) multiphase flows relevant to the design of liquid-infused substrates exhibiting effective slip while retaining the trapped liquid, and (iii) unexpected dynamics in flow at a T-junction. The interplay of experiments and mathematical models and/or simulations is critical to the new understanding developed.
Stability Analysis of Reactive Multiphase Slug Flows in Microchannels
Directory of Open Access Journals (Sweden)
Alejandro A. Munera Parra
2014-05-01
Full Text Available Conducting multiphase reactions in micro-reactors is a promising strategy for intensifying chemical and biochemical processes. A major unresolved challenge is to exploit the considerable benefits offered by micro-scale operation for industrial scale throughputs by numbering-up whilst retaining the underlying advantageous flow characteristics of the single channel system in multiple parallel channels. Fabrication and installation tolerances in the individual micro-channels result in different pressure losses and, thus, a fluid maldistribution. In this work, an additional source of maldistribution, namely the flow multiplicities, which can arise in a multiphase reactive or extractive flow in otherwise identical micro-channels, was investigated. A detailed experimental and theoretical analysis of the flow stability with and without reaction for both gas-liquid and liquid-liquid slug flow has been developed. The model has been validated using the extraction of acetic acid from n-heptane with the ionic liquid 1-Ethyl-3-methylimidazolium ethyl sulfate. The results clearly demonstrate that the coupling between flow structure, the extent of reaction/extraction and pressure drop can result in multiple operating states, thus, necessitating an active measurement and control concept to ensure uniform behavior and optimal performance.
Approaching multiphase flows from the perspective of computational fluid dynamics
International Nuclear Information System (INIS)
Banas, A.O.
1992-01-01
Thermalhydraulic simulation methodologies based on subchannel and porous-medium concepts are briefly reviewed and contrasted with the general approach of Computational Fluid Dynamics (CFD). An outline of the advanced CFD methods for single-phase turbulent flows is followed by a short discussion of the unified formulation of averaged equations for turbulent and multiphase flows. Some of the recent applications of CFD at Chalk River Laboratories are discussed, and the complementary role of CFD with regard to the established thermalhydraulic methods of analysis is indicated. (author). 8 refs
Multiphase flows in complex geometries: a UQ perspective
Icardi, Matteo
2015-01-07
Nowadays computer simulations are widely used in many multiphase flow applications involving interphases, dispersed particles, and complex geometries. Most of these problems are solved with mixed models composed of fundamental physical laws, rigorous mathematical upscaling, and empirical correlations/closures. This means that classical inference techniques or forward parametric studies, for example, becomes computationally prohibitive and must take into account the physical meaning and constraints of the equations. However mathematical techniques commonly used in Uncertainty Quantification can come to the aid for the (i) modeling, (ii) simulation, and (iii) validation steps. Two relevant applications for environmental, petroleum, and chemical engineering will be presented to highlight these aspects and the importance of bridging the gaps between engineering applications, computational physics and mathematical methods. The first example is related to the mathematical modeling of sub-grid/sub-scale information with Probability Density Function (PDF) models in problems involving flow, mixing, and reaction in random environment. After a short overview of the research field, some connections and similarities with Polynomial Chaos techniques, will be investigated. In the second example, averaged correlations laws and effective parameters for multiphase flow and their statistical fluctuations, will be considered and efficient computational techniques, borrowed from high-dimensional stochastic PDE problems, will be applied. In presence of interfacial flow, where small spatial scales and fast time scales are neglected, the assessment of robustness and predictive capabilities are studied. These illustrative examples are inspired by common problems arising, for example, from the modeling and simulation of turbulent and porous media flows.
Applied multiphase flow in pipes and flow assurance oil and gas production
Al-Safran, Eissa M
2017-01-01
Applied Multiphase Flow in Pipes and Flow Assurance - Oil and Gas Production delivers the most recent advancements in multiphase flow technology while remaining easy to read and appropriate for undergraduate and graduate petroleum engineering students. Responding to the need for a more up-to-the-minute resource, this highly anticipated new book represents applications on the fundamentals with new material on heat transfer in production systems, flow assurance, transient multiphase flow in pipes and the TUFFP unified model. The complex computation procedure of mechanistic models is simplified through solution flowcharts and several example problems. Containing over 50 solved example problems and 140 homework problems, this new book will equip engineers with the skills necessary to use the latest steady-state simulators available.
Multiphase flow of immiscible fluids on unstructured moving meshes.
Misztal, Marek Krzysztof; Erleben, Kenny; Bargteil, Adam; Fursund, Jens; Christensen, Brian Bunch; Bærentzen, Jakob Andreas; Bridson, Robert
2014-01-01
In this paper, we present a method for animating multiphase flow of immiscible fluids using unstructured moving meshes. Our underlying discretization is an unstructured tetrahedral mesh, the deformable simplicial complex (DSC), that moves with the flow in a Lagrangian manner. Mesh optimization operations improve element quality and avoid element inversion. In the context of multiphase flow, we guarantee that every element is occupied by a single fluid and, consequently, the interface between fluids is represented by a set of faces in the simplicial complex. This approach ensures that the underlying discretization matches the physics and avoids the additional book-keeping required in grid-based methods where multiple fluids may occupy the same cell. Our Lagrangian approach naturally leads us to adopt a finite element approach to simulation, in contrast to the finite volume approaches adopted by a majority of fluid simulation techniques that use tetrahedral meshes. We characterize fluid simulation as an optimization problem allowing for full coupling of the pressure and velocity fields and the incorporation of a second-order surface energy. We introduce a preconditioner based on the diagonal Schur complement and solve our optimization on the GPU. We provide the results of parameter studies as well as a performance analysis of our method, together with suggestions for performance optimization.
Modelling of transit-time ultrasonic flow meters under multi-phase flow conditions
DEFF Research Database (Denmark)
Simurda, Matej; Duggen, Lars; Lassen, Benny
2016-01-01
of the background flow are included. Spatial derivatives are calculated by a Fourier collocation scheme allowing the use of the Fast Fourier transform. The method is compared against analytical solutions and experimental measurements. Additionally, a study of clamp-on and in-line ultrasonic flowmeters operating......A pseudospectral model for transit time ultrasonic flowmeters under multiphase flow conditions is presented. The method solves first order stress-velocity equations of elastodynamics, with acoustic media being modelled by setting shear modulus to zero. Additional terms to account for the effect...... under multiphase flow conditions is carried out....
4. Workshop - Measurement techniques of stationary and transient multiphase flow
Energy Technology Data Exchange (ETDEWEB)
Prasser, H.M. (ed.)
2001-05-01
In November 2000, the 4th Workshop on Measurement Techniques for Stationary and Transient Multiphase Flows took place in Rossendorf. Three previous workshops of this series were national meetings; this time participants from different countries took part. The programme comprised 14 oral presentations, 9 of which are included in these proceedings in full length. A special highlight of the meeting was the main lecture ''Ultrasonic doppler method for bubbly flow measurement'' of Professor Masanori Aritomi, Dr. Hiroshige Kikura and Dr. Yumiko Suzuki. The workshop again dealt with high-resolution phase distribution and phase velocity measurement techniques based on electrical conductivity, ultrasound, laser light and high-speed cinematography. A number of presentations were dedicated to the application of wire-mesh sensors developed by FZR for different applications used by the Technical Universities of Delft and Munich and the Tokyo Institute of Technology. (orig.)
4. Workshop - Measurement techniques of stationary and transient multiphase flow
International Nuclear Information System (INIS)
Prasser, H.M.
2001-05-01
In November 2000, the 4th Workshop on Measurement Techniques for Stationary and Transient Multiphase Flows took place in Rossendorf. Three previous workshops of this series were national meetings; this time participants from different countries took part. The programme comprised 14 oral presentations, 9 of which are included in these proceedings in full length. A special highlight of the meeting was the main lecture ''Ultrasonic doppler method for bubbly flow measurement'' of Professor Masanori Aritomi, Dr. Hiroshige Kikura and Dr. Yumiko Suzuki. The workshop again dealt with high-resolution phase distribution and phase velocity measurement techniques based on electrical conductivity, ultrasound, laser light and high-speed cinematography. A number of presentations were dedicated to the application of wire-mesh sensors developed by FZR for different applications used by the Technical Universities of Delft and Munich and the Tokyo Institute of Technology. (orig.)
Linear Power-Flow Models in Multiphase Distribution Networks: Preprint
Energy Technology Data Exchange (ETDEWEB)
Bernstein, Andrey; Dall' Anese, Emiliano
2017-05-26
This paper considers multiphase unbalanced distribution systems and develops approximate power-flow models where bus-voltages, line-currents, and powers at the point of common coupling are linearly related to the nodal net power injections. The linearization approach is grounded on a fixed-point interpretation of the AC power-flow equations, and it is applicable to distribution systems featuring (i) wye connections; (ii) ungrounded delta connections; (iii) a combination of wye-connected and delta-connected sources/loads; and, (iv) a combination of line-to-line and line-to-grounded-neutral devices at the secondary of distribution transformers. The proposed linear models can facilitate the development of computationally-affordable optimization and control applications -- from advanced distribution management systems settings to online and distributed optimization routines. Performance of the proposed models is evaluated on different test feeders.
Multiphase flow in lab on chip devices: A real tool for the future
Shui, Lingling; Pennathur, S.; Pennathur, Sumita; Eijkel, Jan C.T.; van den Berg, Albert
2008-01-01
Many applications for lab on a chip (LOC) devices require the use of two or more fluids that are either not chemically related (e.g. oil and water) or in different phases (e.g. liquid and gas). Utilizing multiphase flow in LOC devices allows for both the fundamental study of multiphase flow and the
Multiphase flow dynamics 2 thermal and mechanical interactions
Kolev, Nikolay I
2007-01-01
The industrial use of multi-phase systems requires analytical and numerical strategies for predicting their behavior. This book contains theory, methods and practical experience for describing complex transient multi-phase processes. It provides a systematic presentation of the theory and practice of numerical multi-phase fluid dynamics.
Multicomponent, multiphase flow in porous media with temperature variation
Energy Technology Data Exchange (ETDEWEB)
Wingard, J.S.; Orr, F.M. Jr.
1990-10-01
Recovery of hydrocarbons from porous media is an ongoing concern. Advanced techniques augment conventional recovery methods by injecting fluids that favorably interact with the oil. These fluids interact with the oil by energy transfer, in the case of steam injection, or by mass transfer, as in a miscible gas flood. Often both thermal and compositional considerations are important. An understanding of these injection methods requires knowledge of how temperature variations, phase equilibrium and multiphase flow in porous media interact. The material balance for each component and energy balance are cast as a system of non-strictly hyperbolic partial differential equations. This system of equations is solved using the method of characteristics. The model takes into account the phase behavior by using the Peng-Robinson equation of state to partition the individual components into different phases. Temperature effects are accounted for by the energy balance. Flow effects are modelled by using fractional flow curves and a Stone's three phase relative permeability model. Three problems are discussed. The first problem eliminates the phase behavior aspect of the problem by studying the flow of a single component as it undergoes an isothermal phase change. The second couples the effects of temperature and flow behavior by including a second component that is immiscible with the original component. Phase behavior is added by using a set of three partially miscible components that partition into two or three separate phases. 66 refs., 54 figs., 14 tabs.
Modelling the Multiphase Flow in Dense Medium Cyclones
Directory of Open Access Journals (Sweden)
Kaiwei Chu
2010-12-01
Full Text Available Dense medium cyclone (DMC is widely used in mineral industry to separate solids by density. It is simple in design but the flow pattern within it is complex due to the size and density distributions of the feed and process medium solids, and the turbulent vortex formed. Recently, the so-called combined computational fluid dynamics (CFD and discrete element method (DEM (CFD-DEM was extended from two-phase flow to model the flow in DMCs at the University of New South Wales (UNSW. In the CFD-DEM model, the flow of coal particles is modelled by DEM and that of medium flow by CFD, allowing consideration of medium-coal mutual interaction and particle-particle collisions. In the DEM model, Newton's laws of motion are applied to individual particles, and in the CFD model the local-averaged Navier-Stokes equations combined with the volume of fluid (VOF and mixture multiphase flow models are solved. The application to the DMC studies requires intensive computational effort. Therefore, various simplified versions have been proposed, corresponding to the approaches such as Lagrangian particle tracking (LPT method where dilute phase flow is assumed so that the interaction between particles can be ignored, one-way coupling where the effect of particle flow on fluid flow is ignored, and the use of the concept of parcel particles whose properties are empirically determined. In this paper, the previous works on the modelling of DMCs at UNSW are summarized and the features and applicability of the models used are discussed.
Heat and mass transfer in turbulent multiphase channel flow
Bukhvostova, A.
2015-01-01
Direct numerical simulation is used to assess the importance of compressibility in turbulent channel flow of a mixture of air and water vapor with dispersed water droplets. The dispersed phase is allowed to undergo phase transition, which leads to heat and mass transfer between the phases. We
RF sensor for multiphase flow measurement through an oil pipeline
Wylie, S. R.; Shaw, A.; Al-Shamma'a, A. I.
2006-08-01
We have developed, in conjunction with Solartron ISA, an electromagnetic cavity resonator based sensor for multiphase flow measurement through an oil pipeline. This sensor is non-intrusive and transmits low power (10 mW) radio frequencies (RF) in the range of 100-350 MHz and detects the pipeline contents using resonant peaks captured instantaneously. The multiple resonances from each captured RF spectrum are analysed to determine the phase fractions in the pipeline. An industrial version of the sensor for a 102 mm (4 inch) diameter pipe has been constructed and results from this sensor are compared to those given by simulations performed using the electromagnetic high frequency structure simulator software package HFSS. This paper was presented at the 13th International Conference on Sensors and held in Chatham, Kent, on 6-7 September 2005.
Thermodynamic framework for discrete optimal control in multiphase flow systems
Sieniutycz, Stanislaw
1999-08-01
Bellman's method of dynamic programming is used to synthesize diverse optimization approaches to active (work producing) and inactive (entropy generating) multiphase flow systems. Thermal machines, optimally controlled unit operations, nonlinear heat conduction, spontaneous relaxation processes, and self-propagating wave fronts are all shown to satisfy a discrete Hamilton-Jacobi-Bellman equation and a corresponding discrete optimization algorithm of Pontryagin's type, with the maximum principle for a Hamiltonian. The extremal structures are always canonical. A common unifying criterion is set for all considered systems, which is the criterion of a minimum generated entropy. It is shown that constraints can modify the entropy functionals in a different way for each group of the processes considered; thus the resulting structures of these functionals may differ significantly. Practical conclusions are formulated regarding the energy savings and energy policy in optimally controlled systems.
Yue, Jun
2017-01-01
The convergence of continuous flow chemistry and microreactor technology creates numerous possibilities towards the development of an efficient and sustainable chemical synthesis. In this field, the combination of heterogeneous catalysis and multiphase flow processing in microreactors represents an
Multiphase Flow Technology Impacts on Thermal Control Systems for Exploration
McQuillen, John; Sankovic, John; Lekan, Jack
2006-01-01
The Two-Phase Flow Facility (TPHIFFy) Project focused on bridging the critical knowledge gap by developing and demonstrating critical multiphase fluid products for advanced life support, thermal management and power conversion systems that are required to enable the Vision for Space Exploration. Safety and reliability of future systems will be enhanced by addressing critical microgravity fluid physics issues associated with flow boiling, condensation, phase separation, and system stability. The project included concept development, normal gravity testing, and reduced gravity aircraft flight campaigns, in preparation for the development of a space flight experiment implementation. Data will be utilized to develop predictive models that could be used for system design and operation. A single fluid, two-phase closed thermodynamic loop test bed was designed, assembled and tested. The major components in this test bed include: a boiler, a condenser, a phase separator and a circulating pump. The test loop was instrumented with flow meters, thermocouples, pressure transducers and both high speed and normal speed video cameras. A low boiling point surrogate fluid, FC-72, was selected based on scaling analyses using preliminary designs for operational systems. Preliminary results are presented which include flow regime transitions and some observations regarding system stability.
On the predictive capabilities of multiphase Darcy flow models
Icardi, Matteo
2016-01-09
Darcy s law is a widely used model and the limit of its validity is fairly well known. When the flow is sufficiently slow and the porosity relatively homogeneous and low, Darcy s law is the homogenized equation arising from the Stokes and Navier- Stokes equations and depends on a single effective parameter (the absolute permeability). However when the model is extended to multiphase flows, the assumptions are much more restrictive and less realistic. Therefore it is often used in conjunction with empirical models (such as relative permeability and capillary pressure curves), derived usually from phenomenological speculations and experimental data fitting. In this work, we present the results of a Bayesian calibration of a two-phase flow model, using high-fidelity DNS numerical simulation (at the pore-scale) in a realistic porous medium. These reference results have been obtained from a Navier-Stokes solver coupled with an explicit interphase-tracking scheme. The Bayesian inversion is performed on a simplified 1D model in Matlab by using adaptive spectral method. Several data sets are generated and considered to assess the validity of this 1D model.
Compositional multiphase flow and transport in heterogeneous porous media
Energy Technology Data Exchange (ETDEWEB)
Huber, R.U.
2000-07-01
This work first treats the conceptual models for the description of multiphase flow processes in porous media. The thermodynamic laws are explained and the description and quantification of multi-fluid equilibria are discussed in order to account for fluid composition. The fully and weakly coupled approaches for the mathematical description of such flow processes with respect to systems consisting of two and three fluid phases as well as with respect to compositional single and multiphase systems are assessed. For the discretization of the two-phase flow equations node- and cell-centered finite volume methods and mixed and mixed-hybrid finite element approaches are applied. Based upon these methods five solution algorithms are developed. Four of these algorithms are based on the simultaneous solution of the discretized equations in combination with the Newton-Raphson technique. Methods 1 and 2 treat two- three-phase flow processes, Method 3 applies to the solution of partially miscible three-component systems while Method 4 is created for three-phase three-component systems. The latter method uses a variable substitution dependent on the local presence of the fluid phases. Method 5 is based on the IMPES/IMPESC concept. The time-implicit pressure equation is discretized with the mixed-hybrid finite element method. The saturation and concentration equations, respectively, are solved with a cell-centered finite volume scheme. The developed algorithms are applied to the two- and three-phase Buckley-Leverett problems. A partitioning interwell tracer test is simulated. The propagation behavior of nonaqueous phase liquids (NAPLs) in the saturated and unsaturated ground zone under the influence of heterogeneities are examined. In addition, a larger-scale experiment is simulated, which involves an injection of trichloroethylene into the subsurface and the subsequent distribution. Here, the development of a dissolved contaminant plume as well as the behavior of organic
Krylov methods for compressible flows
Tidriri, M. D.
1995-01-01
We investigate the application of Krylov methods to compressible flows, and the effect of implicit boundary conditions on the implicit solution of nonlinear problems. Two defect-correction procedures, namely, approximate factorization (AF) for structured grids and ILU/GMRES for general grids, are considered. Also considered here are Newton-Krylov matrix-free methods that we combined with the use of mixed discretization schemes in the implicitly defined Jacobian and its preconditioner. Numerical experiments that show the performance of our approaches are then presented.
Multiphase flow dynamics and control; Dynamique et controle des ecoulements polyphasiques
Energy Technology Data Exchange (ETDEWEB)
Duret, E.
2005-02-01
Production in the petroleum industry requires a better knowledge of multiphase flow, as the design of pipelines may cause the flow to become strongly unstable. For instance, for low flow rates and when a sea line ends at a riser, the riser base may accumulate liquid and stop the flow of gas. Then, the upstream gas is compressed until its pressure is large enough to push the liquid slug downstream. Under such conditions, a cyclic process occurs which is called severe slugging, generating large and fast fluctuations in pressure and flow rates. This thesis is devoted to two methods to stabilize this undesirable phenomenon. Using the pipeline's ability to separate phases to pick-up the gas upstream the riser base, they are mainly based on the perturbation theory (fast proportional effect, slow integral effect). The first one uses a secondary riser to transport the gas to the surface facilities. A stability study worked out with the phase diagrams technique shows that it is a good method to control this phenomenon. However, it imposes a high pressure in all the system. Thus, the second controller re-injects the gas at a determined height in the riser to decrease the hydrostatic pressure. A first stability study in open loop give a criterion on the minimal reinjection height. Then, the controller is developed by using the two-time scale control techniques. Finally, let us denote that these two controllers have been validated with a small size experimental set up. (author)
Investigation of hydrate formation and transportability in multiphase flow systems
Grasso, Giovanny A.
The oil and gas industry is moving towards offshore developments in more challenging environments, where evaluating hydrate plugging risks to avoid operational/safety hazards becomes more difficult (Sloan, 2005). Even though mechanistic models for hydrate plug formation have been developed, components for a full comprehensive model are still missing. Prior to this work, research efforts were focused on flowing hydrate particles with relatively little research on hydrate accumulation, leaving hydrate deposition in multiphase flow an unexplored subject. The focus of this thesis was to better understand hydrate deposition as a form of accumu- lation in pipelines. To incorporate the multiphase flow effect, hydrate formation experiments were carried out at varying water cut (WC) from 15 to 100 vol.%, liquid loading (LL) from 50 to 85 vol.%, mixture velocity (vmix) from 0.75 to 3 m/s, for three fluids systems (100 % WC, water in Conroe crude oil emulsions and King Ranch condensate + water) on the ExxonMobil flowloop (4 in. nominal size and 314 ft. long) at Friendswood, TX. For the 100 % WC flowloop tests, hydrate particle distribution transitions beyond a critical hydrate volume concentration, observed values were between 8.2 to 29.4 vol.%, causing a sudden increase in pressure drop (DP). A revised correlation of the transition as a function of Reynolds number and liquid loading was developed. For Conroe emulsions, DP starts increasing at higher hydrate concentrations than King Ranch condensate, many times at 10 vol.%. Experiments with King Ranch show higher relative DP (10 to 25) than Conroe (2 to 10) performed at the same vmix and LL. Cohesive force measurements between cyclopentane hydrate particles were reduced from a value of 3.32 mN/m to 1.26 mN/m when 6 wt.% Conroe was used and to 0.41 mN/m when 5 wt.% Caratinga crude oil was used; similar values were obtained when extracted asphaltenes were used. King Ranch condensate (11 wt.%) did not significantly change the
Dual domain material point method for multiphase flows
Zhang, Duan
2017-11-01
Although the particle-in-cell method was first invented in the 60's for fluid computations, one of its later versions, the material point method, is mostly used for solid calculations. Recent development of the multi-velocity formulations for multiphase flows and fluid-structure interactions requires the Lagrangian capability of the method be combined with Eulerian calculations for fluids. Because of different numerical representations of the materials, additional numerical schemes are needed to ensure continuity of the materials. New applications of the method to compute fluid motions have revealed numerical difficulties in various versions of the method. To resolve these difficulties, the dual domain material point method is introduced and improved. Unlike other particle based methods, the material point method uses both Lagrangian particles and Eulerian mesh, therefore it avoids direct communication between particles. With this unique property and the Lagrangian capability of the method, it is shown that a multiscale numerical scheme can be efficiently built based on the dual domain material point method. In this talk, the theoretical foundation of the method will be introduced. Numerical examples will be shown. Work sponsored by the next generation code project of LANL.
Load Balancing Strategies for Multiphase Flows on Structured Grids
Olshefski, Kristopher; Owkes, Mark
2017-11-01
The computation time required to perform large simulations of complex systems is currently one of the leading bottlenecks of computational research. Parallelization allows multiple processing cores to perform calculations simultaneously and reduces computational times. However, load imbalances between processors waste computing resources as processors wait for others to complete imbalanced tasks. In multiphase flows, these imbalances arise due to the additional computational effort required at the gas-liquid interface. However, many current load balancing schemes are only designed for unstructured grid applications. The purpose of this research is to develop a load balancing strategy while maintaining the simplicity of a structured grid. Several approaches are investigated including brute force oversubscription, node oversubscription through Message Passing Interface (MPI) commands, and shared memory load balancing using OpenMP. Each of these strategies are tested with a simple one-dimensional model prior to implementation into the three-dimensional NGA code. Current results show load balancing will reduce computational time by at least 30%.
Statistical analysis on the signals monitoring multiphase flow patterns in pipeline-riser system
Ye, Jing; Guo, Liejin
2013-07-01
The signals monitoring petroleum transmission pipeline in offshore oil industry usually contain abundant information about the multiphase flow on flow assurance which includes the avoidance of most undesirable flow pattern. Therefore, extracting reliable features form these signals to analyze is an alternative way to examine the potential risks to oil platform. This paper is focused on characterizing multiphase flow patterns in pipeline-riser system that is often appeared in offshore oil industry and finding an objective criterion to describe the transition of flow patterns. Statistical analysis on pressure signal at the riser top is proposed, instead of normal prediction method based on inlet and outlet flow conditions which could not be easily determined during most situations. Besides, machine learning method (least square supported vector machine) is also performed to classify automatically the different flow patterns. The experiment results from a small-scale loop show that the proposed method is effective for analyzing the multiphase flow pattern.
Numerical modelling of multiphase liquid-vapor-gas flows with interfaces and cavitation
Pelanti, Marica
2017-11-01
We are interested in the simulation of multiphase flows where the dynamical appearance of vapor cavities and evaporation fronts in a liquid is coupled to the dynamics of a third non-condensable gaseous phase. We describe these flows by a single-velocity three-phase compressible flow model composed of the phasic mass and total energy equations, the volume fraction equations, and the mixture momentum equation. The model includes stiff mechanical and thermal relaxation source terms for all the phases, and chemical relaxation terms to describe mass transfer between the liquid and vapor phases of the species that may undergo transition. The flow equations are solved by a mixture-energy-consistent finite volume wave propagation scheme, combined with simple and robust procedures for the treatment of the stiff relaxation terms. An analytical study of the characteristic wave speeds of the hierarchy of relaxed models associated to the parent model system is also presented. We show several numerical experiments, including two-dimensional simulations of underwater explosive phenomena where highly pressurized gases trigger cavitation processes close to a rigid surface or to a free surface. This work was supported by the French Government Grant DGA N. 2012.60.0011.00.470.75.01, and partially by the Norwegian Grant RCN N. 234126/E30.
Modeling the multiphase flows in deformable porous media
Directory of Open Access Journals (Sweden)
Perepechko Lyudmila
2017-01-01
Full Text Available This work proposes the nonlinear model for the flow of mixture of compressible liquids in a porous medium with consideration of finite deformations and thermal effects. Development of this model is based on the method of thermodynamically consistent systems of conservation laws. Numerical analysis of the model is based on the WENO-Runge-Kutta method of the high accuracy. The model is developed to solve the problems arising when studying the different-scale fluid dynamic processes. Evolution of the wave fields in inhomogeneous saturated porous media is considered.
Evaluation of 3D Mapping Experimental Non-Intrusive Methods for Multiphase Flows
Directory of Open Access Journals (Sweden)
C Poette
2016-09-01
Full Text Available The present contribution focuses on the evaluation of non-intrusive 3D mapping experimental methods for the investigation of multiphase flows during tank sloshing. This problem is a key issue for launchers and satellites since the feeding in propellants has to be ensured during flight and manoeuvres. At first, an extensive survey of non-intrusive experimental techniques of interest for multiphase flows has been carried out. This task has accounted for new innovative methods developed for space and non-space applications with a focus on the methods used in medicine and other fields such as ultrasound techniques. A particular care has been given to electrical and ultrasonic tomography techniques since they are both non-intrusive, non-invasive, low cost, fast and simple to operate, and suitable for real time measurements. Electrical tomography techniques have demonstrated convincing capabilities for multiphase flow visualization and present numerous advantages for industrial processes and multiphase flow measurements. Ultrasound experimental techniques are extensively used in medicine for a wide range of investigations. They are also largely used for material analysis and fluid mechanics. As a consequence since several years, ultrasound tomography has been applied to multiphase flows. Application of the method to annular, sludge, slug and bubbly flows has demonstrated the potential of this technique for multiphase flow investigations. Additionally, in the context of launchers this technique presents an advantage in term of safety. Using the available results, the advantages and disadvantages of ultrasonic and electrical methods have been identified and this leads to the conclusion that the ultrasonic tomography possesses the best potential for the final application. Finally, using the available experimental results obtained using ultrasound tomography for the mapping of multiphase flows, numerical simulations have been performed to proceed to their
Directory of Open Access Journals (Sweden)
S. Sugiharto1
2013-04-01
Full Text Available Multiphase flow modeling presents great challenges due to its extreme importance in various industrial and environmental applications. In the present study, prediction of separation length of multiphase flow is examined experimentally by injection of two kinds of iodine-based radiotracer solutions into a hydrocarbon transport pipeline (HCT having an inner diameter of 24 in (60,96 m. The main components of fluids in the pipeline are water 95%, crude oil 3% and gas 2%. A radiotracing experiment was carried out at the segment of pipe which is located far from branch points with assumptions that stratified flows in such segment were achieved. Two radiation detectors located at 80 and 100 m from injection point were used to generate residence time distribution (RTD curve resulting from injection of radiotracer solutions. Multiphase computational fluid dynamics (CFD simulations using Eulerian-Eulerian control volume and commercial CFD package Fluent 6.2 were employed to simulate separation length of multiphase flow. The results of study shows that the flow velocity of water is higher than the flow rate of crude oil in water-dominated system despite the higher density of water than the density of the crude oil. The separation length in multiphase flow predicted by Fluent mixture model is approximately 20 m, measured from injection point. This result confirms that the placement of the first radiation detector at the distance 80 m from the injection point was correct
International Nuclear Information System (INIS)
Sugiharto, S.; Kurniadi, R.; Abidin, Z.; Stegowski, Z.; Furman, L.
2013-01-01
Multiphase flow modeling presents great challenges due to its extreme importance in various industrial and environmental applications. In the present study, prediction of separation length of multiphase flow is examined experimentally by injection of two kinds of iodine-based radiotracer solutions into a hydrocarbon transport pipeline (HCT) having an inner diameter of 24 in (60,96 m). The main components of fluids in the pipeline are water 95%, crude oil 3% and gas 2%. A radiotracing experiment was carried out at the segment of pipe which is located far from branch points with assumptions that stratified flows in such segment were achieved. Two radiation detectors located at 80 and 100 m from injection point were used to generate residence time distribution (RTD) curve resulting from injection of radiotracer solutions. Multiphase computational fluid dynamics (CFD) simulations using Eulerian-Eulerian control volume and commercial CFD package Fluent 6.2 were employed to simulate separation length of multiphase flow. The results of study shows that the flow velocity of water is higher than the flow rate of crude oil in water-dominated system despite the higher density of water than the density of the crude oil. The separation length in multiphase flow predicted by Fluent mixture model is approximately 20 m, measured from injection point. This result confirms that the placement of the first radiation detector at the distance 80 m from the injection point was correct. (author)
Nanoscale multi-phase flow and its application to control nanofiber diameter
Directory of Open Access Journals (Sweden)
Liu Yan-Qing
2018-01-01
Full Text Available Nanoscale flows appear widely in nanofiber fabrication especially in electro-spinning, where a nanoscale jet is a multi-phase fluid including solvents and additives. This paper shows that the fiber morphology can be effectively controlled by adjusting the density of the multi-phase jet. TiO2 is used as an additive to produce polyacrylonitrile nanofibers by electrospinning; the results elucidate that uniform nanofiber can be obtained, and this phenomenon is explained theoretically.
Multiphase Flow Dynamics 4 Turbulence, Gas Adsorption and Release, Diesel Fuel Properties
Kolev, Nikolay Ivanov
2012-01-01
The present Volume 4 of the successful monograh package “Multiphase Flow Dynamics”is devoted to selected Chapters of the multiphase fluid dynamics that are important for practical applications but did not find place in the previous volumes. The state of the art of the turbulence modeling in multiphase flows is presented. As introduction, some basics of the single phase boundary layer theory including some important scales and flow oscillation characteristics in pipes and rod bundles are presented. Then the scales characterizing the dispersed flow systems are presented. The description of the turbulence is provided at different level of complexity: simple algebraic models for eddy viscosity, simple algebraic models based on the Boussinesq hypothesis, modification of the boundary layer share due to modification of the bulk turbulence, modification of the boundary layer share due to nucleate boiling. The role of the following forces on the mathematical description of turbulent flows is discussed: the lift fo...
Computer program for compressible flow network analysis
Wilton, M. E.; Murtaugh, J. P.
1973-01-01
Program solves problem of an arbitrarily connected one dimensional compressible flow network with pumping in the channels and momentum balancing at flow junctions. Program includes pressure drop calculations for impingement flow and flow through pin fin arrangements, as currently found in many air cooled turbine bucket and vane cooling configurations.
Pattern recognition techniques for horizontal and vertically upward multiphase flow measurement
Arubi, Tesi I. M.; Yeung, Hoi
2012-03-01
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 that has led oil companies to develop smaller and marginal fields and reservoirs in remote locations and deep offshore, thereby placing great demands for compact and more cost effective solutions of on-line continuous multiphase flow measurement for well testing, production monitoring, production optimisation, process control and automation. The pattern recognition approach for clamp-on multiphase measurement employed in this study provides one means for meeting this need. High speed caesium-137 radioisotope-based densitometers were installed vertically at the top of a 50.8mm and 101.6mm riser as well as horizontally at the riser base in the Cranfield University multiphase flow test facility. A comprehensive experimental campaign comprising flow conditions typical of operating conditions found in the Petroleum Industry was conducted. The application of a single gamma densitometer unit, in conjunction with pattern recognition techniques to determine both the phase volume fractions and velocities to yield the individual phase flow rates of horizontal and vertically upward multiphase flows was investigated. The pattern recognition systems were trained to map the temporal fluctuations in the multiphase mixture density with the individual phase flow rates using statistical features extracted from the gamma counts signals as their inputs. Initial results yielded individual phase flow rate predictions to within ±5% relative error for the two phase airwater flows and ±10% for three phase air-oil-water flows data.
PREFACE: The 6th International Symposium on Measurement Techniques for Multiphase Flows
Okamoto, Koji; Murai, Yuichi
2009-02-01
Research on multi-phase flows is very important for industrial applications, including power stations, vehicles, engines, food processing, and so on. Also, from the environmental viewpoint, multi-phase flows need to be investigated to overcome global warming. Multi-phase flows originally have non-linear features because they are multi-phased. The interaction between the phases plays a very interesting role in the flows. The non-linear interaction causes the multi-phase flows to be very difficult to understand phenomena. The International Symposium on Measurement Techniques for Multi-phase Flows (ISMTMF) is a unique symposium. The target of the symposium is to exchange the state-of-the-art knowledge on the measurement techniques for non-linear multi-phase flows. Measurement technique is the key technology to understanding non-linear phenomena. The ISMTMF began in 1995 in Nanjing, China. The symposium has continuously been held every two or three years. The ISMTMF-2008 was held in Okinawa, Japan as the 6th symposium of ISMTMF on 15-17 December 2008. Okinawa has a long history as the Ryukyus Kingdom. China and Japan have had cultural and economic exchanges through Okinawa for more than 1000 years. Please enjoy Okinawa and experience its history to enhance our international communication. The present symposium was attended by 124 participants, the program included 107 contributions with 5 plenary lectures, 2 keynote lectures, and 100 oral regular paper presentations. The topics include, besides the ordinary measurement techniques for multiphase flows, acoustic and electric sensors, bubbles and microbubbles, computed tomography, gas-liquid interface, laser-imaging and PIV, oil/coal/drop and spray, solid and powder, spectral and multi-physics. This volume includes the presented papers at ISMTMF-2008. In addition to this volume, ten selected papers will be published in a special issue of Measurement Science and Technology. We would like to express special thanks to all
Application of the level set method for multi-phase flow computation in fusion engineering
International Nuclear Information System (INIS)
Luo, X-Y.; Ni, M-J.; Ying, A.; Abdou, M.
2006-01-01
Numerical simulation of multi-phase flow is essential to evaluate the feasibility of a liquid protection scheme for the power plant chamber. The level set method is one of the best methods for computing and analyzing the motion of interface among the multi-phase flow. This paper presents a general formula for the second-order projection method combined with the level set method to simulate unsteady incompressible multi-phase flow with/out phase change flow encountered in fusion science and engineering. The third-order ENO scheme and second-order semi-implicit Crank-Nicholson scheme is used to update the convective and diffusion term. The numerical results show this method can handle the complex deformation of the interface and the effect of liquid-vapor phase change will be included in the future work
Krimi, Abdelkader; Rezoug, Mehdi; Khelladi, Sofiane; Nogueira, Xesús; Deligant, Michael; Ramírez, Luis
2018-04-01
In this work, a consistent Smoothed Particle Hydrodynamics (SPH) model to deal with interfacial multiphase fluid flows simulation is proposed. A modification to the Continuum Stress Surface formulation (CSS) [1] to enhance the stability near the fluid interface is developed in the framework of the SPH method. A non-conservative first-order consistency operator is used to compute the divergence of stress surface tensor. This formulation benefits of all the advantages of the one proposed by Adami et al. [2] and, in addition, it can be applied to more than two phases fluid flow simulations. Moreover, the generalized wall boundary conditions [3] are modified in order to be well adapted to multiphase fluid flows with different density and viscosity. In order to allow the application of this technique to wall-bounded multiphase flows, a modification of generalized wall boundary conditions is presented here for using the SPH method. In this work we also present a particle redistribution strategy as an extension of the damping technique presented in [3] to smooth the initial transient phase of gravitational multiphase fluid flow simulations. Several computational tests are investigated to show the accuracy, convergence and applicability of the proposed SPH interfacial multiphase model.
Numerical Simulation of the Multiphase Flow in the Rheinsahl-Heraeus (RH) System
Geng, Dian-Qiao; Lei, Hong; He, Ji-Cheng
2010-02-01
Knowledge of gas-liquid multiphase flow behavior in the Rheinsahl-Heraeus (RH) system is of great significance to clarify the circulation flow rate, decarburization, and inclusion removal with a reliable description. Thus, based on the separate model of injecting gas behavior, a novel mathematical model of multiphase flow has been developed to give the distribution of gas holdup in the RH system. The numerical results show that the predicted circulation flow rates, the predicted flow velocities, and the predicted mixing times agree with the measured results in a water model and that the predicted tracer concentration curve agrees with the results obtained in an actual RH system. With a lower lifting gas flow rate, the rising gas bubbles are concentrated near the wall; with a higher lifting gas flow rate, gas bubbles can reach the center of the up-snorkel. A critical lifting gas flow rate is used to obtain the maximum circulation flow rate.
Multi-phase flow modeling of soil contamination and soil remediation
Dijke, van M.I.J.
1997-01-01
In this thesis multi-phase flow models are used to study the flow behavior of liquid contaminants in aquifers and of gases that are injected below the groundwater table for remediation purposes. Considered problems are redistribution of a lens of light nonaqueous phase
Paradigm for Subgrid Scale Closure Modeling in Multiphase Geophysical Flows
Calantoni, J.; Simeonov, J.; Penko, A. M.; Bateman, S. P.; Palmsten, M. L.; Holland, K.
2012-12-01
We present a new paradigm for modeling multiphase geophysical flows to produce highly accurate and highly efficient forecasting of the complexity of the natural environment across the full range of relevant length and time scales. The assumption that computing technology will never allow us to perform direct numerical simulations (DNS) of the natural environment often limits our ambition in forward thinking model development and produces only incremental improvements in the state-of-the-art technology. Regional and global forecasting models for earth, ocean, and atmospheric processes based on averaged equations (e.g. RANS) must advance beyond simple closures relations obtained for single-phase fluid turbulence (e.g., k-epsilon, k-omega, and Mellor-Yamada). We propose using a hierarchy of computationally intensive, high fidelity simulations to resolve subgrid processes across a range of cascading length and time scales in the model domain to generate numerical interpolations for the unresolved physical processes. Further, we believe that it is possible to use the cumulative results of these subgrid scale simulations to develop a Bayesian network, for example, which may eventually replace the computationally intensive simulations with a highly efficient probabilistic closure model for the unresolved physical processes. The success of our approach will be greatly enhanced through rigorous validation of our subgrid scale models using three-dimensional laboratory and field measurements of fluid-particle turbulence at the scales of interest. Recent advances in optical imaging techniques have made it possible to make highly resolved three-dimensional measurements of fluid-particle turbulent interactions in the laboratory with spatial and temporal resolutions at or near the Kolmogorov scales. Additional work must be done to transition these technologies for use in the field. As a pilot test case we introduce our new paradigm using a hierarchy of models we have developed
Mathematical theory of compressible fluid flow
von Mises, Richard
2004-01-01
A pioneer in the fields of statistics and probability theory, Richard von Mises (1883-1953) made notable advances in boundary-layer-flow theory and airfoil design. This text on compressible flow, unfinished upon his sudden death, was subsequently completed in accordance with his plans, and von Mises' first three chapters were augmented with a survey of the theory of steady plane flow. Suitable as a text for advanced undergraduate and graduate students - as well as a reference for professionals - Mathematical Theory of Compressible Fluid Flow examines the fundamentals of high-speed flows, with
International Nuclear Information System (INIS)
Freeze, G.A.; Larson, K.W.; Davies, P.B.; Webb, S.W.
1995-01-01
Long-term repository assessment must consider the processes of (1) gas generation, (2) room closure and expansions due to salt creep, and (3) multiphase (brine and gas) fluid flow, as well as the complex coupling between these three processes. The mechanical creep closure code SANCHO was used to simulate the closure of a single, perfectly sealed disposal room filled with water and backfill. SANCHO uses constitutive models to describe salt creep, waste consolidation, and backfill consolidation, Five different gas-generation rate histories were simulated, differentiated by a rate multiplier, f, which ranged from 0.0 (no gas generation) to 1.0 (expected gas generation under brine-dominated conditions). The results of the SANCHO f-series simulations provide a relationship between gas generation, room closure, and room pressure for a perfectly sealed room. Several methods for coupling this relationship with multiphase fluid flow into and out of a room were examined. Two of the methods are described
Energy Technology Data Exchange (ETDEWEB)
Guenther, Chris [National Energy Technology Lab. (NETL), Morgantown, WV (United States); Garg, Rahul [National Energy Technology Lab. (NETL), Morgantown, WV (United States)
2013-08-19
The Department of Energy’s (DOE) National Energy Technology Laboratory (NETL) sponsored a workshop on non-Newtonian multiphase slurry at NETL’s Morgantown campus August 19 and 20, 2013. The objective of this special two-day meeting of 20-30 invited experts from industry, National Labs and academia was to identify and address technical issues associated with handling non-Newtonian multiphase slurries across various facilities managed by DOE. Particular emphasis during this workshop was placed on applications managed by the Office of Environmental Management (EM). The workshop was preceded by two webinars wherein personnel from ORP and NETL provided background information on the Hanford WTP project and discussed the critical design challenges facing this project. In non-Newtonian fluids, viscosity is not constant and exhibits a complex dependence on applied shear stress or deformation. Many applications under EM’s tank farm mission involve non-Newtonian slurries that are multiphase in nature; tank farm storage and handling, slurry transport, and mixing all involve multiphase flow dynamics, which require an improved understanding of the mechanisms responsible for rheological changes in non-Newtonian multiphase slurries (NNMS). To discuss the issues in predicting the behavior of NNMS, the workshop focused on two topic areas: (1) State-of-the-art in non-Newtonian Multiphase Slurry Flow, and (2) Scaling up with Confidence and Ensuring Safe and Reliable Long-Term Operation.
An experimental investigation of the multiphase flows in a photobioreactor for algae cultivation
Yang, Zifeng; Hu, Hui; Del Ninno, Matteo; Wen, Zhiyou
2011-11-01
Algal biomass is a promising feedstock for biofuels production, with photobioreactors being one of the major cultivation systems for algal cells. Light absorption, fluid dynamics, and algal metabolism are three key factors in determining the overall performance of a photobioreactor. The behavior of the multiphase flow (i.e., liquid phase - water, gas phase - CO2 and O2, and solid phase - algal cells) and turbulent mixing inside the reactor are the core connecting the three factors together. One of the major challenges in the optimal design of photobioreactors for algae cultivation is the lack of in-depth understanding of the characteristics of the multiphase flows and turbulent mixing. In this study, we present a comprehensive experimental study to investigate the effects of turbulent mixing in photobioreactors on the performance of a photobioreactor for algae cultivation. A high-resolution particle image velocity (PIV) system is used to achieve time-resolved, in-situ flow field measurements to quantify the turbulent mixing of the multiphase flows inside the bioreactor, while algal cultures are also grown in the same reactor with the same experimental settings. The mixing characteristics of the multiphase flow are correlated with the algal growth performance in the bioreactors to elucidate the underlying physics to explore/optimize design paradigms for the optimization of photobioreactor designs for algae cultivation.
Modelling multiphase flow inside the porous media of a polymer electrolyte membrane fuel cell
DEFF Research Database (Denmark)
Berning, Torsten; Kær, Søren Knudsen
2011-01-01
Transport processes inside polymer electrolyte membrane fuel cells (PEMFC’s) are highly complex and involve convective and diffusive multiphase, multispecies flow through porous media along with heat and mass transfer and electrochemical reactions in conjunction with water transport through...... emerge and be entrained into the gas stream....
Towards advanced one-dimensional numerical models for multiphase flow in pipelines
Van Zwieten, J.S.B.
2013-01-01
In this report we give an overview of models and discretisation techniques for the simulation of multiphase flow in long pipelines. Due to the size of the pipelines we focus on one-dimensional models, which are derived from three-dimensional conservation laws for mass, momentum and energy. All
Experimental and computational analysis of pressure response in a multiphase flow loop
Morshed, Munzarin; Amin, Al; Rahman, Mohammad Azizur; Imtiaz, Syed
2016-07-01
The characteristics of multiphase fluid flow in pipes are useful to understand fluid mechanics encountered in the oil and gas industries. In the present day oil and gas exploration is successively inducing subsea operation in the deep sea and arctic condition. During the transport of petroleum products, understanding the fluid dynamics inside the pipe network is important for flow assurance. In this case the information regarding static and dynamic pressure response, pressure loss, optimum flow rate, pipe diameter etc. are the important parameter for flow assurance. The principal aim of this research is to represents computational analysis and experimental analysis of multi-phase (L/G) in a pipe network. This computational study considers a two-phase fluid flow through a horizontal flow loop with at different Reynolds number in order to determine the pressure distribution, frictional pressure loss profiles by volume of fluid (VOF) method. However, numerical simulations are validated with the experimental data. The experiment is conducted in 76.20 mm ID transparent circular pipe using water and air in the flow loop. Static pressure transducers are used to measure local pressure response in multiphase pipeline.
Is it possible to design universal multi-phase flow analyzer?
International Nuclear Information System (INIS)
Ivanov Kolev, N.
2005-01-01
Transient 3D-multiphase flows consisting of many chemical constituents in nature and technology (Figs. 1 and 2) are the common case of flows. In many technical applications we have to do with particular realization of the multi-phase flows like steady state flows, or single component flows or single phase flows etc. Engineers and scientists created hundreds of computer codes for description of more or less specific realizations of multi-phase flows. If one compares the structure of these codes one is astonished by the waste of the human resources for programming repeating model elements like equations of state, friction lows in variety of geometry, heat transfer coefficients, mathematical equation solvers, data handling procedures, graphical environment etc. It is hardly to expect, that the best solution for the specific sub-phenomenon is available in all codes. Looking in other branches of the technology like computer chips production we realize that the revolutionary idea of having common ''chips'' within complex applications is very far from its practical realization in the computational multi-phase flow dynamics. Following this line of arguments I expressed several times in my publications explicitly or implicitly the idea, that it is possible to create a universal multi-phase flow analyzer in the sense of computer architecture, that is capable to absorb the adequate multi-phase knowledge data base specified in Appendix 1. The subject of this paper is to summarize some of the main ideas, some of them already realized by this author, on the way of creating such computer code architecture, to illustrate haw they work, and to make an outlook regarding what are the challenges in the future developments. We confine deliberately our attention to the solution of the so called local volume and time averaged system of PDE's for a simple reason: Direct numerical resolution of interacting fluids is possible as demonstrated for small scales by many researchers, but for
An efficient numerical approach for transient simulation of multiphase flow behavior in centrifuges
Hammerich, Simon; Nirschl, Hermann
2016-01-01
The separation process of particles and liquids in centrifuge is a widely used operation in industry. In spite of the long term usage of centrifuges, the knowledge for a detailed characterization of the interaction of the macroscopic processes due the separation is lacking. Reason for this is the complex multiphase flow and the sediment built-up within the machines. The sediment shape influences the flow behavior. The shape is dependent of the rheological behavior of the sediment. Computation...
McGrath, Thomas P.; St. Clair, Jeffrey G.; Balachandar, S.
2016-05-01
Multiphase flows are present in many important fields ranging from multiphase explosions to chemical processing. An important subset of multiphase flow applications involves dispersed materials, such as particles, droplets, and bubbles. This work presents an Eulerian-Eulerian model for multiphase flows containing dispersed particles surrounded by a continuous media such as air or water. Following a large body of multiphase literature, the driving force for particle acceleration is modeled as a direct function of both the continuous-phase pressure gradient and the gradient of intergranular stress existing within the particle phase. While the application of these two components of driving force is well accepted in much of the literature, other models exist in which the particle-phase pressure gradient itself drives particle motion. The multiphase model treats all phases as compressible and is derived to ensure adherence to the 2nd Law of Thermodynamics. The governing equations are presented and discussed, and a characteristic analysis shows the model to be hyperbolic, with a degeneracy in the case that the intergranular stress, which is modeled as a configuration pressure, is zero. Finally, results from a two sample problems involving shock-induced particle dispersion are presented. The results agree well with experimental measurements, providing initial confidence in the proposed model.
Lattice-gas models for multiphase flows and magnetohydrodynamics
International Nuclear Information System (INIS)
Chen, H.; Chen, S.; Doolen, G.D.; Matthaeus, W.H.
1990-01-01
Lattice-gas automata are many-body dynamical systems described by discrete space and time variables. The microscopic state of such a system is completely specified by a few integer quantities at each lattice site. The system is updated according to the dynamics of the lattice-gas particles, which are usually determined only by local information. The first lattice-gas model was introduced by Frisch, Hasslacher, and Pomeau (FHP). The FHP model simulates fluid behavior and, in the low-Mach-number limit, obeys the incompressible Navier-Stokes equations. Since the creation of the FHP model, lattice-gas research has developed rapidly, providing not only further insight into the relation between microscopic processes and macroscopic properties but also new procedures for fast computation. Recent improvements and extensions of the FHP model have opened up brand-new fields. Already such research has had some impact on the understanding of the macroscopic properties of physics, in particular, the properties of multiple-fluid systems. Moreover, some potential industrial applications are now being explored. Lattice-gas models for single-phase fluids, multiphase fluids, and magnetohydrodynamic fluids are briefly described. 22 refs., 2 figs
Energy Technology Data Exchange (ETDEWEB)
Sheng, L.Y., E-mail: lysheng@yeah.net [Peking University, Beijing 100871 (China); PKU-HKUST ShenZhen-Hong Kong Institution, Shenzhen 518057 (China); Xie, Y. [Hunan Electric Power Test and Research Institute, Changsha 410007 (China); Xi, T.F. [Peking University, Beijing 100871 (China); Guo, J.T. [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Zheng, Y.F. [Peking University, Beijing 100871 (China); Ye, H.Q. [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)
2011-11-15
Highlights: {yields} The {alpha}-Cr, {sigma} and {mu} phases precipitate and form into network in as cast alloy. {yields} Rapid and intermediate cooling rate after solution treatment break the precipitates network; the lower cooling rate results in some {alpha}-Cr and Ni{sub 3}Al precipitates. {yields} Short-term aging results in massive Ni{sub 3}Al lathes and {alpha}-Cr particles, but long-term aging treatment coarsens the globule-shaped {alpha}-Cr particle and decreases the lath-shaped Ni{sub 3}Al, {mu} and {sigma} phase. {yields} The solid solution with short-term aging treatment improves mechanical properties of the alloy significantly. - Abstract: The alloy of Ni-Al26-Cr15-Co6-Ti3-Mo2-Nb0.5-Ho0.1 (at.%) was heat-treated and studied by microstructure examination and compressive test. The results reveal that in the as-cast alloy, {alpha}-Cr, {sigma} and {mu} phases are segregated along the NiAl phase boundary and form into network. Small Ni{sub 2}AlTi, Cr{sub 2}Nb and Ni{sub 2}Al{sub 3}Ho particles precipitate at NiAl grain boundary. The subsequent solid solution treatment with rapid and intermediate cooling rate transforms the net-like precipitating phases into discontinuous ones, but the rapid cooling leads to micro-cracks along phase boundary. However the lower cooling rate results in spherical {alpha}-Cr particle and needle-like Ni{sub 3}Al phase in NiAl matrix. The short-term aging after solid solution treatment promotes the coarsening of Ni{sub 3}Al lathes and {alpha}-Cr particles, and an orientation relationship of [001-bar]{sub {beta}}||[1-bar 10]{sub {lambda}{sup '}} and (1 1 0){sub {beta}}||(1 1 1){sub {gamma}'} is found between lath-shaped Ni{sub 3}Al phase and NiAl matrix. In addition, the {mu} phases are substituted by {sigma} and some Cr{sub 3}Ni{sub 2} phases. The long-term aging treatment reduces Ni{sub 3}Al, {sigma} and {mu} phases and coarsens the {alpha}-Cr phase further. The solid solution treatment and short-term aging improve the
Non-isothermal effects on multi-phase flow in porous medium
DEFF Research Database (Denmark)
Singh, Ashok; Wang, W; Park, C. H.
2010-01-01
In this paper a ppT -formulation for non-isothermal multi-phase flow is given including diffusion and latent heat effects. Temperature and pressure dependencies of governing parameters are considered, in particular surface tension variation on phase interfaces along with temperature changes. A we...... geotechnical areas. The classic benchmark for two-phase flow by McWhorter and Sunada1 is used as a reference case on which non-isothermal effects and non-linear material behavior are studied.......In this paper a ppT -formulation for non-isothermal multi-phase flow is given including diffusion and latent heat effects. Temperature and pressure dependencies of governing parameters are considered, in particular surface tension variation on phase interfaces along with temperature changes. A weak...
Nonequilibrium Physics and Phase-Field Modeling of Multiphase Flow in Porous Media
Energy Technology Data Exchange (ETDEWEB)
Juanes, Ruben [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
2016-09-01
The overarching goal of this project was to develop a new continuum theory of multiphase flow in porous media. The theory follows a phase-field modeling approach, and therefore has a sound thermodynamical basis. It is a phenomenological theory in the sense that its formulation is driven by macroscopic phenomena, such as viscous instabilities during multifluid displacement. The research agenda was organized around a set of hypothesis on hitherto unexplained behavior of multiphase flow. All these hypothesis are nontrivial, and testable. Indeed, a central aspect of the project was testing each hypothesis by means of carefully-designed laboratory experiments, therefore probing the validity of the proposed theory. The proposed research places an emphasis on the fundamentals of flow physics, but is motivated by important energy-driven applications in earth sciences, as well as microfluidic technology.
Influence of the multiphase flow patterns on the transport properties
Markicevic, Bojan
2016-11-01
The capillary network model with the dynamic boundary condition at free interface for displacement flow in porous media is developed, in which the net flow into each pore at the free interface can be less, equal to or greater than zero. The spread of the liquid and form of the liquid flow patterns are resolved in the networks of different sizes and heterogeneity and for two types of the boundary conditions, the constant inlet pressure or constant flow rate. It has been shown that for the constant flow rate boundary condition, the pressure drop throughout the network remains constant due to the pressure increase at the inlet boundary. The constant pressure drop produces the similar flow patterns during the displacement flow, and the saturation remains constant in the flow direction. The liquid saturation in the network is varied gradually by increasing the liquid flow rate at network inlet. For each distinct flow rate, the sizes of the repeating flow pattern and corresponding pressure drop change accordingly. This implies that for sufficiently large networks in which the flow pattern is fully developed, the transport parameters do not depend on the network size. The flow pattern and transport parameters depend on the network heterogeneity, as the dynamic boundary condition changes at the free interface producing a different distribution of the liquid. A continuous development of the flow pattern is also observed for the constant inlet pressure boundary condition, where the pressure drop decreases as liquid advances into the network. Finally, a summary in changes of transport parameters, relative permeability and capillary pressure, is elaborated.
Adaptive Methods for Compressible Flow
1994-03-01
labor -intensive task of purpose of this work is to demonstrate the generating acceptable surface triangulations, advantages of integrating the CAD/CAM...sintilar results). L 1 (’-1)(2sn~p) boundary error (MUSCL) The flow variables wre then given by .04 .78% M=asOIne/i .02 AM% v= acosO /sintt .01 .0 p
Hao, Y.; Settgast, R. R.; Fu, P.; Tompson, A. F. B.; Morris, J.; Ryerson, F. J.
2016-12-01
It has long been recognized that multiphase flow and transport in fractured porous media is very important for various subsurface applications. Hydrocarbon fluid flow and production from hydraulically fractured shale reservoirs is an important and complicated example of multiphase flow in fractured formations. The combination of horizontal drilling and hydraulic fracturing is able to create extensive fracture networks in low permeability shale rocks, leading to increased formation permeability and enhanced hydrocarbon production. However, unconventional wells experience a much faster production decline than conventional hydrocarbon recovery. Maintaining sustainable and economically viable shale gas/oil production requires additional wells and re-fracturing. Excessive fracturing fluid loss during hydraulic fracturing operations may also drive up operation costs and raise potential environmental concerns. Understanding and modeling processes that contribute to decreasing productivity and fracturing fluid loss represent a critical component for unconventional hydrocarbon recovery analysis. Towards this effort we develop a discrete fracture model (DFM) in GEOS (LLNL multi-physics computational code) to simulate multiphase flow and transfer in hydraulically fractured reservoirs. The DFM model is able to explicitly account for both individual fractures and their surrounding rocks, therefore allowing for an accurate prediction of impacts of fracture-matrix interactions on hydrocarbon production. We apply the DFM model to simulate three-phase (water, oil, and gas) flow behaviors in fractured shale rocks as a result of different hydraulic stimulation scenarios. Numerical results show that multiphase flow behaviors at the fracture-matrix interface play a major role in controlling both hydrocarbon production and fracturing fluid recovery rates. The DFM model developed in this study will be coupled with the existing hydro-fracture model to provide a fully integrated
The application of single particle hydrodynamics in continuum models of multiphase flow
Decker, Rand
1988-01-01
A review of the application of single particle hydrodynamics in models for the exchange of interphase momentum in continuum models of multiphase flow is presented. Considered are the equations of motion for a laminar, mechanical two phase flow. Inherent to this theory is a model for the interphase exchange of momentum due to drag between the dispersed particulate and continuous fluid phases. In addition, applications of two phase flow theory to de-mixing flows require the modeling of interphase momentum exchange due to lift forces. The applications of single particle analysis in deriving models for drag and lift are examined.
Physically Related Coordinate System for Compressible Flow
Gao, Bo; Wu, Zi-Niu
In this paper we apply the unified coordinate system developed by Hui and his co-workers to the steady compressible flow computation in such a way that the grid is generated physically and automatically. At the beginning of computation one only needs to build a narrow layer of grids near the left boundary. It is demonstrated that by continuously injecting layers of grid in the inflow boundary, the grid will gradually fill up the entire flow domain.
Compressed-air flow control system.
Bong, Ki Wan; Chapin, Stephen C; Pregibon, Daniel C; Baah, David; Floyd-Smith, Tamara M; Doyle, Patrick S
2011-02-21
We present the construction and operation of a compressed-air driven flow system that can be used for a variety of microfluidic applications that require rapid dynamic response and precise control of multiple inlet streams. With the use of inexpensive and readily available parts, we describe how to assemble this versatile control system and further explore its utility in continuous- and pulsed-flow microfluidic procedures for the synthesis and analysis of microparticles.
Laboratory setup and results of experiments on two-dimensional multiphase flow in porous media
International Nuclear Information System (INIS)
McBride, J.F.; Graham, D.N.
1990-10-01
In the event of an accidental release into earth's subsurface of an immiscible organic liquid, such as a petroleum hydrocarbon or chlorinated organic solvent, the spatial and temporal distribution of the organic liquid is of great interest when considering efforts to prevent groundwater contamination or restore contaminated groundwater. An accurate prediction of immiscible organic liquid migration requires the incorporation of relevant physical principles in models of multiphase flow in porous media; these physical principles must be determined from physical experiments. This report presents a series of such experiments performed during the 1970s at the Swiss Federal Institute of Technology (ETH) in Zurich, Switzerland. The experiments were designed to study the transient, two-dimensional displacement of three immiscible fluids in a porous medium. This experimental study appears to be the most detailed published to date. The data obtained from these experiments are suitable for the validation and test calibration of multiphase flow codes. 73 refs., 140 figs
Laboratory setup and results of experiments on two-dimensional multiphase flow in porous media
Energy Technology Data Exchange (ETDEWEB)
McBride, J.F. (ed.) (Pacific Northwest Lab., Richland, WA (USA)); Graham, D.N. (ed.); Schiegg, H.O. (SIMULTEC Ltd., Meilen/Zurich (Switzerland))
1990-10-01
In the event of an accidental release into earth's subsurface of an immiscible organic liquid, such as a petroleum hydrocarbon or chlorinated organic solvent, the spatial and temporal distribution of the organic liquid is of great interest when considering efforts to prevent groundwater contamination or restore contaminated groundwater. An accurate prediction of immiscible organic liquid migration requires the incorporation of relevant physical principles in models of multiphase flow in porous media; these physical principles must be determined from physical experiments. This report presents a series of such experiments performed during the 1970s at the Swiss Federal Institute of Technology (ETH) in Zurich, Switzerland. The experiments were designed to study the transient, two-dimensional displacement of three immiscible fluids in a porous medium. This experimental study appears to be the most detailed published to date. The data obtained from these experiments are suitable for the validation and test calibration of multiphase flow codes. 73 refs., 140 figs.
Microgravity Multi-Phase Flow Experiment for Suborbital Testing (MFEST)
National Aeronautics and Space Administration — The primary objective is to conduct a pathfinder, suborbital flight experiment for two-phase fluid flow and separator operations.The primary purpose of this test...
Directory of Open Access Journals (Sweden)
V. V. Myamlin
2011-04-01
Full Text Available The algorithm of computer simulation of the flexible flow for repair of cars as a multiphase polychannel manyobject queuing system is presented. The basic operators of the model are given and their work is described.
Development of an Efficient Meso- scale Multi-phase Flow Solver in Nuclear Applications
Energy Technology Data Exchange (ETDEWEB)
Lee, Taehun [City Univ. (CUNY), NY (United States)
2015-10-20
The proposed research aims at formulating a predictive high-order Lattice Boltzmann Equation for multi-phase flows relevant to nuclear energy related application - namely, saturated and sub-cooled boiling in reactors, and liquid- liquid mixing and extraction for fuel cycle separation. An efficient flow solver will be developed based on the Finite Element based Lattice Boltzmann Method (FE- LBM), accounting for phase-change heat transfer and capable of treating multiple phases over length scales from the submicron to the meter. A thermal LBM will be developed in order to handle adjustable Prandtl number, arbitrary specific heat ratio, a wide range of temperature variations, better numerical stability during liquid-vapor phase change, and full thermo-hydrodynamic consistency. Two-phase FE-LBM will be extended to liquid–liquid–gas multi-phase flows for application to high-fidelity simulations building up from the meso-scale up to the equipment sub-component scale. While several relevant applications exist, the initial applications for demonstration of the efficient methods to be developed as part of this project include numerical investigations of Critical Heat Flux (CHF) phenomena in nuclear reactor fuel bundles, and liquid-liquid mixing and interfacial area generation for liquid-liquid separations. In addition, targeted experiments will be conducted for validation of this advanced multi-phase model.
Smoothed Particle Hydrodynamics model for multiphase flow in porous media
Energy Technology Data Exchange (ETDEWEB)
Tartakovsky, Alexandre M.; Meakin, Paul; Ward, Anderson L.
2007-07-07
A numerical model based on smoothed particle hydrodynamics (SPH) was used to simulate pore-scale liquid and gas flow in synthetic two-dimensional porous media consisting of non-overlapping grains. The model was used to study effects of pore scale heterogeneity and anisotropy on relationship between the average saturation and the Bond number. The effect of the wetting fluid properties on drainage was also investigated. It is shown that pore-scale heterogeneity and anisotropy can cause saturation/Bond number and entry (bubbling) pressures to be dependent on the flow direction suggesting that these properties should be described by tensor rather than scalar quantities.
Surface Tension of Multi-phase Flow with Multiple Junctions Governed by the Variational Principle
International Nuclear Information System (INIS)
Matsutani, Shigeki; Nakano, Kota; Shinjo, Katsuhiko
2011-01-01
We explore a computational model of an incompressible fluid with a multi-phase field in three-dimensional Euclidean space. By investigating an incompressible fluid with a two-phase field geometrically, we reformulate the expression of the surface tension for the two-phase field found by Lafaurie et al. (J Comput Phys 113:134–147, 1994) as a variational problem related to an infinite dimensional Lie group, the volume-preserving diffeomorphism. The variational principle to the action integral with the surface energy reproduces their Euler equation of the two-phase field with the surface tension. Since the surface energy of multiple interfaces even with singularities is not difficult to be evaluated in general and the variational formulation works for every action integral, the new formulation enables us to extend their expression to that of a multi-phase (N-phase, N ≥ 2) flow and to obtain a novel Euler equation with the surface tension of the multi-phase field. The obtained Euler equation governs the equation for motion of the multi-phase field with different surface tension coefficients without any difficulties for the singularities at multiple junctions. In other words, we unify the theory of multi-phase fields which express low dimensional interface geometry and the theory of the incompressible fluid dynamics on the infinite dimensional geometry as a variational problem. We apply the equation to the contact angle problems at triple junctions. We computed the fluid dynamics for a two-phase field with a wall numerically and show the numerical computational results that for given surface tension coefficients, the contact angles are generated by the surface tension as results of balances of the kinematic energy and the surface energy.
Complexity Reduction of Multiphase Flows in Heterogeneous Porous Media
Ghommem, Mehdi
2015-04-22
In this paper, we apply mode decomposition and interpolatory projection methods to speed up simulations of two-phase flows in heterogeneous porous media. We propose intrusive and nonintrusive model-reduction approaches that enable a significant reduction in the size of the subsurface flow problem while capturing the behavior of the fully resolved solutions. In one approach, we use the dynamic mode decomposition. This approach does not require any modification of the reservoir simulation code but rather post-processes a set of global snapshots to identify the dynamically relevant structures associated with the flow behavior. In the second approach, we project the governing equations of the velocity and the pressure fields on the subspace spanned by their proper-orthogonal-decomposition modes. Furthermore, we use the discrete empirical interpolation method to approximate the mobility-related term in the global-system assembly and then reduce the online computational cost and make it independent of the fine grid. To show the effectiveness and usefulness of the aforementioned approaches, we consider the SPE-10 benchmark permeability field, and present a numerical example in two-phase flow. One can efficiently use the proposed model-reduction methods in the context of uncertainty quantification and production optimization.
Simulation of gas compressible flow by free surface water flow
International Nuclear Information System (INIS)
Altafini, C.R.; Silva Ferreira, R.T. da
1981-01-01
The analogy between the water flow with a free surface and the compressible fluid flow, commonly called hydraulic analogy, is analyzed and its limitations are identified. The water table is the equipment used for this simulation, which allows the quatitative analysis of subsonic and supersonic flow with a low cost apparatus. The hydraulic analogy is applied to subsonic flow around circular cylinders and supersonic flow around cones. The results are compared with available theoretical and experimental data and a good agreement is achieved. (Author) [pt
Stochastic Rotation Dynamics simulations of wetting multi-phase flows
Hiller, Thomas; Sanchez de La Lama, Marta; Brinkmann, Martin
2016-06-01
Multi-color Stochastic Rotation Dynamics (SRDmc) has been introduced by Inoue et al. [1,2] as a particle based simulation method to study the flow of emulsion droplets in non-wetting microchannels. In this work, we extend the multi-color method to also account for different wetting conditions. This is achieved by assigning the color information not only to fluid particles but also to virtual wall particles that are required to enforce proper no-slip boundary conditions. To extend the scope of the original SRDmc algorithm to e.g. immiscible two-phase flow with viscosity contrast we implement an angular momentum conserving scheme (SRD+mc). We perform extensive benchmark simulations to show that a mono-phase SRDmc fluid exhibits bulk properties identical to a standard SRD fluid and that SRDmc fluids are applicable to a wide range of immiscible two-phase flows. To quantify the adhesion of a SRD+mc fluid in contact to the walls we measure the apparent contact angle from sessile droplets in mechanical equilibrium. For a further verification of our wettability implementation we compare the dewetting of a liquid film from a wetting stripe to experimental and numerical studies of interfacial morphologies on chemically structured surfaces.
Analysis of multiphase flows using dual-energy gamma densitometry and neural networks
International Nuclear Information System (INIS)
Bishop, C.M.; James, G.D.
1993-01-01
Dual-energy gamma densitometry offers a powerful technique for the non-intrusive analysis of multiphase flows. By employing multiple beam lines, information on the phase configuration can be obtained. Once the configuration is known, it then becomes possible in principle to determine the phase fractions. In practice, however, the extraction of the phase fractions from the densitometer data is complicated by the wide variety of phase configurations which can arise, and by the considerable difficulties of modelling multiphase flows. In this paper we show that neural network techniques provide a powerful approach to the analysis of data from dual-energy gamma densitometers, allowing both the phase configuration and the phase fractions to be determined with high accuracy, whilst avoiding the uncertainties associated with modelling. The technique is well suited to the determination of oil, water and gas fractions in multiphase oil pipelines. Results from linear and non-linear network models are compared, and a new technique for validating the network output is described. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Bernstein, Andrey [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Dall-Anese, Emiliano [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Zhao, Changhong [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Wang, Cong [Ecole Polytechnique Federale de Lausanne (EPFL); Le Boudec, Jean-Yves [Ecole Polytechnique Federale de Lausanne (EPFL)
2018-04-06
This paper considers unbalanced multiphase distribution systems with generic topology and different load models, and extends the Z-bus iterative load-flow algorithm based on a fixed-point interpretation of the AC load-flow equations. Explicit conditions for existence and uniqueness of load-flow solutions are presented. These conditions also guarantee convergence of the load-flow algorithm to the unique solution. The proposed methodology is applicable to generic systems featuring (i) wye connections; (ii) ungrounded delta connections; (iii) a combination of wye-connected and delta-connected sources/loads; and, (iv) a combination of line-to-line and line-to-grounded-neutral devices at the secondary of distribution transformers. Further, a sufficient condition for the non-singularity of the load-flow Jacobian is proposed. Finally, linear load-flow models are derived, and their approximation accuracy is analyzed. Theoretical results are corroborated through experiments on IEEE test feeders.
Multiphase flow problems on thermofluid safety for fusion reactors
International Nuclear Information System (INIS)
Takase, Kazuyuki
2003-01-01
As the thermofluid safety study for the International Thermonuclear Experimental Reactor (ITER), thermal-hydraulic characteristics of Tokamak fusion reactors under transient events were investigated experimentally and analyzed numerically. As severe transient events an ingress-of-coolant event (ICE) and a loss-of-vacuum event (LOVA) were considered. An integrated ICE test facility was constructed to demonstrate that the ITER safety design approach and parameters are adequate. Water-vapor two-phase flow behavior and performance of the ITER pressure suppression system during the ICE were clarified by the integrated ICE experiments. The TRAC was modified to specify the two-phase flow behavior under the ICE. The ICE experimental results were verified using the modified TRAC code. On the other hand, activated dust mobilization and air ingress characteristics in the ITER vacuum vessel during the LOVA were analyzed using a newly developed analysis code. Some physical models on the motion of dust were considered. The rate of dust released from the vacuum vessel through breaches to the outside was characterized quantitatively. The predicted average pressures in the vacuum vessel during the LOVA were in good agreement with the experimental results. Moreover, direct-contact condensation characteristics between water and vapor inside the ITER suppression tank were observed visually and simulated by the direct two-phase flow analysis. Furthermore, chemical reaction characteristics between vapor and ITER plasma-facing component materials were predicted numerically in order to obtain qualitative estimation on generation of inflammable gases such as hydrogen and methane. The experimental and numerical results of the present studies were reflected in the ITER thermofluid safety design. (author)
Research on Underwater Vehicle Based on Multiphase Flow Control
Directory of Open Access Journals (Sweden)
Zhang Xiaoshi
2015-01-01
Full Text Available The commercial software ANSYS CFX is used for modeling the hydrodynamic characteristics of submarine-launched vehicle. In the numerical simulations, the SST (Shear Stress Transport turbulence model is employed to describe the turbulence phenomenon occurring in the continuous fluid. The Rayleigh-Plesset equations are applied to analyze the cavitation phenomenon. Three-dimensional numerical simulation was carried out to study the cavity shape, the surface pressure distribution and the drag force with different flow control. The result shows that the gas and the number of ventilation holes control to show any significant impact on the cavity shape and the surface pressure are effective measures to decrease resistance.
Mathematical modelling of ultrasound propagation in multi-phase flow
DEFF Research Database (Denmark)
Simurda, Matej
violates the repeatability of the measurements and thus impairs the device accuracy. Development of new flow meter designs for these conditions based on a purely experimental approach is expensive both in terms of time and economy. An attractive alternative is the employment of a mathematical model...... is further extended by mesh adaptation techniques to accurately resolve acoustic scattering in complex geometries. The presented numerical model is, to the best of the author's knowledge, the only pseudospectral model available in the open literature that solves propagation of acoustic waves in moving...
Modeling studies of multiphase fluid and heat flow processes in nuclear waste isolation
International Nuclear Information System (INIS)
Pruess, K.
1989-01-01
Multiphase fluid and heat flow plays an important role in many problems relating to the disposal of nuclear wastes in geologic media. Examples include boiling and condensation processes near heat-generating wastes, flow of water and formation gas in partially saturated formations, evolution of a free gas phase from waste package corrosion in initially water-saturated environments, and redistribution (dissolution, transport and precipitation) of rock minerals in non-isothermal flow fields. Such processes may strongly impact upon waste package and repository design considerations and performance. This paper summarizes important physical phenomena occurring in multiphase and nonisothermal flows, as well as techniques for their mathematical modeling and numerical simulation. Illustrative applications are given for a number of specific fluid and heat flow problems, including: thermohydrologic conditions near heat-generating waste packages in the unsaturated zone; repositorywide convection effects in the unsaturated zone; effects of quartz dissolution and precipitation for disposal in the saturated zone; and gas pressurization and flow effects from corrosion of low-level waste packages
Modeling studies for multiphase fluid and heat flow processes in nuclear waste isolation
International Nuclear Information System (INIS)
Pruess, K.
1988-07-01
Multiphase fluid and heat flow plays an important role in many problems relating to the disposal of nuclear wastes in geologic media. Examples include boiling and condensation processes near heat-generating wastes, flow of water and formation gas in partially saturated formations, evolution of a free gas phase from waste package corrosion in initially water-saturated environments, and redistribution (dissolution, transport, and precipitation) of rock minerals in non-isothermal flow fields. Such processes may strongly impact upon waste package and repository design considerations and performance. This paper summarizes important physical phenomena occurring in multiphase and nonisothermal flows, as well as techniques for their mathematical modeling and numerical simulation. Illustrative applications are given for a number of specific fluid and heat flow problems, including: thermohydrologic conditions near heat-generating waste packages in the unsaturated zone; repository-wide convection effects in the unsaturated zone; effects of quartz dissolution and precipitation for disposal in the saturated zone; and gas pressurization and flow corrosion of low-level waste packages. 34 refs; 7 figs; 2 tabs
Massively parallel simulations of multiphase flows using Lattice Boltzmann methods
Ahrenholz, Benjamin
2010-03-01
In the last two decades the lattice Boltzmann method (LBM) has matured as an alternative and efficient numerical scheme for the simulation of fluid flows and transport problems. Unlike conventional numerical schemes based on discretizations of macroscopic continuum equations, the LBM is based on microscopic models and mesoscopic kinetic equations. The fundamental idea of the LBM is to construct simplified kinetic models that incorporate the essential physics of microscopic or mesoscopic processes so that the macroscopic averaged properties obey the desired macroscopic equations. Especially applications involving interfacial dynamics, complex and/or changing boundaries and complicated constitutive relationships which can be derived from a microscopic picture are suitable for the LBM. In this talk a modified and optimized version of a Gunstensen color model is presented to describe the dynamics of the fluid/fluid interface where the flow field is based on a multi-relaxation-time model. Based on that modeling approach validation studies of contact line motion are shown. Due to the fact that the LB method generally needs only nearest neighbor information, the algorithm is an ideal candidate for parallelization. Hence, it is possible to perform efficient simulations in complex geometries at a large scale by massively parallel computations. Here, the results of drainage and imbibition (Degree of Freedom > 2E11) in natural porous media gained from microtomography methods are presented. Those fully resolved pore scale simulations are essential for a better understanding of the physical processes in porous media and therefore important for the determination of constitutive relationships.
Viscosity and surface tension effects during multiphase flow in propped fractures
Dzikowski, Michał; Dąbrowski, Marcin
2017-04-01
Geological sequestration of CO2 was proposed as an important mechanism to reduce its emission into atmosphere. CO2 exhibits a higher affinity to organic matter than methane molecules and, potentially, it could be pumped and stored in shale reservoirs while enhancing late stage shale gas production. A successful analysis of CO2 sequestration in low matrix permeability rocks such as shales requires a thorough understanding of multiphase flow in stimulated rock fractures, which provide most significant pathways for fluids in such systems. Multiphase fracture flows are also of great relevance to brine, oil and gas migration in petroleum systems, water and stream circulation in geothermal reservoirs, and chemical transport of non-aqueous phase liquids in shallow hydrogeological systems, particularly in partially saturated zones. There are various physical models that describe phenomena taking place during multiphase flow through porous media. One of key aspects that need to be considered are pore-scale effects related to capillarity. Unfortunately, detailed models that describe motion and evolution of phase or component boundary require direct numerical simulations and spatial resolutions that are hard to reach when considering industrial relevant systems. Main aim of the presented work was the development of reduced 2.5D models based on Brinkman approximation of thin domain flow that would be able to capture local scale phenomena without expensive 3D simulations. Presented approach was designed specifically to tackle incompressible and immiscible systems and is based on Continuous Surface Force approach presented by Brackbill et al., implemented using Lattice Boltzmann Method. Presented approach where firstly validated against standard test cases with known classical solution and known experimental data. In the second part, we present and discuss two component, immiscible permeability data for rough and propped fracture obtained with our code for a rage of proppants
Shao, H.; Huang, Y.; Kolditz, O.
2015-12-01
Multiphase flow problems are numerically difficult to solve, as it often contains nonlinear Phase transition phenomena A conventional technique is to introduce the complementarity constraints where fluid properties such as liquid saturations are confined within a physically reasonable range. Based on such constraints, the mathematical model can be reformulated into a system of nonlinear partial differential equations coupled with variational inequalities. They can be then numerically handled by optimization algorithms. In this work, two different approaches utilizing the complementarity constraints based on persistent primary variables formulation[4] are implemented and investigated. The first approach proposed by Marchand et.al[1] is using "local complementary constraints", i.e. coupling the constraints with the local constitutive equations. The second approach[2],[3] , namely the "global complementary constrains", applies the constraints globally with the mass conservation equation. We will discuss how these two approaches are applied to solve non-isothermal componential multiphase flow problem with the phase change phenomenon. Several benchmarks will be presented for investigating the overall numerical performance of different approaches. The advantages and disadvantages of different models will also be concluded. References[1] E.Marchand, T.Mueller and P.Knabner. Fully coupled generalized hybrid-mixed finite element approximation of two-phase two-component flow in porous media. Part I: formulation and properties of the mathematical model, Computational Geosciences 17(2): 431-442, (2013). [2] A. Lauser, C. Hager, R. Helmig, B. Wohlmuth. A new approach for phase transitions in miscible multi-phase flow in porous media. Water Resour., 34,(2011), 957-966. [3] J. Jaffré, and A. Sboui. Henry's Law and Gas Phase Disappearance. Transp. Porous Media. 82, (2010), 521-526. [4] A. Bourgeat, M. Jurak and F. Smaï. Two-phase partially miscible flow and transport modeling in
The Pore-scale modeling of multiphase flows in reservoir rocks using the lattice Boltzmann method
Mu, Y.; Baldwin, C. H.; Toelke, J.; Grader, A.
2011-12-01
Digital rock physics (DRP) is a new technology to compute the physical and fluid flow properties of reservoir rocks. In this approach, pore scale images of the porous rock are obtained and processed to create highly accurate 3D digital rock sample, and then the rock properties are evaluated by advanced numerical methods at the pore scale. Ingrain's DRP technology is a breakthrough for oil and gas companies that need large volumes of accurate results faster than the current special core analysis (SCAL) laboratories can normally deliver. In this work, we compute the multiphase fluid flow properties of 3D digital rocks using D3Q19 immiscible LBM with two relaxation times (TRT). For efficient implementation on GPU, we improved and reformulated color-gradient model proposed by Gunstensen and Rothmann. Furthermore, we only use one-lattice with the sparse data structure: only allocate memory for pore nodes on GPU. We achieved more than 100 million fluid lattice updates per second (MFLUPS) for two-phase LBM on single Fermi-GPU and high parallel efficiency on Multi-GPUs. We present and discuss our simulation results of important two-phase fluid flow properties, such as capillary pressure and relative permeabilities. We also investigate the effects of resolution and wettability on multiphase flows. Comparison of direct measurement results with the LBM-based simulations shows practical ability of DRP to predict two-phase flow properties of reservoir rock.
Optimal Power Flow in Multiphase Radial Networks with Delta Connections: Preprint
Energy Technology Data Exchange (ETDEWEB)
Zhao, Changhong [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Dall-Anese, Emiliano [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Low, Steven H. [California Institute of Technology
2017-11-27
This paper focuses on multiphase radial distribution networks with mixed wye and delta connections, and proposes a semidefinite relaxation of the AC optimal power flow (OPF) problem. Two multiphase power-flow models are developed to facilitate the integration of delta-connected generation units/loads in the OPF problem. The first model extends traditional branch flow models - and it is referred to as extended branch flow model (EBFM). The second model leverages a linear relationship between per-phase power injections and delta connections, which holds under a balanced voltage approximation (BVA). Based on these models, pertinent OPF problems are formulated and relaxed to semidefinite programs (SDPs). Numerical studies on IEEE test feeders show that SDP relaxations can be solved efficiently by a generic optimization solver. Numerical evidences indicate that solving the resultant SDP under BVA is faster than under EBFM. Moreover, both SDP solutions are numerically exact with respect to voltages and branch flows. It is also shown that the SDP solution under BVA has a small optimality gap, while the BVA model is accurate in the sense that it reflects actual system voltages.
Examples of the Potential of DNS for the Understanding of Reactive Multiphase Flows
Directory of Open Access Journals (Sweden)
J. Reveillon
2011-03-01
Full Text Available The objective of this article is to point out the ability of the multiphase flow DNS (Direct Numerical Simulation to help to understand basic physics and to interpret some experimental observations. To illustrate the DNS' potential to give access to key phenomena involved in reactive multiphase flows, several recent results obtained by the authors are summed up with a bridge to experimental results. It includes droplet dispersion, laminar spray flame instability, spray combustion regimes or acoustic modulation effect on a two-phase flow Bunsen burner. As a perspective, two-phase flow DNS auto-ignition is considered thanks to a skeletal mechanism for the n-heptane chemistry involving 29 species and 52 reactions. Results highlight evaporating droplet effects on the auto-ignition process that is generally dramatically modified by spray distribution resulting from the turbulent fluid motion. This paper shows that DNS is a powerful tool to understand the intricate coupling between the evaporating spray, the turbulent fluid motion and the detailed chemistry, inseparable in the experimental context.
An open-source toolbox for multiphase flow in porous media
Horgue, P.; Soulaine, C.; Franc, J.; Guibert, R.; Debenest, G.
2015-02-01
Multiphase flow in porous media provides a wide range of applications: from the environmental understanding (aquifer, site-pollution) to industrial process improvements (oil production, waste management). Modeling of such flows involves specific volume-averaged equations and therefore specific computational fluid dynamics (CFD) tools. In this work, we develop a toolbox for modeling multiphase flow in porous media with OpenFOAM®, an open-source platform for CFD. The underlying idea of this approach is to provide an easily adaptable tool that can be used in further studies to test new mathematical models or numerical methods. The package provides the most common effective properties models of the literature (relative permeability, capillary pressure) and specific boundary conditions related to porous media flows. To validate this package, solvers based on the IMplicit Pressure Explicit Saturation (IMPES) method are developed in the toolbox. The numerical validation is performed by comparison with analytical solutions on academic cases. Then, a satisfactory parallel efficiency of the solver is shown on a more complex configuration.
A model and numerical method for compressible flows with capillary effects
Energy Technology Data Exchange (ETDEWEB)
Schmidmayer, Kevin, E-mail: kevin.schmidmayer@univ-amu.fr; Petitpas, Fabien, E-mail: fabien.petitpas@univ-amu.fr; Daniel, Eric, E-mail: eric.daniel@univ-amu.fr; Favrie, Nicolas, E-mail: nicolas.favrie@univ-amu.fr; Gavrilyuk, Sergey, E-mail: sergey.gavrilyuk@univ-amu.fr
2017-04-01
A new model for interface problems with capillary effects in compressible fluids is presented together with a specific numerical method to treat capillary flows and pressure waves propagation. This new multiphase model is in agreement with physical principles of conservation and respects the second law of thermodynamics. A new numerical method is also proposed where the global system of equations is split into several submodels. Each submodel is hyperbolic or weakly hyperbolic and can be solved with an adequate numerical method. This method is tested and validated thanks to comparisons with analytical solutions (Laplace law) and with experimental results on droplet breakup induced by a shock wave.
Energy Technology Data Exchange (ETDEWEB)
Yortsos, Y.C.
2001-05-29
This report is an investigation of various multi-phase and multiscale transport and reaction processes associated with heavy oil recovery. The thrust areas of the project include the following: Internal drives, vapor-liquid flows, combustion and reaction processes, fluid displacements and the effect of instabilities and heterogeneities and the flow of fluids with yield stress. These find respective applications in foamy oils, the evolution of dissolved gas, internal steam drives, the mechanics of concurrent and countercurrent vapor-liquid flows, associated with thermal methods and steam injection, such as SAGD, the in-situ combustion, the upscaling of displacements in heterogeneous media and the flow of foams, Bingham plastics and heavy oils in porous media and the development of wormholes during cold production.
TOUGH2: A general-purpose numerical simulator for multiphase nonisothermal flows
Energy Technology Data Exchange (ETDEWEB)
Pruess, K. [Lawrence Berkeley Lab., CA (United States)
1991-06-01
Numerical simulators for multiphase fluid and heat flows in permeable media have been under development at Lawrence Berkeley Laboratory for more than 10 yr. Real geofluids contain noncondensible gases and dissolved solids in addition to water, and the desire to model such `compositional` systems led to the development of a flexible multicomponent, multiphase simulation architecture known as MULKOM. The design of MULKOM was based on the recognition that the mass-and energy-balance equations for multiphase fluid and heat flows in multicomponent systems have the same mathematical form, regardless of the number and nature of fluid components and phases present. Application of MULKOM to different fluid mixtures, such as water and air, or water, oil, and gas, is possible by means of appropriate `equation-of-state` (EOS) modules, which provide all thermophysical and transport parameters of the fluid mixture and the permeable medium as a function of a suitable set of primary thermodynamic variables. Investigations of thermal and hydrologic effects from emplacement of heat-generating nuclear wastes into partially water-saturated formations prompted the development and release of a specialized version of MULKOM for nonisothermal flow of water and air, named TOUGH. TOUGH is an acronym for `transport of unsaturated groundwater and heat` and is also an allusion to the tuff formations at Yucca Mountain, Nevada. The TOUGH2 code is intended to supersede TOUGH. It offers all the capabilities of TOUGH and includes a considerably more general subset of MULKOM modules with added capabilities. The paper briefly describes the simulation methodology and user features.
Transient compressible flows in porous media
International Nuclear Information System (INIS)
Morrison, F.A. Jr.
1975-09-01
Transient compressible flow in porous media was investigated analytically. The major portion of the investigation was directed toward improving and understanding of dispersion in these flows and developing rapid accurate numerical techniques for predicting the extent of dispersion. The results are of interest in the containment of underground nuclear experiments. The transient one-dimensional transport of a trace component in a gas flow is analyzed. A conservation equation accounting for the effects of convective transport, dispersive transport, and decay, is developed. This relation, as well as a relation governing the fluid flow, is used to predict trace component concentration as a function of position and time. A detailed analysis of transport associated with the isothermal flow of an ideal gas is done. Because the governing equations are nonlinear, numerical calculations are performed. The ideal gas flow is calculated using a highly stable implicit iterative procedure with an Eulerian mesh. In order to avoid problems of anomolous dispersion associated with finite difference calculation, trace component convection and dispersion are calculated using a Lagrangian mesh. Details of the Eulerian-Lagrangian numerical technique are presented. Computer codes have been developed and implemented on the Lawrence Livermore Laboratory computer system
Lagrangian evolution of deformation of finite-size bubbles in turbulent multiphase flow
Masuk, Ashik Ullah Mohammad; Salibindla, Ashwanth; Ni, Rui
2017-11-01
Finite-size bubbles tend to deform in a strong turbulent environment because of the complex interfacial momentum transfer between them. We have utilized the new V-ONSET turbulence multiphase flow facility to track the deformation and the couplings between two phases in a 3D Lagrangian framework. This rich dataset allows us to understand the roles played by the dynamic pressure and viscous stress, as well as different forces that contribute to the interfacial momentum transfer. Financial support for this project was provided by National Science Foundation under Grant Number: 1653389 and 1705246.
Schwarz-Based Algorithms for Compressible Flows
Tidriri, M. D.
1996-01-01
We investigate in this paper the application of Schwarz-based algorithms to compressible flows. First we study the combination of these methods with defect-correction procedures. We then study the effect on the Schwarz-based methods of replacing the explicit treatment of the boundary conditions by an implicit one. In the last part of this paper we study the combination of these methods with Newton-Krylov matrix-free methods. Numerical experiments that show the performance of our approaches are then presented.
Hutnak, M.; Hurwitz, S.; Ingebritsen, S.E.; Hsieh, P.A.
2009-01-01
Ground surface displacement (GSD) in large calderas is often interpreted as resulting from magma intrusion at depth. Recent advances in geodetic measurements of GSD, notably interferometric synthetic aperture radar, reveal complex and multifaceted deformation patterns that often require complex source models to explain the observed GSD. Although hydrothermal fluids have been discussed as a possible deformation agent, very few quantitative studies addressing the effects of multiphase flow on crustal mechanics have been attempted. Recent increases in the power and availability of computing resources allow robust quantitative assessment of the complex time-variant thermal interplay between aqueous fluid flow and crustal deformation. We carry out numerical simulations of multiphase (liquid-gas), multicomponent (H 2O-CO2) hydrothermal fluid flow and poroelastic deformation using a range of realistic physical parameters and processes. Hydrothermal fluid injection, circulation, and gas formation can generate complex, temporally and spatially varying patterns of GSD, with deformation rates, magnitudes, and geometries (including subsidence) similar to those observed in several large calderas. The potential for both rapid and gradual deformation resulting from magma-derived fluids suggests that hydrothermal fluid circulation may help explain deformation episodes at calderas that have not culminated in magmatic eruption.
Energy Technology Data Exchange (ETDEWEB)
Salgado, C.M.; Pereira, Claudio M.N.A.; Brandao, Luis E.B., E-mail: otero@ien.gov.b, E-mail: cmnap@ien.gov.b, E-mail: brandao@ien.gov.b [Instituto de Engenharia Nuclear (DIRA/IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil). Div. de Radiofarmacos
2011-07-01
This work investigates the response of a volume fraction prediction system for water-gas-oil multiphase flows considering variations on water salinity. The approach is based on gamma-ray pulse height distributions pattern recognition by means the artificial neural networks (ANNs). The detection system uses appropriate fan beam geometry, comprised of a dual-energy gamma-ray source and two NaI(Tl) detectors adequately positioned outside the pipe in order measure transmitted and scattered beams. An ideal and static theoretical model for annular flow regime have been developed using MCNP-X code, which was used to provide training, test and validation data for the ANN. More than 500 simulations have been done, in which water salinity have been ranged from 0 to 16% in order to cover a most practical situations. Validation tests have included values of volume fractions and water salinity different from those used in ANN training phase. The results presented here show that the proposed approach may be successfully applied to material volume fraction prediction on watergas- oil multiphase flows considering practical (real) levels of variations in water salinity. (author)
International Nuclear Information System (INIS)
Salgado, C.M.; Pereira, Claudio M.N.A.; Brandao, Luis E.B.
2011-01-01
This work investigates the response of a volume fraction prediction system for water-gas-oil multiphase flows considering variations on water salinity. The approach is based on gamma-ray pulse height distributions pattern recognition by means the artificial neural networks (ANNs). The detection system uses appropriate fan beam geometry, comprised of a dual-energy gamma-ray source and two NaI(Tl) detectors adequately positioned outside the pipe in order measure transmitted and scattered beams. An ideal and static theoretical model for annular flow regime have been developed using MCNP-X code, which was used to provide training, test and validation data for the ANN. More than 500 simulations have been done, in which water salinity have been ranged from 0 to 16% in order to cover a most practical situations. Validation tests have included values of volume fractions and water salinity different from those used in ANN training phase. The results presented here show that the proposed approach may be successfully applied to material volume fraction prediction on watergas- oil multiphase flows considering practical (real) levels of variations in water salinity. (author)
Mohnke, O.; Ahrenholz, B.
2011-12-01
Nuclear Magnetic Resonance (NMR) is a useful tool for analyzing gas (methane) and fluids (water, oil) in rock formations in order to derive transport and storage properties such as pore-size distributions or relative permeability. Even though there is considerable NMR data available about hydraulic properties of rock formations, this information is only empirical. Thus, the aim of this paper is to present joint NMR and multi-phase flow simulations in micro-scale pore systems derived from micro-CT images to quantify relationships between NMR parameters and transport and storage properties of partially saturated rocks. Hereby, the NMR differential equations were implemented using an advection/diffusion lattice-Boltzmann method (LBM) where the flow field is computed by a coupled LBM CFD solver. The results of numerical imbibition and drainage experiments quantitatively agree with laboratory experiments with regard to frequently found peak shifts and bimodal NMR decay time distributions related to residual water in films and corners as well as to fluids/gases trapped in large pores. This numerical framework enables one to quantitatively describe NMR surface and bulk relaxation processes, diffusive coupling along with the multi-phase flow properties of partially saturated porous systems. Furthermore, it is a viable alternative to the more time-consuming and less controllable laboratory experiments. Such virtual experimental setups can considerably help to benchmark and validate statistical network models to better understand hydraulic properties of partially saturated rocks by using experimentally obtained NMR data.
International Nuclear Information System (INIS)
Mishima, K.; Hibiki, T.
1998-01-01
Neutron radiography (NR) is one of the radiographic techniques which makes use of the difference in attenuation characteristics of neutrons in materials. Fluid measurement using the NR technique is a non-intrusive method which enables visualization of dynamic images of multiphase flow of opaque fluids and/or in a metallic duct. To apply the NR technique to multiphase flow research, high frame-rate NR was developed by combining up-to-date technologies for neutron sources, scintillator, high-speed video and image intensifier. This imaging system has several advantages such as a long recording time (up to 21 minutes), high-frame-rate (up to 1000 frames/s) imaging and there is no need for a triggering signal. Visualization studies of air-water two-phase flow in a metallic duct and molten metal-water interaction were performed at recording speeds of 250, 500 and 1000 frames/s. The qualities of the consequent images were sufficient to observe the flow pattern and behavior. It was also demonstrated that some characteristics of two-phase flow could be measured from these images in collaboration with image processing techniques. By utilizing geometrical information extracted from NR images, data on flow regime, bubble rise velocity, and wave height and interfacial area in annular flow were obtained. By utilizing attenuation characteristics of neutrons in materials, measurements of void profile and average void fraction were performed. It was confirmed that this new technique may have significant advantages both in visualizing and measuring high-speed fluid phenomena when other methods, such as an optical method and X-ray radiography, cannot be applied. (author)
Salinas, P.; Pavlidis, D.; Xie, Z.; Osman, H.; Pain, C. C.; Jackson, M. D.
2018-01-01
We present a new, high-order, control-volume-finite-element (CVFE) method for multiphase porous media flow with discontinuous 1st-order representation for pressure and discontinuous 2nd-order representation for velocity. The method has been implemented using unstructured tetrahedral meshes to discretize space. The method locally and globally conserves mass. However, unlike conventional CVFE formulations, the method presented here does not require the use of control volumes (CVs) that span the boundaries between domains with differing material properties. We demonstrate that the approach accurately preserves discontinuous saturation changes caused by permeability variations across such boundaries, allowing efficient simulation of flow in highly heterogeneous models. Moreover, accurate solutions are obtained at significantly lower computational cost than using conventional CVFE methods. We resolve a long-standing problem associated with the use of classical CVFE methods to model flow in highly heterogeneous porous media.
Tsai, C. H.; Yeh, G. T.
2015-12-01
In this investigation, a coupled model of multiphase flow, reactive biogeochemical transport, thermal transport and geo-mechanics in subsurface media is presented. It iteratively solves the mass conservation equation for fluid flow, thermal transport equation for temperature, reactive biogeochemical transport equations for concentration distributions, and solid momentum equation for displacement with successive linearization algorithm. With species-based equations of state, density of a phase in the system is obtained by summing up concentrations of all species. This circumvents the problem of having to use empirical functions. Moreover, reaction rates of all species are incorporated in mass conservation equation for fluid flow. Formation enthalpy of all species is included in the law of energy conservation as a source-sink term. Finite element methods are used to discretize the governing equations. Numerical experiments are presented to examine the accuracy and robustness of the proposed model. The results demonstrate the feasibility and capability of present model in subsurface media.
Two-Fluid Models for Simulating Dispersed Multiphase Flows-A Review
Directory of Open Access Journals (Sweden)
L.X. Zhou
2009-01-01
Full Text Available The development of two-fluid models for simulating dispersed multiphase flows (gas-particle, gas-droplet, bubble-liquid, liquid-particle flows by the present author within the last 20 years is systematically reviewed. The two-fluid models based on Reynolds expansion, time averaging and mass-weighed averaging, and also PDF transport equations are described. Different versions of two-phase turbulence models, including the unified second-order moment (USM and k-ε-kp models, the DSM-PDF model, the SOM-MC model, the nonlinear k-e-kp model, and the USM-Θ model for dense gas-particle flows and their application and experimental validation are discussed.
DENSE MULTIPHASE FLOW SIMULATION: CONTINUUM MODEL FOR POLY-DISPERSED SYSTEMS USING KINETIC THEORY
Energy Technology Data Exchange (ETDEWEB)
Moses Bogere
2011-08-31
The overall objective of the project was to verify the applicability of the FCMOM approach to the kinetic equations describing the particle flow dynamics. For monodispersed systems the fundamental equation governing the particle flow dynamics is the Boltzmann equation. During the project, the FCMOM was successfully applied to several homogeneous and in-homogeneous problems in different flow regimes, demonstrating that the FCMOM has the potential to be used to solve efficiently the Boltzmann equation. However, some relevant issues still need to be resolved, i.e. the homogeneous cooling problem (inelastic particles cases) and the transition between different regimes. In this report, the results obtained in homogeneous conditions are discussed first. Then a discussion of the validation results for in-homogeneous conditions is provided. And finally, a discussion will be provided about the transition between different regimes. Alongside the work on development of FCMOM approach studies were undertaken in order to provide insights into anisotropy or particles kinetics in riser hydrodynamics. This report includes results of studies of multiphase flow with unequal granular temperatures and analysis of momentum re-distribution in risers due to particle-particle and fluid-particle interactions. The study of multiphase flow with unequal granular temperatures entailed both simulation and experimental studies of two particles sizes in a riser and, a brief discussion of what was accomplished will be provided. And finally, a discussion of the analysis done on momentum re-distribution of gas-particles flow in risers will be provided. In particular a discussion of the remaining work needed in order to improve accuracy and predictability of riser hydrodynamics based on two-fluid models and how they can be used to model segregation in risers.
Fundamentals of multiphase, gas-solid and gas-liquid flows in porous media
Mazaheri, Ali Reza
This thesis is concerned with fundamentals and applications of multiphase and particulate flows. The study contains three parts covering gas-liquid flows through porous media, gas-solid flows and Chemical-Mechanical Polishing (CMP). A continuum model for multiphase fluid flows through poro-elastic media is developed. It is shown that the present theory leads to the extended Darcy's law and contains, as its special case, Biot's theory of saturated poro-elastic media. The capillary pressure formulation derived from the new model is used and the equation governing the evolution of the saturation and its temporal variation in porous media is derived. The resulting nonlinear diffusion equation is then solved numerically. The results show that the capillary hysteresis occurs when the temporal variation of saturation is included. Application of the developed model to CO2 sequestration is discussed. Computer simulations of dilute Gas-Solid flows in complex geometry regions are studied. A procedure for handling particle trajectory analysis in unstructured grid is developed. Examples of particle transport and removal in human lung and hot-gas cleaning systems are presented. The simulation results for the human lung show that the capture efficiency is affected by the turbulence in the upper three bifurcation airways. Computer simulations of gas-solid flows in hot-gas cleaning for a demonstration scale filtration system is studied in details. Alternative designs of the filter vessel are proposed. The corresponding vessel performance are numerically simulated. Chemical mechanical polishing (CMP) has become critical to the fabrication of advanced multilevel integrated circuit in microelectronic industry. The effect of course surface roughness of abrasive particles on the polishing rate in CMP is studied. The effects of slurry pH and double layer attraction and repulsion on chemical-mechanical polishing are also studied. It is shown that the slurry pH and colloidal forces
Schwarz-based algorithms for compressible flows
Energy Technology Data Exchange (ETDEWEB)
Tidriri, M.D. [ICASE, Hampton, VA (United States)
1996-12-31
To compute steady compressible flows one often uses an implicit discretization approach which leads to a large sparse linear system that must be solved at each time step. In the derivation of this system one often uses a defect-correction procedure, in which the left-hand side of the system is discretized with a lower order approximation than that used for the right-hand side. This is due to storage considerations and computational complexity, and also to the fact that the resulting lower order matrix is better conditioned than the higher order matrix. The resulting schemes are only moderately implicit. In the case of structured, body-fitted grids, the linear system can easily be solved using approximate factorization (AF), which is among the most widely used methods for such grids. However, for unstructured grids, such techniques are no longer valid, and the system is solved using direct or iterative techniques. Because of the prohibitive computational costs and large memory requirements for the solution of compressible flows, iterative methods are preferred. In these defect-correction methods, which are implemented in most CFD computer codes, the mismatch in the right and left hand side operators, together with explicit treatment of the boundary conditions, lead to a severely limited CFL number, which results in a slow convergence to steady state aerodynamic solutions. Many authors have tried to replace explicit boundary conditions with implicit ones. Although they clearly demonstrate that high CFL numbers are possible, the reduction in CPU time is not clear cut.
A multiphase flow meter for the on-line determination of the flow rates of oil, water and gas
International Nuclear Information System (INIS)
Roach, G.J.; Watt, J.S.
1997-01-01
Multiphase mixtures of crude oil, formation water and gas are carried in pipelines from oil wells to production facilities. Multiphase flow meters (MFMs) are being developed to determine the flow rates of each component of the heterogeneous mixture in the pipeline. CSIRO Minerals has developed and field tested a gamma-ray MFM for the on-line determination of the flow rates of heterogeneous mixtures of oil, water and gas in pipelines. It consists of two specialised gamma-ray transmission gauges, and pressure and temperature sensors, mounted on the pipeline carrying the full flow of the production stream. The MFM separately measures liquids and gas flow rates, and the volume ratio of water and liquids (water cut). The MFM has been trialled at three offshore production facilities in Australia. In each, the MFM was mounted on the pipeline between the test manifold and the test separator. The multiphase streams from the various wells feeding to the platform were sequentially routed past the MFM. The MFM and test separator outputs were compared using regression analysis. The flow rates of oil, water and gas were each determined to relative errors in the range of 5-10% . The MFM has been in routine use on the West Kingfish platform in the Bass Strait since November 1994. The MFM was recently tested over a wide range of flow conditions at a Texaco flow facility near Houston. Water cut, based on pre-trial calibration, was determined to 2% rms over the range 0-100% water cut. The liquids and gas flow results were interpreted based on slip correlations obtained from comparison of the MFM and Texaco flows. Using these, the relative errors were respectively 6.6% for liquid flow, 6.2% for gas, 8% for oil and 8% for water. The MFM is licensed to Kvaerner FSSL of Aberdeen. Kvaerner will supply the gamma-ray MFM for both platform and subsea use. Technology transfer commenced in December 1996, and Kvaerner completed the manufacture of the first MFM in August 1997
A multiphase flow meter for the on-line determination of the flow rates of oil, water and gas
Energy Technology Data Exchange (ETDEWEB)
Roach, G.J.; Watt, J.S. [Commonwealth Scientific and Industrial Research Organisation (CSIRO), Menai, NSW (Australia). Divsion of Minerals
1997-10-01
Multiphase mixtures of crude oil, formation water and gas are carried in pipelines from oil wells to production facilities. Multiphase flow meters (MFMs) are being developed to determine the flow rates of each component of the heterogeneous mixture in the pipeline. CSIRO Minerals has developed and field tested a gamma-ray MFM for the on-line determination of the flow rates of heterogeneous mixtures of oil, water and gas in pipelines. It consists of two specialised gamma-ray transmission gauges, and pressure and temperature sensors, mounted on the pipeline carrying the full flow of the production stream. The MFM separately measures liquids and gas flow rates, and the volume ratio of water and liquids (water cut). The MFM has been trialled at three offshore production facilities in Australia. In each, the MFM was mounted on the pipeline between the test manifold and the test separator. The multiphase streams from the various wells feeding to the platform were sequentially routed past the MFM. The MFM and test separator outputs were compared using regression analysis. The flow rates of oil, water and gas were each determined to relative errors in the range of 5-10% . The MFM has been in routine use on the West Kingfish platform in the Bass Strait since November 1994. The MFM was recently tested over a wide range of flow conditions at a Texaco flow facility near Houston. Water cut, based on pre-trial calibration, was determined to 2% rms over the range 0-100% water cut. The liquids and gas flow results were interpreted based on slip correlations obtained from comparison of the MFM and Texaco flows. Using these, the relative errors were respectively 6.6% for liquid flow, 6.2% for gas, 8% for oil and 8% for water. The MFM is licensed to Kvaerner FSSL of Aberdeen. Kvaerner will supply the gamma-ray MFM for both platform and subsea use. Technology transfer commenced in December 1996, and Kvaerner completed the manufacture of the first MFM in August 1997 4 refs., 7 figs.
Patel, Jitendra Kumar; Natarajan, Ganesh
2017-12-01
We discuss the development and assessment of a robust numerical algorithm for simulating multiphase flows with complex interfaces and high density ratios on arbitrary polygonal meshes. The algorithm combines the volume-of-fluid method with an incremental projection approach for incompressible multiphase flows in a novel hybrid staggered/non-staggered framework. The key principles that characterise the algorithm are the consistent treatment of discrete mass and momentum transport and the similar discretisation of force terms appearing in the momentum equation. The former is achieved by invoking identical schemes for convective transport of volume fraction and momentum in the respective discrete equations while the latter is realised by representing the gravity and surface tension terms as gradients of suitable scalars which are then discretised in identical fashion resulting in a balanced formulation. The hybrid staggered/non-staggered framework employed herein solves for the scalar normal momentum at the cell faces, while the volume fraction is computed at the cell centroids. This is shown to naturally lead to similar terms for pressure and its correction in the momentum and pressure correction equations respectively, which are again treated discretely in a similar manner. We show that spurious currents that corrupt the solution may arise both from an unbalanced formulation where forces (gravity and surface tension) are discretised in dissimilar manner and from an inconsistent approach where different schemes are used to convect the mass and momentum, with the latter prominent in flows which are convection-dominant with high density ratios. Interestingly, the inconsistent approach is shown to perform as well as the consistent approach even for high density ratio flows in some cases while it exhibits anomalous behaviour for other scenarios, even at low density ratios. Using a plethora of test problems of increasing complexity, we conclusively demonstrate that the
Wei, Xiaohui; Li, Weishan; Tian, Hailong; Li, Hongliang; Xu, Haixiao; Xu, Tianfu
2015-07-01
The numerical simulation of multiphase flow and reactive transport in the porous media on complex subsurface problem is a computationally intensive application. To meet the increasingly computational requirements, this paper presents a parallel computing method and architecture. Derived from TOUGHREACT that is a well-established code for simulating subsurface multi-phase flow and reactive transport problems, we developed a high performance computing THC-MP based on massive parallel computer, which extends greatly on the computational capability for the original code. The domain decomposition method was applied to the coupled numerical computing procedure in the THC-MP. We designed the distributed data structure, implemented the data initialization and exchange between the computing nodes and the core solving module using the hybrid parallel iterative and direct solver. Numerical accuracy of the THC-MP was verified through a CO2 injection-induced reactive transport problem by comparing the results obtained from the parallel computing and sequential computing (original code). Execution efficiency and code scalability were examined through field scale carbon sequestration applications on the multicore cluster. The results demonstrate successfully the enhanced performance using the THC-MP on parallel computing facilities.
A hybrid interface tracking - level set technique for multiphase flow with soluble surfactant
Shin, Seungwon; Chergui, Jalel; Juric, Damir; Kahouadji, Lyes; Matar, Omar K.; Craster, Richard V.
2018-04-01
A formulation for soluble surfactant transport in multiphase flows recently presented by Muradoglu and Tryggvason (JCP 274 (2014) 737-757) [17] is adapted to the context of the Level Contour Reconstruction Method, LCRM, (Shin et al. IJNMF 60 (2009) 753-778, [8]) which is a hybrid method that combines the advantages of the Front-tracking and Level Set methods. Particularly close attention is paid to the formulation and numerical implementation of the surface gradients of surfactant concentration and surface tension. Various benchmark tests are performed to demonstrate the accuracy of different elements of the algorithm. To verify surfactant mass conservation, values for surfactant diffusion along the interface are compared with the exact solution for the problem of uniform expansion of a sphere. The numerical implementation of the discontinuous boundary condition for the source term in the bulk concentration is compared with the approximate solution. Surface tension forces are tested for Marangoni drop translation. Our numerical results for drop deformation in simple shear are compared with experiments and results from previous simulations. All benchmarking tests compare well with existing data thus providing confidence that the adapted LCRM formulation for surfactant advection and diffusion is accurate and effective in three-dimensional multiphase flows with a structured mesh. We also demonstrate that this approach applies easily to massively parallel simulations.
Numerical Simulation of Transient Multiphase Flow in a Five-Strand Bloom Tundish during Ladle Change
Directory of Open Access Journals (Sweden)
Hua Zhang
2018-02-01
Full Text Available The steel-slag-air multiphase flow in a bloom tundish with five strands during the transient casting of the ladle change was simulated using the Volume of Fluid (VOF model, and the formation mechanisms of macro-inclusions and the behavior of the steel-slag-air interface during the filling process were investigated. Water model experiments were conducted to validate the multiphase model. The results showed that the numerical results of slag entrapment behavior and the exposed area of steel are basically consistent with the experimental results. The flow of molten steel in the tundish is weak except for the region around the stopper rods at the end of the emptying process. Strong fluctuations in liquid level were formed during the filling process, showing two wave crests in front of and behind the shroud in the impact zone, which intensified with the increase in filling time and then declined gradually. Entrapment phenomena and exposure of liquid steel could not be observed before the filling stage. While the entrapped slag droplets mostly float up and can be removed within 40 s during the filling process, the remainder enters the casting zone through the baffle. The maximum exposed area of molten steel is 252 cm2 when the filling time is 4.0 s.
Persistent Homology to describe Solid and Fluid Structures during Multiphase Flow
Herring, A. L.; Robins, V.; Liu, Z.; Armstrong, R. T.; Sheppard, A.
2017-12-01
The question of how to accurately and effectively characterize essential fluid and solid distributions and structures is a long-standing topic within the field of porous media and fluid transport. For multiphase flow applications, considerable research effort has been made to describe fluid distributions under a range of conditions; including quantification of saturation levels, fluid-fluid pressure differences and interfacial areas, and fluid connectivity. Recent research has effectively used topological metrics to describe pore space and fluid connectivity, with researchers demonstrating links between pore-scale nonwetting phase topology to fluid mobilization and displacement mechanisms, relative permeability, fluid flow regimes, and thermodynamic models of multiphase flow. While topology is clearly a powerful tool to describe fluid distribution, topological metrics by definition provide information only on the connectivity of a phase, not its geometry (shape or size). Physical flow characteristics, e.g. the permeability of a fluid phase within a porous medium, are dependent on the connectivity of the pore space or fluid phase as well as the size of connections. Persistent homology is a technique which provides a direct link between topology and geometry via measurement of topological features and their persistence from the signed Euclidean distance transform of a segmented digital image (Figure 1). We apply persistent homology analysis to measure the occurrence and size of pore-scale topological features in a variety of sandstones, for both the dry state and the nonwetting phase fluid during two-phase fluid flow (drainage and imbibition) experiments, visualized with 3D X-ray microtomography. The results provide key insights into the dominant topological features and length scales of a media which control relevant field-scale engineering properties such as fluid trapping, absolute permeability, and relative permeability.
Dripping and jetting in microfluidic multiphase flows applied to particle and fiber synthesis
Nunes, J K; Tsai, S S H; Wan, J; Stone, H A
2013-01-01
Dripping and jetting regimes in microfluidic multiphase flows have been investigated extensively, and this review summarizes the main observations and physical understandings in this field to date for three common device geometries: coaxial, flow-focusing and T-junction. The format of the presentation allows for simple and direct comparison of the different conditions for drop and jet formation, as well as the relative ease and utility of forming either drops or jets among the three geometries. The emphasis is on the use of drops and jets as templates for microparticle and microfiber syntheses, and a description is given of the more common methods of solidification and strategies for achieving complex multicomponent microparticles and microfibers. PMID:23626378
Directory of Open Access Journals (Sweden)
Farooq Hussain
2018-02-01
Full Text Available The multiphase fluid flow under the influence of electro-magnetohydrodynamics (EHD is investigated in this study. The base fluid contains hafnium particles. Two illustrative models namely fluid phase and particulate phase are considered for three different geometries having great importance in both industrial and mechanical usage. The impact of pertinent parameters from different aspects is illustrated graphically with requisite discussion keeping in view their physical aspects. The stream lines are also erected to highlight their physical importance regarding the flow patterns. In addition, the paper is terminated by making a comparison with the existing literature as a limiting case of considered problem to confirm the validations of achieved results and hence found in excellent agreement. This model can be used to design and engineer for nozzle or diffuser type of injectors in the latest models of automobiles to improve their performance and reduce the consumption of fuel.
Energy Technology Data Exchange (ETDEWEB)
Hornung, R.D. [Duke Univ., Durham, NC (United States)
1996-12-31
An adaptive local mesh refinement (AMR) algorithm originally developed for unsteady gas dynamics is extended to multi-phase flow in porous media. Within the AMR framework, we combine specialized numerical methods to treat the different aspects of the partial differential equations. Multi-level iteration and domain decomposition techniques are incorporated to accommodate elliptic/parabolic behavior. High-resolution shock capturing schemes are used in the time integration of the hyperbolic mass conservation equations. When combined with AMR, these numerical schemes provide high resolution locally in a more efficient manner than if they were applied on a uniformly fine computational mesh. We will discuss the interplay of physical, mathematical, and numerical concerns in the application of adaptive mesh refinement to flow in porous media problems of practical interest.
Subsampling-based compression and flow visualization
Energy Technology Data Exchange (ETDEWEB)
Agranovsky, Alexy; Camp, David; Joy, I; Childs, Hank
2016-01-19
As computational capabilities increasingly outpace disk speeds on leading supercomputers, scientists will, in turn, be increasingly unable to save their simulation data at its native resolution. One solution to this problem is to compress these data sets as they are generated and visualize the compressed results afterwards. We explore this approach, specifically subsampling velocity data and the resulting errors for particle advection-based flow visualization. We compare three techniques: random selection of subsamples, selection at regular locations corresponding to multi-resolution reduction, and introduce a novel technique for informed selection of subsamples. Furthermore, we explore an adaptive system which exchanges the subsampling budget over parallel tasks, to ensure that subsampling occurs at the highest rate in the areas that need it most. We perform supercomputing runs to measure the effectiveness of the selection and adaptation techniques. Overall, we find that adaptation is very effective, and, among selection techniques, our informed selection provides the most accurate results, followed by the multi-resolution selection, and with the worst accuracy coming from random subsamples.
Flux Limiter Lattice Boltzmann for Compressible Flows
International Nuclear Information System (INIS)
Chen Feng; Li Yingjun; Xu Aiguo; Zhang Guangcai
2011-01-01
In this paper, a new flux limiter scheme with the splitting technique is successfully incorporated into a multiple-relaxation-time lattice Boltzmann (LB) model for shacked compressible flows. The proposed flux limiter scheme is efficient in decreasing the artificial oscillations and numerical diffusion around the interface. Due to the kinetic nature, some interface problems being difficult to handle at the macroscopic level can be modeled more naturally through the LB method. Numerical simulations for the Richtmyer-Meshkov instability show that with the new model the computed interfaces are smoother and more consistent with physical analysis. The growth rates of bubble and spike present a satisfying agreement with the theoretical predictions and other numerical simulations. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)
An efficient shock-capturing scheme for simulating compressible homogeneous mixture flow
International Nuclear Information System (INIS)
Dang, Son Tung; Ha, Cong Tu; Park, Warn Gyu; Jung, Chul Min
2016-01-01
This work is devoted to the development of a procedure for the numerical solution of Navier-Stokes equations for cavitating flows with and without ventilation based on a compressible, multiphase, homogeneous mixture model. The governing equations are discretized on a general structured grid using a high-resolution shock-capturing scheme in conjunction with appropriate limiters to prevent the generation of spurious solutions near shock waves or discontinuities. Two well-known limiters are examined, and a new limiter is proposed to enhance the accuracy and stability of the numerical scheme. A sensitivity analysis is first conducted to determine the relative influences of various model parameters on the solution. These parameters are adopted for the computation of water flows over a hemispherical body, conical body and a divergent/convergent nozzle. Finally, numerical calculations of ventilated supercavitating flows over a hemispherical cylinder body with a hot propulsive jet are conducted to verify the capabilities of the numerical scheme
New multiphase choke correlations for a high flow rate Iranian oil field
Directory of Open Access Journals (Sweden)
M. Safar Beiranvand
2012-06-01
Full Text Available The multiphase flow through wellhead restrictions of an offshore oil field in Iran is investigated and two sets of new correlations are presented for high flow rate and water cut conditions. The both correlations are developed by using 748 actual data points, corresponding to critical flow conditions of gas-liquid mixtures through wellhead chokes. The first set of correlations is a modified Gilbert equation and predicts liquid flow rates as a function of flowing wellhead pressure, gas-liquid ratio and surface wellhead choke size. To minimize error in such condition, in the second correlation, free water, sediment and emulsion (BS & W is also considered as an effective parameter. The predicted oil flow rates by the new sets of correlations are in the excellent agreement with the measured ones. These results are found to be statistically superior to those predicted by other relevant published correlations. The both proposed correlations exhibit more accuracy (only 2.95% and 2.0% average error, respectively than the existent correlations. These results should encourage the production engineer which works at such condition to utilize the proposed correlations for future practical answers when a lack of available information, time, and calculation capabilities arises.
International Nuclear Information System (INIS)
Ostrowski, Z; Melka, B; Adamczyk, W; Rojczyk, M; Nowak, A J; Golda, A
2016-01-01
In the research a numerical Computational Fluid Dynamics (CFD) model of the pulsatile blood flow was created and analyzed. A real geometry of aorta and its thoracic branches of 8-year old patient diagnosed with a congenital heart defect - coarctation of aorta was used. The inlet boundary condition were implemented as the User Define Function according to measured values of volumetric blood flow. The blood flow was treated as multiphase: plasma, set as the primary fluid phase, was dominant with volume fraction of 0.585 and morphological elements of blood were treated in Euler-Euler approach as dispersed phases (with 90% Red Blood Cells and White Blood Cells as remaining solid volume fraction). (paper)
Theoretical analysis of multiphase flow during oil-well drilling by a conservative model
Nicolas-Lopez, Ruben
2005-11-01
In order to decrease cost and improve drilling operations is necessary a better understood of the flow mechanisms. Therefore, it was carried out a multiphase conservative model that includes three mass equations and a momentum equation. Also, the measured geothermal gradient is utilized by state equations for estimating physical properties of the phases flowing. The mathematical model is solved by numerical conservative schemes. It is used to analyze the interaction among solid-liquid-gas phases. The circulating system consists as follow, the circulating fluid is pumped downward into the drilling pipe until the bottom of the open hole then it flows through the drill bit, and at this point formation cuttings are incorporated to the circulating fluid and carried upward to the surface. The mixture returns up to the surface by an annular flow area. The real operational conditions are fed to conservative model and the results are matched up to field measurements in several oil wells. Mainly, flow rates, drilling rate, well and tool geometries are data to estimate the profiles of pressure, mixture density, equivalent circulating density, gas fraction and solid carrying capacity. Even though the problem is very complex, the model describes, properly, the hydrodynamics of drilling techniques applied at oil fields. *Authors want to thank to Instituto Mexicano del Petroleo and Petroleos Mexicanos for supporting this research.
Application of the numerical density-enthalpy method to the multi-phase flow through a porous medium
Ibrahim, D.; Vermolen, F.J.; Vuik, C.
2010-01-01
In this paper we apply a new method to solve multi-phase fluid flow problem for 1D1D and 2D2D fluid systems. This method is developed at TNO and presented in [1] for spatially homogeneous systems. We call this method the numerical density-enthalpy method (or ??-hh method) because density-enthalpy
DEFF Research Database (Denmark)
Voigt, Andreas Jauernik; Ludiciani, Piero; Nielsen, Kenny Krogh
2016-01-01
This paper presents a first venture into quantifying stiffness and damping coefficients for turbomachinery seals in multiphase flow using Computational Fluid Dynamics (CFD). The study focusses on the simplest seal type: the smooth annular seal. The investigation is conducted for both wet-gas and ...
Particle methods for simulation of subsurface multiphase fluid flow and biogeochemical processes
International Nuclear Information System (INIS)
Meakin, Paul; Tartakovsky, Alexandre; Scheibe, Tim; Tartakovsky, Daniel; Redden, George; Long, Philip E; Brooks, Scott C; Xu Zhijie
2007-01-01
A number of particle models that are suitable for simulating multiphase fluid flow and biogeochemical processes have been developed during the last few decades. Here we discuss three of them: a microscopic model - molecular dynamics; a mesoscopic model - dissipative particle dynamics; and a macroscopic model - smoothed particle hydrodynamics. Particle methods are robust and versatile, and it is relatively easy to add additional physical, chemical and biological processes into particle codes. However, the computational efficiency of particle methods is low relative to continuum methods. Multiscale particle methods and hybrid (particle-particle and particle-continuum) methods are needed to improve computational efficiency and make effective use of emerging computational capabilities. These new methods are under development
Adverse Condition and Critical Event Prediction in Cranfield Multiphase Flow Facility
DEFF Research Database (Denmark)
Egedorf, Søren; Shaker, Hamid Reza
2017-01-01
Today's complex processes and plants are vulnerable to different faults, misconfiguration, non-holistic and improper control and management which cause abnormal behavior and might eventually result in poor and sub-optimal operation, dissatisfaction, damage to the plant, to personnel and resources......, or even to the environment. To cope with these, adverse condition and critical event prediction plays an important role. Adverse Condition and Critical Event Prediction Toolbox (ACCEPT) is a tool which has been recently developed by NASA to allow for a timely prediction of an adverse event, with low false...... alarm and missed detection rates. While ACCEPT has shown to be an effective tool in some applications, its performance has not yet been evaluated on practical well-known benchmark examples. In this paper, ACCEPT is used for adverse condition and critical event prediction in a multiphase flow facility...
Towards a new method for modeling multicomponent, multiphase flow and transport in porous media
Kong, X. Z.; Schaedle, P.; Leal, A. M. M.; Saar, M. O.
2016-12-01
The ability to computationally simulate multiphase-multicomponent fluid flow, coupled with geochemical reactions between fluid species and rock minerals, in porous and/or fractured subsurface systems is of major importance to a vast number of applications. These include (1) carbon dioxide storage in geologic formations, (2) geothermal energy extraction, (3) combinations of the latter two applications during CO2-Plume Geothermal energy extraction, (4) waste fluid and waste storage, as well as (5) groundwater and contaminant transport. Modeling these systems with such a wide variety of coupled physical and chemical processes is both challenging and computationally expensive. In this work we present a new approach to develop a simulator for multicomponent-multiphase flow and reactive transport in porous media by using state of the art numerical tools, namely FEniCS (fenicsproject.org) and Reaktoro (reaktoro.org). The governing partial differential equations for fluid flow and transport are solved using FEniCS, which enables fast and efficient implementation of computer codes for the simulation of complex physical phenomena using finite element methods on unstructured meshes. FEniCS supports a wide range of finite element schemes of special interest to porous media flow. In addition, FEniCS interfaces with many sparse linear solvers and provides convenient tools for adaptive mesh refinement and the capability of massively parallel calculations. A fundamental component of our contribution is the coupling of our FEniCS based flow and transport solver with our chemical reaction simulator, Reaktoro, which implements efficient, robust, and accurate methods for chemical equilibrium and kinetics calculations at every node of the mesh, at every time step. These numerical methods for reaction modeling have been especially developed for performance-critical applications such as reactive transport modeling. Furthermore, Reaktoro is also used for the calculation of thermodynamic
Huo, Xiaokai; Sun, Weitao; He, Fengjiang; Yang, Zhe; Peng, Yuanping
2014-01-01
Accurate estimation of water content in an oil-water mixture is a key technology in oil exploration and production. Based on the principles of the microwave transmission line (MTL), the logging probe is an important water content measuring apparatus. However, the effects of mixed fluid flow on the measurement of electromagnetic field parameters are rarely considered. This study presents the coupling model for low-speed multiphase flow and high-frequency electromagnetic field in a complex pipe...
A simple mass-conserved level set method for simulation of multiphase flows
Yuan, H.-Z.; Shu, C.; Wang, Y.; Shu, S.
2018-04-01
In this paper, a modified level set method is proposed for simulation of multiphase flows with large density ratio and high Reynolds number. The present method simply introduces a source or sink term into the level set equation to compensate the mass loss or offset the mass increase. The source or sink term is derived analytically by applying the mass conservation principle with the level set equation and the continuity equation of flow field. Since only a source term is introduced, the application of the present method is as simple as the original level set method, but it can guarantee the overall mass conservation. To validate the present method, the vortex flow problem is first considered. The simulation results are compared with those from the original level set method, which demonstrates that the modified level set method has the capability of accurately capturing the interface and keeping the mass conservation. Then, the proposed method is further validated by simulating the Laplace law, the merging of two bubbles, a bubble rising with high density ratio, and Rayleigh-Taylor instability with high Reynolds number. Numerical results show that the mass is a well-conserved by the present method.
Multiphase Flow in Porous Media with Emphasis on Co2 Sequestration
Energy Technology Data Exchange (ETDEWEB)
Be, Alif
2011-07-01
Numerical simulation has been used to predict multiphase flow in porous media. It is of great importance to incorporate accurate flow properties to obtain a proper simulation result thus reducing the risk of making wrong decision. Relative permeability and capillary pressure are important key parameters in multiphase flow as they describe how different fluid will interact in porous media. It is even more important in the case of three-phase flow as there are more fluid phases interact in the system. In most of the three-phase flow studies, capillary pressure has been neglected due to the lack of measured data and assumption that its effect is negligible. In other cases, two-phase capillary pressure has been used instead to describe the process in the system. This study will try to show how significant the impact of three-phase capillary pressure using different rock wettability. The three-phase capillary pressure surfaces are generated using a network model. Prior research shows that rock wettability is altered during Co2 sequestration due to the formation of carbonic acid (H2CO3) which leads to lower ph. In this study the effect of wettability alteration is incorporated to assess the safety of Johansen formation which is a good candidate for Co2 sequestration project. In addition, the wettability alteration effect to different flow parameters such as heterogeneity, solubility and diffusion is investigated. This thesis consists of two parts; the first part presents a theoretical background for the work, and the second part is a collection of papers. The papers are grouped into two main topics. The first three papers are discussing about three-phase flow simulation in porous media. The rest are discussing about wettability alteration during Co2 sequestration. Chapter 2 and 3 of the theoretical background include definitions and descriptions of interfacial tension, wettability, capillary pressure, relative permeability and hysteresis. Network model and technique for
Multiphase Flow in Porous Media with Emphasis on Co2 Sequestration
International Nuclear Information System (INIS)
Be, Alif
2011-01-01
Numerical simulation has been used to predict multiphase flow in porous media. It is of great importance to incorporate accurate flow properties to obtain a proper simulation result thus reducing the risk of making wrong decision. Relative permeability and capillary pressure are important key parameters in multiphase flow as they describe how different fluid will interact in porous media. It is even more important in the case of three-phase flow as there are more fluid phases interact in the system. In most of the three-phase flow studies, capillary pressure has been neglected due to the lack of measured data and assumption that its effect is negligible. In other cases, two-phase capillary pressure has been used instead to describe the process in the system. This study will try to show how significant the impact of three-phase capillary pressure using different rock wettability. The three-phase capillary pressure surfaces are generated using a network model. Prior research shows that rock wettability is altered during Co2 sequestration due to the formation of carbonic acid (H2CO3) which leads to lower ph. In this study the effect of wettability alteration is incorporated to assess the safety of Johansen formation which is a good candidate for Co2 sequestration project. In addition, the wettability alteration effect to different flow parameters such as heterogeneity, solubility and diffusion is investigated. This thesis consists of two parts; the first part presents a theoretical background for the work, and the second part is a collection of papers. The papers are grouped into two main topics. The first three papers are discussing about three-phase flow simulation in porous media. The rest are discussing about wettability alteration during Co2 sequestration. Chapter 2 and 3 of the theoretical background include definitions and descriptions of interfacial tension, wettability, capillary pressure, relative permeability and hysteresis. Network model and technique for
Multiphase integral reacting flow computer code (ICOMFLO): User`s guide
Energy Technology Data Exchange (ETDEWEB)
Chang, S.L.; Lottes, S.A.; Petrick, M.
1997-11-01
A copyrighted computational fluid dynamics computer code, ICOMFLO, has been developed for the simulation of multiphase reacting flows. The code solves conservation equations for gaseous species and droplets (or solid particles) of various sizes. General conservation laws, expressed by elliptic type partial differential equations, are used in conjunction with rate equations governing the mass, momentum, enthalpy, species, turbulent kinetic energy, and turbulent dissipation. Associated phenomenological submodels of the code include integral combustion, two parameter turbulence, particle evaporation, and interfacial submodels. A newly developed integral combustion submodel replacing an Arrhenius type differential reaction submodel has been implemented to improve numerical convergence and enhance numerical stability. A two parameter turbulence submodel is modified for both gas and solid phases. An evaporation submodel treats not only droplet evaporation but size dispersion. Interfacial submodels use correlations to model interfacial momentum and energy transfer. The ICOMFLO code solves the governing equations in three steps. First, a staggered grid system is constructed in the flow domain. The staggered grid system defines gas velocity components on the surfaces of a control volume, while the other flow properties are defined at the volume center. A blocked cell technique is used to handle complex geometry. Then, the partial differential equations are integrated over each control volume and transformed into discrete difference equations. Finally, the difference equations are solved iteratively by using a modified SIMPLER algorithm. The results of the solution include gas flow properties (pressure, temperature, density, species concentration, velocity, and turbulence parameters) and particle flow properties (number density, temperature, velocity, and void fraction). The code has been used in many engineering applications, such as coal-fired combustors, air
Energy Technology Data Exchange (ETDEWEB)
Mukhopadhyay, S.; Tsang, Y.; Finsterle, S.
2009-01-15
A simple conceptual model has been recently developed for analyzing pressure and temperature data from flowing fluid temperature logging (FFTL) in unsaturated fractured rock. Using this conceptual model, we developed an analytical solution for FFTL pressure response, and a semianalytical solution for FFTL temperature response. We also proposed a method for estimating fracture permeability from FFTL temperature data. The conceptual model was based on some simplifying assumptions, particularly that a single-phase airflow model was used. In this paper, we develop a more comprehensive numerical model of multiphase flow and heat transfer associated with FFTL. Using this numerical model, we perform a number of forward simulations to determine the parameters that have the strongest influence on the pressure and temperature response from FFTL. We then use the iTOUGH2 optimization code to estimate these most sensitive parameters through inverse modeling and to quantify the uncertainties associated with these estimated parameters. We conclude that FFTL can be utilized to determine permeability, porosity, and thermal conductivity of the fracture rock. Two other parameters, which are not properties of the fractured rock, have strong influence on FFTL response. These are pressure and temperature in the borehole that were at equilibrium with the fractured rock formation at the beginning of FFTL. We illustrate how these parameters can also be estimated from FFTL data.
MODELING COUPLED PROCESSES OF MULTIPHASE FLOW AND HEAT TRANSFER IN UNSATURATED FRACTURED ROCK
International Nuclear Information System (INIS)
Y. Wu; S. Mukhopadhyay; K. Zhang; G.S. Bodvarsson
2006-01-01
A mountain-scale, thermal-hydrologic (TH) numerical model is developed for investigating unsaturated flow behavior in response to decay heat from the radioactive waste repository at Yucca Mountain, Nevada, USA. The TH model, consisting of three-dimensional (3-D) representations of the unsaturated zone, is based on the current repository design, drift layout, and thermal loading scenario under estimated current and future climate conditions. More specifically, the TH model implements the current geological framework and hydrogeological conceptual models, and incorporates the most updated, best-estimated input parameters. This mountain-scale TH model simulates the coupled TH processes related to mountain-scale multiphase fluid flow, and evaluates the impact of radioactive waste heat on the hydrogeological system, including thermally perturbed liquid saturation, gas- and liquid-phase fluxes, and water and rock temperature elevations, as well as the changes in water flux driven by evaporation/condensation processes and drainage between drifts. For a better description of the ambient geothermal condition of the unsaturated zone system, the TH model is first calibrated against measured borehole temperature data. The ambient temperature calibration provides the necessary surface and water table boundary as well as initial conditions. Then, the TH model is used to obtain scientific understanding of TH processes in the Yucca Mountain unsaturated zone under the designed schedule of repository thermal load
An incompressible two-dimensional multiphase particle-in-cell model for dense particle flows
Energy Technology Data Exchange (ETDEWEB)
Snider, D.M. [SAIC, Albuquerque, NM (United States); O`Rourke, P.J. [Los Alamos National Lab., NM (United States); Andrews, M.J. [Texas A and M Univ., College Station, TX (United States). Dept. of Mechanical Engineering
1997-06-01
A two-dimensional, incompressible, multiphase particle-in-cell (MP-PIC) method is presented for dense particle flows. The numerical technique solves the governing equations of the fluid phase using a continuum model and those of the particle phase using a Lagrangian model. Difficulties associated with calculating interparticle interactions for dense particle flows with volume fractions above 5% have been eliminated by mapping particle properties to a Eulerian grid and then mapping back computed stress tensors to particle positions. This approach utilizes the best of Eulerian/Eulerian continuum models and Eulerian/Lagrangian discrete models. The solution scheme allows for distributions of types, sizes, and density of particles, with no numerical diffusion from the Lagrangian particle calculations. The computational method is implicit with respect to pressure, velocity, and volume fraction in the continuum solution thus avoiding courant limits on computational time advancement. MP-PIC simulations are compared with one-dimensional problems that have analytical solutions and with two-dimensional problems for which there are experimental data.
An Incompressible Three-Dimensional Multiphase Particle-in-Cell Model for Dense Particle Flows
Snider, D. M.
2001-07-01
A three-dimensional, incompressible, multiphase particle-in-cell method is presented for dense particle flows. The numerical technique solves the governing equations of the fluid phase using a continuum model and those of the particle phase using a Lagrangian model. Difficulties associated with calculating interparticle interactions for dense particle flows with volume fractions above 5% have been eliminated by mapping particle properties to an Eulerian grid and then mapping back computed stress tensors to particle positions. A subgrid particle, normal stress model for discrete particles which is robust and eliminates the need for an implicit calculation of the particle normal stress on the grid is presented. Interpolation operators and their properties are defined which provide compact support, are conservative, and provide fast solution for a large particle population. The solution scheme allows for distributions of types, sizes, and density of particles, with no numerical diffusion from the Lagrangian particle calculations. Particles are implicitly coupled to the fluid phase, and the fluid momentum and pressure equations are implicitly solved, which gives a robust solution.
Energy Technology Data Exchange (ETDEWEB)
Aursand, Eskil, E-mail: eskil.aursand@sintef.no; Gjennestad, Magnus Aa.; Yngve Lervåg, Karl; Lund, Halvor
2016-03-15
A one-dimensional multi-phase flow model for thermomagnetically pumped ferrofluid with heat transfer is proposed. The thermodynamic model is a combination of a simplified particle model and thermodynamic equations of state for the base fluid. The magnetization model is based on statistical mechanics, taking into account non-uniform particle size distributions. An implementation of the proposed model is validated against experiments from the literature, and found to give good predictions for the thermomagnetic pumping performance. However, the results reveal a very large sensitivity to uncertainties in heat transfer coefficient predictions. - Highlights: • A multi-phase flow model for thermomagnetically pumped ferrofluid is proposed. • An implementation is validated against experiments from the literature. • Predicted thermomagnetic pumping effect agrees with experiments. • However, a very large sensitivity to heat transfer coefficient is revealed.
Energy Technology Data Exchange (ETDEWEB)
Domingos, Ricardo Golghetto; Cheng, Liang-Yee [Universidade de Sao Paulo (USP), SP (Brazil). Escola Politecnica
2012-07-01
Since the grain scale modeling of multi-phase flow in porous media is of great interest for the oil industry, the aim of the present research is to show an implementation of Moving Particle Semi-Implicit (MPS) method for the grain scale simulation of multi-phase flow in porous media. Geometry data obtained by a high-resolution CT scan of a sandstone sample has been used as input for the simulations. The results of the simulations performed considering different resolutions are given, the head loss and permeability obtained numerically, as well as the influence of the wettability of the fluids inside the sample of the reservoir's sandstone. (author)
Numerical simulation of 2D and 3D compressible flows
Huml, Jaroslav; Kozel, Karel; Příhoda, Jaromír
2013-02-01
The work deals with numerical solutions of 2D inviscid and laminar compressible flows in the GAMM channel and DCA 8% cascade, and of 3D inviscid compressible flows in a 3D modification of the GAMM channel (Swept Wing). The FVM multistage Runge-Kutta method and the Lax-Wendroff scheme (Richtmyer's form) with Jameson's artificial dissipation were applied to obtain the numerical solutions. The results are discussed and compared to other similar results and experiments.
Energy Technology Data Exchange (ETDEWEB)
Modest, Michael
2013-11-15
The effects of radiation in particle-laden flows were the object of the present research. The presence of particles increases optical thickness substantially, making the use of the “optically thin” approximation in most cases a very poor assumption. However, since radiation fluxes peak at intermediate optical thicknesses, overall radiative effects may not necessarily be stronger than in gas combustion. Also, the spectral behavior of particle radiation properties is much more benign, making spectral models simpler (and making the assumption of a gray radiator halfway acceptable, at least for fluidized beds when gas radiation is not large). On the other hand, particles scatter radiation, making the radiative transfer equation (RTE) much more di fficult to solve. The research carried out in this project encompassed three general areas: (i) assessment of relevant radiation properties of particle clouds encountered in fluidized bed and pulverized coal combustors, (ii) development of proper spectral models for gas–particulate mixtures for various types of two-phase combustion flows, and (iii) development of a Radiative Transfer Equation (RTE) solution module for such applications. The resulting models were validated against artificial cases since open literature experimental data were not available. The final models are in modular form tailored toward maximum portability, and were incorporated into two research codes: (i) the open-source CFD code OpenFOAM, which we have extensively used in our previous work, and (ii) the open-source multi-phase flow code MFIX, which is maintained by NETL.
Single layer porous media with entrapped minerals for microscale studies of multiphase flow.
Liefferink, R W; Naillon, A; Bonn, D; Prat, M; Shahidzadeh, N
2018-03-27
The behaviour of minerals (i.e. salts) such as sodium chloride and calcite in porous media is very important in various applications such as weathering of artworks, oil recovery and CO2 sequestration. We report a novel method for manufacturing single layer porous media in which minerals can be entrapped in a controlled way in order to study their dissolution and recrystallization. In addition, our manufacturing method is a versatile tool for creating monomodal, bimodal or multimodal pore size microporous media with controlled porosity ranging from 25% to 50%. These micromodels allow multiphase flows to be quantitatively studied with different microscopy techniques and can serve to validate numerical models that can subsequently be extended to the 3D situation where visualization is experimentally difficult. As an example of their use, deliquescence (dissolution by moisture absorption) of entrapped NaCl crystals is studied; our results show that the invasion of the resulting salt solution is controlled by the capillary pressure within the porous network. For hydrophilic porous media, the liquid preferentially invades the small pores whereas in a hydrophobic network the large pores are filled. Consequently, after several deliquescence/drying cycles in the hydrophilic system, the salt is transported towards the outside of the porous network via small pores; in hydrophobic micromodels, no salt migration is observed. Numerical simulations based on the characteristics of our single layer pore network agree very well with the experimental results and give more insight into the dynamics of salt transport through porous media.
A Multiphase Flow in the Antroduodenal Portion of the Gastrointestinal Tract: A Mathematical Model
Directory of Open Access Journals (Sweden)
P. V. Trusov
2016-01-01
Full Text Available A group of authors has developed a multilevel mathematical model that focuses on functional disorders in a human body associated with various chemical, physical, social, and other factors. At this point, the researchers have come up with structure, basic definitions and concepts of a mathematical model at the “macrolevel” that allow describing processes in a human body as a whole. Currently we are working at the “mesolevel” of organs and systems. Due to complexity of the tasks, this paper deals with only one meso-fragment of a digestive system model. It describes some aspects related to modeling multiphase flow in the antroduodenal portion of the gastrointestinal tract. Biochemical reactions, dissolution of food particles, and motor, secretory, and absorbing functions of the tract are taken into consideration. The paper outlines some results concerning influence of secretory function disorders on food dissolution rate and tract contents acidity. The effect which food density has on inflow of food masses from a stomach to a bowel is analyzed. We assume that the future development of the model will include digestive enzymes and related reactions of lipolysis, proteolysis, and carbohydrates breakdown.
A hybrid interface tracking-level set technique for multiphase flow with soluble surfactant in Blue
Matar, Omar K.; Shin, Seungwon; Chergui, Jalel; Juric, Damir; Kahouadji, Lyes; Craster, Richard V.
2017-11-01
We adapt a formulation for surfactant transport in multiphase flows presented by Muradoglu & Tryggvason to the context of the Level Contour Reconstruction Method, a hybrid method that combines the front-tracking and level-set methods. Attention is paid to the formulation and numerical implementation of the surface gradients of surfactant concentration and surface tension. Various benchmark tests are performed to demonstrate the accuracy of different elements of the algorithm. To verify surfactant mass conservation, values for surfactant diffusion along the interface are compared with the exact solution for the problem of uniform expansion of a sphere. The numerical implementation of the discontinuous boundary condition for the source term in the bulk concentration is compared with the approximate solution. Surface tension forces are tested for Marangoni drop translation. Our numerical results for drop deformation in simple shear are compared with previous experimental and numerical results yielding good agreement. We also demonstrate that our approach applies easily to massively-parallel simulations. EPSRC, UK, MEMPHIS program Grant (EP/K003976/1), RAEng Research Chair (OKM), Basic Science Research Program through the National Research Foundation of Korea (NRF-2014R1A2A1A11051346), computing time at IDRIS of the CNRS in France.
KIVA-hpFE. Predictive turbulent reactive and multiphase flow in engines - An Overview
Energy Technology Data Exchange (ETDEWEB)
Carrington, David Bradley [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2016-05-23
Research and development of KIVA-hpFE for turbulent reactive and multiphase flow particularly as related to engine modeling program has relevance to National energy security and climate change. Climate change is a source problem, and energy national security is consumption of petroleum products problem. Accurately predicting engine processes leads to, lower greenhouse gas (GHG) emission, where engines in the transportation sector currently account for 26% of the U.S. GHG emissions. Less dependence on petroleum products leads to greater energy security. By Environmental Protection Agency standards, some vehicles are now reaching 42 to the 50 mpg mark. These are conventional gasoline engines. Continued investment and research into new technical innovations, the potential exists to save more than 4 million barrels of oil per day or approximately $200 to $400 million per day. This would be a significant decrease in emission and use of petroleum and a very large economic stimulus too! It is estimated with further advancements in combustion, the current emissions can be reduced up to 40%. Enabling better understanding of fuel injection and fuel-air mixing, thermodynamic combustion losses, and combustion/emission formation processes enhances our ability to help solve both problems. To provide adequate capability for accurately simulating these processes, minimize time and labor for development of engine technology, are the goals of our KIVA development program.
Entropic lattice Boltzmann method for multiphase flows: Fluid-solid interfaces.
Mazloomi M, Ali; Chikatamarla, Shyam S; Karlin, Iliya V
2015-08-01
The recently introduced entropic lattice Boltzmann model (ELBM) for multiphase flows [A. Mazloomi M., S. S. Chikatamarla, and I. V. Karlin, Phys. Rev. Lett. 114, 174502 (2015)] is extended to the simulation of dynamic fluid-solid interface problems. The thermodynamically consistent, nonlinearly stable ELBM together with a polynomial representation of the equation of state enables us to investigate the dynamics of the contact line in a wide range of applications, from capillary filling to liquid drop impact onto a flat surfaces with different wettability. The static interface behavior is tested by means of the liquid column in a channel to verify the Young-Laplace law. The numerical results of a capillary filling problem in a channel with wettability gradient show an excellent match with the existing analytical solution. Simulations of drop impact onto both wettable and nonwettable surfaces show that the ELBM reproduces the experimentally observed drop behavior in a quantitative manner. Results reported herein demonstrate that the present model is a promising alternative for studying the vapor-liquid-solid interface dynamics.
Energy Technology Data Exchange (ETDEWEB)
DH Bacon; MD White; BP McGrail
2000-03-07
The Hanford Site, in southeastern Washington State, has been used extensively to produce nuclear materials for the US strategic defense arsenal by the Department of Energy (DOE) and its predecessors, the US Atomic Energy Commission and the US Energy Research and Development Administration. A large inventory of radioactive and mixed waste has accumulated in 177 buried single- and double shell tanks. Liquid waste recovered from the tanks will be pretreated to separate the low-activity fraction from the high-level and transuranic wastes. Vitrification is the leading option for immobilization of these wastes, expected to produce approximately 550,000 metric tons of Low Activity Waste (LAW) glass. This total tonnage, based on nominal Na{sub 2}O oxide loading of 20% by weight, is destined for disposal in a near-surface facility. Before disposal of the immobilized waste can proceed, the DOE must approve a performance assessment, a document that described the impacts, if any, of the disposal facility on public health and environmental resources. Studies have shown that release rates of radionuclides from the glass waste form by reaction with water determine the impacts of the disposal action more than any other independent parameter. This report describes the latest accomplishments in the development of a computational tool, Subsurface Transport Over Reactive Multiphases (STORM), Version 2, a general, coupled non-isothermal multiphase flow and reactive transport simulator. The underlying mathematics in STORM describe the rate of change of the solute concentrations of pore water in a variably saturated, non-isothermal porous medium, and the alteration of waste forms, packaging materials, backfill, and host rocks.
International Nuclear Information System (INIS)
Bacon, D.H.; White, M.D.; McGrail, B.P.
2000-01-01
The Hanford Site, in southeastern Washington State, has been used extensively to produce nuclear materials for the US strategic defense arsenal by the Department of Energy (DOE) and its predecessors, the US Atomic Energy Commission and the US Energy Research and Development Administration. A large inventory of radioactive and mixed waste has accumulated in 177 buried single- and double shell tanks. Liquid waste recovered from the tanks will be pretreated to separate the low-activity fraction from the high-level and transuranic wastes. Vitrification is the leading option for immobilization of these wastes, expected to produce approximately 550,000 metric tons of Low Activity Waste (LAW) glass. This total tonnage, based on nominal Na 2 O oxide loading of 20% by weight, is destined for disposal in a near-surface facility. Before disposal of the immobilized waste can proceed, the DOE must approve a performance assessment, a document that described the impacts, if any, of the disposal facility on public health and environmental resources. Studies have shown that release rates of radionuclides from the glass waste form by reaction with water determine the impacts of the disposal action more than any other independent parameter. This report describes the latest accomplishments in the development of a computational tool, Subsurface Transport Over Reactive Multiphases (STORM), Version 2, a general, coupled non-isothermal multiphase flow and reactive transport simulator. The underlying mathematics in STORM describe the rate of change of the solute concentrations of pore water in a variably saturated, non-isothermal porous medium, and the alteration of waste forms, packaging materials, backfill, and host rocks
International Nuclear Information System (INIS)
Lad, N; Adebayo, D; Aroussi, A
2011-01-01
Particle image velocimetry (PIV) is a successful flow mapping technique which can optically quantify large portions of a flow regime. This enables the method to be completely non-intrusive. The ability to be non-intrusive to any flow has allowed PIV to be used in a large range of industrial sectors for many applications. However, a fundamental disadvantage of the conventional PIV technique is that it cannot easily be used with flows which have no or limited optical access. Flows which have limited optical access for PIV measurement have been addressed using endoscopic PIV techniques. This system uses two separate probes which relay a light sheet and imaging optics to a planar position within the desired flow regime. This system is effective in medical and engineering applications. The present study has been involved in the development of a new endoscopic PIV system which integrates the illumination and imaging optics into one rigid probe. This paper focuses on the validation of the images taken from the novel single stem endoscopic PIV system. The probe is used within atomized spray flow and is compared with conventional PIV measurement and also pitot-static data. The endoscopic PIV system provides images which create localized velocity maps that are comparable with the global measurement of the conventional PIV system. The velocity information for both systems clearly show similar results for the spray characterization and are also validated using the pitot-static data
Calculations of Supersonic and Hypersonic Flows using Compressible Wall Functions
Huang, P. G.; Coakley, T. J.
1993-01-01
The present paper presents a numerical procedure to calculate supersonic and hypersonic flows using the compressible law of the wall. The turbulence models under consideration include the Launder-Reece-Rodi-Gibson Reynolds-stress model and the k-epsilon model. The models coupled with the proposed wall function technique have been tested in both separated and unseparated flows. The flows include (1) an insulated flat plate flow over a range of Mach numbers, (2) a Mach 5 flat plate flow with cold wall conditions, (3) a two dimensional supersonic compression corner flow, (4) a hypersonic flow over an axisymmetric flare, and (5) a hypersonic flow over a 2-D compression corner. Results indicate that the wall function technique gives improved predictions of skin friction and heat transfer in separated flows compared with models using wall dampers. Predictions of the extent of separation are not improved over the wall damper models except with the Reynolds-stress model for the supersonic compression corner flow case.
A finite-volume HLLC-based scheme for compressible interfacial flows with surface tension
Energy Technology Data Exchange (ETDEWEB)
Garrick, Daniel P. [Department of Aerospace Engineering, Iowa State University, Ames, IA (United States); Owkes, Mark [Department of Mechanical and Industrial Engineering, Montana State University, Bozeman, MT (United States); Regele, Jonathan D., E-mail: jregele@iastate.edu [Department of Aerospace Engineering, Iowa State University, Ames, IA (United States)
2017-06-15
Shock waves are often used in experiments to create a shear flow across liquid droplets to study secondary atomization. Similar behavior occurs inside of supersonic combustors (scramjets) under startup conditions, but it is challenging to study these conditions experimentally. In order to investigate this phenomenon further, a numerical approach is developed to simulate compressible multiphase flows under the effects of surface tension forces. The flow field is solved via the compressible multicomponent Euler equations (i.e., the five equation model) discretized with the finite volume method on a uniform Cartesian grid. The solver utilizes a total variation diminishing (TVD) third-order Runge–Kutta method for time-marching and second order TVD spatial reconstruction. Surface tension is incorporated using the Continuum Surface Force (CSF) model. Fluxes are upwinded with a modified Harten–Lax–van Leer Contact (HLLC) approximate Riemann solver. An interface compression scheme is employed to counter numerical diffusion of the interface. The present work includes modifications to both the HLLC solver and the interface compression scheme to account for capillary force terms and the associated pressure jump across the gas–liquid interface. A simple method for numerically computing the interface curvature is developed and an acoustic scaling of the surface tension coefficient is proposed for the non-dimensionalization of the model. The model captures the surface tension induced pressure jump exactly if the exact curvature is known and is further verified with an oscillating elliptical droplet and Mach 1.47 and 3 shock-droplet interaction problems. The general characteristics of secondary atomization at a range of Weber numbers are also captured in a series of simulations.
Miao, Sha; Hendrickson, Kelli; Liu, Yuming
2017-12-01
This work presents a Fully-Coupled Immersed Flow (FCIF) solver for the three-dimensional simulation of fluid-fluid interaction by coupling two distinct flow solvers using an Immersed Boundary (IB) method. The FCIF solver captures dynamic interactions between two fluids with disparate flow properties, while retaining the desirable simplicity of non-boundary-conforming grids. For illustration, we couple an IB-based unsteady Reynolds Averaged Navier Stokes (uRANS) simulator with a depth-integrated (long-wave) solver for the application of slug development with turbulent gas and laminar liquid. We perform a series of validations including turbulent/laminar flows over prescribed wavy boundaries and freely-evolving viscous fluids. These confirm the effectiveness and accuracy of both one-way and two-way coupling in the FCIF solver. Finally, we present a simulation example of the evolution from a stratified turbulent/laminar flow through the initiation of a slug that nearly bridges the channel. The results show both the interfacial wave dynamics excited by the turbulent gas forcing and the influence of the liquid on the gas turbulence. These results demonstrate that the FCIF solver effectively captures the essential physics of gas-liquid interaction and can serve as a useful tool for the mechanistic study of slug generation in two-phase gas/liquid flows in channels and pipes.
CFD of mixing of multi-phase flow in a bioreactor using population balance model.
Sarkar, Jayati; Shekhawat, Lalita Kanwar; Loomba, Varun; Rathore, Anurag S
2016-05-01
Mixing in bioreactors is known to be crucial for achieving efficient mass and heat transfer, both of which thereby impact not only growth of cells but also product quality. In a typical bioreactor, the rate of transport of oxygen from air is the limiting factor. While higher impeller speeds can enhance mixing, they can also cause severe cell damage. Hence, it is crucial to understand the hydrodynamics in a bioreactor to achieve optimal performance. This article presents a novel approach involving use of computational fluid dynamics (CFD) to model the hydrodynamics of an aerated stirred bioreactor for production of a monoclonal antibody therapeutic via mammalian cell culture. This is achieved by estimating the volume averaged mass transfer coefficient (kL a) under varying conditions of the process parameters. The process parameters that have been examined include the impeller rotational speed and the flow rate of the incoming gas through the sparger inlet. To undermine the two-phase flow and turbulence, an Eulerian-Eulerian multiphase model and k-ε turbulence model have been used, respectively. These have further been coupled with population balance model to incorporate the various interphase interactions that lead to coalescence and breakage of bubbles. We have successfully demonstrated the utility of CFD as a tool to predict size distribution of bubbles as a function of process parameters and an efficient approach for obtaining optimized mixing conditions in the reactor. The proposed approach is significantly time and resource efficient when compared to the hit and trial, all experimental approach that is presently used. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:613-628, 2016. © 2016 American Institute of Chemical Engineers.
Robust second-order scheme for multi-phase flow computations
Shahbazi, Khosro
2017-06-01
A robust high-order scheme for the multi-phase flow computations featuring jumps and discontinuities due to shock waves and phase interfaces is presented. The scheme is based on high-order weighted-essentially non-oscillatory (WENO) finite volume schemes and high-order limiters to ensure the maximum principle or positivity of the various field variables including the density, pressure, and order parameters identifying each phase. The two-phase flow model considered besides the Euler equations of gas dynamics consists of advection of two parameters of the stiffened-gas equation of states, characterizing each phase. The design of the high-order limiter is guided by the findings of Zhang and Shu (2011) [36], and is based on limiting the quadrature values of the density, pressure and order parameters reconstructed using a high-order WENO scheme. The proof of positivity-preserving and accuracy is given, and the convergence and the robustness of the scheme are illustrated using the smooth isentropic vortex problem with very small density and pressure. The effectiveness and robustness of the scheme in computing the challenging problem of shock wave interaction with a cluster of tightly packed air or helium bubbles placed in a body of liquid water is also demonstrated. The superior performance of the high-order schemes over the first-order Lax-Friedrichs scheme for computations of shock-bubble interaction is also shown. The scheme is implemented in two-dimensional space on parallel computers using message passing interface (MPI). The proposed scheme with limiter features approximately 50% higher number of inter-processor message communications compared to the corresponding scheme without limiter, but with only 10% higher total CPU time. The scheme is provably second-order accurate in regions requiring positivity enforcement and higher order in the rest of domain.
Kang, Q.; Wang, M.; Lichtner, P. C.
2008-12-01
In geologic CO2 sequestration, pore-scale interfacial phenomena ultimately govern the key processes of fluid mobility, chemical transport, adsorption, and reaction. However, spatial heterogeneity at the pore scale cannot be resolved at the continuum scale, where averaging occurs over length scales much larger than typical pore sizes. Natural porous media, such as sedimentary rocks and other geological media encountered in subsurface formations, are inherently heterogeneous. This pore-scale heterogeneity can produce variabilities in flow, transport, and reaction processes that take place within a porous medium, and can result in spatial variations in fluid velocity, aqueous concentrations, and reaction rates. Consequently, the unresolved spatial heterogeneity at the pore scale may be important for reactive transport modeling at the larger scale. In addition, current continuum models of surface complexation reactions ignore a fundamental property of physical systems, namely conservation of charge. Therefore, to better understand multiphase flow and reaction involving CO2 sequestration in geologic formations, it is necessary to quantitatively investigate the influence of the pore-scale heterogeneity on the emergent behavior at the field scale. We have applied the lattice Boltzmann method to simulating the injection of CO2 saturated brine or supercritical CO2 into geological formations at the pore scale. Multiple pore-scale processes, including advection, diffusion, homogeneous reactions among multiple aqueous species, heterogeneous reactions between the aqueous solution and minerals, ion exchange and surface complexation, as well as changes in solid and pore geometry are all taken into account. The rich pore scale information will provide a basis for upscaling to the continuum scale.
Effect of wettability on scale-up of multiphase flow from core-scale to reservoir fine-grid-scale
Energy Technology Data Exchange (ETDEWEB)
Chang, Y.C.; Mani, V.; Mohanty, K.K. [Univ. of Houston, TX (United States)
1997-08-01
Typical field simulation grid-blocks are internally heterogeneous. The objective of this work is to study how the wettability of the rock affects its scale-up of multiphase flow properties from core-scale to fine-grid reservoir simulation scale ({approximately} 10{prime} x 10{prime} x 5{prime}). Reservoir models need another level of upscaling to coarse-grid simulation scale, which is not addressed here. Heterogeneity is modeled here as a correlated random field parameterized in terms of its variance and two-point variogram. Variogram models of both finite (spherical) and infinite (fractal) correlation length are included as special cases. Local core-scale porosity, permeability, capillary pressure function, relative permeability functions, and initial water saturation are assumed to be correlated. Water injection is simulated and effective flow properties and flow equations are calculated. For strongly water-wet media, capillarity has a stabilizing/homogenizing effect on multiphase flow. For small variance in permeability, and for small correlation length, effective relative permeability can be described by capillary equilibrium models. At higher variance and moderate correlation length, the average flow can be described by a dynamic relative permeability. As the oil wettability increases, the capillary stabilizing effect decreases and the deviation from this average flow increases. For fractal fields with large variance in permeability, effective relative permeability is not adequate in describing the flow.
International Nuclear Information System (INIS)
Espinosa-Paredes, Gilberto
2010-01-01
The aim of this paper is to propose a framework to obtain a new formulation for multiphase flow conservation equations without length-scale restrictions, based on the non-local form of the averaged volume conservation equations. The simplification of the local averaging volume of the conservation equations to obtain practical equations is subject to the following length-scale restrictions: d << l << L, where d is the characteristic length of the dispersed phases, l is the characteristic length of the averaging volume, and L is the characteristic length of the physical system. If the foregoing inequality does not hold, or if the scale of the problem of interest is of the order of l, the averaging technique and therefore, the macroscopic theories of multiphase flow should be modified in order to include appropriate considerations and terms in the corresponding equations. In these cases the local form of the averaged volume conservation equations are not appropriate to describe the multiphase system. As an example of the conservation equations without length-scale restrictions, the natural circulation boiling water reactor was consider to study the non-local effects on the thermal-hydraulic core performance during steady-state and transient behaviors, and the results were compared with the classic local averaging volume conservation equations.
Study of high viscous multiphase phase flow in a horizontal pipe
Baba, Yahaya D.; Aliyu, Aliyu M.; Archibong, Archibong-Eso; Almabrok, Almabrok A.; Igbafe, A. I.
2018-03-01
Heavy oil accounts for a major portion of the world's total oil reserves. Its production and transportation through pipelines is beset with great challenges due to its highly viscous nature. This paper studies the effects of high viscosity on heavy oil two-phase flow characteristics such as pressure gradient, liquid holdup, slug liquid holdup, slug frequency and slug liquid holdup using an advanced instrumentation (i.e. Electrical Capacitance Tomography). Experiments were conducted in a horizontal flow loop with a pipe internal diameter (ID) of 0.0762 m; larger than most reported in the open literature for heavy oil flow. Mineral oil of 1.0-5.0 Pa.s viscosity range and compressed air were used as the liquid and gas phases respectively. Pressure gradient (measured by means differential pressure transducers) and mean liquid holdup was observed to increase as viscosity of oil is increased. Obtained results also revealed that increase in liquid viscosity has significant effects on flow pattern and slug flow features.
Simulating compressible-incompressible two-phase flows
Denner, Fabian; van Wachem, Berend
2017-11-01
Simulating compressible gas-liquid flows, e.g. air-water flows, presents considerable numerical issues and requires substantial computational resources, particularly because of the stiff equation of state for the liquid and the different Mach number regimes. Treating the liquid phase (low Mach number) as incompressible, yet concurrently considering the gas phase (high Mach number) as compressible, can improve the computational performance of such simulations significantly without sacrificing important physical mechanisms. A pressure-based algorithm for the simulation of two-phase flows is presented, in which a compressible and an incompressible fluid are separated by a sharp interface. The algorithm is based on a coupled finite-volume framework, discretised in conservative form, with a compressive VOF method to represent the interface. The bulk phases are coupled via a novel acoustically-conservative interface discretisation method that retains the acoustic properties of the compressible phase and does not require a Riemann solver. Representative test cases are presented to scrutinize the proposed algorithm, including the reflection of acoustic waves at the compressible-incompressible interface, shock-drop interaction and gas-liquid flows with surface tension. Financial support from the EPSRC (Grant EP/M021556/1) is gratefully acknowledged.
Compressible fluid flows driven by stochastic forcing
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard; Maslowski, B.; Novotný, A.
2013-01-01
Roč. 254, č. 3 (2013), s. 1342-1358 ISSN 0022-0396 R&D Projects: GA ČR GA201/09/0917 Institutional research plan: CEZ:AV0Z10190503 Institutional support: RVO:67985840 Keywords : stochastic Navier-Stokes equations * compressible fluid * random driving force Subject RIV: BA - General Mathematics Impact factor: 1.570, year: 2013 http://www.sciencedirect.com/science/article/pii/S0022039612004135
Micro-Ct Imaging of Multi-Phase Flow in Carbonates and Sandstones
Andrew, M. G.; Bijeljic, B.; Blunt, M. J.
2013-12-01
One of the most important mechanisms that limits the escape of CO2 when injected into the subsurface for the purposes of carbon storage is capillary trapping, where CO2 is stranded as pore-scale droplets (ganglia). Prospective storage sites are aquifers or reservoirs that tend to be at conditions where CO2 will reside as a super-critical phase. In order to fully describe physical mechanisms characterising multi-phase flow during and post CO2 injection, experiments need to be conducted at these elevated aquifer/reservoir conditions - this poses a considerable experimental challenge. A novel experimental apparatus has been developed which uses μCT scanning for the non-invasive imaging of the distribution of CO2 in the pore space of rock with resolutions of 7μm at temperatures and pressures representative of the conditions present in prospective saline aquifer CO2 storage sites. The fluids are kept in chemical equilibrium with one-another and with the rock into which they are injected. This is done to prevent the dissolution of the CO2 in the brine to form carbonic acid, which can then react with the rock, particularly carbonates. By eliminating reaction we study the fundamental mechanisms of capillary trapping for an unchanging pore structure. In this study we present a suite of results from three carbonate and two sandstone rock types, showing that, for both cases the CO2 acts as the non-wetting phase and significant quantities of CO2 is trapped. The carbonate examined represent a wide variety of pore topologies with one rock with a very well connected, high porosity pore space (Mt Gambier), one with a lower porosity, poorly connected pore space (Estaillades) and one with a cemented bead pack type pore space (Ketton). Both sandstones (Doddington and Bentheimer) were high permeability granular quartzites. CO2 was injected into each rock, followed by brine injection. After brine injection the entire length of the rock core was scanned, processed and segmented into
A compressible Navier-Stokes code for turbulent flow modeling
Coakley, T. J.
1984-01-01
An implicit, finite volume code for solving two dimensional, compressible turbulent flows is described. Second order upwind differencing of the inviscid terms of the equations is used to enhance stability and accuracy. A diagonal form of the implicit algorithm is used to improve efficiency. Several zero and two equation turbulence models are incorporated to study their impact on overall flow modeling accuracy. Applications to external and internal flows are discussed.
Potential Flow Model for Compressible Stratified Rayleigh-Taylor Instability
Rydquist, Grant; Reckinger, Scott; Owkes, Mark; Wieland, Scott
2017-11-01
The Rayleigh-Taylor Instability (RTI) is an instability that occurs when a heavy fluid lies on top of a lighter fluid in a gravitational field, or a gravity-like acceleration. It occurs in many fluid flows of a highly compressive nature. In this study potential flow analysis (PFA) is used to model the early stages of RTI growth for compressible fluids. In the localized region near the bubble tip, the effects of vorticity are negligible, so PFA is applicable, as opposed to later stages where the induced velocity due to vortices generated from the growth of the instability dominate the flow. The incompressible PFA is extended for compressibility effects by applying the growth rate and the associated perturbation spatial decay from compressible linear stability theory. The PFA model predicts theoretical values for a bubble terminal velocity for single-mode compressible RTI, dependent upon the Atwood (A) and Mach (M) numbers, which is a parameter that measures both the strength of the stratification and intrinsic compressibility. The theoretical bubble terminal velocities are compared against numerical simulations. The PFA model correctly predicts the M dependence at high A, but the model must be further extended to include additional physics to capture the behavior at low A. Undergraduate Scholars Program - Montana State University.
McClure, J. E.; Prins, J. F.; Miller, C. T.
2014-07-01
Multiphase flow implementations of the lattice Boltzmann method (LBM) are widely applied to the study of porous medium systems. In this work, we construct a new variant of the popular "color" LBM for two-phase flow in which a three-dimensional, 19-velocity (D3Q19) lattice is used to compute the momentum transport solution while a three-dimensional, seven velocity (D3Q7) lattice is used to compute the mass transport solution. Based on this formulation, we implement a novel heterogeneous GPU-accelerated algorithm in which the mass transport solution is computed by multiple shared memory CPU cores programmed using OpenMP while a concurrent solution of the momentum transport is performed using a GPU. The heterogeneous solution is demonstrated to provide speedup of 2.6 × as compared to multi-core CPU solution and 1.8 × compared to GPU solution due to concurrent utilization of both CPU and GPU bandwidths. Furthermore, we verify that the proposed formulation provides an accurate physical representation of multiphase flow processes and demonstrate that the approach can be applied to perform heterogeneous simulations of two-phase flow in porous media using a typical GPU-accelerated workstation.
Vortex convection in nonuniform compressible flow
Szumowski, A. P.; Meier, G. E. A.
1988-03-01
Vortex convection in longitudinally nonuniform transonic flow fields was studied. Vortices moving in moderately accelerated flow are distinct in the subsonic and supersonic range. Due to the acceleration, the vortices of the Karman street separate continuously one from another. They form a series of periodically shedding individual vortices. The density distribution of the accelerated vortices stays circular. Vortices in subsonic stream (behind the shock wave in the divergent part of the Laval nozzle) impinging on an obstacle (in this case on the regulating valve) cause shock fronts which move upstream. In a subsonic stream flowing out from the convergent nozzle, the primary vortices inside the stream significantly perturb its boundaries and induce secondary vortices (at the boundaries). Flow patterns in a duct with a sudden enlargement of cross section are influenced by the vortices convected in the flow too. However, the observed perturbations of these patterns are relatively weak. The unsteady behaviour of the free stream is not only the effect of the vortex convection but also of the unsteady interactions with the boundaries, i.e., the adjusting valve and the test-section walls. However, the effect of the vortex convection is the stronger.
Sneddon, Kristen W.; Powers, Michael H.; Johnson, Raymond H.; Poeter, Eileen P.
2002-01-01
Dense nonaqueous phase liquids (DNAPLs) are a pervasive and persistent category of groundwater contamination. In an effort to better understand their unique subsurface behavior, a controlled and carefully monitored injection of PCE (perchloroethylene), a typical DNAPL, was performed in conjunction with the University of Waterloo at Canadian Forces Base Borden in 1991. Of the various geophysical methods used to monitor the migration of injected PCE, the U.S. Geological Survey collected 500-MHz ground penetrating radar (GPR) data. These data are used in determining calibration parameters for a multiphase flow simulation. GPR data were acquired over time on a fixed two-dimensional surficial grid as the DNAPL was injected into the subsurface. Emphasis is on the method of determining DNAPL saturation values from this time-lapse GPR data set. Interactive full-waveform GPR modeling of regularized field traces resolves relative dielectric permittivity versus depth profiles for pre-injection and later-time data. Modeled values are end members in recursive calculations of the Bruggeman-Hanai-Sen (BHS) mixing formula, yielding interpreted pre-injection porosity and post-injection DNAPL saturation values. The resulting interpreted physical properties of porosity and DNAPL saturation of the Borden test cell, defined on a grid spacing of 50 cm with 1-cm depth resolution, are used as observations for calibration of a 3-D multiphase flow simulation. Calculated values of DNAPL saturation in the subsurface at 14 and 22 hours after the start of injection, from both the GPR and the multiphase flow modeling, are interpolated volumetrically and presented for visual comparison.
Johnson, R.H.; Poeter, E.P.
2007-01-01
Perchloroethylene (PCE) saturations determined from GPR surveys were used as observations for inversion of multiphase flow simulations of a PCE injection experiment (Borden 9??m cell), allowing for the estimation of optimal bulk intrinsic permeability values. The resulting fit statistics and analysis of residuals (observed minus simulated PCE saturations) were used to improve the conceptual model. These improvements included adjustment of the elevation of a permeability contrast, use of the van Genuchten versus Brooks-Corey capillary pressure-saturation curve, and a weighting scheme to account for greater measurement error with larger saturation values. A limitation in determining PCE saturations through one-dimensional GPR modeling is non-uniqueness when multiple GPR parameters are unknown (i.e., permittivity, depth, and gain function). Site knowledge, fixing the gain function, and multiphase flow simulations assisted in evaluating non-unique conceptual models of PCE saturation, where depth and layering were reinterpreted to provide alternate conceptual models. Remaining bias in the residuals is attributed to the violation of assumptions in the one-dimensional GPR interpretation (which assumes flat, infinite, horizontal layering) resulting from multidimensional influences that were not included in the conceptual model. While the limitations and errors in using GPR data as observations for inverse multiphase flow simulations are frustrating and difficult to quantify, simulation results indicate that the error and bias in the PCE saturation values are small enough to still provide reasonable optimal permeability values. The effort to improve model fit and reduce residual bias decreases simulation error even for an inversion based on biased observations and provides insight into alternate GPR data interpretations. Thus, this effort is warranted and provides information on bias in the observation data when this bias is otherwise difficult to assess. ?? 2006 Elsevier B
Li-hui, Zheng; Xiao-qing, He; Li-xia, Fu; Xiang-chun, Wang
2009-02-01
Water-based micro-bubble drilling fluid, which is used to exploit depleted reservoirs, is a complicated multiphase flow system that is composed of gas, water, oil, polymer, surfactants and solids. The gas phase is separate from bulk water by two layers and three membranes. They are "surface tension reducing membrane", "high viscosity layer", "high viscosity fixing membrane", "compatibility enhancing membrane" and "concentration transition layer of liner high polymer (LHP) & surfactants" from every gas phase centre to the bulk water. "Surface tension reducing membrane", "high viscosity layer" and "high viscosity fixing membrane" bond closely to pack air forming "air-bag", "compatibility enhancing membrane" and "concentration transition layer of LHP & surfactants" absorb outside "air-bag" to form "incompact zone". From another point of view, "air-bag" and "incompact zone" compose micro-bubble. Dynamic changes of "incompact zone" enable micro-bubble to exist lonely or aggregate together, and lead the whole fluid, which can wet both hydrophilic and hydrophobic surface, to possess very high viscosity at an extremely low shear rate but to possess good fluidity at a higher shear rate. When the water-based micro-bubble drilling fluid encounters leakage zones, it will automatically regulate the sizes and shapes of the bubbles according to the slot width of fracture, the height of cavern as well as the aperture of openings, or seal them by making use of high viscosity of the system at a very low shear rate. Measurements of the rheological parameters indicate that water-based micro-bubble drilling fluid has very high plastic viscosity, yield point, initial gel, final gel and high ratio of yield point and plastic viscosity. All of these properties make the multiphase flow system meet the requirements of petroleum drilling industry. Research on interface between gas and bulk water of this multiphase flow system can provide us with information of synthesizing effective agents to
Directory of Open Access Journals (Sweden)
Shun Takahashi
2014-01-01
Full Text Available A computational code adopting immersed boundary methods for compressible gas-particle multiphase turbulent flows is developed and validated through two-dimensional numerical experiments. The turbulent flow region is modeled by a second-order pseudo skew-symmetric form with minimum dissipation, while the monotone upstream-centered scheme for conservation laws (MUSCL scheme is employed in the shock region. The present scheme is applied to the flow around a two-dimensional cylinder under various freestream Mach numbers. Compared with the original MUSCL scheme, the minimum dissipation enabled by the pseudo skew-symmetric form significantly improves the resolution of the vortex generated in the wake while retaining the shock capturing ability. In addition, the resulting aerodynamic force is significantly improved. Also, the present scheme is successfully applied to moving two-cylinder problems.
Directory of Open Access Journals (Sweden)
Jean-Paul Kone
2017-03-01
Full Text Available A review of published three-dimensional, computational fluid dynamics models for proton exchange membrane fuel cells that accounts for multiphase flow is presented. The models can be categorized as models for transport phenomena, geometry or operating condition effects, and thermal effects. The influences of heat and water management on the fuel cell performance have been repeatedly addressed, and these still remain two central issues in proton exchange membrane fuel cell technology. The strengths and weaknesses of the models, the modelling assumptions, and the model validation are discussed. The salient numerical features of the models are examined, and an overview of the most commonly used computational fluid dynamic codes for the numerical modelling of proton exchange membrane fuel cells is given. Comprehensive three-dimensional multiphase flow computational fluid dynamic models accounting for the major transport phenomena inside a complete cell have been developed. However, it has been noted that more research is required to develop models that include among other things, the detailed composition and structure of the catalyst layers, the effects of water droplets movement in the gas flow channels, the consideration of phase change in both the anode and the cathode sides of the fuel cell, and dissolved water transport.
Spatial correlations in compressible granular flows
Van Noije, T. P. C.; Ernst, M. H.; Brito López, Ricardo
1998-01-01
The clustering instability in freely evolving granular fluids manifests itself in the density-density correlation function and structure factor. These functions are calculated from fluctuating hydrodynamics. As time increases, the structure factor of density fluctuations develops a maximum, which shifts to smaller wave numbers (growing correlation length). Furthermore, the inclusion of longitudinal velocity fluctuations changes long-range correlations in the flow field qualitatively and exten...
International Nuclear Information System (INIS)
Gray, W.G.; Soll, W.E.; Tompson, A.
1998-01-01
'Improved capabilities for modeling multiphase flow in the subsurface requires that several aspects of the system which impact the flow and transport processes be more properly accounted for. A distinguishing feature of multiphase flow in comparison to single phase flow is the existence of interfaces between fluids. At the microscopic (pore) scale, these interfaces are known to influence system behavior by supporting non-zero stresses such that the pressures in adjacent phases are not equal. In problems of interphase transport at the macroscopic (core) scale, knowledge of the total amount of interfacial area in the system provides a clue to the effectiveness of the communication between phases. Although interfacial processes are central to multiphase flow physics, their treatment in traditional porous-media theories has been implicit rather than explicit; and no attempts have been made to systematically account for the evolution of the interfacial area in dynamic systems or to include the dependence of constitutive functions, such as capillary pressure, on the interfacial area. This project implements a three-pronged approach to assessing the importance of various features of multiphase flow to its description. The research contributes to the improved understanding and precise physical description of multiphase subsurface flow by combining: (1) theoretical derivation of equations, (2) lattice Boltzmann modeling of hydrodynamics to identify characteristics and parameters, and (3) solution of the field-scale equations using a discrete numerical method to assess the advantages and disadvantages of the complete theory. This approach includes both fundamental scientific inquiry and a path for inclusion of the scientific results obtained in a technical tool that will improve assessment capabilities for multiphase flow situations that have arisen due to the introduction of organic materials in the natural environment. This report summarizes work after 1.5 years of a 3
Space-time discontinuous Galerkin method for compressible flow
Klaij, C.M.
2006-01-01
The space-time discontinuous Galerkin method allows the simulation of compressible flow in complex aerodynamical applications requiring moving, deforming and locally refined meshes. This thesis contains the space-time discretization of the physical model, a fully explicit solver for the resulting
Analysis of the transient compressible vapor flow in heat pipe
International Nuclear Information System (INIS)
Jang, J.H.; Faghri, A.; Chang, W.S.
1989-07-01
The transient compressible one-dimensional vapor flow dynamics in a heat pipe is modeled. The numerical results are obtained by using the implicit non-iterative Beam-Warming finite difference method. The model is tested for simulated heat pipe vapor flow and actual vapor flow in cylindrical heat pipes. A good comparison of the present transient results for the simulated heat pipe vapor flow with the previous results of a two-dimensional numerical model is achieved and the steady state results are in agreement with the existing experimental data. The transient behavior of the vapor flow under subsonic, sonic, and supersonic speeds and high mass flow rates are successfully predicted. The one-dimensional model also describes the vapor flow dynamics in cylindrical heat pipes at high temperatures
DEFF Research Database (Denmark)
Berning, Torsten; Odgaard, Madeleine; Kær, Søren Knudsen
2010-01-01
This work presents a study of multi-phase flow through the cathode side of a polymer electrolyte membrane fuel cell employing an interdigitated flow field plate. A previously published model has been extended in order to account for phase change kinetics, and a comparison between the interdigitated....... The additional compressor work due to the increased pressure loss will only slightly increase, and this may be offset by operating at lower stoichiometries as the interdigitated design is less mass transfer controlled, which means that the overall efficiency of the interdigitated arrangement will be higher...
Flow-induced vibration of helical coil compression springs
International Nuclear Information System (INIS)
Stokes, F.E.; King, R.A.
1983-01-01
Helical coil compression springs are used in some nuclear fuel assembly designs to maintain holddown and to accommodate thermal expansion. In the reactor environment, the springs are exposed to flowing water, elevated temperatures and pressures, and irradiation. Flow parallel to the longitudinal axis of the spring may excite the spring coils and cause vibration. The purpose of this investigation was to determine the flow-induced vibration (FIV) response characteristics of the helical coil compression springs. Experimental tests indicate that a helical coil spring responds like a single circular cylinder in cross-flow. Two FIV excitation mechanisms control spring vibration. Namely: 1) Turbulent Buffeting causes small amplitude vibration which increases as a function of velocity squared. 2) Vortex Shedding causes large amplitude vibration when the spring natural frequency and Strouhal frequency coincide. Several methods can be used to reduce or to prevent vortex shedding large amplitude vibrations. One method is compressing the spring to a coil pitch-to-diameter ratio of 2 thereby suppressing the vibration amplitude. Another involves modifying the spring geometry to alter its stiffness and frequency characteristics. These changes result in separation of the natural and Strouhal frequencies. With an understanding of how springs respond in the flowing water environment, the spring physical parameters can be designed to avoid large amplitude vibration. (orig.)
Numerical computation of compressible, turbulent high-speed flows
Suzen, Yildirim Bora
Separated flows and subsequent formation of shear layers are important fluid processes which play a dominant role in numerous engineering applications. Accurate prediction of this fluid process is an important element in the design and analysis of high speed vehicles and, ultimately, in performance and trajectory analysis. In this study, a two-dimensional/axisymmetric Navier-Stokes flow solver using Steger-Warming flux vector splitting technique is developed for the accurate simulation of high speed turbulent flows. Computations are performed for an underexpanded, supersonic, turbulent, axisymmetric jet and a two-stream supersonic turbulent wake flowfield behind a two-dimensional thick base as representative of high speed, compressible shear flows. Baldwin-Barth and Spalart-Allmaras one-equation turbulence models and Baseline version of Menter's zonal k - omega/k - varepsilon two-equation turbulence models are used to investigate their performance for the applications considered. Modifications to these models are incorporated in order to improve their prediction capabilities for the types of flows considered. For two-equation models, modifications to include compressibility correction terms are considered and a modeled version of Menter's models including compressible dissipation and pressure dilatation terms is developed. Axisymmetric correction is incorporated to all models by means of coefficient changes. The computational results are compared to available experimental data. Results show that the modifications improve the computed solutions for all models.
Energy Technology Data Exchange (ETDEWEB)
Khattri, Sanjay Kumar
2006-07-01
The thesis is concerned with numerically simulating multicomponent, multiphase, reactive transport in heterogeneous porous medium. Such processes are ubiquitous, for example, deposition of green house gases, flow of hydrocarbons and groundwater remediation. Understanding such processes is important from social and economic point of view. For the success of geological sequestration, an accurate estimation of migration patterns of green-house gases is essential. Due to an ever increasing computer power, computational mathematics has become an important tool for predicting dynamics of porous media fluids. Numerical and mathematical modelling of processes in a domain requires grid generation in the domain, discretization of the continuum equations on the generated grid, solution of the formed linear or nonlinear system of discrete equations and finally visualization of the results. The thesis is composed of three chapters and eight papers. Chapter 2 presents two techniques for generating structured quadrilateral and hexahedral meshes. These techniques are called algebraic and elliptic methods. Algebraic techniques are by far the most simple and computationally efficient method for grid generation. Transfinite interpolation operators are a kind of algebraic grid generation technique. In this chapter, many transfinite interpolation operators for grid generation are derived from 1D projection operators. In this chapter, some important properties of hexahedral elements are also mentioned. These properties are useful in discretization of partial differential equations on hexahedral mesh, improving quality of the hexahedral mesh, mesh generation and visualization. Chapter 3 is about CO{sub 2} flow in porous media. In this chapter, we present the mathematical models and their discretization for capturing major physical processes associated with CO{sub 2} deposition in geological formations. Some important simulations of practical applications in 2D and 3D are presented
Energy Technology Data Exchange (ETDEWEB)
Barreiros, Claudio; Taranto, Cleber; Costa, Alcemir [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil); Pinguet, Bruno; Heluey, Vitor; Bessa, Fabiano; Loicq, Olivier [Schlumberger Servicos de Petroleo Ltda., Rio de Janeiro, RJ (Brazil)
2008-07-01
The Multiphase Venturi Dual Energy Gamma Ray Combination, Vx* technology, arrived in Brazil in 2000. PETROBRAS, Brazilian Oil Company, has been putting big efforts in its production business and also has demonstrated a large interest in having a multiphase meter approved by ANP for back allocation purposes. The oil industry was looking for ways to improve the back allocation process using an approved on line multiphase flow measurement device, thus replacing punctual test done today by a permanent monitoring device. Considering this scenario, a partnership project between PETROBRAS and Schlumberger was created in Brazil. The main objective of this project, which was held in NUEX flow loop, was to demonstrate to INMETRO (Brazilian Metrology Institute) that the Multiphase Venturi Dual Energy Gamma Ray Combination meter is able to be used for back allocation purpose. PETROBRAS and Schlumberger elaborated a complete methodology in the NUEX flow loop to demonstrate the results and benefits of the Multiphase Venturi Dual Energy Gamma Ray Combination meter. The test was witnessed by INMETRO and had a very good performance at the end. The results were within what was expected by Schlumberger, PETROBRAS and INMETRO. These results has been very useful to PETROBRAS in order to start using the Venturi Dual Energy Gamma Ray technology for well allocation purposes. (author)
DEFF Research Database (Denmark)
Voigt, Andreas Jauernik; Mandrup-Poulsen, Christian; Nielsen, Kenny
2017-01-01
of the subsea installed rotating machinery. It is well known that careful design of turbomachinery seals, such as interstage and balance piston seals, is pivotal for the performance of pumps and compressors. Consequently, the ability to predict the complex interaction between fluid dynamics and rotordynamics...... leads to technical challenges for the subsea installed pumps and compressors that are now required to handle multiphase flow of varying gas to liquid ratios. This highlights the necessity for a strong research focus on multiphase flow impact on rotordynamic properties and thereby operational stability...
DEFF Research Database (Denmark)
Voigt, Andreas Jauernik; Mandrup-Poulsen, Christian; Nielsen, Kenny Krogh
2016-01-01
of the subsea installed rotating machinery. It is well known that careful design of turbomachinery seals, such as interstage and balance piston seals, is pivotal for the performance of pumps and compressors. Consequently, the ability to predict the complex interaction between fluid dynamics and rotordynamics...... leads to technical challenges for the subsea installed pumps and compressors that are now required to handle multiphase flow of varying gas to liquid ratios. This highlights the necessity for a strong research focus on multiphase flow impact on rotordynamic properties and thereby operational stability...
Vortex breakdown of compressible swirling flows in a pipe
Lee, Harry; Rusak, Zvi; Wang, Shixiao
2017-11-01
The manifold of branches of steady and axisymmetric states of compressible subsonic swirling flows in a finite-length straight circular pipe are developed. The analysis is based on Rusak et al. (2015) nonlinear partial differential equation for the solution of the flow stream function in terms of the inlet flow total enthalpy, entropy and circulation functions. This equation reflects the complicated thermo-physical interactions in the flows. The flow problem is solved numerically using a finite difference approach with a penalty procedure for identifying vortex breakdown and wall-separation states. Several types of solutions are found and used to form the bifurcation diagram of steady compressible flows with swirl as the inlet swirl level is increased at a fixed inlet Mach number. Results are compared with predictions from the global analysis approach of Rusak et al. (2015). The computed results provide theoretical predictions of the critical swirl levels for the first appearance of vortex breakdown states as a function of the inlet Mach number. The shows the delay in the appearance of breakdown with increase of the inlet axial flow Mach number in the subsonic range of operation.
Hua, Jinsong; Rudshaug, Magne; Droste, Christian; Jorgensen, Robert; Giskeodegard, Nils-Haavard
2018-02-01
A computational fluid dynamics based multiphase magnetohydrodynamic (MHD) flow model for simulating the melt flow and bath-metal interface deformation in realistic aluminum reduction cells is presented. The model accounts for the complex physics of the MHD problem in aluminum reduction cells by coupling two immiscible fluids, electromagnetic field, Lorentz force, flow turbulence, and complex cell geometry with large length scale. Especially, the deformation of bath-metal interface is tracked directly in the simulation, and the condition of constant anode-cathode distance (ACD) is maintained by moving anode bottom dynamically with the deforming bath-metal interface. The metal pad deformation and melt flow predicted by the current model are compared to the predictions using a simplified model where the bath-metal interface is assumed flat. The effects of the induced electric current due to fluid flow and the magnetic field due to the interior cell current on the metal pad deformation and melt flow are investigated. The presented model extends the conventional simplified box model by including detailed cell geometry such as the ledge profile and all channels (side, central, and cross-channels). The simulations show the model sensitivity to different side ledge profiles and the cross-channel width by comparing the predicted melt flow and metal pad heaving. In addition, the model dependencies upon the reduction cell operation conditions such as ACD, current distribution on cathode surface and open/closed channel top, are discussed.
Conjugate Compressible Fluid Flow and Heat Transfer in Ducts
Cross, M. F.
2011-01-01
A computational approach to modeling transient, compressible fluid flow with heat transfer in long, narrow ducts is presented. The primary application of the model is for analyzing fluid flow and heat transfer in solid propellant rocket motor nozzle joints during motor start-up, but the approach is relevant to a wide range of analyses involving rapid pressurization and filling of ducts. Fluid flow is modeled through solution of the spatially one-dimensional, transient Euler equations. Source terms are included in the governing equations to account for the effects of wall friction and heat transfer. The equation solver is fully-implicit, thus providing greater flexibility than an explicit solver. This approach allows for resolution of pressure wave effects on the flow as well as for fast calculation of the steady-state solution when a quasi-steady approach is sufficient. Solution of the one-dimensional Euler equations with source terms significantly reduces computational run times compared to general purpose computational fluid dynamics packages solving the Navier-Stokes equations with resolved boundary layers. In addition, conjugate heat transfer is more readily implemented using the approach described in this paper than with most general purpose computational fluid dynamics packages. The compressible flow code has been integrated with a transient heat transfer solver to analyze heat transfer between the fluid and surrounding structure. Conjugate fluid flow and heat transfer solutions are presented. The author is unaware of any previous work available in the open literature which uses the same approach described in this paper.
Unsteady compressible flows in channel with varying walls
Pořízková, P.; Kozel, K.; Horáček, J.
2014-03-01
This study deals with numerical solution of a 2D and 3D unsteady flows of a compressible viscous fluid in 2D and 3D channel for low inlet airflow velocity. The unsteadiness of the flow is caused by a prescribed periodic motion of a part of the channel wall, nearly closing the channel during oscillations. The channels shape is a simplified geometry of the glottal space in the human vocal tract. Goal is numerical simulation of flow in the channels which involves attributes of real flow causing acoustic perturbations. The system of Navier-Stokes equations closed with static pressure expression for ideal gas describes the unsteady laminar flow of compressible viscous fluid. The numerical solution is implemented using the finite volume method and the predictor-corrector MacCormack scheme with artificial viscosity using a grid of quadrilateral cells. The unsteady grid of quadrilateral cells is considered in the form of conservation laws using Arbitrary Lagrangian-Eulerian method. The application of developed method for numerical simulations of flow fields in the 2D and 3D channels, acquired from a developed program, are presented for inlet velocity u=4.12 m/s, inlet Reynolds number Re=4481 and the wall motion frequency 100 Hz.
High speed inviscid compressible flow by the finite element method
Zienkiewicz, O. C.; Loehner, R.; Morgan, K.
1984-01-01
The finite element method and an explicit time stepping algorithm which is based on Taylor-Galerkin schemes with an appropriate artificial viscosity is combined with an automatic mesh refinement process which is designed to produce accurate steady state solutions to problems of inviscid compressible flow in two dimensions. The results of two test problems are included which demonstrate the excellent performance characteristics of the proposed procedures.
Directory of Open Access Journals (Sweden)
Xiaokai Huo
2014-01-01
Full Text Available Accurate estimation of water content in an oil-water mixture is a key technology in oil exploration and production. Based on the principles of the microwave transmission line (MTL, the logging probe is an important water content measuring apparatus. However, the effects of mixed fluid flow on the measurement of electromagnetic field parameters are rarely considered. This study presents the coupling model for low-speed multiphase flow and high-frequency electromagnetic field in a complex pipeline structure. We derived the S-parameter equations for the stratified oil/water flow model. The corresponding relationship between the S-parameters and water holdup is established. Evident coupling effects of the fluid flow and the electromagnetic field are confirmed by comparing the calculated S-parameters for both stratified and homogeneous flow patterns. In addition, a multiple-solution problem is analyzed for the inversion of dielectric constant from the S-parameters. The most sensitive phase angle range is determined to improve the detection of variation in the dielectric constant. Suggestions are proposed based on the influence of the oil/water layer on measurement sensitivity to optimize the geometric parameters of a device structure. The method proposed elucidates how accuracy and sensitivity can be improved in water holdup measurements under high water content conditions.
Cebeci, Tuncer
2005-01-01
This second edition of our book extends the modeling and calculation of boundary-layer flows to include compressible flows. The subjects cover laminar, transitional and turbulent boundary layers for two- and three-dimensional incompressible and compressible flows. The viscous-inviscid coupling between the boundary layer and the inviscid flow is also addressed. The book has a large number of homework problems.
A weakly-compressible Cartesian grid approach for hydrodynamic flows
Bigay, P.; Oger, G.; Guilcher, P.-M.; Le Touzé, D.
2017-11-01
The present article aims at proposing an original strategy to solve hydrodynamic flows. In introduction, the motivations for this strategy are developed. It aims at modeling viscous and turbulent flows including complex moving geometries, while avoiding meshing constraints. The proposed approach relies on a weakly-compressible formulation of the Navier-Stokes equations. Unlike most hydrodynamic CFD (Computational Fluid Dynamics) solvers usually based on implicit incompressible formulations, a fully-explicit temporal scheme is used. A purely Cartesian grid is adopted for numerical accuracy and algorithmic simplicity purposes. This characteristic allows an easy use of Adaptive Mesh Refinement (AMR) methods embedded within a massively parallel framework. Geometries are automatically immersed within the Cartesian grid with an AMR compatible treatment. The method proposed uses an Immersed Boundary Method (IBM) adapted to the weakly-compressible formalism and imposed smoothly through a regularization function, which stands as another originality of this work. All these features have been implemented within an in-house solver based on this WCCH (Weakly-Compressible Cartesian Hydrodynamic) method which meets the above requirements whilst allowing the use of high-order (> 3) spatial schemes rarely used in existing hydrodynamic solvers. The details of this WCCH method are presented and validated in this article.
Development of a Water Based, Critical Flow, Non-Vapor Compression cooling Cycle
Energy Technology Data Exchange (ETDEWEB)
Hosni, Mohammad H.
2014-03-30
Expansion of a high-pressure liquid refrigerant through the use of a thermostatic expansion valve or other device is commonplace in vapor-compression cycles to regulate the quality and flow rate of the refrigerant entering the evaporator. In vapor-compression systems, as the condensed refrigerant undergoes this expansion, its pressure and temperature drop, and part of the liquid evaporates. We (researchers at Kansas State University) are developing a cooling cycle that instead pumps a high-pressure refrigerant through a supersonic converging-diverging nozzle. As the liquid refrigerant passes through the nozzle, its velocity reaches supersonic (or critical-flow) conditions, substantially decreasing the refrigerant’s pressure. This sharp pressure change vaporizes some of the refrigerant and absorbs heat from the surrounding conditions during this phase change. Due to the design of the nozzle, a shockwave trips the supersonic two-phase refrigerant back to the starting conditions, condensing the remaining vapor. The critical-flow refrigeration cycle would provide space cooling, similar to a chiller, by running a secondary fluid such as water or glycol over one or more nozzles. Rather than utilizing a compressor to raise the pressure of the refrigerant, as in a vapor-cycle system, the critical-flow cycle utilizes a high-pressure pump to drive refrigerant liquid through the cooling cycle. Additionally, the design of the nozzle can be tailored for a given refrigerant, such that environmentally benign substances can act as the working fluid. This refrigeration cycle is still in early-stage development with prototype development several years away. The complex multi-phase flow at supersonic conditions presents numerous challenges to fully understanding and modeling the cycle. With the support of DOE and venture-capital investors, initial research was conducted at PAX Streamline, and later, at Caitin. We (researchers at Kansas State University) have continued development
Assessment of closure coefficients for compressible-flow turbulence models
Huang, P. G.; Bradshaw, P.; Coakley, T. J.
1992-01-01
A critical assessment is made of the closure coefficients used for turbulence length scale in existing models of the transport equation, with reference to the extension of these models to compressible flow. It is shown that to satisfy the compressible 'law of the wall', the model coefficients must actually be functions of density gradients. The magnitude of the errors that result from neglecting this dependence on density varies with the variable used to specify the length scale. Among the models investigated, the k-omega model yields the best performance, although it is not completely free from errors associated with density terms. Models designed to reduce the density-gradient effect to an insignificant level are proposed.
A Cell-Centered Multiphase ALE Scheme With Structural Coupling
Energy Technology Data Exchange (ETDEWEB)
Dunn, Timothy Alan [Univ. of California, Davis, CA (United States)
2012-04-16
A novel computational scheme has been developed for simulating compressible multiphase flows interacting with solid structures. The multiphase fluid is computed using a Godunov-type finite-volume method. This has been extended to allow computations on moving meshes using a direct arbitrary-Eulerian- Lagrangian (ALE) scheme. The method has been implemented within a Lagrangian hydrocode, which allows modeling the interaction with Lagrangian structural regions. Although the above scheme is general enough for use on many applications, the ultimate goal of the research is the simulation of heterogeneous energetic material, such as explosives or propellants. The method is powerful enough for application to all stages of the problem, including the initial burning of the material, the propagation of blast waves, and interaction with surrounding structures. The method has been tested on a number of canonical multiphase tests as well as fluid-structure interaction problems.
Pencil: Finite-difference Code for Compressible Hydrodynamic Flows
Brandenburg, Axel; Dobler, Wolfgang
2010-10-01
The Pencil code is a high-order finite-difference code for compressible hydrodynamic flows with magnetic fields. It is highly modular and can easily be adapted to different types of problems. The code runs efficiently under MPI on massively parallel shared- or distributed-memory computers, like e.g. large Beowulf clusters. The Pencil code is primarily designed to deal with weakly compressible turbulent flows. To achieve good parallelization, explicit (as opposed to compact) finite differences are used. Typical scientific targets include driven MHD turbulence in a periodic box, convection in a slab with non-periodic upper and lower boundaries, a convective star embedded in a fully nonperiodic box, accretion disc turbulence in the shearing sheet approximation, self-gravity, non-local radiation transfer, dust particle evolution with feedback on the gas, etc. A range of artificial viscosity and diffusion schemes can be invoked to deal with supersonic flows. For direct simulations regular viscosity and diffusion is being used. The code is written in well-commented Fortran90.
Acceleration methods for multi-physics compressible flow
Peles, Oren; Turkel, Eli
2018-04-01
In this work we investigate the Runge-Kutta (RK)/Implicit smoother scheme as a convergence accelerator for complex multi-physics flow problems including turbulent, reactive and also two-phase flows. The flows considered are subsonic, transonic and supersonic flows in complex geometries, and also can be either steady or unsteady flows. All of these problems are considered to be a very stiff. We then introduce an acceleration method for the compressible Navier-Stokes equations. We start with the multigrid method for pure subsonic flow, including reactive flows. We then add the Rossow-Swanson-Turkel RK/Implicit smoother that enables performing all these complex flow simulations with a reasonable CFL number. We next discuss the RK/Implicit smoother for time dependent problem and also for low Mach numbers. The preconditioner includes an intrinsic low Mach number treatment inside the smoother operator. We also develop a modified Roe scheme with a corresponding flux Jacobian matrix. We then give the extension of the method for real gas and reactive flow. Reactive flows are governed by a system of inhomogeneous Navier-Stokes equations with very stiff source terms. The extension of the RK/Implicit smoother requires an approximation of the source term Jacobian. The properties of the Jacobian are very important for the stability of the method. We discuss what the chemical physics theory of chemical kinetics tells about the mathematical properties of the Jacobian matrix. We focus on the implication of the Le-Chatelier's principle on the sign of the diagonal entries of the Jacobian. We present the implementation of the method for turbulent flow. We use a two RANS turbulent model - one equation model - Spalart-Allmaras and a two-equation model - k-ω SST model. The last extension is for two-phase flows with a gas as a main phase and Eulerian representation of a dispersed particles phase (EDP). We present some examples for such flow computations inside a ballistic evaluation
Numerical simulation of compressible, turbulent, two-phase flow
Coakley, t. J.; Champney, J. M.
1985-01-01
A computer program for numerically simulating compressible, turbulent, two-phase flows is described and applied. Special attention is given to flows in which dust is ingested into the turbulent boundary layer behind shock waves moving over the earth's surface. it is assumed that the two phases are interpenetrating continua which are coupled by drag forces and heat transfer. The particle phase is assumed to be dilute, and turbulent effects are modeled by zero- and two-equation eddy viscosity models. An important feature of the turbulence modeling is the treatment of surface boundary conditions which control the ingestion of particles into the boundary layer by turbulent friction and diffusion. The numerical method uses second-order implicit upwind differencing of the inviscid terms of the equations and second-order central differencing of the viscous terms. A diagonal form of the implicit algorithm is used to improve efficiency, and the transformation to a curvilinear coordinate system is accomplished by the finite volume techniques. Applications to a series of representative flows include a two-phase nozzle flow, the steady flow of air over a sand bed, and the air flow behind a normal shock wave in uniform motion over a sand bed. Results of the latter two applications are compared with experimental results.
Study of geometry to obtain the volume fraction of multiphase flows using the MCNP-X code
International Nuclear Information System (INIS)
Peixoto, Philippe N.B.; Salgado, Cesar M.
2015-01-01
The gamma ray attenuation technique is used in many works to obtaining volume fraction of multiphase flows in the oil industry, because it is a noninvasive technique with good precision. In these studies are simulated various geometries with different flow regime, compositions of materials, source-detector positions and types of collimation for sources. This work aim evaluate the interference in the results of the geometry changes and obtaining the best measuring geometry to provide the volume fractions accurately by evaluating different geometries simulations (ranging the source-detector position, flow schemes and homogeneity Makeup) in the MCNP-X code. The study was performed for two types of biphasic compositions of materials (oil-water and oil-air), two flow regimes (annular and smooth stratified) and was varied the position of each material in relative to source and detector positions. Another study to evaluate the interference of homogeneity of the compositions in the results was also conducted in order to verify the possibility of removing part of the composition and make a homogeneous blend using a mixer equipment. All these variations were simulated with two different types of beam, divergent beam and pencil beam. From the simulated geometries, it was possible to compare the differences between the areas of the spectra generated for each model. The results indicate that the flow regime and the differences in the material's densities interfere in the results being necessary to establish a specific simulation geometry for each flows regime. However, the simulations indicate that changing the type of collimation of sources do not affect the results, but improving the counts statistics, increasing the accurate. (author)
Coherent structures in compressible free-shear-layer flows
Energy Technology Data Exchange (ETDEWEB)
Aeschliman, D.P.; Baty, R.S. [Sandia National Labs., Albuquerque, NM (United States). Engineering Sciences Center; Kennedy, C.A.; Chen, J.H. [Sandia National Labs., Livermore, CA (United States). Combustion and Physical Sciences Center
1997-08-01
Large scale coherent structures are intrinsic fluid mechanical characteristics of all free-shear flows, from incompressible to compressible, and laminar to fully turbulent. These quasi-periodic fluid structures, eddies of size comparable to the thickness of the shear layer, dominate the mixing process at the free-shear interface. As a result, large scale coherent structures greatly influence the operation and efficiency of many important commercial and defense technologies. Large scale coherent structures have been studied here in a research program that combines a synergistic blend of experiment, direct numerical simulation, and analysis. This report summarizes the work completed for this Sandia Laboratory-Directed Research and Development (LDRD) project.
Simple numerical method for predicting steady compressible flows
Vonlavante, Ernst; Nelson, N. Duane
1986-01-01
A numerical method for solving the isenthalpic form of the governing equations for compressible viscous and inviscid flows was developed. The method was based on the concept of flux vector splitting in its implicit form. The method was tested on several demanding inviscid and viscous configurations. Two different forms of the implicit operator were investigated. The time marching to steady state was accelerated by the implementation of the multigrid procedure. Its various forms very effectively increased the rate of convergence of the present scheme. High quality steady state results were obtained in most of the test cases; these required only short computational times due to the relative efficiency of the basic method.
Energy Technology Data Exchange (ETDEWEB)
S. Dartevelle
2005-09-05
The objective of this manuscript is to fully derive a geophysical multiphase model able to ''accommodate'' different multiphase turbulence approaches; viz., the Reynolds Averaged Navier-Stokes (RANS), the Large Eddy Simulation (LES), or hybrid RANSLES. This manuscript is the first part of a larger geophysical multiphase project--lead by LANL--that aims to develop comprehensive modeling tools for large-scale, atmospheric, transient-buoyancy dusty jets and plume (e.g., plinian clouds, nuclear ''mushrooms'', ''supercell'' forest fire plumes) and for boundary-dominated geophysical multiphase gravity currents (e.g., dusty surges, diluted pyroclastic flows, dusty gravity currents in street canyons). LES is a partially deterministic approach constructed on either a spatial- or a temporal-separation between the large and small scales of the flow, whereas RANS is an entirely probabilistic approach constructed on a statistical separation between an ensemble-averaged mean and higher-order statistical moments (the so-called ''fluctuating parts''). Within this specific multiphase context, both turbulence approaches are built up upon the same phasic binary-valued ''function of presence''. This function of presence formally describes the occurrence--or not--of any phase at a given position and time and, therefore, allows to derive the same basic multiphase Navier-Stokes model for either the RANS or the LES frameworks. The only differences between these turbulence frameworks are the closures for the various ''turbulence'' terms involving the unknown variables from the fluctuating (RANS) or from the subgrid (LES) parts. Even though the hydrodynamic and thermodynamic models for RANS and LES have the same set of Partial Differential Equations, the physical interpretations of these PDEs cannot be the same, i.e., RANS models an averaged field, while LES simulates a
Energy Technology Data Exchange (ETDEWEB)
Yorstos, Yannis C.
2003-03-19
The report describes progress made in the various thrust areas of the project, which include internal drives for oil recovery, vapor-liquid flows, combustion and reaction processes and the flow of fluids with yield stress.
A Vortex Particle-Mesh method for subsonic compressible flows
Parmentier, Philippe; Winckelmans, Grégoire; Chatelain, Philippe
2018-02-01
This paper presents the implementation and validation of a remeshed Vortex Particle-Mesh (VPM) method capable of simulating complex compressible and viscous flows. It is supplemented with a radiation boundary condition in order for the method to accommodate the radiating quantities of the flow. The efficiency of the methodology relies on the use of an underlying grid; it allows the use of a FFT-based Poisson solver to calculate the velocity field, and the use of high-order isotropic finite differences to evaluate the non-advective terms in the Lagrangian form of the conservation equations. The Möhring analogy is then also used to further obtain the far-field sound produced by two co-rotating Gaussian vortices. It is demonstrated that the method is in excellent quantitative agreement with reference results that were obtained using a high-order Eulerian method and using a high-order remeshed Vortex Particle (VP) method.
FT-IR spectroscopic imaging of reactions in multiphase flow in microfluidic channels.
Chan, K L Andrew; Kazarian, Sergei G
2012-05-01
Rapid, in situ, and label-free chemical analysis in microfluidic devices is highly desirable. FT-IR spectroscopic imaging has previously been shown to be a powerful tool to visualize the distribution of different chemicals in flows in a microfluidic device at near video rate imaging speed without tracers or dyes. This paper demonstrates the possibility of using this imaging technology to capture the chemical information of all reactants and products at different points in time and space in a two-phase system. Differences in the rates of chemical reactions in laminar flow and segmented flow systems are also compared. Neutralization of benzoic acid in decanol with disodium phosphate in water has been used as the model reaction. Quantitative information, such as concentration profiles of reactant and products, can be extracted from the imaging data. The same feed flow rate was used in both the laminar flow and segmented flow systems. The laminar flow pattern was achieved using a plain wide T-junction, whereas the segmented flow was achieved by introducing a narrowed section and a nozzle at the T-junction. The results show that the reaction rate is limited by diffusion and is much slower with the laminar flow pattern, whereas the reaction is completed more quickly in the segmented flow due to better mixing.
A GPU-accelerated implicit meshless method for compressible flows
Zhang, Jia-Le; Ma, Zhi-Hua; Chen, Hong-Quan; Cao, Cheng
2018-05-01
This paper develops a recently proposed GPU based two-dimensional explicit meshless method (Ma et al., 2014) by devising and implementing an efficient parallel LU-SGS implicit algorithm to further improve the computational efficiency. The capability of the original 2D meshless code is extended to deal with 3D complex compressible flow problems. To resolve the inherent data dependency of the standard LU-SGS method, which causes thread-racing conditions destabilizing numerical computation, a generic rainbow coloring method is presented and applied to organize the computational points into different groups by painting neighboring points with different colors. The original LU-SGS method is modified and parallelized accordingly to perform calculations in a color-by-color manner. The CUDA Fortran programming model is employed to develop the key kernel functions to apply boundary conditions, calculate time steps, evaluate residuals as well as advance and update the solution in the temporal space. A series of two- and three-dimensional test cases including compressible flows over single- and multi-element airfoils and a M6 wing are carried out to verify the developed code. The obtained solutions agree well with experimental data and other computational results reported in the literature. Detailed analysis on the performance of the developed code reveals that the developed CPU based implicit meshless method is at least four to eight times faster than its explicit counterpart. The computational efficiency of the implicit method could be further improved by ten to fifteen times on the GPU.
Advanced high speed X-ray CT scanner for measurement and visualization of multi-phase flow
International Nuclear Information System (INIS)
Hori, Keiichi; Fujimoto, Tetsuro; Kawanishi, Kohei; Nishikawa, Hideo
1998-01-01
The development of an ultra-fast X-ray computed tomography (CT) scanner has been performed. The object of interest is in a transient or unsettled state, which makes the conventional CT scanner inappropriate. A concept of electrical switching of electron beam of X-ray generation unit is adopted to reduce the scanning time instead of a mechanical motion adopted by a conventional CT scanner. The mechanical motion is a major obstacle to improve the scanning speed. A prototype system with a scanning time of 3.6 milliseconds was developed at first. And, the feasibility was confirmed to measure the dynamic events of two-phase flow. However, faster scanning speed is generally required for the practical use in the thermalhydraulics research field. Therefore, the development of advanced type has been performed. This advanced type can operate under the scanning time of 0.5 milliseconds and is applicable for the measurement of the multi-phase flow with velocity up to 4-5 m/s. (author)
International Nuclear Information System (INIS)
Chaparro, M.C.; Saaltink, M.W.
2015-01-01
El Cabril is the low and intermediate level radioactive waste disposal facility for Spain. After sealing the cells that stored the radioactive waste, water was collected from a drainpipe, indicating the flow of water within the cell. A hypothesis had been proposed to explain this phenomenon which consists of capillary rise from groundwater and evaporation and condensation within the cell produced by temperature gradients caused by seasonal temperature fluctuations outside. To corroborate this hypothesis a 2D numerical model was made taking into account all relevant processes such as multiphase flow and heat transport. Data were used measured by sensors in the cells and data from laboratory test. There is a good agreement between the temperature measured by the sensors and the ones calculated by the model. The model shows a drying of the concrete at the hot side (that is the wall during summer and the container during winter). The concrete is saturated with water at the cold side (that is the container during summer and the wall in winter), leading to runoff of water to the drainpipe. The flux at this drainpipe occurred in the two yearly periods, being higher in winter than in summer. (authors)
TOUGH+CO 2: A multiphase fluid-flow simulator for CO 2 geologic sequestration in saline aquifers
Zhang, Keni; Moridis, George; Pruess, Karsten
2011-06-01
TOUGH+CO 2 is a new simulator for modeling of CO 2 geologic sequestration in saline aquifers. It is a member of TOUGH+, the successor to the TOUGH2 family of codes for multicomponent, multiphase fluid and heat flow simulation. The code accounts for heat and up to 3 mass components, which are partitioned into three possible phases. In the code, the thermodynamics and thermophysical properties of H 2O-NaCl-CO 2 mixtures are determined based on system status and subdivided into six different phase combinations. By solving coupled mass and heat balance equations, TOUGH+CO 2 can model non-isothermal or isothermal CO 2 injection, phase behavior and flow of fluids and heat under typical conditions of temperature, pressure and salinity in CO 2 geologic storage projects. The code takes into account effects of salt precipitation on porosity and permeability changes, and the wettability phenomena. The new simulator inherits all capabilities of TOUGH2 in handling fractured media and using unstructured meshes for complex simulation domains. The code adds additional relative permeability and capillary pressure functions. The FORTRAN 95 OOP architecture and other new language features have been extensively used to enhance memory use and computing efficiency. In addition, a domain decomposition approach has been implemented for parallel simulation. All these features lead to increased computational efficiency, and allow applicability of the code to multi-core/processor parallel computing platforms with excellent scalability.
Wildenschild, D.; Porter, M. L.
2009-04-01
Significant strides have been made in recent years in imaging fluid flow in porous media using x-ray computerized microtomography (CMT) with 1-20 micron resolution; however, difficulties remain in combining representative sample sizes with optimal image resolution and data quality; and in precise quantification of the variables of interest. Tomographic imaging was for many years focused on volume rendering and the more qualitative analyses necessary for rapid assessment of the state of a patient's health. In recent years, many highly quantitative CMT-based studies of fluid flow processes in porous media have been reported; however, many of these analyses are made difficult by the complexities in processing the resulting grey-scale data into reliable applicable information such as pore network structures, phase saturations, interfacial areas, and curvatures. Yet, relatively few rigorous tests of these analysis tools have been reported so far. The work presented here was designed to evaluate the effect of image resolution and quality, as well as the validity of segmentation and surface generation algorithms as they were applied to CMT images of (1) a high-precision glass bead pack and (2) gas-fluid configurations in a number of glass capillary tubes. Interfacial areas calculated with various algorithms were compared to actual interfacial geometries and we found very good agreement between actual and measured surface and interfacial areas. (The test images used are available for download at the website listed below). http://cbee.oregonstate.edu/research/multiphase_data/index.html
Modeling Coupled Processes for Multiphase Fluid Flow in Mechanically Deforming Faults
McKenna, S. A.; Pike, D. Q.
2011-12-01
Modeling of coupled hydrological-mechanical processes in fault zones is critical for understanding the long-term behavior of fluids within the shallow crust. Here we utilize a previously developed cellular-automata (CA) model to define the evolution of permeability within a 2-D fault zone under compressive stress. At each time step, the CA model calculates the increase in fluid pressure within the fault at every grid cell. Pressure surpassing a critical threshold (e.g., lithostatic stress) causes a rupture in that cell, and pressure is then redistributed across the neighboring cells. The rupture can cascade through the spatial domain and continue across multiple time steps. Stress continues to increase and the size and location of rupture events are recorded until a percolating backbone of ruptured cells exists across the fault. Previous applications of this model consider uncorrelated random fields for the compressibility of the fault material. The prior focus on uncorrelated property fields is consistent with development of a number of statistical physics models including percolation processes and fracture propagation. However, geologic materials typically express spatial correlation and this can have a significant impact on the results of the pressure and permeability distributions. We model correlation of the fault material compressibility as a multiGaussian random field with a correlation length defined as the full-width at half maximum (FWHM) of the kernel used to create the field. The FWHM is varied from contract DE-AC04-94AL85000
Modelling compressible dense and dilute two-phase flows
Saurel, Richard; Chinnayya, Ashwin; Carmouze, Quentin
2017-06-01
Many two-phase flow situations, from engineering science to astrophysics, deal with transition from dense (high concentration of the condensed phase) to dilute concentration (low concentration of the same phase), covering the entire range of volume fractions. Some models are now well accepted at the two limits, but none are able to cover accurately the entire range, in particular regarding waves propagation. In the present work, an alternative to the Baer and Nunziato (BN) model [Baer, M. R. and Nunziato, J. W., "A two-phase mixture theory for the deflagration-to-detonation transition (DDT) in reactive granular materials," Int. J. Multiphase Flow 12(6), 861 (1986)], initially designed for dense flows, is built. The corresponding model is hyperbolic and thermodynamically consistent. Contrarily to the BN model that involves 6 wave speeds, the new formulation involves 4 waves only, in agreement with the Marble model [Marble, F. E., "Dynamics of a gas containing small solid particles," Combustion and Propulsion (5th AGARD Colloquium) (Pergamon Press, 1963), Vol. 175] based on pressureless Euler equations for the dispersed phase, a well-accepted model for low particle volume concentrations. In the new model, the presence of pressure in the momentum equation of the particles and consideration of volume fractions in the two phases render the model valid for large particle concentrations. A symmetric version of the new model is derived as well for liquids containing gas bubbles. This model version involves 4 characteristic wave speeds as well, but with different velocities. Last, the two sub-models with 4 waves are combined in a unique formulation, valid for the full range of volume fractions. It involves the same 6 wave speeds as the BN model, but at a given point of space, 4 waves only emerge, depending on the local volume fractions. The non-linear pressure waves propagate only in the phase with dominant volume fraction. The new model is tested numerically on various
Energy Technology Data Exchange (ETDEWEB)
Yortsos, Yanis C.
2002-10-08
In this report, the thrust areas include the following: Internal drives, vapor-liquid flows, combustion and reaction processes, fluid displacements and the effect of instabilities and heterogeneities and the flow of fluids with yield stress. These find respective applications in foamy oils, the evolution of dissolved gas, internal steam drives, the mechanics of concurrent and countercurrent vapor-liquid flows, associated with thermal methods and steam injection, such as SAGD, the in-situ combustion, the upscaling of displacements in heterogeneous media and the flow of foams, Bingham plastics and heavy oils in porous media and the development of wormholes during cold production.
Self-organization in three-dimensional compressible magnetohydrodynamic flow
International Nuclear Information System (INIS)
Horiuchi, Ritoku; Sato, Tetsuya.
1987-07-01
A three-dimensional self-organization process of a compressible dissipative plasma with a velocity-magnetic field correlation is investigated in detail by means of a variational method and a magnetohydrodynamic simulation. There are two types of relaxation, i.e., fast relaxation in which the cross helicity is not conserved, and slow relaxation in which the cross helicity is approximately conserved. In the slow relaxation case the cross helicity consists of two components with opposite sign which have almost the same amplitude in the large wavenumber region. In both cases the system approaches a high correlation state, dependent on the initial condition. These results are consistent with an observational data of the solar wind. Selective dissipation of magnetic energy, normal cascade of magnetic energy spectrum and inverse cascade of magnetic helicity spectrum are observed for the sub-Alfvenic flow case as was previously observed for the zero flow case. When the flow velocity is super-Alfvenic, the relaxation process is significantly altered from the zero flow case. (author)
Low-Reynolds number compressible flow around a triangular airfoil
Munday, Phillip; Taira, Kunihiko; Suwa, Tetsuya; Numata, Daiju; Asai, Keisuke
2013-11-01
We report on the combined numerical and experimental effort to analyze the nonlinear aerodynamics of a triangular airfoil in low-Reynolds number compressible flow that is representative of wings on future Martian air vehicles. The flow field around this airfoil is examined for a wide range of angles of attack and Mach numbers with three-dimensional direct numerical simulations at Re = 3000 . Companion experiments are conducted in a unique Martian wind tunnel that is placed in a vacuum chamber to simulate the Martian atmosphere. Computational findings are compared with pressure sensitive paint and direct force measurements and are found to be in agreement. The separated flow from the leading edge is found to form a large leading-edge vortex that sits directly above the apex of the airfoil and provides enhanced lift at post stall angles of attack. For higher subsonic flows, the vortical structures elongate in the streamwise direction resulting in reduced lift enhancement. We also observe that the onset of spanwise instability for higher angles of attack is delayed at lower Mach numbers. Currently at Mitsubishi Heavy Industries, Ltd., Nagasaki.
Martin, R.
2001-12-01
In many volcanoes like the Popocatepetl, it is not well known if seismicity induces explosive eruptions, or inversely if the dynamics induces seismicity, or how both mechanisms trigger each other. In order to understand this mechanisms we numerically simulate, at greater scales than in laboratory, the behaviour of highly viscous magmas submitted to an incoming PSV wave involving high stresses. For that purpose we use a finite volume scheme of second order with a semi implicit algorithm in time for the fluid and a classical velocity/stress formulation at the second order to describe the elastic waves. The magma is considered as compressible and consists in a high viscous fluid and volatile gases. The gas fractions are computed following a power state law of the pressure. The disturbance of the fluid by the wave causes the pressure to increase and the gas to exsolve. The magma is then submitted to a convection behaviour and can arise through the conduit till reaching a certain depth which defines the location of fragmentation of the mixture. These simulations allow us to conclude that, depending on the magnitude of the wave, a viscous compressible fluid like a magma can be highly disturbed and differ strongly then from the quasistatic and acoustic behaviour classically taken into account in classical modelling of waves travelling through acoustic fluid/elastic solid structures. Depending on the Reynolds number, from laminar to turbulent, the fluid can not any longer be assumed incompressible, irrotational and non viscous. Inversely, when the magma has reached the fragmentation depth in the conduit, the fluid becomes multiphasic with specific exit velocities, pressures, temperatures, particle fractions. It is modelled with one particle phase and one gas phase interacting with drag forces and heat exchange terms. With a similar algorithm as described before, we show that the flow can be expelled at shock speeds and produce travelling elastic waves in the ground through
Multiphase imaging of gas flow in a nanoporous material using remote-detection NMR.
Harel, Elad; Granwehr, Josef; Seeley, Juliette A; Pines, Alex
2006-04-01
Pore structure and connectivity determine how microstructured materials perform in applications such as catalysis, fluid storage and transport, filtering or as reactors. We report a model study on silica aerogel using a time-of-flight magnetic resonance imaging technique to characterize the flow field and explain the effects of heterogeneities in the pore structure on gas flow and dispersion with 129Xe as the gas-phase sensor. The observed chemical shift allows the separate visualization of unrestricted xenon and xenon confined in the pores of the aerogel. The asymmetrical nature of the dispersion pattern alludes to the existence of a stationary and a flow regime in the aerogel. An exchange time constant is determined to characterize the gas transfer between them. As a general methodology, this technique provides insights into the dynamics of flow in porous media where several phases or chemical species may be present.
Thermofluidynamics of the multiphase flow inside cylindroconical fermenters with different scales
Directory of Open Access Journals (Sweden)
Meironke Heiko
2014-01-01
Full Text Available In this work the experimental investigations of the flow and the temperature field during the fermentation of beer in cylindroconical tanks are presented. The flow stability is affected of the height/diameter ratio. Increasing the ratio leads to an unsteady, three-dimensional flow with several smaller vortices. In the course of our research the experiments have been performed with real fermentation fluid (wort under various height/diameter ratio. In the study, two tanks have been used in the laboratory and on an industrial scale, which were equipped with special design features. The velocity fields during a real fermentation process are measured by means of Ultrasound Doppler Velocimetry. It permits measurements in opaque fluids. Furthermore temperature measurements are conducted to analyse the interrelationship between the heat transfer and flow structure.
Yuan, H. Z.; Wang, Y.; Shu, C.
2017-12-01
This paper presents an adaptive mesh refinement-multiphase lattice Boltzmann flux solver (AMR-MLBFS) for effective simulation of complex binary fluid flows at large density ratios. In this method, an AMR algorithm is proposed by introducing a simple indicator on the root block for grid refinement and two possible statuses for each block. Unlike available block-structured AMR methods, which refine their mesh by spawning or removing four child blocks simultaneously, the present method is able to refine its mesh locally by spawning or removing one to four child blocks independently when the refinement indicator is triggered. As a result, the AMR mesh used in this work can be more focused on the flow region near the phase interface and its size is further reduced. In each block of mesh, the recently proposed MLBFS is applied for the solution of the flow field and the level-set method is used for capturing the fluid interface. As compared with existing AMR-lattice Boltzmann models, the present method avoids both spatial and temporal interpolations of density distribution functions so that converged solutions on different AMR meshes and uniform grids can be obtained. The proposed method has been successfully validated by simulating a static bubble immersed in another fluid, a falling droplet, instabilities of two-layered fluids, a bubble rising in a box, and a droplet splashing on a thin film with large density ratios and high Reynolds numbers. Good agreement with the theoretical solution, the uniform-grid result, and/or the published data has been achieved. Numerical results also show its effectiveness in saving computational time and virtual memory as compared with computations on uniform meshes.
Negara, Ardiansyah
2015-03-04
Numerical investigations of two-phase flows in anisotropic porous media have been conducted. In the flow model, the permeability has been considered as a full tensor and is implemented in the numerical scheme using the multipoint flux approximation within the framework of finite difference method. In addition, the experimenting pressure field approach is used to obtain the solution of the pressure field, which makes the matrix of coefficient of the global system easily constructed. A number of numerical experiments on the flow of two-phase system in two-dimensional porous medium domain are presented. In this work, the gravity is included in the model to capture the possible buoyancy-driven effects due to density differences between the two phases. Different anisotropy scenarios have been considered. From the numerical results, interesting patterns of the flow, pressure, and saturation fields emerge, which are significantly influenced by the anisotropy of the absolute permeability field. It is found that the two-phase system moves along the principal direction of anisotropy. Furthermore, the effects of anisotropy orientation on the flow rates and the cross flow index are also discussed in the paper.
The role of fault zones in affecting multiphase flow at Yucca Mountain
International Nuclear Information System (INIS)
Tsang, Y.W.; Pruess, K.; Wang, J.S.Y.
1993-01-01
Within Yucca Mountain, the potential High Level Nuclear-Waste Repository site, there are large scale fault zones, most notably the Ghost Dance Fault. The effect of such high-permeability, large scale discontinuities on the flow and transport is a question of concern in assessing the ability of the site to isolate radio-nuclides from the biosphere. In this paper, we present a numerical study to investigate the role of the fault in affecting both the liquid and gas phase flows in the natural state at Yucca Mountain prior to waste emplacement, as well as after the waste emplacement when the fluid flow is strongly heat-driven. Our study shows that if the characteristic curves of the Ghost Dance Fault obey the same relationship between saturated permeability and capillary scaling parameter, as is observed from the measured data of Yucca Mountain welded and nonwelded tuffs. Apache Leap tuffs, and Las Cruces soil, then a large saturated permeability of the Ghost Dance Fault will play little role in channeling water into the fault, or inenhancing the flow of water down the fault. However, the Fault may greatly enhance the upward gas flow after emplacement of waste. This may have implications on the transport of gaseous radio-nuclides such as C 14 . The results of this study also focus attention on the need for field measurements of fluid flow in the fault zones
International Nuclear Information System (INIS)
Park, Chan Wook; Lee, Sung Su
2008-01-01
Two-phase compressible flow fields of air-water are investigated numerically in the fixed Eulerian grid framework. The phase interface is captured via volume fractions of ech phase. A way to model two phase compressible flows as a single phase one is found based on an equivalent equation of states of Tait's type for a multiphase cell. The equivalent single phase field is discretized using the Roe's approximate Riemann solver. Two approaches are tried to suppress the pressure oscillation phenomena at the phase interface, a passive advection of volume fraction and a direct pressure relaxation with the compressible form of volume fraction equation. The direct pressure equalizing method suppresses pressure oscillation successfully and generates sharp discontinuities, transmitting and reflecting acoustic waves naturally at the phase interface. In discretizing the compressible form of volume fraction equation, phase interfaces are geometrically reconstructed to minimize the numerical diffusion of volume fraction and relevant variables. The motion of a projectile in a water-filled tube which is fired by the release of highly pressurized air is simulated presuming the flow field as a two dimensional one, and several design factors affecting the projectile movement are investigated
Lagrangian transported MDF methods for compressible high speed flows
Gerlinger, Peter
2017-06-01
This paper deals with the application of thermochemical Lagrangian MDF (mass density function) methods for compressible sub- and supersonic RANS (Reynolds Averaged Navier-Stokes) simulations. A new approach to treat molecular transport is presented. This technique on the one hand ensures numerical stability of the particle solver in laminar regions of the flow field (e.g. in the viscous sublayer) and on the other hand takes differential diffusion into account. It is shown in a detailed analysis, that the new method correctly predicts first and second-order moments on the basis of conventional modeling approaches. Moreover, a number of challenges for MDF particle methods in high speed flows is discussed, e.g. high cell aspect ratio grids close to solid walls, wall heat transfer, shock resolution, and problems from statistical noise which may cause artificial shock systems in supersonic flows. A Mach 2 supersonic mixing channel with multiple shock reflection and a model rocket combustor simulation demonstrate the eligibility of this technique to practical applications. Both test cases are simulated successfully for the first time with a hybrid finite-volume (FV)/Lagrangian particle solver (PS).
Stable low-dissipation schemes for turbulent compressible flows
Subbareddy, Pramod Kumar V.
Shock capturing schemes, which are commonly used in compressible flow simulations, introduce excessive amounts of numerical viscosity which smears out small scale flow features. A few low-dissipation methods have been proposed in the recent literature. They are more selective in the sense that they explicitly identify the portion of the numerical flux that is diffusive and damp its effect in 'smooth' regions of the flow. This work employs flux vector splitting methods; the dissipative portions of the Steger-Warming schemes are explicitly identified and various shock detection switches are explored. For high Reynolds number flows, especially when the energetic scales are close to the Nyquist limits of the grids used, aliasing errors become noticeable. These high frequency oscillations that arise due to the nonlinear nature of the Navier-Stokes equations cause solutions to become unstable. When dissipative methods are used, these errors are suppressed; however when using low-dissipation schemes, they can be prominent and need to be addressed by some other means. In this thesis, we focus on methods that enhance stability by enforcing 'secondary conservation' - the fluxes are constrained in such a way that a conservation law for a secondary, positive quantity is also satisified. In particular, we focus on kinetic energy, and a fully discrete (in time and space) 'kinetic energy consistent' scheme is derived and tested. Hybrid RAMS-LES methods such as Detached Eddy Simulations are necessary in order to make simulations of high speed flows with attached boundary layers affordable. A popular DES model is based on the Spalart-Allmaras RANS equation; a minor modification to the length scale makes the model behave in a hybrid manner. The S-A model itself was constructed using mostly empirical arguments by the authors. This model is analyzed and its connection to other turbulence models, in particular, the ksgs equation, is explored. A dynamic version of the model is proposed
Energy Technology Data Exchange (ETDEWEB)
Carrington, David Bradley [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Waters, Jiajia [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2017-09-26
Research and development of KIVA-hpFE for turbulent reactive and multiphase flow particularly as related to engine modeling program has relevance to National energy security and climate change. Climate change is a source problem, and energy national security is consumption of petroleum products problem. Accurately predicting engine processes leads to, lower greenhouse gas (GHG) emission, where engines in the transportation sector currently account for 26% of the U.S. GHG emissions. Less dependence on petroleum products leads to greater energy security. By Environmental Protection Agency standards, some vehicles are now reaching 42 to the 50 mpg mark. These are conventional gasoline engines. Continued investment and research into new technical innovations, the potential exists to save more than 4 million barrels of oil per day or approximately $200 to $400 million per day. This would be a significant decrease in emission and use of petroleum and a very large economic stimulus too! It is estimated with further advancements in combustion, the current emissions can be reduced up to 40%. Enabling better understanding of fuel injection and fuel-air mixing, thermodynamic combustion losses, and combustion/emission formation processes enhances our ability to help solve both problems. To provide adequate capability for accurately simulating these processes, minimize time and labor for development of engine technology, are the goals of our KIVA development program.
Nili, Samaun; Park, Chanyoung; Haftka, Raphael T.; Kim, Nam H.; Balachandar, S.
2017-11-01
Point particle methods are extensively used in simulating Euler-Lagrange multiphase dispersed flow. When particles are much smaller than the Eulerian grid the point particle model is on firm theoretical ground. However, this standard approach of evaluating the gas-particle coupling at the particle center fails to converge as the Eulerian grid is reduced below particle size. We present an approach to model the interaction between particles and fluid for finite size particles that permits convergence. We use the generalized Faxen form to compute the force on a particle and compare the results against traditional point particle method. We apportion the different force components on the particle to fluid cells based on the fraction of particle volume or surface in the cell. The application is to a one-dimensional model of shock propagation through a particle-laden field at moderate volume fraction, where the convergence is achieved for a well-formulated force model and back coupling for finite size particles. Comparison with 3D direct fully resolved numerical simulations will be used to check if the approach also improves accuracy compared to the point particle model. Work supported by the U.S. Department of Energy, National Nuclear Security Administration, Advanced Simulation and Computing Program, as a Cooperative Agreement under the Predictive Science Academic Alliance Program, under Contract No. DE-NA0002378.
Directory of Open Access Journals (Sweden)
Xiaojun Zhang
2013-01-01
particle contaminant, moisture and gas simultaneously. As the major unit of HIGEE, the RPB uses centrifugal force to intensify mass transfer. Because of the special structure of RPB, the hydraulic characteristics of the RPB are very important. In this study, the multiphase flow model in porous media of the RPB is presented, and the dynamical oil-water separation in the RPB is simulated using a commercial computational fluid dynamics code. The operating conditions and configuration on the hydraulic performance of the RPB are investigated. The results have indicated that the separation efficiency of HIGEE rotating oil purifier is predominantly affected by operating conditions and the configurations. The best inlet pressure is 0.002 MPa. When the liquid inlet is placed in the outside of the lower surface of RPB; oil outlet is placed in the upper surface, where it is near the rotation axis; and water outlet is placed in the middle of the RPB, where it is far away from the oil outlet, the separating efficiency is the best.
Towards multi-phase flow simulations in the PDE framework Peano
Bungartz, Hans-Joachim
2011-07-27
In this work, we present recent enhancements and new functionalities of our flow solver in the partial differential equation framework Peano. We start with an introduction including an overview of the Peano development and a short description of the basic concepts of Peano and the flow solver in Peano concerning the underlying structured but adaptive Cartesian grids, the data structure and data access optimisation, and spatial and time discretisation of the flow solver. The new features cover geometry interfaces and additional application functionalities. The two geometry interfaces, a triangulation-based description supported by the tool preCICE and a built-in geometry using geometry primitives such as cubes, spheres, or tetrahedra allow for the efficient treatment of complex and changing geometries, an essential ingredient for most application scenarios. The new application functionality concerns a coupled heat-flow problem and two-phase flows. We present numerical examples, performance and validation results for these new functionalities. © 2011 Springer-Verlag.
International Nuclear Information System (INIS)
Ray A. Berry
2005-01-01
At the INL researchers and engineers routinely encounter multiphase, multi-component, and/or multi-material flows. Some examples include: Reactor coolant flows Molten corium flows Dynamic compaction of metal powders Spray forming and thermal plasma spraying Plasma quench reactor Subsurface flows, particularly in the vadose zone Internal flows within fuel cells Black liquor atomization and combustion Wheat-chaff classification in combine harvesters Generation IV pebble bed, high temperature gas reactor The complexity of these flows dictates that they be examined in an averaged sense. Typically one would begin with known (or at least postulated) microscopic flow relations that hold on the ''small'' scale. These include continuum level conservation of mass, balance of species mass and momentum, conservation of energy, and a statement of the second law of thermodynamics often in the form of an entropy inequality (such as the Clausius-Duhem inequality). The averaged or macroscopic conservation equations and entropy inequalities are then obtained from the microscopic equations through suitable averaging procedures. At this stage a stronger form of the second law may also be postulated for the mixture of phases or materials. To render the evolutionary material flow balance system unique, constitutive equations and phase or material interaction relations are introduced from experimental observation, or by postulation, through strict enforcement of the constraints or restrictions resulting from the averaged entropy inequalities. These averaged equations form the governing equation system for the dynamic evolution of these mixture flows. Most commonly, the averaging technique utilized is either volume or time averaging or a combination of the two. The flow restrictions required for volume and time averaging to be valid can be severe, and violations of these restrictions are often found. A more general, less restrictive (and far less commonly used) type of averaging known as
International Nuclear Information System (INIS)
Freeze, G.A.; Larson, K.W.; Davies, P.B.; Webb, S.W.
1995-01-01
The Waste Isolation Pilot Plant (WIPP) is a US Department of Energy facility designed to demonstrate the safe underground disposal of transuranic waste. Following waste emplacement, each room will be backfilled with crushed salt. Due to deviatoric stress introduced by excavation, the walls of the waste disposal rooms in the repository will deform over time, consolidating waste containers and salt backfill, thereby decreasing the void volume of the repository. Long-term repository assessment must consider the processes of gas generation, room closure and expansion due to salt creep, and multiphase (brine and gas) fluid flow, as well as the complex coupling between these three processes. Stone (1992) used the mechanical creep closure code SANCHO to simulate the closure of a single, perfectly sealed disposal room filled with waste and backfill. The results of the SANCHO f-series simulations provide a relationship between gas generation, room closure, and room pressure. Several methods for coupling this relationship with multiphase fluid flow into and out of a room were examined by Freeze et al. TOUGH2 was employed to couple the processes of gas generation, room closure/consolidation, and multiphase brine and gas flow. Two empirically-based methods for approximating salt creep and room consolidation were implemented in TOUGH2: the pressure-time-porosity line interpolation approach and the fluid-phase-salt approach. Both approaches utilized links to the SANCHO f-series simulation results to calculate room-void-volume changes with time during a simulation
International Nuclear Information System (INIS)
Christian-Frear, T.; Freeze, G.
1997-01-01
Underground excavations produce damaged zones surrounding the excavations which have disturbed hydrologic and geomechanical properties. Prediction of fluid flow in these zones must consider both the mechanical and fluid flow processes. Presented here is a methodology which utilizes a mechanical model to predict damage and disturbed rock zone (DRZ) development around the excavation and then uses the predictions to develop time-dependent DRZ porosity relationships. These relationships are then used to adjust the porosity of the DRZ in the fluid flow model based upon the time and distance from the edge of the excavation. The application of this methodology is presented using a site-specific example from the Waste Isolation Pilot Plant, a US Department of Energy facility in bedded salts being evaluated for demonstration of the safe underground disposal of transuranic waste from US defense-related activities
International Nuclear Information System (INIS)
Saurel, Richard; Franquet, Erwin; Daniel, Eric; Le Metayer, Olivier
2007-01-01
A new projection method is developed for the Euler equations to determine the thermodynamic state in computational cells. It consists in the resolution of a mechanical relaxation problem between the various sub-volumes present in a computational cell. These sub-volumes correspond to the ones traveled by the various waves that produce states with different pressures, velocities, densities and temperatures. Contrarily to Godunov type schemes the relaxed state corresponds to mechanical equilibrium only and remains out of thermal equilibrium. The pressure computation with this relaxation process replaces the use of the conventional equation of state (EOS). A simplified relaxation method is also derived and provides a specific EOS (named the Numerical EOS). The use of the Numerical EOS gives a cure to spurious pressure oscillations that appear at contact discontinuities for fluids governed by real gas EOS. It is then extended to the computation of interface problems separating fluids with different EOS (liquid-gas interface for example) with the Euler equations. The resulting method is very robust, accurate, oscillation free and conservative. For the sake of simplicity and efficiency the method is developed in a Lagrange-projection context and is validated over exact solutions. In a companion paper [F. Petitpas, E. Franquet, R. Saurel, A relaxation-projection method for compressible flows. Part II: computation of interfaces and multiphase mixtures with stiff mechanical relaxation. J. Comput. Phys. (submitted for publication)], the method is extended to the numerical approximation of a non-conservative hyperbolic multiphase flow model for interface computation and shock propagation into mixtures
Flow Dynamic Analysis of Core Shooting Process through Experiment and Multiphase Modeling
Directory of Open Access Journals (Sweden)
Changjiang Ni
2016-01-01
Full Text Available Core shooting process is the most widely used technique to make sand cores and it plays an important role in the quality of sand cores as well as the manufacture of complicated castings in metal casting industry. In this paper, the flow behavior of sand particles in the core box was investigated synchronously with transparent core box, high-speed camera, and pressure measuring system. The flow pattern of sand particles in the shooting head of the core shooting machine was reproduced with various colored core sand layers. Taking both kinetic and frictional stress into account, a kinetic-frictional constitutive correlation was established to describe the internal momentum transfer in the solid phase. Two-fluid model (TFM simulations with turbulence model were then performed and good agreement was achieved between the experimental and simulation results on the flow behavior of sand particles in both the shooting head and the core box. Based on the experimental and simulation results, the flow behavior of sand particles in the core box, the formation of “dead zone” in the shooting head, and the effect of drag force were analyzed in terms of sand volume fraction (αs, sand velocity (Vs, and pressure variation (P.
Energy Technology Data Exchange (ETDEWEB)
Katoh, Yasuo [Yamaguchi Univ. (Japan); Matsubayasi, Masahito
1998-01-01
Concerning the transient phenomenon of solid-gas two-phase flow, an attempt was made to visualize and measure a flow phenomenon in which three-dimensional bubbles occurred, grew and collapsed in the vicinity of a gas injection nozzle while solid particles were circulating. Such a phenomenon could not or hardly be visualized and measured by conventional methods. Such two-phase flow was visualized using neutron radiography, its characteristics measured and the usefulness of the visualization by neutron radiography confirmed. For this purpose, three-dimensional fluidized bed vessels, rectangular or cylindrical-shaped, made of steel or aluminum sheet, were prepared. Polyethylene or glass beads were used as solid particles and activated carbon particles as the tracer. In the experiment, nitrogen gas was blown into the vessel from one nozzle and distributors provided at the bottom of the vessel and exhausted from the top via the exhaust valve, by which the pressure in the vessel was controlled. The imaging was done in the following way: A test chamber was provided beside the vessel to receive neutron beams from the JRR-3M system, the intensity of transmitted neutrons was converted to visible light by scintillator and the images were videotaped. The initial objectives of visualizing and measuring bubbles occurring, growing and collapsing and solid particles circulating in the solid-gas two-phase flow have been achieved by means of neutron radiography. (N.H.)
Experimental Study of Stable Surfaces for Anti-Slug Control in Multi-phase Flow
DEFF Research Database (Denmark)
Pedersen, Simon; Løhndorf, Petar Durdevic; Yang, Zhenyu
2014-01-01
-phase flow dynamics, the slug can be avoided or eliminated by proper facility design and control of operational conditions. Based on a testing facility which can emulate a pipeline-riser or a gas-lifted production well in a scaled-down manner, this paper experimentally studies the correlations of key...
An Experimental and Computational Study of Multiphase Flow Behaviour in Circulating Fluidized Beds
Energy Technology Data Exchange (ETDEWEB)
Mathiesen, Vidar
1997-12-31
Gas/solid flows have been studied extensively, mainly because they are important in nuclear, chemical and petroleum industries. This thesis describes an experiment done at two different circulating fluidized bed systems. Laser Doppler anemometry (LDA) and phase Doppler anemometry (PDA) were used to measure mean and fluctuating velocity, diameter and solids concentration. A typical core-annulus flow was obtained in both cases. The measurements show a relative mean velocity as well as a relative fluctuating velocity between different particle sizes. An axial segregation by size and its variation with the superficial gas velocity are demonstrated. Significant radial segregation is found in both risers. A three-dimensional Computational Fluid Dynamics model was developed based on Eulerian description of the phases where the kinetic theory of granular flow is the basis of the turbulence modelling in the solid phases. There are one gas phase and any number of solid phases. Simulations of flow behaviour in two- and three-dimensions agree well with experiments and the model is able to handle axial segregation by size for different superficial gas velocities and particle size distributions. 107 refs., 79 figs., 6 tabs.
Complexity reduction of multi-phase flows in heterogeneous porous media
Ghommem, Mehdi
2013-01-01
In this paper, we apply mode decomposition and interpolatory projection methods to speed up simulations of two-phase flows in highly heterogeneous porous media. We propose intrusive and non-intrusive model reduction approaches that enable a significant reduction in the dimension of the flow problem size while capturing the behavior of the fully-resolved solutions. In one approach, we employ the dynamic mode decomposition (DMD) and the discrete empirical interpolation method (DEIM). This approach does not require any modification of the reservoir simulation code but rather postprocesses a set of global snapshots to identify the dynamically-relevant structures associated with the flow behavior. In a second approach, we project the governing equations of the velocity and the pressure fields on the subspace spanned by their proper orthogonal decomposition (POD) modes. Furthermore, we use DEIM to approximate the mobility related term in the global system assembly and then reduce the online computational cost and make it independent of the fine grid. To show the effectiveness and usefulness of the aforementioned approaches, we consider the SPE 10 benchmark permeability field and present a variety of numerical examples of two-phase flow and transport. The proposed model reduction methods can be efficiently used when performing uncertainty quantification or optimization studies and history matching.
Energy Technology Data Exchange (ETDEWEB)
Yannis C. Yortsos
2003-02-01
This is final report for contract DE-AC26-99BC15211. The report describes progress made in the various thrust areas of the project, which include internal drives for oil recovery, vapor-liquid flows, combustion and reaction processes and the flow of fluids with yield stress. The report consists mainly of a compilation of various topical reports, technical papers and research reports published produced during the three-year project, which ended on May 6, 2002 and was no-cost extended to January 5, 2003. Advances in multiple processes and at various scales are described. In the area of internal drives, significant research accomplishments were made in the modeling of gas-phase growth driven by mass transfer, as in solution-gas drive, and by heat transfer, as in internal steam drives. In the area of vapor-liquid flows, we studied various aspects of concurrent and countercurrent flows, including stability analyses of vapor-liquid counterflow, and the development of novel methods for the pore-network modeling of the mobilization of trapped phases and liquid-vapor phase changes. In the area of combustion, we developed new methods for the modeling of these processes at the continuum and pore-network scales. These models allow us to understand a number of important aspects of in-situ combustion, including steady-state front propagation, multiple steady-states, effects of heterogeneity and modes of combustion (forward or reverse). Additional aspects of reactive transport in porous media were also studied. Finally, significant advances were made in the flow and displacement of non-Newtonian fluids with Bingham plastic rheology, which is characteristic of various heavy oil processes. Various accomplishments in generic displacements in porous media and corresponding effects of reservoir heterogeneity are also cited.
Directory of Open Access Journals (Sweden)
Drouffe J. M.
2006-11-01
Full Text Available L'exploitation des hydrocarbures en mer reste une activité coûteuse et qui peut, même, se révéler, éventuellement dangereuse. Les concepts de production polyphasique tels que Poséidon permettent à la fois : - une réduction importante des coûts de production; - la suppression des risques humains liés à la présence permanente en mer d'équipes importantes. Les programmes de simulation des écoulements diphasiques actuellement disponibles pour la mise en oeuvre de ces concepts, sont tous basés sur une approche déterministeclassique. Cet article présente une nouvelle approche statistiquenon conventionnelle qui devrait nous permettre de mieux préciser les caractéristiques des écoulements à bouchons et donc de pouvoir mieux dimensionner et exploiter nos futures installations de production et transport polyphasique longue distance. Offshore hydrocarbon production remains a costly venture, and even one that might possibly be dangerous. Multiphase production concepts such as Poseidon make for both a considerable reduction in production costs and the elimination of human risks linked to the constant offshore presence of large crews. The two-phase flow simulation programs now available for implementing such concepts are all based on a standard deterministicapproach. This article describes a new and unconventional statisticalapproach that we feel more accurately describes the characteristics of slug flows and hence is more effecting for the sizing and operating of future production and long-distance pipelining installations.
Talbot, C.; McClure, J. E.; Armstrong, R. T.; Mostaghimi, P.; Hu, Y.; Miller, C. T.
2017-12-01
Microscale experimental and computational methods can be used to evaluate fundamental microscale mechanisms and deduce macroscale constitutive relationships and parameter values. The link between the microscale and the macroscale is especially demanding, because technical issues arise regarding the necessary scale of the system needed for a meaningful set of macroscale measures to be insensitive to the size of the system, which is known as a representative elementary volume (REV). While the REV scale is routinely determined for single-phase flow in porous media, no systematic study of the scale of a REV for the comprehensive set of macroscale measures considered here has been reported in the literature. A comprehensive set of measures of the macroscale state is developed. We further develop and apply methods to predict the REV scale and quantify the uncertainty of the estimate for this set of macroscale quantities. We model the system state in terms of standard errors of macroscale quantities as a multivariate Gaussian process dependent on the size of the domain simulated. We determine predictive distributions of function values and a posterior distributions of weights using standard kernels, as well as a kernel constructed using relationships between physical quantities. For each kernel, we discuss the decay of the mean and covariance with increasing domain size, and use cross-validation to facilitate model selection. The procedure yields a model of the domain size needed to achieve a REV with quantifiable uncertainty. We present results in the context of multiphase fluid flow through a highly resolved realization of sandstone imaged using micro-CT. A 1440x1440x4320 section of the full 2520x2520x5280 imaged medium is simulated using the lattice-Boltzmann method. We compare the fidelity of the predictive model with results obtained by an analogous approach using polynomial regression.
Polar-coordinate lattice Boltzmann modeling of compressible flows
Lin, Chuandong; Xu, Aiguo; Zhang, Guangcai; Li, Yingjun; Succi, Sauro
2014-01-01
We present a polar coordinate lattice Boltzmann kinetic model for compressible flows. A method to recover the continuum distribution function from the discrete distribution function is indicated. Within the model, a hybrid scheme being similar to, but different from, the operator splitting is proposed. The temporal evolution is calculated analytically, and the convection term is solved via a modified Warming-Beam (MWB) scheme. Within the MWB scheme a suitable switch function is introduced. The current model works not only for subsonic flows but also for supersonic flows. It is validated and verified via the following well-known benchmark tests: (i) the rotational flow, (ii) the stable shock tube problem, (iii) the Richtmyer-Meshkov (RM) instability, and (iv) the Kelvin-Helmholtz instability. As an original application, we studied the nonequilibrium characteristics of the system around three kinds of interfaces, the shock wave, the rarefaction wave, and the material interface, for two specific cases. In one of the two cases, the material interface is initially perturbed, and consequently the RM instability occurs. It is found that the macroscopic effects due to deviating from thermodynamic equilibrium around the material interface differ significantly from those around the mechanical interfaces. The initial perturbation at the material interface enhances the coupling of molecular motions in different degrees of freedom. The amplitude of deviation from thermodynamic equilibrium around the shock wave is much higher than those around the rarefaction wave and material interface. By comparing each component of the high-order moments and its value in equilibrium, we can draw qualitatively the main behavior of the actual distribution function. These results deepen our understanding of the mechanical and material interfaces from a more fundamental level, which is indicative for constructing macroscopic models and other kinds of kinetic models.
Hamrick, Joseph T; Ginsburg, Ambrose; Osborn, Walter M
1952-01-01
A method is presented for analysis of the compressible flow between the hub and the shroud of mixed-flow impellers of arbitrary design. Axial symmetry was assumed, but the forces in the meridional (hub to shroud) plane, which are derived from tangential pressure gradients, were taken into account. The method was applied to an experimental mixed-flow impeller. The analysis of the flow in the meridional plane of the impeller showed that the rotational forces, the blade curvature, and the hub-shroud profile can introduce severe velocity gradients along the hub and the shroud surfaces. Choked flow at the impeller inlet as determined by the analysis was verified by experimental results.
Kaur, K.; Laanearu, J.; Annus, I.
2017-10-01
The numerical experiments are carried out for qualitative and quantitative interpretation of a multi-phase flow processes associated with malfunctioning of the Tallinn storm-water system during rain storms. The investigations are focused on the single-line inverted siphon, which is used as under-road connection of pipes of the storm-water system under interest. A multi-phase flow solver of Computational Fluid Dynamics software OpenFOAM is used for simulating the three-phase flow dynamics in the hydraulic system. The CFD simulations are performed with different inflow rates under same initial conditions. The computational results are compared essentially in two cases 1) design flow rate and 2) larger flow rate, for emptying the initially filled inverted siphon from a slurry-fluid. The larger flow-rate situations are under particular interest to detected possible flooding. In this regard, it is anticipated that the CFD solutions provide an important insight to functioning of inverted siphon under a restricted water-flow conditions at simultaneous presence of air and slurry-fluid.
Bagchi, Prosenjit
2016-11-01
In this talk, two problems in multiphase biological flows will be discussed. The first is the direct numerical simulation of whole blood and drug particulates in microvascular networks. Blood in microcirculation behaves as a dense suspension of heterogeneous cells. The erythrocytes are extremely deformable, while inactivated platelets and leukocytes are nearly rigid. A significant progress has been made in recent years in modeling blood as a dense cellular suspension. However, many of these studies considered the blood flow in simple geometry, e.g., straight tubes of uniform cross-section. In contrast, the architecture of a microvascular network is very complex with bifurcating, merging and winding vessels, posing a further challenge to numerical modeling. We have developed an immersed-boundary-based method that can consider blood cell flow in physiologically realistic and complex microvascular network. In addition to addressing many physiological issues related to network hemodynamics, this tool can be used to optimize the transport properties of drug particulates for effective organ-specific delivery. Our second problem is pseudopod-driven motility as often observed in metastatic cancer cells and other amoeboid cells. We have developed a multiscale hydrodynamic model to simulate such motility. We study the effect of cell stiffness on motility as the former has been considered as a biomarker for metastatic potential. Funded by the National Science Foundation.
Li, Y.; Kazemifar, F.; Blois, G.; Christensen, K. T.
2017-12-01
Geological sequestration of CO2 within saline aquifers is a viable technology for reducing CO2 emissions. Central to this goal is accurately predicting both the fidelity of candidate sites pre-injection of CO2 and its post-injection migration. Moreover, local fluid pressure buildup may cause activation of small pre-existing unidentified faults, leading to micro-seismic events, which could prove disastrous for societal acceptance of CCS, and possibly compromise seal integrity. Recent evidence shows that large-scale events are coupled with pore-scale phenomena, which necessitates the representation of pore-scale stress, strain, and multiphase flow processes in large-scale modeling. To this end, the pore-scale flow of water and liquid/supercritical CO2 is investigated under reservoir-relevant conditions, over a range of wettability conditions in 2D heterogeneous micromodels that reflect the complexity of a real sandstone. High-speed fluorescent microscopy, complemented by a fast differential pressure transmitter, allows for simultaneous measurement of the flow field within and the instantaneous pressure drop across the micromodels. A flexible micromodel is also designed and fabricated, to be used in conjunction with the micro-PIV technique, enabling the quantification of coupled solid-liquid interactions.
S-bend erosion in particulated multiphase flow with air and sand
Directory of Open Access Journals (Sweden)
Quamrul H Mazumder
2016-09-01
Full Text Available Solid particle erosion is a micro-mechanical process that removes material from a surface by repeated impact of entrained particles in the flow. Erosion is a leading cause of failure in fluid handling equipment such as pumps, pipes, valves, and fittings. The S-bend geometry is used to redirect flows in automotive, chemical processing, oil, gas, and food handling industries. An investigation was conducted using both computational fluid dynamics analysis and experimental methods to identify the location of maximum erosion. Three S-bend geometries with 12.7 mm inside diameter, r/D ratio of 1.5, three different air velocities and six different particle sizes were used in the current study. The experimental test section was of 12.7 mm inside diameter, r/D ratio of 1.5, and used 150 and 300 µm particle sizes.
Salibindla, Ashwanth; Masuk, Ashik Ullah Mohammad; Ni, Rui
2017-11-01
We have designed and constructed a new vertical water tunnel, V-ONSET, to investigate interfacial mass, momentum and energy transfer between two phases in a Lagrangian frame. This system features an independent control of mean flow and turbulence level. The mean flow opposes the rising/falling velocity of the second phase, ``suspending'' the particles and increasing tracking time in the view area. Strong turbulence is generated by shooting 88 digitally-controlled water jets into the test section. The second phase, either bubbles or oil droplets, can be introduced into the test section through a capillary island. In addition to this flow control system, V-ONSET comes with a 3D two-phase visualization system, consisting of high-speed cameras, two-colored LED system, and in-house Lagrangian particle tracking algorithm. This enables us to acquire the Lagrangian evolution of both phases and the interfacial transfer dynamics in between, paving the way for new closure models for two-phase simulations. Financial support for this project was provided by National Science Foundation under Grant Number: 1653389 and 1705246.
Ye, J.; Guo, L. J.; Zhou, H. L.
2012-03-01
A type of capacitance probe performance with two brass electrodes intertwined on the outer wall of insulation pipe like a double helix is investigated numerically in this paper, which can measure water fraction in air-oil-water two or three-phase flow in oil industry. The motivation of this paper is to optimize this kind of probe to improve its electric response and spatial resolution and so a 3-D numerical simulation using finite element method is employed to evaluate the effect of electrodes configuration of this capacitance probe on measuring water fraction in horizontal pipes. The electrostatic field of the probe is preliminarily analyzed referred to stratified flow of air-water two-phase flow regime. Several parameters are considered as main variables which have an important effect on the precision of the probe, such as central angle, position angle and length of the two electrodes. From the electrostatic field analysis, lumped capacitance between the two electrodes is obtained in every different electrode geometry model and the results of each model are compared to each other in order to select a better arrangement of the electrodes that has a better response to water fraction. And by using circuit simulation method, the numerical calculated lumped capacitance is transferred to voltage output through the circuit used in the experiment. The relationship between voltage and water fraction of calculated and experimental result are compared in order to test the reasonableness of the simulation. The results show that at high water fraction, the difference between numerical and measured data agrees very well.
The effect of stratigraphic dip on multiphase flow at the Waste Isolation Pilot Plant
International Nuclear Information System (INIS)
Webb, S.W.; Larson, K.W.
1995-01-01
The natural stratigraphic dip at the Waste Isolation Pilot Plant (WIPP), although regionally only about 1 degree, has the potential to affect brine inflow and gas migration distances due to buoyancy forces. Brine inflow may increase due to countercurrent flow, and gas may preferentially migrate updip. Analytical and numerical modeling was used to evaluate the impact of the dip on brine inflow and gas migration distances at the WIPP in one, two, and three dimensions. Results show that the effect of dip on brine inflow and gas migration distance may be significant
Nicolleau, FCGA; Redondo, J-M
2012-01-01
This book contains a collection of the main contributions from the first five workshops held by Ercoftac Special Interest Group on Synthetic Turbulence Models (SIG42. It is intended as an illustration of the sig's activities and of the latest developments in the field. This volume investigates the use of Kinematic Simulation (KS) and other synthetic turbulence models for the particular application to environmental flows. This volume offers the best syntheses on the research status in KS, which is widely used in various domains, including Lagrangian aspects in turbulence mixing/stirring, partic
Energy Technology Data Exchange (ETDEWEB)
Paul Meakin; Zhijie Xu
2008-06-01
Particle methods are much less computationally efficient than grid based numerical solution of the Navier Stokes equation, and they have been used much less extensively, particularly for engineering applications. However, they have important advantages for some applications. These advantages include rigorous mast conservation, momentum conservation and isotropy. In addition, there is no need for explicit interface tracking/capturing. Code development effort is relatively low, and it is relatively simple to simulate flows with moving boundaries. In addition, it is often quite easy to include coupling of fluid flow with other physical phenomena such a phase separation. Here we describe the application of three particle methods: molecular dynamics, dissipative particle dynamics and smoothed particle hydrodynamics. While these methods were developed to simulate fluids and other materials on three quite different scales – the molecular, meso and continuum scales, they are very closely related from a computational point of view. The mesoscale (between the molecular and continuum scales) dissipative particle dynamics method can be used to simulate systems that are too large to simulate using molecular dynamics but small enough for thermal fluctuations to play an important role. Important examples include polymer solutions, gels, small particle suspensions and membranes. In these applications inter particle and intra molecular hydrodynamic interactions are automatically included
The role of pore space morphology in multi-phase flow in porous media
Wildenschild, D.; Prodanovic, M.; Jansik, D. P.
2008-12-01
Porous medium morphology can play an important role when we use numerical models to predict subsurface flow and transport behavior at larger scales. Yet, understanding the role that pore structure plays at smaller scales is a necessary first step. Fluid-fluid configuration in particular is highly influenced by the surface characteristics of the porous medium. Fluid configurations vary significantly between drainage and imbibiton (due to spontaneous, irreversible changes of the interface between fluids). We specifically measure large differences in wetting-nonwetting interfacial area as a function of different pore space morphology: as observed for a crushed volcanic tuff with high surface area and affinity for fluid films, and for smooth glass beads. The observed imbibition process for the glass beads resembles a piston-flow situation, whereas imbibition into the tuff appears dominated by fluid film connectivity with growth from pendular rings in spatially distant locations of the imaged system. The latter process leads to a very different distribution of fluids and overall lower saturations and interfacial areas than in the glass bead system. Characteristics such as pore- scale Pc-S curves and related interfacial area per volume have been quantified using computed microtomography. In addition, we present pore network characterization (pore connectivity, pore throats to pore body aspect ratio, pore body volumes and throat areas) of the two porous media.
Multiphase Fluid Flow in Deformable Variable-Aperture Fractures - Final Report
Energy Technology Data Exchange (ETDEWEB)
Detwiler, Russell
2014-04-30
Fractures provide flow paths that can potentially lead to fast migration of fluids or contaminants. A number of energy-related applications involve fluid injections that significantly perturb both the pressures and chemical composition of subsurface fluids. These perturbations can cause both mechanical deformation and chemical alteration of host rocks with potential for significant changes in permeability. In fractured rock subjected to coupled chemical and mechanical stresses, it can be difficult to predict the sign of permeability changes, let alone the magnitude. This project integrated experimental and computational studies to improve mechanistic understanding of these coupled processes and develop and test predictive models and monitoring techniques. The project involved three major components: (1) study of two-phase flow processes involving mass transfer between phases and dissolution of minerals along fracture surfaces (Detwiler et al., 2009; Detwiler, 2010); (2) study of fracture dissolution in fractures subjected to normal stresses using experimental techniques (Ameli, et al., 2013; Elkhoury et al., 2013; Elkhoury et al., 2014) and newly developed computational models (Ameli, et al., 2014); (3) evaluation of electrical resistivity tomography (ERT) as a method to detect and quantify gas leakage through a fractured caprock (Breen et al., 2012; Lochbuhler et al., 2014). The project provided support for one PhD student (Dr. Pasha Ameli; 2009-2013) and partially supported a post-doctoral scholar (Dr. Jean Elkhoury; 2010-2013). In addition, the project provided supplemental funding to support collaboration with Dr. Charles Carrigan at Lawrence Livermore National Laboratory in connection with (3) and supported one MS student (Stephen Breen; 2011-2013). Major results from each component of the project include the following: (1) Mineral dissolution in fractures occupied by two fluid phases (e.g., oil-water or water-CO{sub 2}) causes changes in local
Directory of Open Access Journals (Sweden)
S. Sathiyamoorthy
2007-09-01
Full Text Available Electrical Capacitance Tomography (ECT was used to develop image of various multi phase flow of gas-liquid-solid in a closed pipe. The principal difficulties to obtained real time image from ECT sensor are permittivity distribution across the plate and capacitance is nonlinear; the electric field is distorted by the material present and is also sensitive to measurement errors and noise. This work present a detailed description is given on method employed for image reconstruction from the capacitance measurements. The discretization and iterative algorithm is developed for improving the predictions with minimum error. The author analyzed eight electrodes square sensor ECT system with two-phase water-gas and solid-gas.
Fakhari, Abbas; Li, Yaofa; Bolster, Diogo; Christensen, Kenneth T.
2018-04-01
We implement a phase-field based lattice-Boltzmann (LB) method for numerical simulation of multiphase flows in heterogeneous porous media at pore scales with wettability effects. The present method can handle large density and viscosity ratios, pertinent to many practical problems. As a practical application, we study multiphase flow in a micromodel representative of CO2 invading a water-saturated porous medium at reservoir conditions, both numerically and experimentally. We focus on two flow cases with (i) a crossover from capillary fingering to viscous fingering at a relatively small capillary number, and (ii) viscous fingering at a relatively moderate capillary number. Qualitative and quantitative comparisons are made between numerical results and experimental data for temporal and spatial CO2 saturation profiles, and good agreement is found. In particular, a correlation analysis shows that any differences between simulations and results are comparable to intra-experimental differences from replicate experiments. A key conclusion of this work is that system behavior is highly sensitive to boundary conditions, particularly inlet and outlet ones. We finish with a discussion on small-scale flow features, such as the emergence of strong recirculation zones as well as flow in which the residual phase is trapped, including a close look at the detailed formation of a water cone. Overall, the proposed model yields useful information, such as the spatiotemporal evolution of the CO2 front and instantaneous velocity fields, which are valuable for understanding the mechanisms of CO2 infiltration at the pore scale.
Hydrodynamic and thermal modeling of solid particles in a multi-phase, multi-component flow
International Nuclear Information System (INIS)
Tentner, A.M.; Wider, H.U.
1983-01-01
This paper presents the new thermal hydraulic models describing the hydrodynamics of the solid fuel/steel chunks during an LMFBR hypothetical core-disruptive accident. These models, which account for two-way coupling between the solid and fluid phases, describe the mass, momentum, and energy exchanges which occur when the chunks are present at any axial location. They have been incorporated in LEVITATE, a code for the analysis of fuel and cladding dynamics under Loss-of-Flow (LOF) conditions. Their influence on fuel motion is presented in the context of the L6 TREAT experiment analysis. It is shown that the overall hydrodynamic behavior of the molten fuel and solid-fuel chunks is dependent on both the size of the chunks and the power level. At low and intermediate power levels the fuel motion is more dispersive when small chunks, rather than large ones, are present. At high power levels the situation is reversed. These effects are explained in detail
Towards an integrated petrophysical tool for multiphase flow properties of core samples
Energy Technology Data Exchange (ETDEWEB)
Lenormand, R. [Institut Francais du Petrole, Rueil Malmaison (France)
1997-08-01
This paper describes the first use of an Integrated Petrophysical Tool (IPT) on reservoir rock samples. The IPT simultaneously measures the following petrophysical properties: (1) Complete capillary pressure cycle: primary drainage, spontaneous and forced imbibitions, secondary drainage (the cycle leads to the wettability of the core by using the USBM index); End-points and parts of the relative permeability curves; Formation factor and resistivity index. The IPT is based on the steady-state injection of one fluid through the sample placed in a Hassler cell. The experiment leading to the whole Pc cycle on two reservoir sandstones consists of about 30 steps at various oil or water flow rates. It takes about four weeks and is operated at room conditions. Relative permeabilities are in line with standard steady-state measurements. Capillary pressures are in accordance with standard centrifuge measurements. There is no comparison for the resistivity index, but the results are in agreement with literature data. However, the accurate determination of saturation remains the main difficulty and some improvements are proposed. In conclusion, the Integrated Petrophysical Tool is as accurate as standard methods and has the advantage of providing the various parameters on the same sample and during a single experiment. The FIT is easy to use and can be automated. In addition, it can be operated in reservoir conditions.
Shock tube Multiphase Experiments
Middlebrooks, John; Allen, Roy; Paudel, Manoj; Young, Calvin; Musick, Ben; McFarland, Jacob
2017-11-01
Shock driven multiphase instabilities (SDMI) are unique physical phenomena that have far-reaching practical applications in engineering and science. The instability is present in high energy explosions, scramjet combustors, and supernovae events. The SDMI arises when a multiphase interface is impulsively accelerated by the passage of a shockwave. It is similar in development to the Richtmyer-Meshkov (RM) instability however, particle-to-gas coupling is the driving mechanism of the SDMI. As particle effects such as lag and phase change become more prominent, the SDMI's development begins to significantly deviate from the RM instability. We have developed an experiment for studying the SDMI in our shock tube facility. In our experiments, a multiphase interface is created using a laminar jet and flowed into the shock tube where it is accelerated by the passage of a planar shockwave. The interface development is captured using CCD cameras synchronized with planar laser illumination. This talk will give an overview of new experiments conducted to examine the development of a shocked cylindrical multiphase interface. The effects of Atwood number, particle size, and a second acceleration (reshock) of the interface will be discussed.
Energy Technology Data Exchange (ETDEWEB)
Miller, Aubrey L. [WSU Research Corporation, Morgantown, WV (USA)
2005-07-01
This work was carried out to understand the behavior of the solid and gas phases in a CFB riser. Only the riser is modeled as a straight pipe. A model with linear algebraic approximation to solids viscosity of the form, {musubs} = 5.34{epsisubs}, ({espisubs} is the solids volume fraction) with an appropriate boundary condition at the wall obtained by approximate momentum balance solution at the wall to acount for the solids recirculation is tested against experimental results. The work done was to predict the flow patterns in the CFB risers from available experimental data, including data from a 7.5-cm-ID CFB riser at the Illinois Institute of Technology and data from a 20.0-cm-ID CFB riser at the Particulate Solid Research, Inc., facility. This research aims at modeling the removal of hydrogen sulfide from hot coal gas using zinc oxide as the sorbent in a circulating fluidized bed and in the process indentifying the parameters that affect the performance of the sulfidation reactor. Two different gas-solid reaction models, the unreacted shrinking core (USC) and the grain model were applied to take into account chemical reaction resistances. Also two different approaches were used to affect the hydrodynamics of the process streams. The first model takes into account the effect of micro-scale particle clustering by adjusting the gas-particle drag law and the second one assumes a turbulent core with pseudo-steady state boundary condition at the wall. A comparison is made with experimental results.
Advanced Fluid Reduced Order Models for Compressible Flow.
Energy Technology Data Exchange (ETDEWEB)
Tezaur, Irina Kalashnikova [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Fike, Jeffrey A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Carlberg, Kevin Thomas [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Barone, Matthew F. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Maddix, Danielle [Stanford Univ., CA (United States); Mussoni, Erin E. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Balajewicz, Maciej [Univ. of Illinois, Urbana-Champaign, IL (United States)
2017-09-01
This report summarizes fiscal year (FY) 2017 progress towards developing and implementing within the SPARC in-house finite volume flow solver advanced fluid reduced order models (ROMs) for compressible captive-carriage flow problems of interest to Sandia National Laboratories for the design and qualification of nuclear weapons components. The proposed projection-based model order reduction (MOR) approach, known as the Proper Orthogonal Decomposition (POD)/Least- Squares Petrov-Galerkin (LSPG) method, can substantially reduce the CPU-time requirement for these simulations, thereby enabling advanced analyses such as uncertainty quantification and de- sign optimization. Following a description of the project objectives and FY17 targets, we overview briefly the POD/LSPG approach to model reduction implemented within SPARC . We then study the viability of these ROMs for long-time predictive simulations in the context of a two-dimensional viscous laminar cavity problem, and describe some FY17 enhancements to the proposed model reduction methodology that led to ROMs with improved predictive capabilities. Also described in this report are some FY17 efforts pursued in parallel to the primary objective of determining whether the ROMs in SPARC are viable for the targeted application. These include the implemen- tation and verification of some higher-order finite volume discretization methods within SPARC (towards using the code to study the viability of ROMs on three-dimensional cavity problems) and a novel structure-preserving constrained POD/LSPG formulation that can improve the accuracy of projection-based reduced order models. We conclude the report by summarizing the key takeaways from our FY17 findings, and providing some perspectives for future work.
International Nuclear Information System (INIS)
Pradeep, Chaminda; Yan, Ru; Mylvaganam, Saba; Vestøl, Sondre; Melaaen, Morten C
2014-01-01
The electrical capacitance tomographic (ECT) approach is increasingly seen as attractive for measurement and control applications in the process industries. Recently, there is increased interest in using the tomographic details from ECT for comparing with and validating and tuning CFD models of multiphase flow. Collaboration with researchers working in the field of computational fluid dynamics (CFD) modeling of multiphase flows gives valuable information for both groups of researchers in the field of ECT and CFD. By studying the ECT tomograms of multiphase flows under carefully monitored inflow conditions of the different media and by obtaining the capacitance values, C(i, j, t) with i = 1…N, j = 1, 2,…N and i ≠ j obtained from ECT modules with N electrodes, it is shown how the interface heights in a pipe with stratified flow of oil and air can be fruitfully compared to the values of those obtained from ECT and gamma radiation meter (GRM) for improving CFD modeling. Monitored inflow conditions in this study are flow rates of air, water and oil into a pipe which can be positioned at varying inclinations to the horizontal, thus emulating the pipelines laid in subsea installations. It is found that ECT-based tomograms show most of the features seen in the GRM-based visualizations with nearly one-to-one correspondence to interface heights obtained from these two methods, albeit some anomalies at the pipe wall. However, there are some interesting features the ECT manages to capture: features which the GRM or the CFD modeling apparently do not show, possibly due to parameters not defined in the inputs to the CFD model or much slower response of the GRM. Results presented in this paper indicate that a combination of ECT and GRM and preferably with other modalities with enhanced data fusion and analysis combined with CFD modeling can help to improve the modeling, measurement and control of multiphase flow in the oil and gas industries and in the process industries
Pradeep, Chaminda; Yan, Ru; Vestøl, Sondre; Melaaen, Morten C.; Mylvaganam, Saba
2014-07-01
The electrical capacitance tomographic (ECT) approach is increasingly seen as attractive for measurement and control applications in the process industries. Recently, there is increased interest in using the tomographic details from ECT for comparing with and validating and tuning CFD models of multiphase flow. Collaboration with researchers working in the field of computational fluid dynamics (CFD) modeling of multiphase flows gives valuable information for both groups of researchers in the field of ECT and CFD. By studying the ECT tomograms of multiphase flows under carefully monitored inflow conditions of the different media and by obtaining the capacitance values, C(i, j, t) with i = 1…N, j = 1, 2,…N and i ≠ j obtained from ECT modules with N electrodes, it is shown how the interface heights in a pipe with stratified flow of oil and air can be fruitfully compared to the values of those obtained from ECT and gamma radiation meter (GRM) for improving CFD modeling. Monitored inflow conditions in this study are flow rates of air, water and oil into a pipe which can be positioned at varying inclinations to the horizontal, thus emulating the pipelines laid in subsea installations. It is found that ECT-based tomograms show most of the features seen in the GRM-based visualizations with nearly one-to-one correspondence to interface heights obtained from these two methods, albeit some anomalies at the pipe wall. However, there are some interesting features the ECT manages to capture: features which the GRM or the CFD modeling apparently do not show, possibly due to parameters not defined in the inputs to the CFD model or much slower response of the GRM. Results presented in this paper indicate that a combination of ECT and GRM and preferably with other modalities with enhanced data fusion and analysis combined with CFD modeling can help to improve the modeling, measurement and control of multiphase flow in the oil and gas industries and in the process industries
Ezzedine, S. M.
2015-12-01
Leakage to the atmosphere of a significant fraction of injected CO2 would constitute a failure of a geological CO2 storage project from a greenhouse gas mitigation perspective. We present a numerical model that simulates flow and transport of CO2 into heterogeneous subsurface systems. The model, StoTran, is a flexible numerical environment that uses state-of-the-art finite element and finite volume methods and unstructured adaptive mesh refinement scheme implemented using MPI and OpenMP protocols. Multiphase flow equations and the geomechanical equations are implicitly solved and either fully or sequentially coupled. StoTran can address inverse and forward problems under deterministic or stochastic conditions. For the current study, StoTran has been used to simulate several scenarios spanning from a homogeneous single layered reservoir to heterogeneous multi-layered systems, which including cap-rock with embedded fractures, have been simulated under different operations of CO2 injection and CO2 leakages conditions. Results show the impact of the injection and leakage rates on the time evolution of the spread of the CO2 plume, its interception of the fractured cap-rock and the risk associated with the contamination of the overlaying aquifer. Spatial and temporal moments have been calculated for different, deterministic of stochastic, subsurface physical and chemical properties. Spatial moments enable assessing the extent of the region of investigation under conditions of uncertainty. Furthermore, several leakage scenarios show the intermittence behavior and development of the CO2 plume in the subsurface; its first interception with the fractures located further far from the injection well then, at a second stage, its interception with the fracture within the immediate vicinity of the injection well. We will present a remedy to CO2 leakages from the reservoir in order to enhance a long term containment of the injected CO2. This work performed under the auspices of
Energy Technology Data Exchange (ETDEWEB)
Donna Post Guillen; Tami Grimmett; Anastasia M. Gribik; Steven P. Antal
2010-09-01
The Hybrid Energy Systems Testing (HYTEST) Laboratory is being established at the Idaho National Laboratory to develop and test hybrid energy systems with the principal objective to safeguard U.S. Energy Security by reducing dependence on foreign petroleum. A central component of the HYTEST is the slurry bubble column reactor (SBCR) in which the gas-to-liquid reactions will be performed to synthesize transportation fuels using the Fischer Tropsch (FT) process. SBCRs are cylindrical vessels in which gaseous reactants (for example, synthesis gas or syngas) is sparged into a slurry of liquid reaction products and finely dispersed catalyst particles. The catalyst particles are suspended in the slurry by the rising gas bubbles and serve to promote the chemical reaction that converts syngas to a spectrum of longer chain hydrocarbon products, which can be upgraded to gasoline, diesel or jet fuel. These SBCRs operate in the churn-turbulent flow regime which is characterized by complex hydrodynamics, coupled with reacting flow chemistry and heat transfer, that effect reactor performance. The purpose of this work is to develop a computational multiphase fluid dynamic (CMFD) model to aid in understanding the physico-chemical processes occurring in the SBCR. Our team is developing a robust methodology to couple reaction kinetics and mass transfer into a four-field model (consisting of the bulk liquid, small bubbles, large bubbles and solid catalyst particles) that includes twelve species: (1) CO reactant, (2) H2 reactant, (3) hydrocarbon product, and (4) H2O product in small bubbles, large bubbles, and the bulk fluid. Properties of the hydrocarbon product were specified by vapor liquid equilibrium calculations. The absorption and kinetic models, specifically changes in species concentrations, have been incorporated into the mass continuity equation. The reaction rate is determined based on the macrokinetic model for a cobalt catalyst developed by Yates and Satterfield [1]. The
Uncertainty quantification tools for multiphase gas-solid flow simulations using MFIX
Energy Technology Data Exchange (ETDEWEB)
Fox, Rodney O. [Iowa State Univ., Ames, IA (United States); Passalacqua, Alberto [Iowa State Univ., Ames, IA (United States)
2016-02-01
Computational fluid dynamics (CFD) has been widely studied and used in the scientific community and in the industry. Various models were proposed to solve problems in different areas. However, all models deviate from reality. Uncertainty quantification (UQ) process evaluates the overall uncertainties associated with the prediction of quantities of interest. In particular it studies the propagation of input uncertainties to the outputs of the models so that confidence intervals can be provided for the simulation results. In the present work, a non-intrusive quadrature-based uncertainty quantification (QBUQ) approach is proposed. The probability distribution function (PDF) of the system response can be then reconstructed using extended quadrature method of moments (EQMOM) and extended conditional quadrature method of moments (ECQMOM). The report first explains the theory of QBUQ approach, including methods to generate samples for problems with single or multiple uncertain input parameters, low order statistics, and required number of samples. Then methods for univariate PDF reconstruction (EQMOM) and multivariate PDF reconstruction (ECQMOM) are explained. The implementation of QBUQ approach into the open-source CFD code MFIX is discussed next. At last, QBUQ approach is demonstrated in several applications. The method is first applied to two examples: a developing flow in a channel with uncertain viscosity, and an oblique shock problem with uncertain upstream Mach number. The error in the prediction of the moment response is studied as a function of the number of samples, and the accuracy of the moments required to reconstruct the PDF of the system response is discussed. The QBUQ approach is then demonstrated by considering a bubbling fluidized bed as example application. The mean particle size is assumed to be the uncertain input parameter. The system is simulated with a standard two-fluid model with kinetic theory closures for the particulate phase implemented into
Directory of Open Access Journals (Sweden)
Massimiliano Tirone
2017-10-01
Full Text Available The complex process of melting in the Earth's interior is studied by combining a multiphase numerical flow model with the program AlphaMELTS which provides a petrological description based on thermodynamic principles. The objective is to address the fundamental question of the effect of the mantle and melt dynamics on the composition and abundance of the melt and the residual solid. The conceptual idea is based on a 1-D description of the melting process that develops along an ideal vertical column where local chemical equilibrium is assumed to apply at some level in space and time. By coupling together the transport model and the chemical thermodynamic model, the evolution of the melting process can be described in terms of melt distribution, temperature, pressure and solid and melt velocities but also variation of melt and residual solid composition and mineralogical abundance at any depth over time. In this first installment of a series of three contributions, a two-phase flow model (melt and solid assemblage is developed under the assumption of complete local equilibrium between melt and a peridotitic mantle (dynamic equilibrium melting, DEM. The solid mantle is also assumed to be completely dry. The present study addresses some but not all the potential factors affecting the melting process. The influence of permeability and viscosity of the solid matrix are considered in some detail. The essential features of the dynamic model and how it is interfaced with AlphaMELTS are clearly outlined. A detailed and explicit description of the numerical procedure should make this type of numerical models less obscure. The general observation that can be made from the outcome of several simulations carried out for this work is that the melt composition varies with depth, however the melt abundance not necessarily always increases moving upwards. When a quasi-steady state condition is achieved, that is when melt abundance does not varies significantly
International Nuclear Information System (INIS)
Fassmann-Glaser, I.
1984-01-01
A study with 25 patients was performed in order to find out whether intermittent, sequential, pneumatic leg compression is of value in the preventive management of thrombosis due to its effect on the venous flow rates. For this purpose, xenon 133 was injected into one of the foot veins and the flow rate in each case determined for the distance between instep and inguen using different compression strengths, with pressure being exerted on the ankle, calf and thigh. Increased flow rates were already measured at an average pressure value of 34.5 mmHg, while the maximum effect was achieved by exerting a pressure of 92.5 mmHg, which increased the flow rate by 366% as compared to the baseline value. The results point to a significant improvement of the venous flow rates due to intermittent, sequential, pneumatic leg compression and thus provide evidence to prove the value of this method in the prevention of hemostasis and thrombosis. (TRV) [de
Modeling turbulent compressible flows - The mass fluctuating velocity and squared density
Taulbee, D.; Vanosdol, J.
1991-01-01
This paper deals with single-point closure theory for compressible turbulent flow, including the effects of compressibility on the turbulence. In particular, the combination of the pressure dilatation and the dilatation dissipation, terms which appear on the turbulent kinetic energy equation, are modeled. Model parameters in these transport equations are determined by comparing predictions with boundary layer measurements. Finally, predictions with a k-epsilon model, including the new formulations, are presented for the compressible shear layer.
Developments in the simulation of compressible inviscid and viscous flow on supercomputers
International Nuclear Information System (INIS)
Steger, J.L.; Buning, P.G.; Tel Aviv Univ., Israel)
1985-01-01
In anticipation of future supercomputers, finite difference codes are rapidly being extended to simulate three-dimensional compressible flow about complex configurations. Some of these developments are reviewed. The importance of computational flow visualization and diagnostic methods to three-dimensional flow simulation is also briefly discussed. 46 references
Numerical Solution of Compressible Steady Flows around the RAE 2822 Airfoil
Directory of Open Access Journals (Sweden)
Kryštůfek P.
2014-03-01
Full Text Available The article presents results of a numerical solution of subsonic, transonic and supersonic flows described by the system of Navier-Stokes equations in 2D laminar compressible flows around the RAE 2822 airfoil. Authors used FVM multistage Runge-Kutta method to numerically solve the flows around the RAE 2822 airfoil.
Numerical Solution of Compressible Steady Flows around the NACA 0012 Airfoil
Kryštůfek, P.; Kozel, K.
2013-04-01
The article presents results of a numerical solution of subsonic and transonic flows described by the system of Navier-Stokes equations in 2D laminar compressible flows around the NACA 0012 airfoil. Authors used Runge-Kutta method to numerically solve the flows around the NACA 0012 airfoil.
Numerical Solution of Compressible Steady Flows around the NACA 0012 Airfoil
Directory of Open Access Journals (Sweden)
Kozel K
2013-04-01
Full Text Available The article presents results of a numerical solution of subsonic and transonic flows described by the system of Navier-Stokes equations in 2D laminar compressible flows around the NACA 0012 airfoil. Authors used Runge-Kutta method to numerically solve the flows around the NACA 0012 airfoil.
Numerical Solution of Compressible Steady Flows around the RAE 2822 Airfoil
Kryštůfek, P.; Kozel, K.
2014-03-01
The article presents results of a numerical solution of subsonic, transonic and supersonic flows described by the system of Navier-Stokes equations in 2D laminar compressible flows around the RAE 2822 airfoil. Authors used FVM multistage Runge-Kutta method to numerically solve the flows around the RAE 2822 airfoil.
Free-surface modelling technology for compressible and violent flows
CSIR Research Space (South Africa)
Heyns, Johan A
2011-06-01
Full Text Available formulation reduces the degree of numerical smearing while maintaining the interface shape. It involves combining the approaches of blended higher-resolution discretisation and adding an artificial compressive term in a manner which retains the strength...
Sakamoto, Yasuhide; Nishiwaki, Junko; Hara, Junko; Kawabe, Yoshishige; Sugai, Yuichi; Komai, Takeshi
In late years, soil contamination due to mineral oil in vacant lots of oil factory and oil field has become obvious. Measure for soil contamina tion and risk assessment are neces sary for sustainable development of industrial activity. Especially, in addition to contaminated sites, various exposure paths for human body such as well water, soil and farm crop are supposed. So it is very important to comprehend the transport phenomena of contaminated material under the environments of soil and ground water. In this study, mineral oil as c ontaminated material consisting of mu lti-component such as aliphatic and aromatic series was modeled. Then numerical mode l for transport phenomena in surface soil and aquifer was constructed. On the basis of modeling for mineral oil, our numerical model consists of three-phase (oil, water and gas) forty three-component. This numerical model becomes base program for risk assessment system on soil contamination due to mineral oil. Using this numerical model, we carried out some numerical simulation for a laboratory-scale experiment on oil-water multi-phase flow. Relative permeability that dominate flow behavior in multi-phase condition was formulated and the validity of the numerical model developed in this study was considered.
Chatterjee, Saikat; Li, Donghui; Chattopadhyay, Kinnor
2018-04-01
Multiphase flows are frequently encountered in metallurgical operations. One of the most effective ways to understand these processes is by flow modeling. The process of tundish open eye (TOE) formation involves three-phase interaction between liquid steel, slag, and argon gas. The two-phase interaction involving argon gas bubbles and liquid steel can be modeled relatively easily using the discrete phase modeling technique. However, the effect of an upper slag layer cannot be captured using this approach. The presence of an upper buoyant phase can have a major effect on the behavior of TOEs. Hence, a multiphase model, including three phases, viz. liquid steel, slag, and argon gas, in a two-strand slab caster tundish, was developed to study the formation and evolution of TOEs. The volume of fluid model was used to track the interphase between liquid steel and slag phases, while the discrete phase model was used to trace the movement of the argon gas bubbles in liquid steel. The variation in the TOE areas with different amounts of aspirated argon gas was examined in the presence of an overlying slag phase. The mathematical model predictions were compared against steel plant measurements.
International Nuclear Information System (INIS)
White, R.D.; Higgins, C.B.
1986-01-01
The authors evaluated abnormal MR imaging signal patterns in the pulmonary arteries of 22 patients with pulmonary hypertension (n = 13), pulmonary embolus (n = 4), or both (n = 5). Using multiphasic (five or six phases; 19 patients) or standard (three patients with pulmonary embolus) ECG-gated, double spin-echo techniques, they were able to differentiate between causes of such abnormal signal patterns. The pattern of slow blood flow (abnormal signal in systole with fluctuating distribution during cardiac cycle, and intensity increasing visually from first to second echo) was noted in 89% of patients with pulmonary hypertension alone or in combination with pulmonary embolism, and was characteristic of high systolic pulmonary pressures (12 of 12 patients with pressure > 80 mm Hg, vs. 3 of 5 patients with pressure 55 mm Hg vs. 5 of 7 patients with pressures <55 mm Hg). This pattern was differentiated from that of thrombus (persistent signal with fixed distribution during cardiac cycle, and little to no visible intensity change from first to second echo), which was noted in six of seven proved embolus cases. Thus, gated multiphase MR imaging shows potential for the noninvasive visualization of pulmonary embolus and the differentiation of this entity from the slow blood flow of pulmonary hypertension
Martí, Joan Daniel; Li Bassi, Gianluigi; Rigol, Montserrat; Saucedo, Lina; Ranzani, Otavio Tavares; Esperatti, Mariano; Luque, Nestor; Ferrer, Miquel; Vilaro, Jordi; Kolobow, Theodor; Torres, Antoni
2013-03-01
We investigated the effects of two different types of manual rib cage compression on expiratory flow and mucus clearance during prolonged mechanical ventilation in pigs. Prospective randomized animal study. Animal research facility, University of Barcelona, Spain. Nine healthy pigs. Pigs were tracheally intubated, sedated, paralyzed, and mechanically ventilated. The animals were prone on a surgical bed in the anti-Trendelenburg position. The experiments were carried out at approximately 60 and 80 hrs from the beginning of mechanical ventilation. Two types of manual rib cage compressions were tested: Hard and brief rib cage compressions synchronized with early expiratory phase (hard manual rib cage compression) and soft and gradual rib cage compressions applied during the late expiratory phase (soft manual rib cage compression). The interventions were randomly applied for 15min with a 15-min interval between treatments. Respiratory flow and mucus movement were assessed during the interventions. Respiratory mechanics and hemodynamics were assessed prior to and after the interventions. Peak expiratory flow increased to 60.1±7.1L/min in comparison to 51.2±4.6L/min without treatment (p < 0.0015) and 48.7±4.3L/min with soft manual rib cage compression (p = 0.0002). Similarly, mean expiratory flow increased to 28.4±5.2L/min during hard manual rib cage compression vs. 15.9±2.2 and 16.6±2.8L/min without treatment and soft manual rib cage compression, respectively (p = 0.0006). During hard manual rib cage compression, mucus moved toward the glottis (1.01 ± 2.37mm/min); conversely, mucus moved toward the lungs during no treatment and soft manual rib cage compression, -0.28 ± 0.61 and -0.15±0.95mm/min, respectively (p = 0.0283). Soft manual rib cage compression slightly worsened static lung elastance and cardiac output (p = 0.0391). Hard manual rib cage compression improved mucus clearance in animals positioned in the anti-Trendelenburg position. The technique
Rozema, W.; Kok, J. C.; Verstappen, R. W. C. P.; Veldman, A. E. P.
2014-01-01
Most simulation methods for compressible flow attain numerical stability at the cost of swamping the fine turbulent flow structures by artificial dissipation. This article demonstrates that numerical stability can also be attained by preserving conservation laws at the discrete level. A new
DEFF Research Database (Denmark)
Wildenschild, Dorthe; Porter, M.L.; Schaap, M.G.
Quantitative non-invasive imaging has evolved rapidly in the last decade, and is now being used to assess a variety of problems in vadose zone research, including unsaturated flow and transport of water and contaminants, macropore-dominated processes, soil-water-root interactions, more recent work...... on colloidal processes, and significant work on NAPL-water interactions . We are now able to use non-invasive imaging to probe processes that could not previously be quantified because of lack of opacity, resolution, or accurate techniques for quantitative measurement. This work presents an overview of recent...... advances in x-ray microtomography techniques that can generate high-resolution image-based data for (1) validation of pore-scale multi-phase flow models such as the lattice-Boltzmann technique and pore network models (with respect to fluid saturations, fluid distribution, and relationships among capillary...
DEFF Research Database (Denmark)
Voigt, Andreas Jauernik
important contact free force measurement capabilities. The third module houses the smooth annular test seals and the fourth module adds a single phase air flow supply to the test facility infrastructure. For experimental identification purposes the ability to acquire precise information of the forces...... and compressors for which reason the ability to predict the complex interaction between fluid dynamics and rotordynamics within these seals is a key aspect in the design of rotating equipment. Numerical tools offering predictive capabilities for seals subjected to multiphase flow conditions are currently being...... developed and refined, however a pronounced lack of experimental data renders benchmarking and validation impossible. This thesis focusses on documenting the design and commissioning of a test facility enabling the much needed experimental identification of rotordynamic properties for turbomachinery seals...
Buys, Gerhard M; du Plessis, Lissinda H; Marais, Andries F; Kotze, Awie F; Hamman, Josias H
2013-06-01
Chitosan is a polymer derived from chitin that is widely available at relatively low cost, but due to compression challenges it has limited application for the production of direct compression tablets. The aim of this study was to use certain process and formulation variables to improve manufacturing of tablets containing chitosan as bulking agent. Chitosan particle size and flow properties were determined, which included bulk density, tapped density, compressibility and moisture uptake. The effect of process variables (i.e. compression force, punch depth, percentage compaction in a novel double fill compression process) and formulation variables (i.e. type of glidant, citric acid, pectin, coating with Eudragit S®) on chitosan tablet performance (i.e. mass variation, tensile strength, dissolution) was investigated. Moisture content of the chitosan powder, particle size and the inclusion of glidants had a pronounced effect on its flow ability. Varying the percentage compaction during the first cycle of a double fill compression process produced chitosan tablets with more acceptable tensile strength and dissolution rate properties. The inclusion of citric acid and pectin into the formulation significantly decreased the dissolution rate of isoniazid from the tablets due to gel formation. Direct compression of chitosan powder into tablets can be significantly improved by the investigated process and formulation variables as well as applying a double fill compression process.
Solution of weakly compressible isothermal flow in landfill gas collection networks
Nec, Y.; Huculak, G.
2017-12-01
Pipe networks collecting gas in sanitary landfills operate under the regime of a weakly compressible isothermal flow of ideal gas. The effect of compressibility has been traditionally neglected in this application in favour of simplicity, thereby creating a conceptual incongruity between the flow equations and thermodynamic equation of state. Here the flow is solved by generalisation of the classic Darcy–Weisbach equation for an incompressible steady flow in a pipe to an ordinary differential equation, permitting continuous variation of density, viscosity and related fluid parameters, as well as head loss or gain due to gravity, in isothermal flow. The differential equation is solved analytically in the case of ideal gas for a single edge in the network. Thereafter the solution is used in an algorithm developed to construct the flow equations automatically for a network characterised by an incidence matrix, and determine pressure distribution, flow rates and all associated parameters therein.
Solution of weakly compressible isothermal flow in landfill gas collection networks
International Nuclear Information System (INIS)
Nec, Y; Huculak, G
2017-01-01
Pipe networks collecting gas in sanitary landfills operate under the regime of a weakly compressible isothermal flow of ideal gas. The effect of compressibility has been traditionally neglected in this application in favour of simplicity, thereby creating a conceptual incongruity between the flow equations and thermodynamic equation of state. Here the flow is solved by generalisation of the classic Darcy–Weisbach equation for an incompressible steady flow in a pipe to an ordinary differential equation, permitting continuous variation of density, viscosity and related fluid parameters, as well as head loss or gain due to gravity, in isothermal flow. The differential equation is solved analytically in the case of ideal gas for a single edge in the network. Thereafter the solution is used in an algorithm developed to construct the flow equations automatically for a network characterised by an incidence matrix, and determine pressure distribution, flow rates and all associated parameters therein. (paper)
CSIR Research Space (South Africa)
Heyns, Johan A
2013-05-01
Full Text Available This paper presents a weakly compressible volume-of-fluid formulation for modelling immiscible high density ratio two-fluid flow under low Mach number conditions. This follows findings of experimental analyses that concluded the compressibility...
A physical five-equation model for compressible two-fluid flow, and its numerical treatment
J.J. Kreeft (Jasper); B. Koren (Barry)
2009-01-01
htmlabstractA novel five-equation model for inviscid, non-heat-conducting, compressible two-fluid flow is derived, together with an appropriate numerical method. The model uses flow equations based on conservation laws and exchange laws only. The two fluids exchange momentum and energy, for which
Fazeli, Mohammadreza; Hinebaugh, James; Fishman, Zachary; Tötzke, Christian; Lehnert, Werner; Manke, Ingo; Bazylak, Aimy
2016-12-01
Understanding how compression affects the distribution of liquid water and gaseous oxygen in the polymer electrolyte membrane fuel cell gas diffusion layer (GDL) is vital for informing the design of improved porous materials for effective water management strategies. Pore networks extracted from synchrotron-based micro-computed tomography images of compressed GDLs were employed to simulate liquid water transport in GDL materials over a range of compression pressures. The oxygen transport resistance was predicted for each sample under dry and partially saturated conditions. A favorable GDL compression value for a preferred liquid water distribution and oxygen diffusion was found for Toray TGP-H-090 (10%), yet an optimum compression value was not recognized for SGL Sigracet 25BC. SGL Sigracet 25BC exhibited lower transport resistance values compared to Toray TGP-H-090, and this is attributed to the additional diffusion pathways provided by the microporous layer (MPL), an effect that is particularly significant under partially saturated conditions.
International Nuclear Information System (INIS)
Freeze, G.A.; Larson, K.W.; Davies, P.B.
1995-10-01
A long-term assessment of the Waste Isolation Pilot Plant (WIPP) repository performance must consider the impact of gas generation resulting from the corrosion and microbial degradation of the emplaced waste. A multiphase fluid flow code, TOUGH2/EOS8, was adapted to model the processes of gas generation, disposal room creep closure, and multiphase (brine and gas) fluid flow, as well as the coupling between the three processes. System response to gas generation was simulated with a single, isolated disposal room surrounded by homogeneous halite containing two anhydrite interbeds, one above and one below the room. The interbeds were assumed to have flow connections to the room through high-permeability, excavation-induced fractures. System behavior was evaluated by tracking four performance measures: (1) peak room pressure; (2) maximum brine volume in the room; (3) total mass of gas expelled from the room; and (4) the maximum gas migration distance in an interbed. Baseline simulations used current best estimates of system parameters, selected through an evaluation of available data, to predict system response to gas generation under best-estimate conditions. Sensitivity simulations quantified the effects of parameter uncertainty by evaluating the change in the performance measures in response to parameter variations. In the sensitivity simulations, a single parameter value was varied to its minimum and maximum values, representative of the extreme expected values, with all other parameters held at best-estimate values. Sensitivity simulations identified the following parameters as important to gas expulsion and migration away from a disposal room: interbed porosity; interbed permeability; gas-generation potential; halite permeability; and interbed threshold pressure. Simulations also showed that the inclusion of interbed fracturing and a disturbed rock zone had a significant impact on system performance
Energy Technology Data Exchange (ETDEWEB)
Freeze, G.A.; Larson, K.W. [INTERA Inc., Austin, TX (United States); Davies, P.B. [Sandia National Laboratories, Albuquerque, NM (United States)
1995-10-01
A long-term assessment of the Waste Isolation Pilot Plant (WIPP) repository performance must consider the impact of gas generation resulting from the corrosion and microbial degradation of the emplaced waste. A multiphase fluid flow code, TOUGH2/EOS8, was adapted to model the processes of gas generation, disposal room creep closure, and multiphase (brine and gas) fluid flow, as well as the coupling between the three processes. System response to gas generation was simulated with a single, isolated disposal room surrounded by homogeneous halite containing two anhydrite interbeds, one above and one below the room. The interbeds were assumed to have flow connections to the room through high-permeability, excavation-induced fractures. System behavior was evaluated by tracking four performance measures: (1) peak room pressure; (2) maximum brine volume in the room; (3) total mass of gas expelled from the room; and (4) the maximum gas migration distance in an interbed. Baseline simulations used current best estimates of system parameters, selected through an evaluation of available data, to predict system response to gas generation under best-estimate conditions. Sensitivity simulations quantified the effects of parameter uncertainty by evaluating the change in the performance measures in response to parameter variations. In the sensitivity simulations, a single parameter value was varied to its minimum and maximum values, representative of the extreme expected values, with all other parameters held at best-estimate values. Sensitivity simulations identified the following parameters as important to gas expulsion and migration away from a disposal room: interbed porosity; interbed permeability; gas-generation potential; halite permeability; and interbed threshold pressure. Simulations also showed that the inclusion of interbed fracturing and a disturbed rock zone had a significant impact on system performance.
International Nuclear Information System (INIS)
Asahi, Kouichi; Hori, M; Hamasaki, N; Sato, S; Nakanishi, H; Kuwatsuru, R; Sasai, K; Aoki, S
2012-01-01
It is difficult to non-invasively visualize changes in regional cerebral blood flow caused by manual compression of the carotid artery. To visualize dynamic changes in regional cerebral blood flow during and after manual compression of the carotid artery. Two healthy volunteers were recruited. Anatomic features and flow directions in the circle of Willis were evaluated with time-of-flight magnetic resonance angiography (MRA) and two-dimensional phase-contrast (2DPC) MRA, respectively. Regional cerebral blood flow was visualized with territorial arterial spin-labeling magnetic resonance imaging (TASL-MRI). TASL-MRI and 2DPC-MRA were performed in three states: at rest, during manual compression of the right carotid artery, and after decompression. In one volunteer, time-space labeling inversion pulse (Time-SLIP) MRA was performed to confirm collateral flow. During manual carotid compression, in one volunteer, the right thalamus changed to be fed only by the vertebrobasilar system, and the right basal ganglia changed to be fed by the left internal carotid artery. In the other volunteer, the right basal ganglia changed to be fed by the vertebrobasilar system. 2DPC-MRA showed that the flow direction changed in the right A1 segment of the anterior cerebral artery and the right posterior communicating artery. Perfusion patterns and flow directions recovered after decompression. Time-SLIP MRA showed pial vessels and dural collateral circulation when the right carotid artery was manually compressed. Use of TASL-MRI and 2DPC-MRA was successful for non-invasive visualization of the dynamic changes in regional cerebral blood flow during and after manual carotid compression
Energy Technology Data Exchange (ETDEWEB)
Ray A. Berry; Richard Saurel; Tamara Grimmett
2009-07-01
Typically, multiphase modeling begins with an averaged (or homogenized) system of partial differential equations (traditionally ill-posed) then discretizes this system to form a numerical scheme. Assuming that the ill-posedness problem is avoided by using a well-posed formulation such as the seven-equation model, this presents problems for the numerical approximation of non-conservative terms at discontinuities (interfaces, shocks) as well as unwieldy treatment of fluxes with seven waves. To solve interface problems without conservation errors and to avoid this questionable determination of average variables and the numerical approximation of the non-conservative terms associated with 2 velocity mixture flows we employ a new homogenization method known as the Discrete Equations Method (DEM). Contrary to conventional methods, the averaged equations for the mixture are not used, and this method directly obtains a (well-posed) discrete equation system from the single-phase system to produce a numerical scheme which accurately computes fluxes for arbitrary numbers of phases and solves non-conservative products. The method effectively uses a sequence of single phase Riemann equation solves. Phase interactions are accounted for by Riemann solvers at each interface. Flow topology can change with changing expressions for the fluxes. Non-conservative terms are correctly approximated. Some of the closure relations missing from the traditional approach are automatically obtained. Lastly, we can often times identify the continuous equation system, resulting from taking the continuous limit with weak wave assumptions, of the discrete equations. This can be very useful from a theoretical standpoint. As a first step toward implict integration of the DEM method in multidimensions, in this paper we construct a DEM model for the flow of two compressible phases in 1-D ducts of spatially varying cross-section to test this approach. To relieve time step size restrictions due to
Modelling and simulation of the compressible turbulence in supersonic shear flows
International Nuclear Information System (INIS)
Guezengar, Dominique
1997-02-01
This research thesis addresses the modelling of some specific physical problems of fluid mechanics: compressibility (issue of mixing layers), large variations of volumetric mass (boundary layers), and anisotropy (compression ramps). After a presentation of the chosen physical modelling and numerical approximation, the author pays attention to flows at the vicinity of a wall, and to boundary conditions. The next part addresses existing compressibility models and their application to the calculation of supersonic mixing layers. A critical assessment is also performed through calculations of boundary layers and of compression ramps. The next part addresses problems related to large variations of volumetric mass which are not taken by compressibility models into account. A modification is thus proposed for the diffusion term, and is tested for the case of supersonic boundary layers and of mixing layers with high density rates. Finally, anisotropy effects are addressed through the implementation of Explicit Algebraic Stress k-omega Turbulence models (EARSM), and their tests on previously studied cases [fr
Investigation of turbulence models with compressibility corrections for hypersonic boundary flows
Directory of Open Access Journals (Sweden)
Han Tang
2015-12-01
Full Text Available The applications of pressure work, pressure-dilatation, and dilatation-dissipation (Sarkar, Zeman, and Wilcox models to hypersonic boundary flows are investigated. The flat plate boundary layer flows of Mach number 5–11 and shock wave/boundary layer interactions of compression corners are simulated numerically. For the flat plate boundary layer flows, original turbulence models overestimate the heat flux with Mach number high up to 10, and compressibility corrections applied to turbulence models lead to a decrease in friction coefficients and heating rates. The pressure work and pressure-dilatation models yield the better results. Among the three dilatation-dissipation models, Sarkar and Wilcox corrections present larger deviations from the experiment measurement, while Zeman correction can achieve acceptable results. For hypersonic compression corner flows, due to the evident increase of turbulence Mach number in separation zone, compressibility corrections make the separation areas larger, thus cannot improve the accuracy of calculated results. It is unreasonable that compressibility corrections take effect in separation zone. Density-corrected model by Catris and Aupoix is suitable for shock wave/boundary layer interaction flows which can improve the simulation accuracy of the peak heating and have a little influence on separation zone.
International Nuclear Information System (INIS)
Castillo, Edward; Guerrero, Thomas; Castillo, Richard; White, Benjamin; Rojo, Javier
2012-01-01
Compressible flow based image registration operates under the assumption that the mass of the imaged material is conserved from one image to the next. Depending on how the mass conservation assumption is modeled, the performance of existing compressible flow methods is limited by factors such as image quality, noise, large magnitude voxel displacements, and computational requirements. The Least Median of Squares Filtered Compressible Flow (LFC) method introduced here is based on a localized, nonlinear least squares, compressible flow model that describes the displacement of a single voxel that lends itself to a simple grid search (block matching) optimization strategy. Spatially inaccurate grid search point matches, corresponding to erroneous local minimizers of the nonlinear compressible flow model, are removed by a novel filtering approach based on least median of squares fitting and the forward search outlier detection method. The spatial accuracy of the method is measured using ten thoracic CT image sets and large samples of expert determined landmarks (available at www.dir-lab.com). The LFC method produces an average error within the intra-observer error on eight of the ten cases, indicating that the method is capable of achieving a high spatial accuracy for thoracic CT registration. (paper)
Kolarova, Julieta D; Ayoub, Iyad M; Gazmuri, Raúl J
2005-06-01
When given during closed-chest resuscitation, cariporide (4-isopropyl-methylsulfonylbenzoyl-guanidine methanesulfonate; a selective inhibitor of the Na(+)/H(+) exchanger isoform-1) enables generation of viable perfusion pressures with less depth of compression. We hypothesized that this effect results from greater blood flows generated for a given depth of compression. Two series of 14 rats each underwent 10 min of untreated ventricular fibrillation followed by 8 min of chest compression before defibrillation was attempted. Compression depth was adjusted to maintain an aortic diastolic pressure (ADP) between 26 and 28 mmHg in the first series and between 36 and 38 mmHg in the second series. Within each series, rats were randomized to receive cariporide (3 mg/kg) or NaCl (0.9%; control) before chest compression was started. Blood flow was measured using 15-mum fluorescent microspheres. Less depth of compression was required to maintain the target ADP when cariporide was present in both series 1 (13.6 +/- 1.2 vs. 16.6 +/- 1.2 mm; P < 0.001) and series 2 (15.3 +/- 1.0 vs. 18.9 +/- 1.5 mm; P < 0.001). Despite less compression depth, the cardiac index in cariporide-treated rats was comparable to control rats in series 1 (11.1 +/- 0.7 vs. 11.3 +/- 1.4 ml.min(-1).kg(-1); P = not significant) but higher in series 2 (15.5 +/- 2.3 vs. 9.9 +/- 1.4 ml.min(-1).kg(-1); P < 0.05). Increases in compression depth (from series 1 to series 2) increased myocardial, cerebral, and adrenal blood flow in cariporide-treated rats. We conclude that cariporide enhances the efficacy of closed-chest resuscitation by leftward shift of the flow-depth relationship.
Khatami, F.; van der Weide, Edwin Theodorus Antonius; Hoeijmakers, Hendrik Willem Marie
2015-01-01
In this paper a numerical simulation of unsteady sheet cavitation is presented as it occurs on an NACA-0015 hydrofoil. The computational approach is based on the Euler equations for unsteady compressible flow, using an equilibrium cavitation model of Schnerr, Schmidt, and Saurel. It was found that
Numerical Solution of Inviscid Compressible Steady Flows around the RAE 2822 Airfoil
Directory of Open Access Journals (Sweden)
Kryštůfek P.
2015-01-01
Full Text Available The article presents results of a numerical solution of subsonic, transonic and supersonic flows described by the system of Euler equations in 2D compressible flows around the RAE 2822 airfoil. Authors used FVM multistage Runge-Kutta method to numerically solve the flows around the RAE 2822 airfoil. The results are compared with the solution using the software Ansys Fluent 15.0.7.
Numerical Solution of Inviscid Compressible Steady Flows around the RAE 2822 Airfoil
Kryštůfek, P.; Kozel, K.
2015-05-01
The article presents results of a numerical solution of subsonic, transonic and supersonic flows described by the system of Euler equations in 2D compressible flows around the RAE 2822 airfoil. Authors used FVM multistage Runge-Kutta method to numerically solve the flows around the RAE 2822 airfoil. The results are compared with the solution using the software Ansys Fluent 15.0.7.
Directory of Open Access Journals (Sweden)
Vladimir Alexis Neri Quezadas
2017-11-01
Full Text Available In a three stages compression module at an offshore installation was detected a sudden decrease in managed flow decreasing from 108 to 87 million standard cubic feet by day MMSCFD. Thermodynamic analysis on performance of three stages of compression axial compressor and power turbine was carried out. Each compression stage were found operating efficiently according to ranges indicated by manufacturer. However a power loss about 1200 hp was detected in turbine so that the problem between the power turbine and the main gearbox MG was focused. Boroscopic and thermographic inspections were carried out detecting hot spots and contaminants deposition. Upon disassembling MG lubrication ducts were detected partially obstructed by silicone.
Zhang, Y.; Zhang, G.; Lu, P.; Hu, B.; Zhu, C.
2017-12-01
The extent of CO2 mineralization after CO2 injection into deep saline aquifers is a result of the complex coupling of multiphase fluid flow, mass transport, and brine-mineral reactions. The effects of dissolution rate laws and groundwater flow on the long-term fate of CO2 have been seriously overlooked. To investigate these effects, we conducted multiphase (CO2 and brine) coupled reactive transport modeling of CO2 storage in two sandy formations (Utsira Sand, Norway1,2 and Mt. Simon formation, USA 3) using ToughReact and simulated a series of scenarios. The results indicated that: (1) Different dissolution rate laws for feldspars can significantly affect the amount of CO2 mineralization. Increased feldspar dissolution will promote CO2 mineral trapping through the coupling between feldspar dissolution and carbonate mineral precipitation at raised pH. The predicted amount of CO2 mineral trapping when using the principle of detailed balancing-based rate law for feldspar dissolution is about twice as much as that when using sigmoidal rate laws in the literature. (2) Mineral trapping is twice as much when regional groundwater flow is taken into consideration in long-term simulations (e.g., 10,000 years) whereas most modeling studies neglected the regional groundwater flow back and effectively simulated a batch reactor process. Under the influence of regional groundwater flow, the fresh brine from upstream continuously dissolves CO2 at the tail of CO2 plume, generating a large acidified area where large amount of CO2 mineralization takes place. The upstream replenishment of groundwater results in ˜22% mineral trapping at year 10,000, compared to ˜4% when this effect is ignored. Refs: 1Zhang, G., Lu, P., Wei, X., Zhu, C. (2016). Impacts of Mineral Reaction Kinetics and Regional Groundwater Flow on Long-Term CO2 Fate at Sleipner. Energy & Fuels, 30(5), 4159-4180. 2Zhu, C., Zhang, G., Lu, P., Meng, L., Ji, X. (2015). Benchmark modeling of the Sleipner CO2 plume
Multiphase-flow numerical modeling of the 18 May 1980 lateral blast at Mount St. Helens, USA
Ongaro, T.E.; Widiwijayanti, C.; Clarke, A.B.; Voight, B.; Neri, A.
2011-01-01
Volcanic lateral blasts are among the most spectacular and devastating of natural phenomena, but their dynamics are still poorly understood. Here we investigate the best documented and most controversial blast at Mount St. Helens (Washington State, United States), on 18 May 1980. By means of three-dimensional multiphase numerical simulations we demonstrate that the blast front propagation, fi nal runout, and damage can be explained by the emplacement of an unsteady, stratifi ed pyroclastic density current, controlled by gravity and terrain morphology. Such an interpretation is quantitatively supported by large-scale observations at Mount St. Helens and will infl uence the defi nition and predictive mapping of hazards on blast-dangerous volcanoes worldwide. ?? 2011 Geological Society of America.
Li, Yaofa; Kazemifar, Farzan; Blois, Gianluca; Christensen, Kenneth; Kenneth Christensen, Notre Dame Team
2017-11-01
Multiphase flow in porous media is relevant to a range of applications in the energy and environmental sectors. Recently, the interest has been renewed by geological storage of CO2 within saline aquifers. Central to this goal is predicting the fidelity of candidate sites pre-injection of CO2 and its post-injection migration. Moreover, local pressure buildup may cause micro-seismic events, which could prove disastrous, and possibly compromise seal integrity. Evidence shows that the large-scale events are coupled with pore-scale phenomena, necessitating the understanding of pore-scale stress, strain, and flow processes and their representation in large-scale modeling. To this end, the pore-scale flow of water and supercritical CO2 is investigated under reservoir-relevant conditions over a range of wettability conditions in 2D heterogeneous micromodels that reflect the complexity of real sandstone. High-speed fluorescent microscopy, complemented by a fast differential pressure transmitter, allows for simultaneous measurement of the flow field within and the instantaneous pressure drop across the micromodels. A flexible micromodel is also designed, to be used in conjunction with the micro-PIV technique, enabling the quantification of coupled solid-liquid interactions. This work was supported as part of the GSCO2, an EFRC funded by the US DOE, Office of Science, and partially supported by WPI-I2CNER.
Interaction of high-speed compressible viscous flow and structure by adaptive finite element method
International Nuclear Information System (INIS)
Limtrakarn, Wiroj; Dechaumphai, Pramote
2004-01-01
Interaction behaviors of high-speed compressible viscous flow and thermal-structural response of structure are presented. The compressible viscous laminar flow behavior based on the Navier-Stokes equations is predicted by using an adaptive cell-centered finite-element method. The energy equation and the quasi-static structural equations for aerodynamically heated structures are solved by applying the Galerkin finite-element method. The finite-element formulation and computational procedure are described. The performance of the combined method is evaluated by solving Mach 4 flow past a flat plate and comparing with the solution from the finite different method. To demonstrate their interaction, the high-speed flow, structural heat transfer, and deformation phenomena are studied by applying the present method to Mach 10 flow past a flat plate
International Nuclear Information System (INIS)
Costa, Gustavo Koury
2004-11-01
Although incompressible fluid flows can be regarded as a particular case of a general problem, numerical methods and the mathematical formulation aimed to solve compressible and incompressible flows have their own peculiarities, in such a way, that it is generally not possible to attain both regimes with a single approach. In this work, we start from a typically compressible formulation, slightly modified to make use of pressure variables and, through augmenting the stabilising parameters, we end up with a simplified model which is able to deal with a wide range of flow regimes, from supersonic to low speed gas flows. The resulting methodology is flexible enough to allow for the simulation of liquid flows as well. Examples using conservative and pressure variables are shown and the results are compared to those published in the literature, in order to validate the method. (author)
An Improved Ghost-cell Immersed Boundary Method for Compressible Inviscid Flow Simulations
Chi, Cheng
2015-05-01
This study presents an improved ghost-cell immersed boundary approach to represent a solid body in compressible flow simulations. In contrast to the commonly used approaches, in the present work ghost cells are mirrored through the boundary described using a level-set method to farther image points, incorporating a higher-order extra/interpolation scheme for the ghost cell values. In addition, a shock sensor is in- troduced to deal with image points near the discontinuities in the flow field. Adaptive mesh refinement (AMR) is used to improve the representation of the geometry efficiently. The improved ghost-cell method is validated against five test cases: (a) double Mach reflections on a ramp, (b) supersonic flows in a wind tunnel with a forward- facing step, (c) supersonic flows over a circular cylinder, (d) smooth Prandtl-Meyer expansion flows, and (e) steady shock-induced combustion over a wedge. It is demonstrated that the improved ghost-cell method can reach the accuracy of second order in L1 norm and higher than first order in L∞ norm. Direct comparisons against the cut-cell method demonstrate that the improved ghost-cell method is almost equally accurate with better efficiency for boundary representation in high-fidelity compressible flow simulations. Implementation of the improved ghost-cell method in reacting Euler flows further validates its general applicability for compressible flow simulations.
Development of an app for compressible flow “App4Comp”
Adam Alberdi, Andrés; Gámez Montero, Pedro Javier
2015-01-01
In this paper is discussed the development and operation of a new Android App made through Google’s platform App Inventor 2. This App is focused on solving classic problems related to compressible flow, dealing with the typical cases seen in the subject of Fluid Mechanics of a degree in Aeronautics. It is downloadable from [1], or through the QR code at the end of this paper. The main objective of this project was to bring in a new, useful app about compressible flow to the market, but als...
On heat transfer of weakly compressible power-law flows
Directory of Open Access Journals (Sweden)
Li Botong
2017-01-01
Full Text Available This paper completes a numerical research on steady momentum and heat transfer in power-law fluids in a channel. Weakly compressible laminar fluids are studied with no slip at the walls and uniform wall temperatures. The full governing equations are solved by continuous finite element method. Three thermal conductivity models are adopted in this paper, that is, constant thermal conductivity model, thermal conductivity varying as a function of temperature gradient, and a modified temperature-gradient-dependent thermal conductivity model. The results are compared with each other and the physical characteristics for values of parameters are also discussed in details. It is shown that the velocity curve from the solution becomes straight at higher power-law index. The effects of Reynolds numbers on the dilatant fluid and the pseudo-plastic look similar to each other and their trends can be easily predicted. Furthermore, for different models, the temperature curves also present pseudo-plastic and dilatant properties.
Construction and analysis of compressible flow calculation algorithms
International Nuclear Information System (INIS)
Desideri, Jean-Antoine
1993-01-01
The aim of this study is to give a theoretical rationale of a 'paradox' related to the behavior at the stagnation point of some numerical solutions obtained by conventional methods for Eulerian non-equilibrium flows. This 'paradox' concerns the relationship between the solutions given by equilibrium and non-equilibrium models and was raised by several experts during the 'Workshop on Hypersonic Flows for Reentry Problems, Part 1. Antibes 1990'. In the first part, we show that equilibrium conditions are reached at the stagnation point and we analyse the sensitivity of these equilibrium conditions to the flow variables. In the second part, we develop an analysis of the behavior of the mathematical solution to an Eulerian non-equilibrium flow in the vicinity of the stagnation point, which gives an explanation to the described 'paradox'. Then, a numerical procedure, integrating the species convection equations projected on the stagnation point streamline in a Lagrangian time approach, gives a numerical support to the theoretical predictions. We also propose two numerical integration procedures, that allow us to recompute, starting from the equilibrium conditions at the stagnation point, the flow characteristics at the body. The validity limits of these procedures are discussed and the results obtained for a Workshop test-case are compared with the results given by several contributors. Finally, we survey briefly the influence of the local behavior of the solution on the coupling technique to a boundary layer calculation. (author) [fr
Control volume based modelling of compressible flow in reciprocating machines
DEFF Research Database (Denmark)
Andersen, Stig Kildegård; Thomsen, Per Grove; Carlsen, Henrik
2004-01-01
conservation laws for mass, energy, and momentum applied to a staggered mesh consisting of two overlapping strings of control volumes. Loss mechanisms can be included directly in the governing equations of models by including them as terms in the conservation laws. Heat transfer, flow friction......, and multidimensional effects must be calculated using empirical correlations; correlations for steady state flow can be used as an approximation. A transformation that assumes ideal gas is presented for transforming equations for masses and energies in control volumes into the corresponding pressures and temperatures...
Numerical modelling of compressible viscous flow in turbine cascades
Louda, P.; Kozel, K.; Příhoda, J.
2014-03-01
The work deals with mathematical models of turbulent flow through turbine cascade in 2D and 3D. It is based on the Favre-averaged Navier-Stokes equations with SST or EARSM turbulence models. A two-equation model of transition to turbulence is considered too. The solution is obtained by implicit AUSM finite volume method. The 2D and 3D results are shown flow through the SE1050 cascade including simulation of a range of off-design angles of attack.
International Nuclear Information System (INIS)
Zhou Jianhua; Zhang Yuwen; Chen, J.K.
2007-01-01
In this study, a numerical model is developed to investigate the coupled compressible gas flow and heat transfer in a microchannel surrounded by solid media. To accommodate the varying flow cross-section, the compressible gas flow model is established in a non-orthogonal curvilinear coordinate system. An iterative numerical procedure is employed to solve the coupled heat transfer and gas flow equations. The computer code for the compressible gas flow is first validated against two test problems, and then extended by including the heat conduction in the solid media. The effect of the inlet Mach number on the Nusselt number is examined. It is found that the pressure difference from the pyrolysis front to the heated surface is induced essentially by the gas addition from the channel wall, instead from the pyrolysis front. The necessity of accounting for the gas compressibility is clearly demonstrated when severe heating is applied. The pressure distribution obtained along the channel axial direction is useful for further structural analysis of composite materials
A blended pressure/density based method for the computation of incompressible and compressible flows
Rossow, C.-C.
2003-03-01
An alternative method to low speed preconditioning for the computation of nearly incompressible flows with compressible methods is developed. For this approach the leading terms of the flux difference splitting (FDS) approximate Riemann solver are analyzed in the incompressible limit. In combination with the requirement of the velocity field to be divergence-free, an elliptic equation to solve for a pressure correction to enforce the divergence-free velocity field on the discrete level is derived. The pressure correction equation established is shown to be equivalent to classical methods for incompressible flows. In order to allow the computation of flows at all speeds, a blending technique for the transition from the incompressible, pressure based formulation to the compressible, density based formulation is established. It is found necessary to use preconditioning with this blending technique to account for a remaining "compressible" contribution in the incompressible limit, and a suitable matrix directly applicable to conservative residuals is derived. Thus, a coherent framework is established to cover the discretization of both incompressible and compressible flows. Compared with standard preconditioning techniques, the blended pressure/density based approach showed improved robustness for high lift flows close to separation.
Yayama, Takafumi; Kobayashi, Shigeru; Nakanishi, Yoshitaka; Uchida, Kenzo; Kokubo, Yasuo; Miyazaki, Tsuyoshi; Takeno, Kenichi; Awara, Kosuke; Mwaka, Erisa S; Iwamoto, Yukihide; Baba, Hisatoshi
2010-04-01
Entrapment neuropathy is a frequent clinical problem that can be caused by, among other factors, mechanical compression; however, exactly how a compressive force affects the peripheral nerves remains poorly understood. In this study, using a rabbit model of sciatic nerve injury (n=12), we evaluated the time-course of changes in intraneural blood flow, compound nerve action potentials, and functioning of the blood-nerve barrier during graded mechanical compression. Nerve injury was applied using a compressor equipped with a custom-made pressure transducer. Cessation of intraneural blood flow was noted at a mean compressive force of 0.457+/-0.022 N (+/-SEM), and the compound action potential became zero at 0.486+/-0.031 N. Marked extravasation of Evans blue albumin was noted after 20 min of intraneural ischemia. The functional changes induced by compression are likely due to intraneural edema, which could subsequently result in impairment of nerve function. These changes may be critical factors in the development of symptoms associated with nerve compression. (c) 2009 Elsevier Ltd. All rights reserved.
Numerical solver for compressible two-fluid flow
J. Naber (Jorick)
2005-01-01
textabstractThis report treats the development of a numerical solver for the simulation of flows of two non-mixing fluids described by the two-dimensional Euler equations. A level-set equation in conservative form describes the interface. After each time step the deformed level-set function is
Compressible Turbulent Flow Numerical Simulations of Tip Vortex Cavitation
Khatami, F.; van der Weide, Edwin Theodorus Antonius; Hoeijmakers, Hendrik Willem Marie
2015-01-01
For an elliptic Arndt’s hydrofoil numerical simulations of vortex cavitation are presented. An equilibrium cavitation model is employed. This single-fluid model assumes local thermodynamic and mechanical equilibrium in the mixture region of the flow, is employed. Furthermore, for characterizing the
Kari, Fabian A; Kocher, Nadja; Beyersdorf, Friedhelm; Tscheuschler, Anke; Meffert, Philipp; Rylski, Bartosz; Siepe, Matthias; Russe, Maximilian F; Hope, Michael D
2015-05-01
The impact of specific blood flow patterns within ascending aortic and/or aortic root aneurysms on aortic morphology is unknown. We investigated the interrelation of ascending aortic flow compression/peripheralization and aneurysm morphology with respect to sinotubuar junction (STJ) definition. Thirty-one patients (aortic root/ascending aortic aneurysm >45 mm) underwent flow-sensitive 4D magnetic resonance thoracic aortic flow measurement at 3 Tesla (Siemens, Germany) at two different institutions (Freiburg, Germany, and San Francisco, CA, USA). Time-resolved image data post-processing and visualization of mid-systolic, mid-ascending aortic flow were performed using local vector fields. The Flow Compression Index (FCI) was calculated individually as a fraction of the area of high-velocity mid-systolic flow over the complete cross-sectional ascending aortic area. According to aortic aneurysm morphology, patients were grouped as (i) small root, eccentric ascending aortic aneurysm (STJ definition) and (ii) enlarged aortic root, non-eccentric ascending aortic aneurysm with diffuse root and tubular enlargement. The mean FCI over all patients was 0.47 ± 0.5 (0.37-0.99). High levels of flow compression/peripheralization (FCI 0.8) occurred more often in Group B (n = 20). The FCI was 0.48 ± 0.05 in Group A and 0.78 ± 0.14 in Group B (P valve (P = 0.6) and type of valve dysfunction (P = 0.22 for aortic stenosis) was not found to be different between groups. Irrespective of aortic valve morphology and function, ascending aortic blood flow patterns are linked to distinct patterns of ascending aortic aneurysm morphology. Implementation of quantitative local blood flow analyses might help to improve aneurysm risk stratification in the future. © The Author 2015. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Specht, O.; Fiedler, O. [Rostock Univ. (Germany). Fachbereich Elektrotechnik; Skerl, O.
1997-12-01
In many areas of technology and in industry, there is an increasing requirement for a flexible, non-invasive measurement technique for flow speeds and through flows. The ultrasonic clamp-on measurement technique can fulfil these requirements and is being used to an increasing extent. The application of this technique only presupposes the acoustic transparency of the pipe wall, which is the case for most materials, such as metals, plastics and glass. The ultrasonic running time process is preferred to the Doppler process for mainly one-phase fluids. Due to its working principle, the ultrasonic Doppler process depends on multi-phase fluids, because it uses the frequency displacement of the sound waves backscattered at the phase boundaries as the measurement parameter for the speed of flow. [Deutsch] In vielen Bereichen der Technik und in der Industrie besteht zunehmend die Forderung nach einer flexiblen, nichtinvasiven Messtechnik fuer Stroemungsgeschwindigkeiten und Durchfluesse. Die Ultraschall-Clamp-On-Messtechnik kann diese Anforderungen erfuellen und wird in wachsendem Umfang eingesetzt. Die Anwendung dieser Technik setzt nur die akustische Transparenz der Rohrwand voraus, was fuer die meisten Materialien wie Metalle, Kunststoffe und Glas der Fall ist. Bei ueberwiegend einphasigen Fluiden wird das Ultraschall-Laufzeit-Verfahren gegenueber dem Doppler-Verfahren bevorzugt. Das Ultraschall-Doppler-Verfahren ist nach seinem Wirkprinzip auf mehrphasige Fluide angewiesen, denn es nutzt die Frequenzverschiebung der an den Phasengrenzen rueckgestreuten Schallwellen als Messgroesse fuer die Stroemungsgeschwindigkeit. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Pinkerton, Gary Wayne [Univ. of Illinois, Urbana-Champaign, IL (United States)
1993-01-01
The purpose of this study is to find aluminum alloys that are effective for use as wire vacuum seals in the 800MeV particle accelerator located at the Louis Anderson Meson Physics Facility (LAMPF) in Los Alamos, NM. Three alloys, Al 1100, Al 3003, and Al 6061, are investigated under uniaxial compression to determine stresses for a given height reduction from 0 to 70 percent, and to find plastic flow and surface interaction effects. Right-circular cylindrical specimens are compressed on-end (cylindrically) and radially (for modeling as compressed wire). Aluminum 1100 and 3003 alloys are compared for length to diameter ratios of 1 and 2 for both compression types, and are then compared to results of radial compression of annealed small diameter Al 1100 wire currently used at LAMPE. The specimens are also compressed between three different platen surfaces, polished steel, etched steel, and aluminum 6061-T6, to determine effects of friction. The Al 3003 alloy exhibits 20 to 25% lower stresses at all height reductions than Al 1100 for both cylindrical and radial compression.
International Nuclear Information System (INIS)
Pinkerton, G.W.
1993-01-01
The purpose of this study is to find aluminum alloys that are effective for use as wire vacuum seals in the 800MeV particle accelerator located at the Louis Anderson Meson Physics Facility (LAMPF) in Los Alamos, NM. Three alloys, Al 1100, Al 3003, and Al 6061, are investigated under uniaxial compression to determine stresses for a given height reduction from 0 to 70 percent, and to find plastic flow and surface interaction effects. Right-circular cylindrical specimens are compressed on-end (cylindrically) and radially (for modeling as compressed wire). Aluminum 1100 and 3003 alloys are compared for length to diameter ratios of 1 and 2 for both compression types, and are then compared to results of radial compression of annealed small diameter Al 1100 wire currently used at LAMPE. The specimens are also compressed between three different platen surfaces, polished steel, etched steel, and aluminum 6061-T6, to determine effects of friction. The Al 3003 alloy exhibits 20 to 25% lower stresses at all height reductions than Al 1100 for both cylindrical and radial compression
Hamamoto, Yuichiro; Ogata, Tadanori; Morino, Tadao; Hino, Masayuki; Yamamoto, Haruyasu
2007-08-15
An in vivo study to measure rat spinal cord blood flow in real-time at the site of compression using a newly developed device. To evaluate the change in thoracic spinal cord blood flow by compression force and to clarify the association between blood flow recovery and motor deficiency after a spinal cord compression injury. Until now, no real-time measurement of spinal cord blood flow at the site of compression has been conducted. In addition, it has not been clearly determined whether blood flow recovery is related to motor function after a spinal cord injury. Our blood flow measurement system was a combination of a noncontact type laser Doppler system and a spinal cord compression device. The rat thoracic spinal cord was exposed at the 11th vertebra and spinal cord blood flow at the site of compression was continuously measured before, during, and after the compression. The functioning of the animal's hind-limbs was evaluated by the Basso, Beattie and Bresnahan scoring scale and the frequency of voluntary standing. Histologic changes such as permeability of blood-spinal cord barrier, microglia proliferation, and apoptotic cell death were examined in compressed spinal cord tissue. The spinal blood flow decreased on each increase in the compression force. After applying a 5-g weight, the blood flow decreased to compression), while no significant difference was observed between the 20-minute ischemia group and the sham group. In the 20-minute ischemia group, the rats whose spinal cord blood flow recovery was incomplete showed significant motor function loss compared with rats that completely recovered blood flow. Extensive breakdown of blood-spinal cord barrier integrity and the following microglia proliferation and apoptotic cell death were detected in the 40-minute complete ischemia group. Duration of ischemia/compression and blood flow recovery of the spinal cord are important factors in the recovery of motor function after a spinal cord injury.
Spectral Element Method for the Simulation of Unsteady Compressible Flows
Diosady, Laslo Tibor; Murman, Scott M.
2013-01-01
This work uses a discontinuous-Galerkin spectral-element method (DGSEM) to solve the compressible Navier-Stokes equations [1{3]. The inviscid ux is computed using the approximate Riemann solver of Roe [4]. The viscous fluxes are computed using the second form of Bassi and Rebay (BR2) [5] in a manner consistent with the spectral-element approximation. The method of lines with the classical 4th-order explicit Runge-Kutta scheme is used for time integration. Results for polynomial orders up to p = 15 (16th order) are presented. The code is parallelized using the Message Passing Interface (MPI). The computations presented in this work are performed using the Sandy Bridge nodes of the NASA Pleiades supercomputer at NASA Ames Research Center. Each Sandy Bridge node consists of 2 eight-core Intel Xeon E5-2670 processors with a clock speed of 2.6Ghz and 2GB per core memory. On a Sandy Bridge node the Tau Benchmark [6] runs in a time of 7.6s.
Symmetries of the Euler compressible flow equations for general equation of state
Energy Technology Data Exchange (ETDEWEB)
Boyd, Zachary M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Ramsey, Scott D. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Baty, Roy S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2015-10-15
The Euler compressible flow equations exhibit different Lie symmetries depending on the equation of state (EOS) of the medium in which the flow occurs. This means that, in general, different types of similarity solution will be available in different flow media. We present a comprehensive classification of all EOS’s to which the Euler equations apply, based on the Lie symmetries admitted by the corresponding flow equations, restricting to the case of 1-D planar, cylindrical, or spherical geometry. The results are conveniently summarized in tables. This analysis also clarifies past work by Axford and Ovsiannikov on symmetry classification.
Symmetries of the Euler compressible flow equations for general equation of state
International Nuclear Information System (INIS)
Boyd, Zachary M.; Ramsey, Scott D.; Baty, Roy S.
2015-01-01
The Euler compressible flow equations exhibit different Lie symmetries depending on the equation of state (EOS) of the medium in which the flow occurs. This means that, in general, different types of similarity solution will be available in different flow media. We present a comprehensive classification of all EOS's to which the Euler equations apply, based on the Lie symmetries admitted by the corresponding flow equations, restricting to the case of 1-D planar, cylindrical, or spherical geometry. The results are conveniently summarized in tables. This analysis also clarifies past work by Axford and Ovsiannikov on symmetry classification.
Ziaei-Rad, Masoud; Nouri-Broujerdi, Ali
2008-12-01
In this paper, the compressible gas flow through a pipe subjected to wall heat flux in unsteady condition in the entrance region is investigated numerically. The coupled conservation equations governing turbulent compressible viscous flow in the developing region of a pipe are solved numerically under different thermal boundary conditions. The numerical procedure is a finite-volume-based finite-element method applied to unstructured grids. The convection terms are discretized by the well-defined Roe method, whereas the diffusion terms are discretized by a Galerkin finite-element formulation. The temporal terms are evaluated based on an explicit fourth-order Runge-Kutta scheme. The effect of different thermal conditions on the pressure loss of unsteady flow is investigated. The results show that increase in the inflow temperature or pipe-wall heat flux increases the pressure drop or decreases the mass flow rate in the pipe.
Scalar conservation and boundedness in simulations of compressible flow
Subbareddy, Pramod K.; Kartha, Anand; Candler, Graham V.
2017-11-01
With the proper combination of high-order, low-dissipation numerical methods, physics-based subgrid-scale models, and boundary conditions it is becoming possible to simulate many combustion flows at relevant conditions. However, non-premixed flows are a particular challenge because the thickness of the fuel/oxidizer interface scales inversely with Reynolds number. Sharp interfaces can also be present in the initial or boundary conditions. When higher-order numerical methods are used, there are often aphysical undershoots and overshoots in the scalar variables (e.g. passive scalars, species mass fractions or progress variable). These numerical issues are especially prominent when low-dissipation methods are used, since sharp jumps in flow variables are not always coincident with regions of strong variation in the scalar fields: consequently, special detection mechanisms and dissipative fluxes are needed. Most numerical methods diffuse the interface, resulting in artificial mixing and spurious reactions. In this paper, we propose a numerical method that mitigates this issue. We present methods for passive and active scalars, and demonstrate their effectiveness with several examples.
DEFF Research Database (Denmark)
Andersen, Stig Kildegård; Carlsen, Henrik; Thomsen, Per Grove
2006-01-01
We present an approach for modelling unsteady, primarily one-dimensional, compressible flow. The conservation laws for mass, energy, and momentum are applied to a staggered mesh of control volumes and loss mechanisms are included directly as extra terms. Heat transfer, flow friction......, and multidimensional effects are calculated using empirical correlations. Transformations of the conservation equations into new variables, artificial dissipation for dissipating acoustic phenomena, and an asymmetric interpolation method for minimising numerical diffusion and non physical temperature oscillations...
Applications of Taylor-Galerkin finite element method to compressible internal flow problems
Sohn, Jeong L.; Kim, Yongmo; Chung, T. J.
1989-01-01
A two-step Taylor-Galerkin finite element method with Lapidus' artificial viscosity scheme is applied to several test cases for internal compressible inviscid flow problems. Investigations for the effect of supersonic/subsonic inlet and outlet boundary conditions on computational results are particularly emphasized.
Simulation techniques for spatially evolving instabilities in compressible flow over a flat plate
Wasistho, B.; Geurts, Bernardus J.; Kuerten, Johannes G.M.
1997-01-01
In this paper we present numerical techniques suitable for a direct numerical simulation in the spatial setting. We demonstrate the application to the simulation of compressible flat plate flow instabilities. We compare second and fourth order accurate spatial discretization schemes in combination
SU2 : The Open-Source Software for Non-ideal Compressible Flows
Pini, M.; Vitale, S.; Colonna di Paliano, Piero; Gori, G; Guardone, A.M.A.; Economon, TD; Alonso, J; Palacios, F
2017-01-01
The capabilities of the open-source SU2 software suite for the numerical simulation of viscous flows over unstructured grid are extended to non-ideal compressible-fluid dynamics (NICFD). A built-in thermodynamic library is incorporated to account for the non-ideal thermodynamic characteristics of
Compressible fluid flow through rocks of variable permeability
International Nuclear Information System (INIS)
Lin, W.
1977-01-01
The effectiveness of course-grained igneous rocks as shelters for burying radioactive waste can be assessed by determining the rock permeabilities at their in situ pressures and stresses. Analytical and numerical methods were used to solve differential equations of one-dimensional fluid flow through rocks with permeabilities from 10 4 to 1 nD. In these calculations, upstream and downstream reservoir volumes of 5, 50, and 500 cm 3 were used. The optimal size combinations of the two reservoirs were determined for measurements of permeability, stress, strain, acoustic velocity, and electrical conductivity on low-porosity, coarse-grained igneous rocks
Muñoz-Cobo, José Luis; Chiva, Sergio; Méndez, Santos; Monrós, Guillem; Escrivá, Alberto; Cuadros, José Luis
2017-05-10
This paper describes all the procedures and methods currently used at UPV (Universitat Politécnica de Valencia) and UJI (University Jaume I) for the development and use of sensors for multi-phase flow analysis in vertical pipes. This paper also describes the methods that we use to obtain the values of the two-phase flow magnitudes from the sensor signals and the validation and cross-verification methods developed to check the consistency of the results obtained for these magnitudes with the sensors. First, we provide information about the procedures used to build the multi-sensor conductivity probes and some of the tests performed with different materials to avoid sensor degradation issues. In addition, we provide information about the characteristics of the electric circuits that feed the sensors. Then the data acquisition of the conductivity probe, the signal conditioning and the data processing including the device that have been designed to automatize all the measurement process of moving the sensors inside the channels by means of stepper electric motors controlled by computer are shown in operation. Then, we explain the methods used for bubble identification and categorization. Finally, we describe the methodology used to obtain the two-phase flow information from the sensor signals. This includes the following items: void fraction, gas velocity, Sauter mean diameter and interfacial area concentration. The last part of this paper is devoted to the conductance probes developed for the annular flow analysis, which includes the analysis of the interfacial waves produced in annular flow and that requires a different type of sensor.
International Nuclear Information System (INIS)
Cao, Yan Fei; Chen, Yun; Li, Dian Zhong
2016-01-01
Recent experimental dissections of steel ingots and multi-scale simulations have led to the discovery of a potential driving force for channel segregation: the flotation of oxide-based inclusion (D. Li et al., Nat. Commun. 5:5572 (2014)). Further experimental analysis and numerical modeling are necessary to clarify this mechanism in detail. In this work, the inclusions in a carbon steel ingot that exhibits severe channel segregations were characterized by the 3D X-ray microtomography, which revealed a significant enrichment and growth of inclusions in the channels. Based on above microtomography characterization, a 2D macrosegregation model encompassing the inclusion flotation was established. In the model, the motions of solid inclusions and liquid were described using the multi-phase flow scheme within the Euler-Lagrange framework. The benchmark simulations showed that sufficient inclusion populations with appropriate sizes are capable of altering the local flow patterns and destabilize the mushy zone, initiating the subsequent channel segregation. The continuous interplay between melt convection, inclusion flotation and solidification eventually causes the formation of macroscale channel. The predicted sizes and volume fraction of inclusions that are able to trigger the channel segregation effectively are consistent with the data obtained via microtomography characterization. The macrosegregation model was then applied to predict the channel segregations in an industrial carbon steel ingot. A rather good agreement of A-segregates was achieved between the simulation and the dissected ingot.
Energy Technology Data Exchange (ETDEWEB)
Martins, Rodrigo S.; Maitelli, Andr L.; Doria Neto, Adriao D.; Salazar, Andres O. [Rio Grande do Norte Univ., Natal, RN (Brazil)
2005-07-01
This paper presents signals processing techniques and artificial neural networks to identify leaks in multiphase flow pipeline. The greatest difficulty on traditional methods of leak detection (volume balance, pressure point analysis, etc) is that they are insufficient to design an adequate profile for the real conditions of oil pipeline transport. These difficult conditions goes since unevenly soil, that cause columns or vacuum throughout pipelines, until the presence of multi phases like water, gas and oil; plus other components as sand, which use to produce discontinuous flow off and diverse variations. To attenuate these difficulties, the transform wavelet was used to map the signal pressure in different resolution plan allowing the extraction of descriptors that identify leaks patterns and with then to provide training for the neural network multilayer perceptron (MLP) to learning of how to classify this pattern and report whenever this characterize leaks. During the tests were used transient and regime signals and pipelines with punctures with size variations from 1/2'' to 1'' of diameter to simulate leaks and, this way, it was possible to detect leaks with a time window of two minutes. The result show that the proposed descriptors considered, based in statistical methods applied in domain transform, are sufficient to identify leaks patterns and make it possible to train the neural classifier to indicate the occurrence of pipeline leaks. (author)
International Nuclear Information System (INIS)
Santini, Maurizio
2015-01-01
X-ray computed tomography (CT) is a well-known technique nowadays, since its first practical application by Sir. G. Hounsfield (Nobel price for medicine 1979) has continually benefited from optimising improvements, especially in medical applications. Indeed, also application of CT in various engineering research fields provides fundamental informations on a wide range of applications, considering that the technique is not destructive, allowing 3D visualization without perturbation of the analysed material. Nowadays, it is technologically possible to design and realize an equipment that achieve a micrometric resolution and even improve the sensibility in revealing differences in materials having very radiotransparency, allowing i.e. to distinguish between different fluids (with different density) or states of matter (like with two-phase flows). At the University of Bergamo, a prototype of an X-ray microCT system was developed since 2008, so being fully operative from 2012, with specific customizations for investigations in thermal-fluid dynamics and multiphase flow researches. A technical session held at the UIT International Conference in L'Aquila (Italy), at which this paper is referring, has presented some microCT fundamentals, to allow the audience to gain basics to follow the “fil-rouge” that links all the instrumentation developments, till the recent applications. Hereinafter are reported some applications currently developed at Bergamo University at the X-ray computed micro-tomography laboratory. (paper)
Wildenschild, D.; Porter, M. L.; Schaap, M. G.; Joekar-Niasar, V.; Schjonning, P.; Wollesen de Jonge, L.; Moldrup, P.
2010-12-01
Quantitative non-invasive imaging has evolved rapidly in the last decade, and is now being used to assess a variety of problems in vadose zone research, including unsaturated flow and transport of water and contaminants, macropore-dominated processes, soil-water-root interactions, more recent work on colloidal processes, and significant work on NAPL-water interactions . We are now able to use non-invasive imaging to probe processes that could not previously be quantified because of lack of opacity, resolution, or accurate techniques for quantitative measurement. This work presents an overview of recent advances in x-ray microtomography techniques that can generate high-resolution image-based data for (1) validation of pore-scale multi-phase flow models such as the lattice-Boltzmann technique and pore network models (with respect to fluid saturations, fluid distribution, and relationships among capillary pressure, saturation, fluid-fluid interfacial area, etc.), and (2) making the link between tomographic data and more traditional laboratory-based soil/vadose zone characterization such as hydraulic conductivity, air permeability, and pycnometer-based porosity measurements). Finally, limitations and advantages of these various approaches, as well as tomography specific issues such as resolution vs. REV requirement, access to the different types of equipment, etc. will be discussed.
Effect of lower limb compression on blood flow and performance in elite wheelchair rugby athletes.
Vaile, Joanna; Stefanovic, Brad; Askew, Christopher D
2016-01-01
To investigate the effects of compression socks worn during exercise on performance and physiological responses in elite wheelchair rugby athletes. In a non-blinded randomized crossover design, participants completed two exercise trials (4 × 8 min bouts of submaximal exercise, each finishing with a timed maximal sprint) separated by 24 hr, with or without compression socks. National Sports Training Centre, Queensland, Australia. Ten national representative male wheelchair rugby athletes with cervical spinal cord injuries volunteered to participate. Participants wore medical grade compression socks on both legs during the exercise task (COMP), and during the control trial no compression was worn (CON). The efficacy of the compression socks was determined by assessments of limb blood flow, core body temperature, heart rate, and ratings of perceived exertion, perceived thermal strain, and physical performance. While no significant differences between conditions were observed for maximal sprint time, average lap time was better maintained in COMP compared to CON (Pbenefit may be associated with an augmentation of upper limb blood flow.
Fu, Lin; Hu, Xiangyu Y.; Adams, Nikolaus A.
2017-12-01
We propose efficient single-step formulations for reinitialization and extending algorithms, which are critical components of level-set based interface-tracking methods. The level-set field is reinitialized with a single-step (non iterative) "forward tracing" algorithm. A minimum set of cells is defined that describes the interface, and reinitialization employs only data from these cells. Fluid states are extrapolated or extended across the interface by a single-step "backward tracing" algorithm. Both algorithms, which are motivated by analogy to ray-tracing, avoid multiple block-boundary data exchanges that are inevitable for iterative reinitialization and extending approaches within a parallel-computing environment. The single-step algorithms are combined with a multi-resolution conservative sharp-interface method and validated by a wide range of benchmark test cases. We demonstrate that the proposed reinitialization method achieves second-order accuracy in conserving the volume of each phase. The interface location is invariant to reapplication of the single-step reinitialization. Generally, we observe smaller absolute errors than for standard iterative reinitialization on the same grid. The computational efficiency is higher than for the standard and typical high-order iterative reinitialization methods. We observe a 2- to 6-times efficiency improvement over the standard method for serial execution. The proposed single-step extending algorithm, which is commonly employed for assigning data to ghost cells with ghost-fluid or conservative interface interaction methods, shows about 10-times efficiency improvement over the standard method while maintaining same accuracy. Despite their simplicity, the proposed algorithms offer an efficient and robust alternative to iterative reinitialization and extending methods for level-set based multi-phase simulations.
Numerical simulation of compressible two-phase flow using a diffuse interface method
International Nuclear Information System (INIS)
Ansari, M.R.; Daramizadeh, A.
2013-01-01
Highlights: ► Compressible two-phase gas–gas and gas–liquid flows simulation are conducted. ► Interface conditions contain shock wave and cavitations. ► A high-resolution diffuse interface method is investigated. ► The numerical results exhibit very good agreement with experimental results. -- Abstract: In this article, a high-resolution diffuse interface method is investigated for simulation of compressible two-phase gas–gas and gas–liquid flows, both in the presence of shock wave and in flows with strong rarefaction waves similar to cavitations. A Godunov method and HLLC Riemann solver is used for discretization of the Kapila five-equation model and a modified Schmidt equation of state (EOS) is used to simulate the cavitation regions. This method is applied successfully to some one- and two-dimensional compressible two-phase flows with interface conditions that contain shock wave and cavitations. The numerical results obtained in this attempt exhibit very good agreement with experimental results, as well as previous numerical results presented by other researchers based on other numerical methods. In particular, the algorithm can capture the complex flow features of transient shocks, such as the material discontinuities and interfacial instabilities, without any oscillation and additional diffusion. Numerical examples show that the results of the method presented here compare well with other sophisticated modeling methods like adaptive mesh refinement (AMR) and local mesh refinement (LMR) for one- and two-dimensional problems
Improving the performance of a compression ignition engine by directing flow of inlet air
Kemper, Carlton
1946-01-01
The object of this report is to present the results of tests performed by the National Advisory Committee for Aeronautics to determine the effect on engine performance of directing the flow of the inlet air to a 5-inch by 7-inch cylinder, solid injection, compression ignition engine, After a few preliminary tests, comparative runs were made at a speed of 1500 r.p.m. with and without directed air flow. It was found that directing the flow of the inlet air toward the fuel injection valve gave steadier engine operation, and an appreciable increase in power, and decreased fuel consumption. The results indicate the possibility of improving the performance of a given type of combustion chamber without changing its shape and with no change in valve timing. They would also seem to prove that directional turbulence, set up before the inlet valve of a four-stroke cycle engine, continues in the engine cylinder throughout the compression stroke.
Gao, Ying; Lin, Qingyang; Bijeljic, Branko; Blunt, Martin J.
2017-12-01
We imaged the steady state flow of brine and decane in Bentheimer sandstone. We devised an experimental method based on differential imaging to examine how flow rate impacts impact the pore-scale distribution of fluids during coinjection. This allows us to elucidate flow regimes (connected, or breakup of the nonwetting phase pathways) for a range of fractional flows at two capillary numbers, Ca, namely 3.0 × 10-7 and 7.5 × 10-6. At the lower Ca, for a fixed fractional flow, the two phases appear to flow in connected unchanging subnetworks of the pore space, consistent with conventional theory. At the higher Ca, we observed that a significant fraction of the pore space contained sometimes oil and sometimes brine during the 1 h scan: this intermittent occupancy, which was interpreted as regions of the pore space that contained both fluid phases for some time, is necessary to explain the flow and dynamic connectivity of the oil phase; pathways of always oil-filled portions of the void space did not span the core. This phase was segmented from the differential image between the 30 wt % KI brine image and the scans taken at each fractional flow. Using the grey scale histogram distribution of the raw images, the oil proportion in the intermittent phase was calculated. The pressure drops at each fractional flow at low and high flow rates were measured by high-precision differential pressure sensors. The relative permeabilities and fractional flow obtained by our experiment at the mm-scale compare well with data from the literature on cm-scale samples.
Bijeljic, B.; Andrew, M. G.; Menke, H. P.; Blunt, M. J.
2013-12-01
Advances in X ray imaging techniques made it possible not only to accurately describe solid and fluid(s) distributions in the pore space but also to study dynamics of multi-phase flow and reactive transport in-situ. This has opened up a range of new opportunities to better understand fundamental physics at the pore scale by experiment, and test and validate theoretical models in order to develop predictive tools at the pore scale and use it for upscaling. Firstly, we illustrate this concept by describing a new methodology for predicting non-Fickian transport in millimeter-sized three-dimensional micro-CT images of a beadpack, a sandstone, and a carbonate, representing porous media with an increasing degree of pore-scale complexity. The key strategy is to retain the full information on flow and transport signature of a porous medium by using probability distribution functions (PDFs) of voxel velocities for flow, and both PDFs of particle displacements and PDFs of particle transit times between voxels for transport. For this purpose, direct-simulation flow and transport model is used to analyse the relationship between pore structure, velocity, and the dynamics of the evolving plume. The model predictions for PDFs of particle displacements obtained by the model are in excellent agreement with those measured on similar cores in nuclear magnetic resonance experiments. A key determinant for non-Fickian transport is the spread in velocity distribution in the pore space. Further, we present micro-CT imaging of capillary trapping of scCO2 at reservoir conditions in a range of carbonates and sandstones having different pore structure and demonstrate that substantial quantities of scCO2 can be trapped in the pore space. Higher residual scCO2 saturations are found in sandstones compared to carbonates. The trapped ganglia exhibit different distribution of size, related to the inherent structure of pore space. Pore structures with large, open pores that are well connected lead
Directory of Open Access Journals (Sweden)
Lynch J.
2006-11-01
Full Text Available Cet article présente les différentes techniques de débitmétrie polyphasique non intrusive décrites dans la littérature du domaine public. Ces techniques sont considérées du point de vue de leur application dans le cadre de la production pétrolière sous-marine (mélange eau/huile/gaz. A partir d'une analyse des différentes méthodes physiques qui peuvent être utilisées, des perspectives d'avenir sont proposées. Several operations in the oil reservoir exploitation industry call for flowmeters capable of delivering information on the quantity and rate of flow of the different phases (gas, oil, water, solids . . . present in a pipeline. Amongst these are the estimation of remaining reserves and of well performance, control of production units such as multiphase pumping systems and fiscal monitoring in the case of pipeline networking. Existing methods, based on phase separation, require separate test lines and thus tend to be cumbersome, give only intermittent values of flow parameters and need to be calibrated due to the intrusive nature of the measurements. These drawbacks are seen to be all the more critical in subsea production where the ideal flowmeter would be compact, require little maintenance and supply precise real time data for network and multiphase pump control. In recent years flow measurement in two or more phase systems has received increasing attention both in laboratory studies and for applications in a variety of industries (for example : nuclear power production and food processing as well as of course oil production. We review here the many methods considered for non-intrusive flow metering with two or more components from the point of view of an industrial (in particular subsea oil production application. The situation is rendered delicate, in particular for density measurement, by the uncontrolled nature of the flow which may occur in any of several regimes with differing spatial distributions of the components
International Nuclear Information System (INIS)
Klimachkov, D. A.; Petrosyan, A. S.
2016-01-01
Shallow water magnetohydrodynamic (MHD) theory describing incompressible flows of plasma is generalized to the case of compressible flows. A system of MHD equations is obtained that describes the flow of a thin layer of compressible rotating plasma in a gravitational field in the shallow water approximation. The system of quasilinear hyperbolic equations obtained admits a complete simple wave analysis and a solution to the initial discontinuity decay problem in the simplest version of nonrotating flows. In the new equations, sound waves are filtered out, and the dependence of density on pressure on large scales is taken into account that describes static compressibility phenomena. In the equations obtained, the mass conservation law is formulated for a variable that nontrivially depends on the shape of the lower boundary, the characteristic vertical scale of the flow, and the scale of heights at which the variation of density becomes significant. A simple wave theory is developed for the system of equations obtained. All self-similar discontinuous solutions and all continuous centered self-similar solutions of the system are obtained. The initial discontinuity decay problem is solved explicitly for compressible MHD equations in the shallow water approximation. It is shown that there exist five different configurations that provide a solution to the initial discontinuity decay problem. For each configuration, conditions are found that are necessary and sufficient for its implementation. Differences between incompressible and compressible cases are analyzed. In spite of the formal similarity between the solutions in the classical case of MHD flows of an incompressible and compressible fluids, the nonlinear dynamics described by the solutions are essentially different due to the difference in the expressions for the squared propagation velocity of weak perturbations. In addition, the solutions obtained describe new physical phenomena related to the dependence of the
Directory of Open Access Journals (Sweden)
Chang-jiang Ni
2017-03-01
Full Text Available The influence of core sand properties on flow dynamics was investigated synchronously with various core sands, transparent core-box and high-speed camera. To confirm whether the core shooting process has significant turbulence, the flow pattern of sand particles in the shooting head and core box was reproduced with colored core sands. By incorporating the kinetic theory of granular flow (KTGF, kinetic-frictional constitutive correlation and turbulence model, a two-fluid model (TFM was established to study the flow dynamics of the core shooting process. Two-fluid model (TFM simulations were then performed and a areasonable agreement was achieved between the simulation and experimental results. Based on the experimental and simulation results, the effects of turbulence, sand density, sand diameter and binder ratio were analyzed in terms of filling process, sand volume fraction (αs and sand velocity (Vs.
Nonaffine deformation under compression and decompression of a flow-stabilized solid
Ortiz, Carlos P.; Riehn, Robert; Daniels, Karen E.
2016-08-01
Understanding the particle-scale transition from elastic deformation to plastic flow is central to making predictions about the bulk material properties and response of disordered materials. To address this issue, we perform experiments on flow-stabilized solids composed of micron-scale spheres within a microfluidic channel, in a regime where particle inertia is negligible. Each solid heap exists within a stress field imposed by the flow, and we track the positions of particles in response to single impulses of fluid-driven compression or decompression. We find that the resulting deformation field is well-decomposed into an affine field, with a constant strain profile throughout the solid, and a non-affine field. The magnitude of this non-affine response decays with the distance from the free surface in the long-time limit, suggesting that the distance from jamming plays a significant role in controlling the length scale of plastic flow. Finally, we observe that compressive pulses create more rearrangements than decompressive pulses, an effect that we quantify using the D\\text{min}2 statistic for non-affine motion. Unexpectedly, the time scale for the compression response is shorter than for decompression at the same strain (but unequal pressure), providing insight into the coupling between deformation and cage-breaking.
Two compressible and immiscible flow in porous media: mathematical and numerical analysis
International Nuclear Information System (INIS)
Khalil, Z.
2010-01-01
The aim of this thesis is the study of Cauchy problem (existence of weak solutions) for three degenerate highly coupled parabolic systems modeling compressible immiscible flow in porous media. The motivation of this work is a benchmark of the GNR MoMaS, to study the impact of the gas flow due to the corrosion of ferrous materials in a radioactive waste storage site. This thesis is divided into three independent chapters. Firstly, we look at a problem modeling the flow of two immiscible phases and considering one phase is compressible and the other is incompressible (water/gas). Secondly, we consider the problem modeling two-compressible immiscible flow in porous media. An existence results for both problems established by a semi-discretization method. Finally, The fourth chapter is devoted to the construction and convergence of a multi-dimensional finite volume method (upwind scheme) for the gas-water model under the assumption that the gas density is a function of a global pressure. (author)
Numerical Simulation of Unsteady Compressible Flow in Convergent Channel: Pressure Spectral Analysis
Directory of Open Access Journals (Sweden)
Petra Pořízková
2012-01-01
Full Text Available This study deals with the numerical solution of a 2D unsteady flow of a compressible viscous fluid in a channel for low inlet airflow velocity. The unsteadiness of the flow is caused by a prescribed periodic motion of a part of the channel wall with large amplitudes, nearly closing the channel during oscillations. The flow is described by the system of Navier-Stokes equations for laminar flows. The numerical solution is implemented using the finite volume method (FVM and the predictor-corrector Mac-Cormack scheme with Jameson artificial viscosity using a grid of quadrilateral cells. Due to the motion of the grid, the basic system of conservation laws is considered in the arbitrary Lagrangian-Eulerian (ALE form. The numerical results of unsteady flows in the channel are presented for inlet Mach number M∞=0.012, Reynolds number Re∞=4481, and the wall motion frequency 100 Hz.
International Nuclear Information System (INIS)
Kolev, N.I.
1991-12-01
This work contains description of the physical and mathematical basis on which the IVA3 computer code relies. After describing the state of the art of the 3D modeling for transient multiphase flows, the model assumptions and the modeling technique used in IVA3 are described. Starting with the principles of conservation of mass, momentum, and energy, the non averaged conservation equations are derived for each of the velocity fields which consist of different isothermal components. Thereafter averaging is applied and the working form of the system of 21 partial differential equations is derived. Special attention is paid to the strict consistence of the modeling technique used in IVA3 with the second principle of thermodynamics. The entropy concept used is derived starting with the unaveraged conservation equations and subsequent averaging. The source terms of the entropy production are carefully defined and the final form of the averaged entropy equation is given ready for direct practical applications. The idea of strong analytical thermodynamic coupling between pressure field and changes of the other thermodynamic properties, which is used for the first time in 3D multi fluid modeling, is presented in detail. After obtaining the working form of the conservation equations, the discretization procedure and the reduction to algebraic problems is presented. The mathematical solution method together with some information about the architecture of IVA3 including the local momentum decoupling and accuracy control is presented too. (orig./GL) [de
An improved ghost-cell immersed boundary method for compressible flow simulations
Chi, Cheng
2016-05-20
This study presents an improved ghost-cell immersed boundary approach to represent a solid body in compressible flow simulations. In contrast to the commonly used approaches, in the present work ghost cells are mirrored through the boundary described using a level-set method to farther image points, incorporating a higher-order extra/interpolation scheme for the ghost cell values. A sensor is introduced to deal with image points near the discontinuities in the flow field. Adaptive mesh refinement (AMR) is used to improve the representation of the geometry efficiently in the Cartesian grid system. The improved ghost-cell method is validated against four test cases: (a) double Mach reflections on a ramp, (b) smooth Prandtl-Meyer expansion flows, (c) supersonic flows in a wind tunnel with a forward-facing step, and (d) supersonic flows over a circular cylinder. It is demonstrated that the improved ghost-cell method can reach the accuracy of second order in L1 norm and higher than first order in L∞ norm. Direct comparisons against the cut-cell method demonstrate that the improved ghost-cell method is almost equally accurate with better efficiency for boundary representation in high-fidelity compressible flow simulations. Copyright © 2016 John Wiley & Sons, Ltd.
Effects of cord compression on fetal blood flow distribution and O2 delivery
International Nuclear Information System (INIS)
Itskovitz, J.; LaGamma, E.F.; Rudolph, A.M.
1987-01-01
The authors used the radionuclide microsphere technique in nine fetal lambs to examine the effect of partial cord compression on distribution of cardiac output and O 2 delivery to fetal organs and venous flow patterns. With a 50% reduction in umbilical blood flow the fraction of fetal cardiac output distributed to the brain, heart, carcass, kidneys, and gastrointestinal tract increased. Pulmonary blood flow fell. O 2 delivery to the brain and myocardium was maintained but was reduced to peripheral, renal, and gastrointestinal circulations. Hepatic blood flow decreased and O 2 delivery fell by 75%. The proportion of umbilical venous blood passing through the ductus venosus increased from 43.9 to 71.8%. The preferential distribution of ductus venosus blood flow through the foramen ovale was enhanced and the proportion of O 2 delivery to upper body organs derived from the ductus venosus increased. Abdominal inferior vena caval blood flow increased, and it was also preferentially distributed through the foramen ovale and constituted the major fraction of the arterial blood supply to the upper body organs. Thus cord compression modified the distribution of cardiac output and the patterns of venous returns in the fetus. This pattern of circulatory response differs from that observed with other causes of reduced O 2 delivery
Well-posed continuum equations for granular flow with compressibility and μ(I)-rheology
Schaeffer, D. G.; Shearer, M.; Gray, J. M. N. T.
2017-01-01
Continuum modelling of granular flow has been plagued with the issue of ill-posed dynamic equations for a long time. Equations for incompressible, two-dimensional flow based on the Coulomb friction law are ill-posed regardless of the deformation, whereas the rate-dependent μ(I)-rheology is ill-posed when the non-dimensional inertial number I is too high or too low. Here, incorporating ideas from critical-state soil mechanics, we derive conditions for well-posedness of partial differential equations that combine compressibility with I-dependent rheology. When the I-dependence comes from a specific friction coefficient μ(I), our results show that, with compressibility, the equations are well-posed for all deformation rates provided that μ(I) satisfies certain minimal, physically natural, inequalities. PMID:28588402
International Nuclear Information System (INIS)
Kambe, Tsutomu
2013-01-01
A new representation of the solution to Euler's equation of motion is presented by using a system of expressions for compressible rotational flows of an ideal fluid. This is regarded as a generalization of Bernoulli's theorem to compressible rotational flows. The present expressions are derived from the variational principle. The action functional for the principle consists of the main terms of the total kinetic, potential and internal energies, together with three additional terms yielding the equations of continuity, entropy and a third term that provides the rotational component of velocity field. The last term has the form of scalar product satisfying gauge symmetry with respect to both translation and rotation. This is a generalization of the Clebsch transformation from a physical point of view. It is verified that the system of new expressions, in fact, satisfies Euler's equation of motion. (paper)
Czech Academy of Sciences Publication Activity Database
Punčochářová-Pořízková, P.; Kozel, K.; Horáček, Jaromír
2011-01-01
Roč. 46, č. 1 (2011), s. 404-410 ISSN 0045-7930 R&D Projects: GA MŠk OC09019 Institutional research plan: CEZ:AV0Z20760514 Keywords : finite volume method * unsteady flow * low Mach number * viscous compressible fluid Subject RIV: BI - Acoustics Impact factor: 1.810, year: 2011 http://www.sciencedirect.com/science/article/pii/S0045793010003439
Cross-coupling effects in chemically non-equilibrium viscous compressible flows
International Nuclear Information System (INIS)
Kustova, E.V.; Giordano, D.
2011-01-01
Graphical abstract: Self-cosistent kinetic-theory description of chemical-reaction rates and mean normal stress in one-temperature viscous compressible gas flows. Reaearch highlights: → In chemically non-equilibrium viscous compressible flows, the rate of each reaction depends on the velocity divergence and rates of all other reactions. → Cross effects between the rates of chemical reactions and normal mean stress can be found in the symmetric form and expressed in terms of the reaction affinities. → In the case of small affinities, the entropy production is unconditionally non-negative; in the case of finite affinities, the entropy production related to the scalar forces has no definite sign. - Abstract: A closed self-consistent description of a one-temperature non-equilibrium reacting flow is presented on the basis of the kinetic theory methods. A general case including internal degrees of freedom, dissociation-recombination and exchange reactions, and arbitrary values of affinities of chemical reactions is considered. Chemical-reaction rates and mean normal stress in viscous compressible flows are studied and a symmetric cross coupling between these terms is found. It is shown that the rate of each chemical reaction and the mean normal stress depend on velocity divergence and affinities of all chemical reactions; the law of mass action is violated in viscous flows. The results obtained in the frame of linear irreversible thermodynamics can be deduced from the proposed model for the particular case of small affinities. The reciprocal Onsager-Casimir relations are verified, the symmetry of kinetic coefficients is demonstrated, and the entropy production in a viscous flow is studied.
Jiang, Jiamin; Younis, Rami M.
2017-10-01
In the presence of counter-current flow, nonlinear convergence problems may arise in implicit time-stepping when the popular phase-potential upwinding (PPU) scheme is used. The PPU numerical flux is non-differentiable across the co-current/counter-current flow regimes. This may lead to cycles or divergence in the Newton iterations. Recently proposed methods address improved smoothness of the numerical flux. The objective of this work is to devise and analyze an alternative numerical flux scheme called C1-PPU that, in addition to improving smoothness with respect to saturations and phase potentials, also improves the level of scalar nonlinearity and accuracy. C1-PPU involves a novel use of the flux limiter concept from the context of high-resolution methods, and allows a smooth variation between the co-current/counter-current flow regimes. The scheme is general and applies to fully coupled flow and transport formulations with an arbitrary number of phases. We analyze the consistency property of the C1-PPU scheme, and derive saturation and pressure estimates, which are used to prove the solution existence. Several numerical examples for two- and three-phase flows in heterogeneous and multi-dimensional reservoirs are presented. The proposed scheme is compared to the conventional PPU and the recently proposed Hybrid Upwinding schemes. We investigate three properties of these numerical fluxes: smoothness, nonlinearity, and accuracy. The results indicate that in addition to smoothness, nonlinearity may also be critical for convergence behavior and thus needs to be considered in the design of an efficient numerical flux scheme. Moreover, the numerical examples show that the C1-PPU scheme exhibits superior convergence properties for large time steps compared to the other alternatives.
Online slug detection in multi-phase transportation pipelines using electrical tomography
DEFF Research Database (Denmark)
Pedersen, Simon; Mai, Christian; Hansen, Leif
2015-01-01
Slugging flow in offshore oil & gas multi-phase transportation pipelines cause big challenges as the flow regime induces flow and pressure oscillations in the multi-phase pipelines. The negative impacts of the most severe slugs are significant and thus the elimination of slugging flow in the pipe......Slugging flow in offshore oil & gas multi-phase transportation pipelines cause big challenges as the flow regime induces flow and pressure oscillations in the multi-phase pipelines. The negative impacts of the most severe slugs are significant and thus the elimination of slugging flow...
Lattice Boltzmann method for simulation of compressible flows on standard lattices.
Prasianakis, Nikolaos I; Karlin, Iliya V
2008-07-01
The recently introduced lattice Boltzmann model for thermal flow simulation on a standard lattice [Prasianakis and Karlin, Phys. Rev. E 76, 016702 (2007)] is studied numerically in the case where compressibility effects are essential. It is demonstrated that the speed of sound and shock propagation are described correctly in a wide temperature range, and that it is possible to take into account additional physics such as heat sources and sinks. A remarkable simplicity of the model makes it viable for engineering applications in subsonic flows with large temperature and density variations.
Energy Technology Data Exchange (ETDEWEB)
Joyce, E.L.
1997-03-01
The Virtual Center For Multiphase Dynamics (VCMD) integrates and develops the resources of industry, government, academia, and professional societies to enable reliable analysis in multiphase computational fluid dynamics. The primary means of the VCMD focus will be by the creation, support, and validation of a computerized simulation capability for multiphase flow and multiphase flow applications. This paper briefly describes the capabilities of the National Laboratories in this effort.
Kunz, P.; Zarikos, I. M.; Karadimitriou, N. K.; Huber, M.; Nieken, U.; Hassanizadeh, S. M.
2016-01-01
We present simulations and experiments of drainage processes in a micro-model. A direct numerical simulation is introduced which is capable of describing wetting phenomena on the pore scale. A numerical smoothed particle hydrodynamics model was developed and used to simulate the two-phase flow of immiscible fluids. The experiments were performed in a micro-model which allows the visualization of interface propagation in detail. We compare the experiments and simulations of a quasistatic drain...
Energy Technology Data Exchange (ETDEWEB)
Baptista, R.M.; Maricato, A.L.G. [Petrobras Research and Development Center, Rio de Janeiro (Brazil)
2004-07-01
The 214 km, 16-inch diameter Merluza wet gas pipeline transports gas from the offshore Merluza gas field to an onshore treatment facility at Presidente Barnardes Refinery in Sao Paulo, Brazil. It is unique in that it carries a considerable amount of condensate, requiring frequent pigging. In addition, the capacity requirements at the pipeline tail are variable. The cycling nature has necessitated a survival analysis for both packing and drafting operations, accounting for up to 4 pigs operating simultaneously within the line. Operational limits of the slug catcher also present pressure constraints downstream of the pipeline. This paper presented the results of a set of pipeline flow numerical simulations for the pipeline. The objective was to estimate the imbalances caused by the presence of more than one pig within the line. Pig motion was evaluated by tracking and the pressure was explained by the accumulated volume downstream of the pig. The work was conceived under the two-phase flow domain, using OlgaS, a well known commercial two-phase flow numerical simulator. The results of the simulation were in good agreement with measured operational data, and allowed the operational programmer to optimize pig launching. The simulation also made it possible to take full advantage of the maximum pipeline capacity. 1 tab., 10 figs.
Numerical simulation of the compressible flow in a valve-cylinder assembly
Kourta, A.; Ha Minh, H.; Vandromme, D.
Unsteady compressible flow in a simple valve-cylinder configuration is simulated numerically. The Navier-Stokes equations are solved by means of an implicit two-step MacCormack method with finite-volume discretization, second-order-accurate flux splitting (Steger and Warming, 1982), and line-Gauss-Seidel relaxation; the model of Baldwin and Lomax (1978) is used to describe turbulence. The derivation of the method is outlined, and results are presented in graphs for (1) two-dimensional laminar flow, (2) axisymmetric laminar flow, and (3) axisymmetric turbulent flow. Significant differences are found between (1) and (2), with lower jet momentum and main circulation separated from the upper boundary in case (2); case (3) differs only slightly from (2), but the simulation fails to predict wall heat transfer accurately. The applicability of the method to the design of advanced internal-combustion engines is indicated.
Sub-grid combustion modeling for compressible two-phase reacting flows
Sankaran, Vaidyanathan
2003-06-01
A generic formulation for modeling the turbulent combustion in compressible, high Reynolds number, two-phase; reacting flows has been developed and validated. A sub-grid mixing/combustion model called Linear Eddy Mixing (LEM) model has been extended to compressible flows and used inside the framework of Large Eddy Simulation (LES) in this LES-LEM approach. The LES-LEM approach is based on the proposition that the basic mechanistic distinction between the convective and the molecular effects should be preserved for accurate prediction of complex flow-fields such as those encountered in many combustion systems. Liquid droplets (represented by computational parcels) are tracked using the Lagrangian approach wherein the Newton's equation of motion for the discrete particles are integrated explicitly in the Eulerian gas field. The gas phase LES velocity fields are used to estimate the instantaneous gas velocity at the droplet location. Drag effects due to the droplets on the gas phase and the heat transfer between the gas and the liquid phase are explicitly included. Thus, full coupling is achieved between the two phases in the simulation. Validation of the compressible LES-LEM approach is conducted by simulating the flow-field in an operational General Electric Aircraft Engines combustor (LM6000). The results predicted using the proposed approach compares well with the experiments and a conventional (G-equation) thin-flame model. Particle tracking algorithms used in the present study are validated by simulating droplet laden temporal mixing layers. Quantitative and qualitative comparison with the results of spectral DNS exhibits good agreement. Simulations using the current LES-LEM for freely propagating partially premixed flame in a droplet-laden isotropic turbulent field correctly captures the flame structure in the partially premixed flames. Due to the strong spatial variation of equivalence ratio a broad flame similar to a premixed flame is realized. The current
Wright, Stuart F.; Zadrazil, Ivan; Markides, Christos N.
2017-09-01
Experimental techniques based on optical measurement principles have experienced significant growth in recent decades. They are able to provide detailed information with high-spatiotemporal resolution on important scalar (e.g., temperature, concentration, and phase) and vector (e.g., velocity) fields in single-phase or multiphase flows, as well as interfacial characteristics in the latter, which has been instrumental to step-changes in our fundamental understanding of these flows, and the development and validation of advanced models with ever-improving predictive accuracy and reliability. Relevant techniques rely upon well-established optical methods such as direct photography, laser-induced fluorescence, laser Doppler velocimetry/phase Doppler anemometry, particle image/tracking velocimetry, and variants thereof. The accuracy of the resulting data depends on numerous factors including, importantly, the refractive indices of the solids and liquids used. The best results are obtained when the observational materials have closely matched refractive indices, including test-section walls, liquid phases, and any suspended particles. This paper reviews solid-liquid and solid-liquid-liquid refractive-index-matched systems employed in different fields, e.g., multiphase flows, turbomachinery, bio-fluid flows, with an emphasis on liquid-liquid systems. The refractive indices of various aqueous and organic phases found in the literature span the range 1.330-1.620 and 1.251-1.637, respectively, allowing the identification of appropriate combinations to match selected transparent or translucent plastics/polymers, glasses, or custom materials in single-phase liquid or multiphase liquid-liquid flow systems. In addition, the refractive indices of fluids can be further tuned with the use of additives, which also allows for the matching of important flow similarity parameters such as density and viscosity.
Roy, James W; Smith, James E
2007-01-30
Disconnected bubbles or ganglia of trapped gas may occur below the top of the capillary fringe through a number of mechanisms. In the presence of dense non-aqueous phase liquid (DNAPL), the disconnected gas phase experiences mass transfer of dissolved gases, including volatile components from the DNAPL. The properties of the gas phase interface can also change. This work shows for the first time that when seed gas bubbles exist spontaneous gas phase growth can be expected to occur and can significantly affect water-gas-DNAPL distributions, fluid flow, and mass transfer. Source zone behaviour was observed in three different experiments performed in a 2-dimensional flow cell. In each case, a DNAPL pool was created in a zone of larger glass beads over smaller glass beads, which served as a capillary barrier. In one experiment effluent water samples were analyzed to determine the vertical concentration profile of the plume above the pool. The experiments effectively demonstrated a) a cycle of spontaneous gas phase expansion and vertical advective mobilization of gas bubbles and ganglia above the DNAPL source zone, b) DNAPL redistribution caused by gas phase growth and mobilization, and c) that these processes can significantly affect mass transport from a NAPL source zone.
International Nuclear Information System (INIS)
Andersson, M.; Beale, S.B.; Espinoza, M.; Wu, Z.; Lehnert, W.
2016-01-01
Highlights: • The transport expressions inside PEFC GDLs are developed to describe significantly different systems. • Insight into the fundamental processes of liquid water evolution and transport in the GDL and GC is still lacking. • One important feature is the possibility to track the front between the liquid and the gas phases. • The two phase micro channels pressure drop correlations may not be applicable for GCs since one wall being porous. - Abstract: The PEFC has emerged as the most viable fuel cell type for automotive and some portable applications, and also has potential back-up power unit applications due to its low operating temperature, comparative simplicity of construction, high power density, and ease of operation. In spite of tremendous scientific advances, as well as engineering progress over the last few decades, the commercialization of PEFCs remains unrealized, owing primarily to economic viability associated with the high prices of materials and components and technical problems relating primarily to water management. The difficulty in addressing the water management issues lies mostly in the two-phase multi-component flow involving phase-change in porous media, coupled heat and mass transfer, interactions between the porous layers and gas channel (GC) and the complex relationship between water content and cell performance. Due to the low temperature of operation, water generated by the electrochemical reactions often condenses into liquid form, potentially flooding the gas diffusion layer (GDL), GC or other components. Insight into the fundamental processes of liquid water evolution and transport is still lacking, preventing further enhanced PEFC development. The aim of this paper is to give a comprehensive introduction to PEFC modeling inside GCs and GDLs, with a focus on two-phase flow and related phase-change and transport processes. Relevant momentum, mass and heat transport processes are introduced and the microstructural effects
A renormalization group scaling analysis for compressible two-phase flow
International Nuclear Information System (INIS)
Chen, Y.; Deng, Y.; Glimm, J.; Li, G.; Zhang, Q.; Sharp, D.H.
1993-01-01
Computational solutions to the Rayleigh--Taylor fluid mixing problem, as modeled by the two-fluid two-dimensional Euler equations, are presented. Data from these solutions are analyzed from the point of view of Reynolds averaged equations, using scaling laws derived from a renormalization group analysis. The computations, carried out with the front tracking method on an Intel iPSC/860, are highly resolved and statistical convergence of ensemble averages is achieved. The computations are consistent with the experimentally observed growth rates for nearly incompressible flows. The dynamics of the interior portion of the mixing zone is simplified by the use of scaling variables. The size of the mixing zone suggests fixed-point behavior. The profile of statistical quantities within the mixing zone exhibit self-similarity under fixed-point scaling to a limited degree. The effect of compressibility is also examined. It is found that, for even moderate compressibility, the growth rates fail to satisfy universal scaling, and moreover, increase significantly with increasing compressibility. The growth rates predicted from a renormalization group fixed-point model are in a reasonable agreement with the results of the exact numerical simulations, even for flows outside of the incompressible limit
Li, Yaofa; Kazemifar, Farzan; Blois, Gianluca; Christensen, Kenneth T.
2017-07-01
We present an experimental study of pore-scale flow dynamics of liquid CO2 and water in a two-dimensional heterogeneous porous micromodel, inspired by the structure of a reservoir rock, at reservoir-relevant conditions (80 bar, 21°C). The entire process of CO2 infiltration into a water-saturated micromodel was captured using fluorescence microscopy and the micro-PIV method, which together reveal complex fluid displacement patterns and abrupt changes in velocity. The CO2 front migrated through the resident water in an intermittent manner, forming dendritic structures, termed fingers, in directions along, normal to, and even opposing the bulk pressure gradient. Such characteristics indicate the dominance of capillary fingering through the micromodel. Velocity burst events, termed Haines jumps, were also captured in the heterogeneous micromodel, during which the local Reynolds number was estimated to be ˜21 in the CO2 phase, exceeding the range of validity of Darcy's law. Furthermore, these drainage events were observed to be cooperative (i.e., across multiple pores simultaneously), with the zone of influence of such events extending beyond tens of pores, confirming, in a quantitative manner, that Haines jumps are nonlocal phenomena. After CO2 completely breaks through the porous section, shear-induced circulations caused by flowing CO2 were also observed, in agreement with previous studies using a homogeneous porous micromodel. To our knowledge, this study is the first quantitative measurement that incorporates both reservoir-relevant conditions and rock-inspired heterogeneity, and thus will be useful for pore-scale model development and validation.
Gresse, Marceau; Vandemeulebrouck, Jean; Byrdina, Svetlana; Chiodini, Giovanni; Revil, André; Johnson, Timothy C.; Ricci, Tullio; Vilardo, Giuseppe; Mangiacapra, Annarita; Lebourg, Thomas; Grangeon, Jacques; Bascou, Pascale; Metral, Laurent
2017-11-01
The Solfatara volcano is the main degassing area of the Campi Flegrei caldera, characterized by 60 years of unrest. Assessing such renewal activity is a challenging task because hydrothermal interactions with magmatic gases remain poorly understood. In this study, we decipher the complex structure of the shallow Solfatara hydrothermal system by performing the first 3-D, high-resolution, electrical resistivity tomography of the volcano. The 3-D resistivity model was obtained from the inversion of 43,432 resistance measurements performed on an area of 0.68 km2. The proposed interpretation of the multiphase hydrothermal structures is based on the resistivity model, a high-resolution infrared surface temperature image, and 1,136 soil CO2 flux measurements. In addition, we realized 27 soil cation exchange capacity and pH measurements demonstrating a negligible contribution of surface conductivity to the shallow bulk electrical conductivity. Hence, we show that the resistivity changes are mainly controlled by fluid content and temperature. The high-resolution tomograms identify for the first time the structure of the gas-dominated reservoir at 60 m depth that feeds the Bocca Grande fumarole through a 10 m thick channel. In addition, the resistivity model reveals a channel-like conductive structure where the liquid produced by steam condensation around the main fumaroles flows down to the Fangaia area within a buried fault. The model delineates the emplacement of the main geological structures: Mount Olibano, Solfatara cryptodome, and tephra deposits. It also reveals the anatomy of the hydrothermal system, especially two liquid-dominated plumes, the Fangaia mud pool and the Pisciarelli fumarole, respectively.
Energy Technology Data Exchange (ETDEWEB)
Kaura, Jiten D.; Finley, D.B. [PT Halliburton Indonesia, Jakarta (Indonesia); Sudradjat, Wangsa; Riyanto, Latief [Tota E and P Indonesie, Jakarta (Indonesia); Halverson, Martin [FlowSys AS, Bergen (Norway)
2004-07-01
Recently, testing was needed on production wells in East Kalimantan. The wells were in a mature field, and productivity from the wells field featured high water cut (WC) and extremely high gas-volume fractions (GVF). The WC and GVF ranged from 80 to 100% and 90 to 100%, respectively. Moreover, most of the wells are low productivity so they are very sensitive to back-pressure. The high WC, high GVF and low-productivity from these wells in this area present an extreme challenge for accurate production measurement. Barges are commonly used to perform well services in the swamp area of this marginal field, and production allocations from wells in this difficult area were previously monitored and measured with conventional well-test equipment on-board a well testing barge. The well test equipment traditionally used requires a large footprint, and the associated flaring presents an environmental situation in this sensitive swamp area. Hence, the MPFM solution was chosen. To better meet the challenges presented by the testing conditions, a portable multiphase flow meter (MPFM) was chosen to perform the testing from the well-testing barge. For comparative purposes, the MPFM was installed on the barge immediately upstream of the well testing equipment. Initial measurements with the MPFM yielded results that were {+-} 30% of the test separator reading. A slight modification was introduced to the MPFM system in the form of a gas knock-out (GKO) vessel. Subsequent measurements with the modified MPFM system yielded readings that were {+-}10% of the test separator reading. (author)
Computation of steady and unsteady compressible quasi-axisymmetric vortex flow and breakdown
Kandil, Osama A.; Kandil, Hamdy A.; Liu, C. H.
1991-01-01
The unsteady, compressible Navier-Stokes equations are used to compute and analyze compressible quasi-axisymmetric isolated vortices. The Navier-Stokes equations are solved using an implicit, upwind, flux-difference splitting finite-volume scheme. The developed three-dimensional solver has been verified by comparing its solution profiles with those of a slender, quasi-axisymmetric vortex solver for a subsonic, isolated quasi-axisymmetric vortex in an unbounded domain. The Navier-Stokes solver is then used to solve for a supersonic quasi-axisymmetric vortex flow in a configured circular duct. Steady and unsteady vortex-shock interactions and breakdown have been captured. The problem has also been calculated using the Euler solver of the same code and the results are compared with those of the Navier-Stokes solver. The effect of the initial swirl has been tentatively studied.
Computation of compressible quasi-axisymmetric slender vortex flow and breakdown
Kandil, Osama A.; Kandil, Hamdy A.
1991-01-01
The unsteady, compressible Navier-Stokes equations are used to compute and analyze compressible quasi-axisymmetric isolated vortices. The Navier-Stokes equations are solved using an implicit, upwind, flux difference splitting finite volume scheme. The developed three dimensional solver was verified by comparing its solution profiles with those of a slender, quasi-axisymmetric vortex solver for a subsonic, quasi-axisymmetric vortex in an unbounded domain. The Navier-Stokes solver is then used to solve for a supersonic, quasi-axisymmetric vortex flow in a configured circular duct. Steady and unsteady vortex-shock interactions and breakdown were captured. The problem was also calculated using the Euler solver of the same code; the results were compared with those of the Navier-Stokes solver. The effect of the initial swirl was investigated.
Thermodynamic Modelling of an Ejector with Compressible Flow by a One-Dimensional Approach
Directory of Open Access Journals (Sweden)
Claude Chacoux
2012-03-01
Full Text Available The purpose of this study is the dimensioning of the cylindrical mixing chamber of a compressible fluid ejector used in particular in sugar refineries for degraded vapor re‑compression at the calandria exit, during the evaporation phase. The method used, known as the “integral” or “thermodynamic model”, is based on the model of the one‑dimensional isentropic flow of perfect gases with the addition of a model of losses. Characteristic curves and envelope curves are plotted. The latter are an interesting tool from which the characteristic dimensions of the ejector can be rapidly obtained for preliminary dimensioning (for an initial contact with a customer for example. These ejectors, which were specifically designed for the process rather than selected from a catalog of standard devices, will promote energy saving.
A multiscale method for compressible liquid-vapor flow with surface tension*
Directory of Open Access Journals (Sweden)
Jaegle Felix
2013-01-01
Full Text Available Discontinuous Galerkin methods have become a powerful tool for approximating the solution of compressible flow problems. Their direct use for two-phase flow problems with phase transformation is not straightforward because this type of flows requires a detailed tracking of the phase front. We consider the fronts in this contribution as sharp interfaces and propose a novel multiscale approach. It combines an efficient high-order Discontinuous Galerkin solver for the computation in the bulk phases on the macro-scale with the use of a generalized Riemann solver on the micro-scale. The Riemann solver takes into account the effects of moderate surface tension via the curvature of the sharp interface as well as phase transformation. First numerical experiments in three space dimensions underline the overall performance of the method.
Observation of dual-mode, Kelvin-Helmholtz instability vortex merger in a compressible flow
Wan, W. C.; Malamud, G.; Shimony, A.; Di Stefano, C. A.; Trantham, M. R.; Klein, S. R.; Shvarts, D.; Drake, R. P.; Kuranz, C. C.
2017-05-01
We report the first observations of Kelvin-Helmholtz vortices evolving from well-characterized, dual-mode initial conditions in a steady, supersonic flow. The results provide the first measurements of the instability's vortex merger rate and supplement data on the inhibition of the instability's growth rate in a compressible flow. These experimental data were obtained by sustaining a shockwave over a foam-plastic interface with a precision-machined seed perturbation. This technique produced a strong shear layer between two plasmas at high-energy-density conditions. The system was diagnosed using x-ray radiography and was well-reproduced using hydrodynamic simulations. Experimental measurements imply that we observed the anticipated vortex merger rate and growth inhibition for supersonic shear flow.
International Nuclear Information System (INIS)
Asano, H.; Takenaka, N.; Fujii, T.; Shibata, Y.; Ebisu, T.; Matsubayashi, M.
1999-01-01
The refrigerant two-phase flows in a capillary tube and a distributor used in a compression-type refrigerator were visualized by real-time neutron radiography. The thermal neutron radiography system of JRR-3M at the Japan Atomic Energy Research Institute was used. In the visualization experiments of the two-phase flow in the capillary tube of 2 mm I.D., a cooled CCD camera was used, and the axial one-dimensional distributions of void fraction were measured. For the distributor, a high sensitivity video camera with a silicone intensified target tube was used. From the visualized images, the refrigerant behaviors in the distributor were clearly shown, and the liquid fraction in each tube was measured. As a result, it was shown that the refrigerant behaviors in the distributor effected the distributing performance of the refrigerant flow
Mixing across fluid interfaces compressed by convective flow in porous media
Hidalgo, Juan J.; Dentz, Marco
2018-03-01
We study the mixing in the presence of convective flow in a porous medium. Convection is characterized by the formation of vortices and stagnation points, where the fluid interface is stretched and compressed enhancing mixing. We analyze the behavior of the mixing dynamics in different scenarios using an interface deformation model. We show that the scalar dissipation rate, which is related to the dissolution fluxes, is controlled by interfacial processes, specifically the equilibrium between interface compression and diffusion, which depends on the flow field configuration. We consider different scenarios of increasing complexity. First, we analyze a double-gyre synthetic velocity field. Second, a Rayleigh-B\\'enard instability (the Horton-Rogers-Lapwood problem), in which stagnation points are located at a fixed interface. This system experiences a transition from a diffusion controlled mixing to a chaotic convection as the Rayleigh number increases. Finally, a Rayleigh-Taylor instability with a moving interface, in which mixing undergoes three different regimes: diffusive, convection dominated, and convection shutdown. The interface compression model correctly predicts the behavior of the systems. It shows how the dependency of the compression rate on diffusion explains the change in the scaling behavior of the scalar dissipation rate. The model indicates that the interaction between stagnation points and the correlation structure of the velocity field is also responsible for the transition between regimes. We also show the difference in behavior between the dissolution fluxes and the mixing state of the systems. We observe that while the dissolution flux decreases with the Rayleigh number, the system becomes more homogeneous. That is, mixing is enhanced by reducing diffusion. This observation is explained by the effect of the instability patterns.
An Experimenting Field Approach for the Numerical Solution of Multiphase Flow in Porous Media
Salama, Amgad
2015-07-14
In this work, we apply the experimenting pressure field technique to the problem of the flow of two or more immiscible phases in porous media. In this technique, a set of predefined pressure fields are introduced to the governing partial differential equations. This implies that the velocity vector field and the divergence at each cell of the solution mesh can be determined. However, since none of these fields is the true pressure field entailed by the boundary conditions and/or the source terms, the divergence at each cell will not be the correct one. Rather the residue which is the difference between the true divergence and the calculated one is obtained. These fields are designed such that these residuals are used to construct the matrix of coefficients of the pressure equation and the right-hand side. The experimenting pressure fields are generated in the solver routine and are fed to the different routines, which may be called physics routines, which return to the solver the elements of the matrix of coefficients. Therefore, this methodology separates the solver routines from the physics routines and therefore results in simpler, easy to construct, maintain, and update algorithms.
Jordan, Amy
Open challenges remain in using numerical models of subsurface flow and transport systems to make useful predictions related to nuclear waste storage and nonproliferation. The work presented here addresses the sensitivity of model results to unknown parameters, states, and processes, particularly uncertainties related to incorporating previously unrepresented processes (e.g., explosion-induced fracturing, hydrous mineral dehydration) into a subsurface flow and transport numerical simulator. The Finite Element Heat and Mass (FEHM) transfer code is used for all numerical models in this research. An experimental campaign intended to validate the predictive capability of numerical models that include the strongly coupled thermal, hydrological, and chemical processes in bedded salt is also presented. Underground nuclear explosions (UNEs) produce radionuclide gases that may seep to the surface over weeks to months. The estimated timing of gas arrival at the surface may be used to deploy personnel and equipment to the site of a suspected UNE, if allowed under the terms of the Comprehensive Nuclear Test-Ban Treaty. A model was developed using FEHM that considers barometrically pumped gas transport through a simplified fractured medium and was used to quantify the impact of uncertainties in hydrologic parameters (fracture aperture, matrix permeability, porosity, and saturation) and season of detonation on the timing of gas breakthrough. Numerical sensitivity analyses were performed for the case of a 1 kt UNE at a 400 m burial depth. Gas arrival time was found to be most affected by matrix permeability and fracture aperture. Gases having higher diffusivity were more sensitive to uncertainty in the rock properties. The effect of seasonality in the barometric pressure forcing was found to be important, with detonations in March the least likely to be detectable based on barometric data for Rainier Mesa, Nevada. Monte Carlo modeling was also used to predict the window of
Experiments in a flighted conveyor comparing shear rates in compressed versus free surface flows
Pohlman, Nicholas; Higgins, Hannah; Krupiarz, Kamila; O'Connor, Ryan
2017-11-01
Uniformity of granular flow rate is critical in industry. Experiments in a flighted conveyor system aim to fill a gap in knowledge of achieving steady mass flow rate by correlating velocity profile data with mass flow rate measurements. High speed images were collected for uniformly-shaped particles in a bottom-driven flow conveyor belt system from which the velocity profiles can be generated. The correlation of mass flow rates from the velocity profiles to the time-dependent mass measurements will determine energy dissipation rates as a function of operating conditions. The velocity profiles as a function of the size of the particles, speed of the belt, and outlet size, will be compared to shear rate relationships found in past experiments that focused on gravity-driven systems. The dimension of the linear shear and type of decaying transition to the stationary bed may appear different due to the compression versus dilation space in open flows. The application of this research can serve to validate simulations in discrete element modeling and physically demonstrate a process that can be further developed and customized for industry applications, such as feeding a biomass conversion reactor. Sponsored by NIU's Office of Student Engagement and Experiential Learning.
Hejranfar, Kazem; Parseh, Kaveh
2017-09-01
The preconditioned characteristic boundary conditions based on the artificial compressibility (AC) method are implemented at artificial boundaries for the solution of two- and three-dimensional incompressible viscous flows in the generalized curvilinear coordinates. The compatibility equations and the corresponding characteristic variables (or the Riemann invariants) are mathematically derived and then applied as suitable boundary conditions in a high-order accurate incompressible flow solver. The spatial discretization of the resulting system of equations is carried out by the fourth-order compact finite-difference (FD) scheme. In the preconditioning applied here, the value of AC parameter in the flow field and also at the far-field boundary is automatically calculated based on the local flow conditions to enhance the robustness and performance of the solution algorithm. The code is fully parallelized using the Concurrency Runtime standard and Parallel Patterns Library (PPL) and its performance on a multi-core CPU is analyzed. The incompressible viscous flows around a 2-D circular cylinder, a 2-D NACA0012 airfoil and also a 3-D wavy cylinder are simulated and the accuracy and performance of the preconditioned characteristic boundary conditions applied at the far-field boundaries are evaluated in comparison to the simplified boundary conditions and the non-preconditioned characteristic boundary conditions. It is indicated that the preconditioned characteristic boundary conditions considerably improve the convergence rate of the solution of incompressible flows compared to the other boundary conditions and the computational costs are significantly decreased.
The effect of compressed air massage on skin blood flow and temperature.
Mars, Maurice; Maharaj, Sunil S; Tufts, Mark
2005-01-01
Compressed air massage is a new treatment modality that uses air under pressure to massage skin and muscle. It is claimed to improve skin blood flow but this has not been verified. Several pilot studies were undertaken to determine the effects of compressed air massage on skin blood flow and temperature. Skin blood flow (SBF), measured using laser Doppler fluxmetry and skin temperature was recorded under several different situations: (i) treatment, at 1 Bar pressure using a single-hole (5-mm) applicator head, for 1 min at each of several sites on the right and left lower legs, with SBF measured on the dorsum of the left foot; (ii) at the same treatment pressure, SBF was measured over the left tibialis anterior when treatment was performed at different distances from the probe; (iii) SBF and skin temperature of the lower leg were measured with treatment at 0 or 1 Bar for 45 min, using two different applicator heads; (iv) SBF was measured on the dorsum of the foot of 10 subjects with treatment for 1 min at 0, 0.5, 1, 1.5 and 2 Bar using three different applicator heads. (i) SBF of the left foot was not altered by treatment of the right leg or chest, but was significantly increased during treatment of the left sole and first web, p Compressed air massage causes an immediate increase in SBF, and an immediate fall in SBF when treatment is stopped. The effect appears to be locally and not centrally mediated and is related to the pressure used. Treatment cools the skin for at least 15 min after a 45-min treatment.
Analysis of compressible light dynamic stall flow at transitional Reynolds numbers
DEFF Research Database (Denmark)
Dyken, R.D. Van; Ekaterinaris, John A.; Chandrasekhara, M.S.
1996-01-01
Numerical and experimental results of steady and light dynamic stall flow over an oscillating NACA 0012 airfoil at a freestream Mach number of 0.3 and Reynolds number of 0.54 x 10(6) are compared, The experimental observation that dynamic stall is induced from the bursting of a laminar separation...... point is specified suitably and a simple transition length model is incorporated to determine the extent of the laminar separation bubble. The thin-layer approximations of compressible, Reynolds-averaged, Navier-Stokes equations are used for the numerical solution, with an implicit, upwind-biased, third...
An implicit three-dimensional Navier-Stokes solver for compressible flow
International Nuclear Information System (INIS)
Yoon, Seokkwan; Kwak, Dochan.
1991-01-01
A three-dimensional numerical method based on the lower-upper symmetric-Gauss-Seidel implicit scheme in conjunction with the flux-limited dissipation model is developed for solving the compressible Navier-Stokes equations. A new computer code which is based on this method requires only 9 microsec per grid-point per iteration on a single processor of a Cray YMP computer and executes at the sustained rate of 170 MFLOPS. A reduction of 4 orders of magnitude in the residual for a high Reynolds number flow using 230 K grid points is obtained in 24 minutes. The computational results compare well with available experimental data. 39 refs
Integrated LTCC pressure/flow/temperature multisensor for compressed air diagnostics.
Fournier, Yannick; Maeder, Thomas; Boutinard-Rouelle, Grégoire; Barras, Aurélie; Craquelin, Nicolas; Ryser, Peter
2010-01-01
We present a multisensor designed for industrial compressed air diagnostics and combining the measurement of pressure, flow, and temperature, integrated with the corresponding signal conditioning electronics in a single low-temperature co-fired ceramic (LTCC) package. The developed sensor may be soldered onto an integrated electro-fluidic platform by using standard surface mount device (SMD) technology, e.g., as a standard electronic component would be on a printed circuit board, obviating the need for both wires and tubes and thus paving the road towards low-cost integrated electro-fluidic systems. Several performance aspects of this device are presented and discussed, together with electronics design issues.
Integrated LTCC Pressure/Flow/Temperature Multisensor for Compressed Air Diagnostics†
Fournier, Yannick; Maeder, Thomas; Boutinard-Rouelle, Grégoire; Barras, Aurélie; Craquelin, Nicolas; Ryser, Peter
2010-01-01
We present a multisensor designed for industrial compressed air diagnostics and combining the measurement of pressure, flow, and temperature, integrated with the corresponding signal conditioning electronics in a single low-temperature co-fired ceramic (LTCC) package. The developed sensor may be soldered onto an integrated electro-fluidic platform by using standard surface mount device (SMD) technology, e.g., as a standard electronic component would be on a printed circuit board, obviating the need for both wires and tubes and thus paving the road towards low-cost integrated electro-fluidic systems. Several performance aspects of this device are presented and discussed, together with electronics design issues. PMID:22163518
A Gallium multiphase equation of state
Energy Technology Data Exchange (ETDEWEB)
Crockett, Scott D [Los Alamos National Laboratory; Greeff, Carl [Los Alamos National Laboratory
2009-01-01
A new SESAME multiphase Gallium equation of state (EOS) has been developed. The equation of state includes three of the solid phases (Ga I, Ga II, Ga III) and a fluid phase (liquid/gas). The EOS includes consistent latent heat between the phases. We compare the results to the liquid Hugoniol data. We also explore the possibility of re-freezing via dynamic means such as isentropic and shock compression.
Breakdown of the Karman vortex street due to forced convection and flow compressibility
Chen, Shu-Cheng
1992-07-01
Low speed compressible flow around a heated/cooled circular cylinder was investigated. The phenomenon of sudden disappearing of the Karman vortex street was numerically simulated and studied. The vortex street at Re(sub d) = 100 and M(sub infinity) = 0.3 is primarily an effect of forced convection. The contribution of natural convection to the current event is inconsequential. The reason for the breakdown of vortex street is believed to be due to a high temperature zone in the wake generated by a high level of wall heating. This produces an effectively lower Reynolds number flow in the near wall region when a compressible gaseous media is used. Vortex shedding stops for a reason similar when flow Reynolds number is reduced globally below its minimum value. Periodic vortex sheddings were observed when the wall heating ratio was less than 0.6. In that region, the coefficient of lift decreased sharply to zero, drag increased slowly, and the Strouhal number reduced monotonically with respect to the wall heating. When the heating ratio was greater than or equal to 0.6, vortex shedding stopped, and steady flows with symmetric twin trailing vortices were observed. In this region, both lift and Strouhal number remained zero, the drag increased sharply, and the Nusselt number maintained the same decreasing slope as the one obtained from the previous region. In this paper quantitative results such as Strouhal number, lift, drag, and Nusselt number, as well as qualitative results such as streamline, isothermal, and vorticity contours obtained at various flow conditions are presented and compared with the results of Noto et al. and Chang et al. Contrast between the two are discussed.
International Nuclear Information System (INIS)
Oh, Kyeongmin; Won, Seongyeon; Ju, Hyunchul
2015-01-01
Highlights: • The effects of electrode compression on VRFB are examined. • The electronic conductivity is improved when the compression is increased. • The kinetic losses are similar regardless of the electrode compression level. • The vanadium distribution is more uniform within highly compressed electrode. - Abstract: The porous carbon felt electrode is one of the major components of all-vanadium redox flow batteries (VRFBs). These electrodes are necessarily compressed during stack assembly to prevent liquid electrolyte leakage and diminish the interfacial contact resistance among VRFB stack components. The porous structure and properties of carbon felt electrodes have a considerable influence on the electrochemical reactions, transport features, and cell performance. Thus, a numerical study was performed herein to investigate the effects of electrode compression on the charge and discharge behavior of VRFBs. A three-dimensional, transient VRFB model developed in a previous study was employed to simulate VRFBs under two degrees of electrode compression (10% vs. 20%). The effects of electrode compression were precisely evaluated by analysis of the solid/electrolyte potential profiles, transfer current density, and vanadium concentration distributions, as well as the overall charge and discharge performance. The model predictions highlight the beneficial impact of electrode compression; the electronic conductivity of the carbon felt electrode is the main parameter improved by electrode compression, leading to reduction in ohmic loss through the electrodes. In contrast, the kinetics of the redox reactions and transport of vanadium species are not significantly altered by the degree of electrode compression (10% to 20%). This study enhances the understanding of electrode compression effects and demonstrates that the present VRFB model is a valuable tool for determining the optimal design and compression of carbon felt electrodes in VRFBs.
Subramanian, Ramanathan Vishnampet Ganapathi
Methods and computing hardware advances have enabled accurate predictions of complex compressible turbulence phenomena, such as the generation of jet noise that motivates the present effort. However, limited understanding of underlying physical mechanisms restricts the utility of such predictions since they do not, by themselves, indicate a route to design improvement. Gradient-based optimization using adjoints can circumvent the flow complexity to guide designs. Such methods have enabled sensitivity analysis and active control of turbulence at engineering flow conditions by providing gradient information at computational cost comparable to that of simulating the flow. They accelerate convergence of numerical design optimization algorithms, though this is predicated on the availability of an accurate gradient of the discretized flow equations. This is challenging to obtain, since both the chaotic character of the turbulence and the typical use of discretizations near their resolution limits in order to efficiently represent its smaller scales will amplify any approximation errors made in the adjoint formulation. Formulating a practical exact adjoint that avoids such errors is especially challenging if it is to be compatible with state-of-the-art simulation methods used for the turbulent flow itself. Automatic differentiation (AD) can provide code to calculate a nominally exact adjoint, but existing general-purpose AD codes are inefficient to the point of being prohibitive for large-scale turbulence simulations. We analyze the compressible flow equations as discretized using the same high-order workhorse methods used for many high-fidelity compressible turbulence simulations, and formulate a practical space--time discrete-adjoint method without changing the basic discretization. A key step is the definition of a particular discrete analog of the continuous norm that defines our cost functional; our selection leads directly to an efficient Runge--Kutta-like scheme
Analysis of a discrete element method and coupling with a compressible fluid flow method
International Nuclear Information System (INIS)
Monasse, L.
2011-01-01
This work aims at the numerical simulation of compressible fluid/deformable structure interactions. In particular, we have developed a partitioned coupling algorithm between a Finite Volume method for the compressible fluid and a Discrete Element method capable of taking into account fractures in the solid. A survey of existing fictitious domain methods and partitioned algorithms has led to choose an Embedded Boundary method and an explicit coupling scheme. We first showed that the Discrete Element method used for the solid yielded the correct macroscopic behaviour and that the symplectic time-integration scheme ensured the preservation of energy. We then developed an explicit coupling algorithm between a compressible inviscid fluid and an un-deformable solid. Mass, momentum and energy conservation and consistency properties were proved for the coupling scheme. The algorithm was then extended to the coupling with a deformable solid, in the form of a semi implicit scheme. Finally, we applied this method to unsteady inviscid flows around moving structures: comparisons with existing numerical and experimental results demonstrate the excellent accuracy of our method. (author) [fr
Bergomi, Marzio; Wiskott, H W Anselm; Botsis, John; Mellal, Aïssa; Belser, Urs C
2010-01-01
The periodontal ligament (PDL) functions both in tension and in compression. The presence of an extensive vascular network inside the tissue suggests a significant contribution of the fluid phase to the mechanical response. This study examined the load response of bovine PDL under different pore pressure levels. A custom-made pressure chamber was constructed. Rod-shaped specimens comprising portions of dentine, bone, and intervening layer of PDL were extracted from bovine mandibular molars. The dentine ends of the specimens were secured to the actuator while the bone ends were affixed to the load cell. The entire assemblage was surrounded by the pressure chamber, which was then filled with saline. Specimens loaded at 1.0 Hz sinusoidal displacement were subjected to four different environmental fluid pressures (i.e., pressures of 0.0-1.0 MPa). The video images recorded during the tests were analyzed to determine whether or not fluid exchange between the PDL and the surrounding medium took place during mechanical loading. A value for the tissue's apparent Poisson ratio was also determined. The following observations were made: (1) fluid was squeezed out and pumped into the ligament during the compressive and tensile loading phases, (2) the PDL was highly compressible, and (3) the pore pressure had no influence on the mechanical response of the PDL. The present tests emphasized the biphasic structure of PDL tissue, which should be considered as a porous solid matrix through which fluid can freely flow.
Zuj, K A; Prince, C N; Hughson, R L; Peterson, S D
2018-02-01
This study tested the hypothesis that intermittent compression of the lower limb would increase blood flow during exercise and postexercise recovery. Data were collected from 12 healthy individuals (8 men) who performed 3 min of standing plantar flexion exercise. The following three conditions were tested: no applied compression (NoComp), compression during the exercise period only (ExComp), and compression during 2 min of standing postexercise recovery. Doppler ultrasound was used to determine superficial femoral artery (SFA) blood flow responses. Mean arterial pressure (MAP) and cardiac stroke volume (SV) were assessed using finger photoplethysmography, with vascular conductance (VC) calculated as VC = SFA flow/MAP. Compared with the NoComp condition, compression resulted in increased MAP during exercise [+3.5 ± 4.1 mmHg (mean ± SD)] but not during postexercise recovery (+1.6 ± 5.9 mmHg). SV increased with compression during both exercise (+4.8 ± 5.1 ml) and recovery (+8.0 ± 6.6 ml) compared with NoComp. There was a greater increase in SFA flow with compression during exercise (+52.1 ± 57.2 ml/min) and during recovery (+58.6 ± 56.7 ml/min). VC immediately following exercise was also significantly greater in the ExComp condition compared with the NoComp condition (+0.57 ± 0.42 ml·min -1 ·mmHg -1 ), suggesting the observed increase in blood flow during exercise was in part because of changes in VC. Results from this study support the hypothesis that intermittent compression applied during exercise and recovery from exercise results in increased limb blood flow, potentially contributing to changes in exercise performance and recovery. NEW & NOTEWORTHY Blood flow to working skeletal muscle is achieved in part through the rhythmic actions of the skeletal muscle pump. This study demonstrated that the application of intermittent pneumatic compression during the diastolic phase of the cardiac cycle, to mimic the mechanical
Schmid, L. A.
1977-01-01
The first and second variations are calculated for the irreducible form of Hamilton's Principle that involves the minimum number of dependent variables necessary to describe the kinetmatics and thermodynamics of inviscid, compressible, baroclinic flow in a specified gravitational field. The form of the second variation shows that, in the neighborhood of a stationary point that corresponds to physically stable flow, the action integral is a complex saddle surface in parameter space. There exists a form of Hamilton's Principle for which a direct solution of a flow problem is possible. This second form is related to the first by a Friedrichs transformation of the thermodynamic variables. This introduces an extra dependent variable, but the first and second variations are shown to have direct physical significance, namely they are equal to the free energy of fluctuations about the equilibrium flow that satisfies the equations of motion. If this equilibrium flow is physically stable, and if a very weak second order integral constraint on the correlation between the fluctuations of otherwise independent variables is satisfied, then the second variation of the action integral for this free energy form of Hamilton's Principle is positive-definite, so the action integral is a minimum, and can serve as the basis for a direct trail and error solution. The second order integral constraint states that the unavailable energy must be maximum at equilibrium, i.e. the fluctuations must be so correlated as to produce a second order decrease in the total unavailable energy.
Online slug detection in multi-phase transportation pipelines using electrical tomography
DEFF Research Database (Denmark)
Pedersen, Simon; Mai, Christian; Hansen, Leif
2015-01-01
Slugging flow in offshore oil & gas multi-phase transportation pipelines cause big challenges as the flow regime induces flow and pressure oscillations in the multi-phase pipelines. The negative impacts of the most severe slugs are significant and thus the elimination of slugging flow in the pipe...
Numerical Study On Local Entropy Generation In Compressible Flow Through A Suddenly Expanding Pipe
Directory of Open Access Journals (Sweden)
Gamze BastÃƒÂ¼rk
2005-02-01
Full Text Available Abstract: This study presents the investigation of the local entropy generation in compressible flow through a suddenly expanding pipe. Air is used as fluid. The air enters into the pipe with a turbulent profile using 1/7 th power law. The simulations are extended to include different expansion ratios reduced gradually from 5 to 1. To determine the effects of the mass flux, ÃÂ†" the ambient heat transfer coefficient, hamb, and the inlet temperature, Tin, on the entropy generation rate, the compressible flow is examined for various cases of these parameters. The flow and temperature fields are computed numerically with the help of the Fluent computational fluid dynamics (CFD code. In addition to this CFD code, a computer program has been developed to calculate numerically the entropy generation and other thermodynamic parameters by using the results of the calculations performed for the flow and temperature fields. The values of thermodynamic parameters in the sudden expansion. (SE case are normalized by dividing by their base quantities obtained from the calculations in the uniform cross-section (UC case. The contraction of the radius of the throat (from 0.05 to 0.01 m increases significantly the maximum value of the volumetric entropy generation rate, (about 60% and raises exponentially 11 times the total entropy generation rate with respect to the its base value. The normalized merit number decreases 73% and 40% with the contraction of the cross-section and with the increase of the ambient heat transfer coefficient (from 20 to 100 W/m2-K, respectively, whereas it rises 226% and 43% with the decrease of the maximum mass flux (from 5 to 1 kg/m2-s and with the increase of the inlet temperature (from 400 to 1000 K, respectively. Consequently, the useful energy transfer rate to irreversibility rate improves as the mass flux decreases and as the inlet temperature increases.
Liang, Xiuyu; Zhan, Hongbin; Zhang, You-Kuan; Schilling, Keith
2017-09-01
Unsaturated flow is an important process in base flow recessions and its effect is rarely investigated. A mathematical model for a coupled unsaturated-saturated flow in a horizontally unconfined aquifer with time-dependent infiltrations is presented. The effects of the lateral discharge of the unsaturated zone and aquifer compressibility are specifically taken into consideration. Semianalytical solutions for hydraulic heads and discharges are derived using Laplace transform and Cosine transform. The solutions are compared with solutions of the linearized Boussinesq equation (LB solution) and the linearized Laplace equation (LL solution), respectively. A larger dimensionless constitutive exponent κD (a smaller retention capacity) of the unsaturated zone leads to a smaller discharge during the infiltration period and a larger discharge after the infiltration. The lateral discharge of the unsaturated zone is significant when κD≤1, and becomes negligible when κD≥100. The compressibility of the aquifer has a nonnegligible impact on the discharge at early times. For late times, the power index b of the recession curve -dQ/dt˜ aQb, is 1 and independent of κD, where Q is the base flow and a is a constant lumped aquifer parameter. For early times, b is approximately equal to 3 but it approaches infinity when t→0. The present solution is applied to synthetic and field cases. The present solution matched the synthetic data better than both the LL and LB solutions, with a minimum relative error of 16% for estimate of hydraulic conductivity. The present solution was applied to the observed streamflow discharge in Iowa, and the estimated values of the aquifer parameters were reasonable.
Numerically stable fluid–structure interactions between compressible flow and solid structures
Grétarsson, Jón Tómas
2011-04-01
We propose a novel method to implicitly two-way couple Eulerian compressible flow to volumetric Lagrangian solids. The method works for both deformable and rigid solids and for arbitrary equations of state. The method exploits the formulation of [11] which solves compressible fluid in a semi-implicit manner, solving for the advection part explicitly and then correcting the intermediate state to time tn+1 using an implicit pressure, obtained by solving a modified Poisson system. Similar to previous fluid-structure interaction methods, we apply pressure forces to the solid and enforce a velocity boundary condition on the fluid in order to satisfy a no-slip constraint. Unlike previous methods, however, we apply these coupled interactions implicitly by adding the constraint to the pressure system and combining it with any implicit solid forces in order to obtain a strongly coupled, symmetric indefinite system (similar to [17], which only handles incompressible flow). We also show that, under a few reasonable assumptions, this system can be made symmetric positive-definite by following the methodology of [16]. Because our method handles the fluid-structure interactions implicitly, we avoid introducing any new time step restrictions and obtain stable results even for high density-to-mass ratios, where explicit methods struggle or fail. We exactly conserve momentum and kinetic energy (thermal fluid-structure interactions are not considered) at the fluid-structure interface, and hence naturally handle highly non-linear phenomenon such as shocks, contacts and rarefactions. © 2011 Elsevier Inc.
Particle flow of ceramic breeder pebble beds in bi-axial compression experiments
International Nuclear Information System (INIS)
Hermsmeyer, S.; Reimann, J.
2002-01-01
Pebble beds of Tritium breeding ceramic material are investigated within the framework of developing solid breeder blankets for future nuclear fusion power plants. For the thermo-mechanical characterisation of such pebble beds, bed compression experiments are the standard tools. New bi-axial compression experiments on 20 and 30 mm high pebble beds show pebble flow effects much more pronounced than in previous 10 mm beds. Owing to the greater bed height, conditions are reached where the bed fails in cross direction and unhindered flow of the pebbles occurs. The paper presents measurements for the orthosilicate and metatitanate breeder materials that are envisaged to be used in a solid breeder blanket. The data are compared with calculations made with a Drucker-Prager soil model within the finite-element code ABAQUS, calibrated with data from other experiments. It is investigated empirically whether internal bed friction angles can be determined from pebble beds of the considered heights, which would simplify, and broaden the data base for, the calibration of the Drucker-Prager pebble bed models
Nagatani, Kosuke; Shihata, Yoshinori; Matsushita, Takahiro; Tsukagoshi, Kazuhiko
2016-01-01
Ionic liquid aqueous two-phase systems were delivered into a capillary tube to achieve tube radial distribution flow (TRDF) or annular flow in a microspace. The phase diagram, viscosity of the phases, and TRDF image of the 1-butyl-3-methylimidazolium chloride and NaOH system were examined. The TRDF was formed with inner ionic liquid-rich and outer ionic liquid-poor phases in the capillary tube. The phase configuration was explained using the viscous dissipation principle. We also examined the distribution of rhodamine B in a three-branched microchannel on a microchip with ionic liquid aqueous two-phase systems for the first time.
Abe, Hidaka; Yasui, Shinichiro; Kuwata, Aya; Takeuchi, Hirofumi
2009-07-01
To improve powder flow of a high-dose direct compression formulation (drug content 30%), we compared a two-step operation for mixing glidants with a conventional one-step glidant mixing process. This two-step mixing operation was studied with two kinds of mixtures; an active pharmaceutical ingredient (API)-glidant combination and a direct compression excipient-glidant combination. The two-step operation permitted the selection of the optimum glidant type and concentration in each glidant-mixing procedure even though the formulation had different powder properties such as micronized API and enlarged direct compression vehicles, whereas the conventional approaches forced the selection of a certain glidant type and concentration at one-step mixing. The addition of 0.5% nonporous silica markedly improved API flow. In contrast, 1.0% porous silica was the appropriate glidant to enhance excipient flow at direct compression excipient-glidant mixing. The two-step operation dominantly enhanced powder flow when the appropriate API-glidant mixture and the suitable direct compression excipients-glidant mixture were blended compared to the one-step operation with its optimum glidant concentration. The results showed that the angle of repose was 43 degrees and the critical orifice diameter was 10 mm in the two-step operation, whereas it was 47 degrees and 16 mm in the one-step operation. The two-step operation of glidant mixing enhanced powder flow of the high-dose direct compression formulation compared with the one-step operation. The two-step operation eliminates the bottleneck of powder flow and allows direct compression to be more worth applying for formulation and process development trials.
Transport phenomena in multiphase flows
Mauri, Roberto
2015-01-01
This textbook provides a thorough presentation of the phenomena related to the transport of mass, momentum and energy. It lays all the basic physical principles, then for the more advanced readers, it offers an in-depth treatment with advanced mathematical derivations and ends with some useful applications of the models and equations in specific settings. The important idea behind the book is to unify all types of transport phenomena, describing them within a common framework in terms of cause and effect, respectively represented by the driving force and the flux of the transported quantity. The approach and presentation are original in that the book starts with a general description of transport processes, providing the macroscopic balance relations of fluid dynamics and heat and mass transfer, before diving into the mathematical realm of continuum mechanics to derive the microscopic governing equations at the microscopic level. The book is a modular teaching tool and can be used either for an introductory...
Seers, Thomas; Andrew, Matthew; Bijeljic, Branko; Blunt, Martin; Dobson, Kate; Hodgetts, David; Lee, Peter; Menke, Hannah; Singh, Kamaljit; Parsons, Aaron
2015-04-01
Applied shear stresses within high porosity granular rocks result in characteristic deformation responses (rigid grain reorganisation, dilation, isovolumetric strain, grain fracturing and/or crushing) emanating from elevated stress concentrations at grain contacts. The strain localisation features produced by these processes are generically termed as microfaults (also shear bands), which occur as narrow tabular regions of disaggregated, rotated and/or crushed grains. Because the textural priors that favour microfault formation make their host rocks (esp. porous sandstones) conducive to the storage of geo-fluids, such structures are often abundant features within hydrocarbon reservoirs, aquifers and potential sites of CO2 storage (i.e. sandstone saline aquifers). The porosity collapse which accompanies microfault formation typically results in localised permeability reduction, often encompassing several orders of magnitude. Given that permeability is the key physical parameter that governs fluid circulation in the upper crust, this petrophysical degradation implicates microfaults as being flow impeding structures which may act as major baffles and/or barriers to fluid flow within the subsurface. Such features therefore have the potential to negatively impact upon hydrocarbon production or CO2 injection, making their petrophysical characterisation of considerable interest. Despite their significance, little is known about the pore-scale processes involved in fluid trapping and transfer within microfaults, particularly in the presence of multiphase flow analogous to oil accumulation, production and CO2 injection. With respect to the geological storage of CO2 within sandstone saline aquifers it has been proposed that even fault rocks with relatively low phyllosilicate content or minimal quartz cementation may act as major baffles or barriers to migrating CO2 plume. Alternatively, as ubiquitous intra-reservoir heterogeneities, micro-faults also have the potential to
Do Suan Zoan; M. I. Lipatov; Pham Tuan Vinh
2014-01-01
The Couette-Taylor flow of compressible gas at high Reynolds numbers is studied. Problem statement is formulated on the basis of the differential equation system (the Navier-Stockes equations) for compressible gas in cylindrical coordinates. On the basis of physical model built in CFD, the numerical results for various temperatures of the cylinder’s surfaces and rotational speed are obtained. The relation between vortice dimensions and surface temperatures and rotational speed is established.
Beardsell, Guillaume; Blanquart, Guillaume
2017-11-01
In direct numerical simulations (DNS) of turbulent flows, it is often prohibitively expensive to simulate complete flow geometries. For example, to study turbulence-flame interactions, one cannot perform a DNS of a full combustor. Usually, a well-selected portion of the domain is chosen, in this particular case the region around the flame front. In this work, we perform a Reynolds decomposition of the velocity field and solve for the fluctuating part only. The resulting equations are the same as the original Navier-Stokes equations, except for turbulence-generating large scale features of the flow such as mean shear, which appear as forcing terms. This approach allows us to achieve high Reynolds numbers and sustained turbulence while keeping the computational cost reasonable. We have already applied this strategy to incompressible flows, but not to compressible ones, where special care has to be taken regarding the energy equation. Implementation of the resulting additional terms in the finite-difference code NGA is discussed and preliminary results are presented. In particular, we look at the budget of turbulent kinetic energy and internal energy. We are considering applying this technique to turbulent premixed flames.
Thermodynamic bounds for existence of normal shock in compressible fluid flow in pipes
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SERGIO COLLE
Full Text Available Abstract The present paper is concerned with the thermodynamic theory of the normal shock in compressible fluid flow in pipes, in the lights of the pioneering works of Lord Rayleigh and G. Fanno. The theory of normal shock in pipes is currently presented in terms of the Rayleigh and Fanno curves, which are shown to cross each other in two points, one corresponding to a subsonic flow and the other corresponding to a supersonic flow. It is proposed in this paper a novel differential identity, which relates the energy flux density, the linear momentum flux density, and the entropy, for constant mass flow density. The identity so obtained is used to establish a theorem, which shows that Rayleigh and Fanno curves become tangent to each other at a single sonic point. At the sonic point the entropy reaches a maximum, either as a function of the pressure and the energy density flux or as a function of the pressure and the linear momentum density flux. A Second Law analysis is also presented, which is fully independent of the Second Law analysis based on the Rankine-Hugoniot adiabatic carried out by Landau and Lifshitz (1959.
A wave-envelope of sound propagation in nonuniform circular ducts with compressible mean flows
Nayfeh, A. H.; Kaiser, J. E.; Shaker, B. S.
1979-01-01
An acoustic theory is developed to determine the sound transmission and attenuation through an infinite, hard-walled or lined circular duct carrying compressible, sheared, mean flows and having a variable cross section. The theory is applicable to large as well as small axial variations, as long as the mean flow does not separate. The technique is based on solving for the envelopes of the quasi-parallel acoustic modes that exist in the duct instead of solving for the actual wave, thereby reducing the computation time and the round-off error encountered in purely numerical techniques. The solution recovers the solution based on the method of multiple scales for slowly varying duct geometry. A computer program was developed based on the wave-envelope analysis for general mean flows. Results are presented for the reflection and transmission coefficients as well as the acoustic pressure distributions for a number of conditions: both straight and variable area ducts with and without liners and mean flows from very low to high subsonic speeds are considered.
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Wagner Henrik
2011-12-01
Full Text Available Abstract Background Mechanical chest compressions (CCs have been shown capable of maintaining circulation in humans suffering cardiac arrest for extensive periods of time. Reports have documented a visually normalized coronary blood flow during angiography in such cases (TIMI III flow, but it has never been actually measured. Only indirect measurements of the coronary circulation during cardiac arrest with on-going mechanical CCs have been performed previously through measurement of the coronary perfusion pressure (CPP. In this study our aim was to correlate average peak coronary flow velocity (APV to CPP during mechanical CCs. Methods In a closed chest porcine model, cardiac arrest was established through electrically induced ventricular fibrillation (VF in eleven pigs. After one minute, mechanical chest compressions were initiated and then maintained for 10 minutes upon which the pigs were defibrillated. Measurements of coronary blood flow in the left anterior descending artery were made at baseline and during VF with a catheter based Doppler flow fire measuring APV. Furthermore measurements of central (thoracic venous and arterial pressures were also made in order to calculate the theoretical CPP. Results Average peak coronary flow velocity was significantly higher compared to baseline during mechanical chests compressions and this was observed during the entire period of mechanical chest compressions (12 - 39% above baseline. The APV slowly declined during the 10 min period of mechanical chest compressions, but was still higher than baseline at the end of mechanical chest compressions. CPP was simultaneously maintained at > 20 mmHg during the 10 minute episode of cardiac arrest. Conclusion Our study showed good correlation between CPP and APV which was highly significant, during cardiac arrest with on-going mechanical CCs in a closed chest porcine model. In addition APV was even higher during mechanical CCs compared to baseline. Mechanical
A Parallel Reconstructed Discontinuous Galerkin Method for the Compressible Flows on Aritrary Grids
Energy Technology Data Exchange (ETDEWEB)
Hong Luo; Amjad Ali; Robert Nourgaliev; Vincent A. Mousseau
2010-01-01
A reconstruction-based discontinuous Galerkin method is presented for the solution of the compressible Navier-Stokes equations on arbitrary grids. In this method, an in-cell reconstruction is used to obtain a higher-order polynomial representation of the underlying discontinuous Galerkin polynomial solution and an inter-cell reconstruction is used to obtain a continuous polynomial solution on the union of two neighboring, interface-sharing cells. The in-cell reconstruction is designed to enhance the accuracy of the discontinuous Galerkin method by increasing the order of the underlying polynomial solution. The inter-cell reconstruction is devised to remove an interface discontinuity of the solution and its derivatives and thus to provide a simple, accurate, consistent, and robust approximation to the viscous and heat fluxes in the Navier-Stokes equations. A parallel strategy is also devised for the resulting reconstruction discontinuous Galerkin method, which is based on domain partitioning and Single Program Multiple Data (SPMD) parallel programming model. The RDG method is used to compute a variety of compressible flow problems on arbitrary meshes to demonstrate its accuracy, efficiency, robustness, and versatility. The numerical results demonstrate that this RDG method is third-order accurate at a cost slightly higher than its underlying second-order DG method, at the same time providing a better performance than the third order DG method, in terms of both computing costs and storage requirements.
International Nuclear Information System (INIS)
Faccanoni, Gloria; Kokh, Samuel; Allaire, Gregoire
2012-01-01
In the present work we investigate the numerical simulation of liquid-vapor phase change in compressible flows. Each phase is modeled as a compressible fluid equipped with its own equation of state (EOS). We suppose that inter-phase equilibrium processes in the medium operate at a short time-scale compared to the other physical phenomena such as convection or thermal diffusion. This assumption provides an implicit definition of an equilibrium EOS for the two-phase medium. Within this framework, mass transfer is the result of local and instantaneous equilibria between both phases. The overall model is strictly hyperbolic. We examine properties of the equilibrium EOS and we propose a discretization strategy based on a finite-volume relaxation method. This method allows to cope with the implicit definition of the equilibrium EOS, even when the model involves complex EOS's for the pure phases. We present two-dimensional numerical simulations that shows that the model is able to reproduce mechanism such as phase disappearance and nucleation. (authors)
PEVC-FMDF for Large Eddy Simulation of Compressible Turbulent Flows
Nouri Gheimassi, Arash; Nik, Mehdi; Givi, Peyman; Livescu, Daniel; Pope, Stephen
2017-11-01
The filtered density function (FDF) closure is extended to a ``self-contained'' format to include the subgrid scale (SGS) statistics of all of the hydro-thermo-chemical variables in turbulent flows. These are the thermodynamic pressure, the specific internal energy, the velocity vector, and the composition field. In this format, the model is comprehensive and facilitates large eddy simulation (LES) of flows at both low and high compressibility levels. A transport equation is developed for the joint ``pressure-energy-velocity-composition filtered mass density function (PEVC-FMDF).'' In this equation, the effect of convection appears in closed form. The coupling of the hydrodynamics and thermochemistry is modeled via a set of stochastic differential equation (SDE) for each of the transport variables. This yields a self-contained SGS closure. For demonstration, LES is conducted of a turbulent shear flow with transport of a passive scalar. The consistency of the PEVC-FMDF formulation is established, and its overall predictive capability is appraised via comparison with direct numerical simulation (DNS) data.
Turbulence modification and multiphase turbulence transport modeling
International Nuclear Information System (INIS)
Besnard, D.C.; Kataoka, I.; Serizawa, A.
1991-01-01
It is shown here that in the derivation of turbulence transport models for multiphase flows, terms naturally appear that can be interpreted as related to turbulence modification of one field by the other. We obtain two such terms, one suggesting turbulence enhancement due to instabilities in two-phase flow, the second one showing turbulence damping due to the presence of the other field, both in gas-particle and gas-liquid cases
Linearly decoupled energy-stable numerical methods for multi-component two-phase compressible flow
Kou, Jisheng
2017-12-06
In this paper, for the first time we propose two linear, decoupled, energy-stable numerical schemes for multi-component two-phase compressible flow with a realistic equation of state (e.g. Peng-Robinson equation of state). The methods are constructed based on the scalar auxiliary variable (SAV) approaches for Helmholtz free energy and the intermediate velocities that are designed to decouple the tight relationship between velocity and molar densities. The intermediate velocities are also involved in the discrete momentum equation to ensure a consistency relationship with the mass balance equations. Moreover, we propose a component-wise SAV approach for a multi-component fluid, which requires solving a sequence of linear, separate mass balance equations. We prove that the methods have the unconditional energy-dissipation feature. Numerical results are presented to verify the effectiveness of the proposed methods.
International Nuclear Information System (INIS)
Kimura, Toshiya.
1997-03-01
A two-dimensional explicit Euler solver has been implemented for five MIMD parallel computers of different machine architectures in Center for Promotion of Computational Science and Engineering of Japan Atomic Energy Research Institute. These parallel computers are Fujitsu VPP300, NEC SX-4, CRAY T94, IBM SP2, and Hitachi SR2201. The code was parallelized by several parallelization methods, and a typical compressible flow problem has been calculated for different grid sizes changing the number of processors. Their effective performances for parallel calculations, such as calculation speed, speed-up ratio and parallel efficiency, have been investigated and evaluated. The communication time among processors has been also measured and evaluated. As a result, the differences on the performance and the characteristics between vector-parallel and scalar-parallel computers can be pointed, and it will present the basic data for efficient use of parallel computers and for large scale CFD simulations on parallel computers. (author)
Integrated LTCC Pressure/Flow/Temperature Multisensor for Compressed Air Diagnostics†
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Nicolas Craquelin
2010-12-01
Full Text Available We present a multisensor designed for industrial compressed air diagnostics and combining the measurement of pressure, flow, and temperature, integrated with the corresponding signal conditioning electronics in a single low-temperature co-fired ceramic (LTCC package. The developed sensor may be soldered onto an integrated electro-fluidic platform by using standard surface mount device (SMD technology, e.g., as a standard electronic component would be on a printed circuit board, obviating the need for both wires and tubes and thus paving the road towards low-cost integrated electro-fluidic systems. Several performance aspects of this device are presented and discussed, together with electronics design issues.
An Embedded Ghost-Fluid Method for Compressible Flow in Complex Geometry
Almarouf, Mohamad Abdulilah Alhusain Alali
2016-06-03
We present an embedded ghost-fluid method for numerical solutions of the compressible Navier Stokes (CNS) equations in arbitrary complex domains. The PDE multidimensional extrapolation approach of Aslam [1] is used to reconstruct the solution in the ghost-fluid regions and impose boundary conditions at the fluid-solid interface. The CNS equations are numerically solved by the second order multidimensional upwind method of Colella [2] and Saltzman [3]. Block-structured adaptive mesh refinement implemented under the Chombo framework is utilized to reduce the computational cost while keeping high-resolution mesh around the embedded boundary and regions of high gradient solutions. Numerical examples with different Reynolds numbers for low and high Mach number flow will be presented. We compare our simulation results with other reported experimental and computational results. The significance and advantages of our implementation, which revolve around balancing between the solution accuracy and implementation difficulties, are briefly discussed as well. © 2016 Trans Tech Publications.
Bresch, D.; Fernández-Nieto, E. D.; Ionescu, I. R.; Vigneaux, P.
In this paper we propose a well-balanced finite volume/augmented Lagrangian method for compressible visco-plastic models focusing on a compressible Bingham type system with applications to dense avalanches. For the sake of completeness we also present a method showing that such a system may be derived for a shallow flow of a rigid-viscoplastic incompressible fluid, namely for incompressible Bingham type fluid with free surface. When the fluid is relatively shallow and spreads slowly, lubrication-style asymptotic approximations can be used to build reduced models for the spreading dynamics, see for instance [N.J. Balmforth et al., J. Fluid Mech (2002)]. When the motion is a little bit quicker, shallow water theory for non-Newtonian flows may be applied, for instance assuming a Navier type boundary condition at the bottom. We start from the variational inequality for an incompressible Bingham fluid and derive a shallow water type system. In the case where Bingham number and viscosity are set to zero we obtain the classical Shallow Water or Saint-Venant equations obtained for instance in [J.F. Gerbeau, B. Perthame, DCDS (2001)]. For numerical purposes, we focus on the one-dimensional in space model: We study associated static solutions with sufficient conditions that relate the slope of the bottom with the Bingham number and domain dimensions. We also propose a well-balanced finite volume/augmented Lagrangian method. It combines well-balanced finite volume schemes for spatial discretization with the augmented Lagrangian method to treat the associated optimization problem. Finally, we present various numerical tests.
Gupta, Akanksha; Ganesh, Rajaraman
2018-01-01
We study compressibility effects on the two-dimensional strongly coupled dusty plasma by means of computational fluid dynamics (CFD) with the Kolmogorov flow as an initial shear flow profile. Nonlinear compressible vortex flow dynamics and other linear and nonlinear properties of such flow in the presence of variable density, pressure, and electrostatic potential are addressed using a generalised compressible hydrodynamic model. The stabilizing effect of compressibility on the unstable shear flows in the presence of strong correlation ( τm>0 ) is presented. Increasing the Mach number relatively reduces the growth-rate of perturbation. On the other hand, strong correlation makes the medium to be more unstable and increases the growth rate. Using an eigen value solver, various linear properties of compressible Kolmogorov flow have been investigated for a range of variable parameters, for example, Mach number, Reynolds number, and viscoelastic coefficient (τm). Compressible Kolmogorov flow becomes unstable above a critical value of the Reynolds number (Rc), and below Rc, the shear flow is found to be neutrally stable. In this study, it is found that the viscoelasticity reduces the value of Rc. For our choice of parameters, at τm=τmc , the compressible Kolmogorov flow becomes unconditionally unstable and no Rc exists for values of τm higher than τmc . To address the nonlinear properties, for example, mode-mode interaction due to the presence of nonlinearity in the fluid, vortex formation, etc., a massively parallelized Advanced Generalized SPECTral Code (AG-Spect) has been developed. AG-Spect, a newly developed code, is an efficient tool to solve any set of nonlinear fluid dynamic equations. A good agreement in linear growth rates obtained from the eigen value solver and time dependent simulation (AG-Spect) is found. In our CFD study, the suppression of instability, elongated vortex structures, pattern formation, nonlinear saturation, and visco
Numerical simulation of complex multi-phase fluid of casting process and its applications
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CHEN Li-liang
2006-05-01
Full Text Available The fluid of casting process is a typical kind of multi-phase flow. Actually, many casting phenomena have close relationship with the multi-phase flow, such as molten metal filling process, air entrapment, slag movement, venting process of die casting, gas escaping of lost foam casting and so on. Obviously, in order to analyze these phenomena accurately, numerical simulation of the multi-phase fluid is necessary. Unfortunately, so far, most of the commercial casting simulation systems do not have the ability of multi-phase flow modeling due to the difficulty in the multi-phase flow calculation. In the paper, Finite Different Method (FDM technique was adopt to solve the multi-phase fluid model. And a simple object of the muiti-phase fluid was analyzed to obtain the fluid rates of the liquid phase and the entrapped air phase.
Central upwind scheme for a compressible two-phase flow model.
Ahmed, Munshoor; Saleem, M Rehan; Zia, Saqib; Qamar, Shamsul
2015-01-01
In this article, a compressible two-phase reduced five-equation flow model is numerically investigated. The model is non-conservative and the governing equations consist of two equations describing the conservation of mass, one for overall momentum and one for total energy. The fifth equation is the energy equation for one of the two phases and it includes source term on the right-hand side which represents the energy exchange between two fluids in the form of mechanical and thermodynamical work. For the numerical approximation of the model a high resolution central upwind scheme is implemented. This is a non-oscillatory upwind biased finite volume scheme which does not require a Riemann solver at each time step. Few numerical case studies of two-phase flows are presented. For validation and comparison, the same model is also solved by using kinetic flux-vector splitting (KFVS) and staggered central schemes. It was found that central upwind scheme produces comparable results to the KFVS scheme.
Central upwind scheme for a compressible two-phase flow model.
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Munshoor Ahmed
Full Text Available In this article, a compressible two-phase reduced five-equation flow model is numerically investigated. The model is non-conservative and the governing equations consist of two equations describing the conservation of mass, one for overall momentum and one for total energy. The fifth equation is the energy equation for one of the two phases and it includes source term on the right-hand side which represents the energy exchange between two fluids in the form of mechanical and thermodynamical work. For the numerical approximation of the model a high resolution central upwind scheme is implemented. This is a non-oscillatory upwind biased finite volume scheme which does not require a Riemann solver at each time step. Few numerical case studies of two-phase flows are presented. For validation and comparison, the same model is also solved by using kinetic flux-vector splitting (KFVS and staggered central schemes. It was found that central upwind scheme produces comparable results to the KFVS scheme.
Numerical analysis of a non equilibrium two-component two-compressible flow in porous media
Saad, Bilal Mohammed
2013-09-01
We propose and analyze a finite volume scheme to simulate a non equilibrium two components (water and hydrogen) two phase flow (liquid and gas) model. In this model, the assumption of local mass non equilibrium is ensured and thus the velocity of the mass exchange between dissolved hydrogen and hydrogen in the gas phase is supposed finite. The proposed finite volume scheme is fully implicit in time together with a phase-by-phase upwind approach in space and it is discretize the equations in their general form with gravity and capillary terms We show that the proposed scheme satisfies the maximum principle for the saturation and the concentration of the dissolved hydrogen. We establish stability results on the velocity of each phase and on the discrete gradient of the concentration. We show the convergence of a subsequence to a weak solution of the continuous equations as the size of the discretization tends to zero. At our knowledge, this is the first convergence result of finite volume scheme in the case of two component two phase compressible flow in several space dimensions.
CFD Simulations of the IHF Arc-Jet Flow: Compression-Pad Separation Bolt Wedge Tests
Gokcen, Tahir; Skokova, Kristina A.
2017-01-01
This paper reports computational analyses in support of two wedge tests in a high enthalpy arc-jet facility at NASA Ames Research Center. These tests were conducted using two different wedge models, each placed in a free jet downstream of a corresponding different conical nozzle in the Ames 60-MW Interaction Heating Facility. Each panel test article included a metallic separation bolt imbedded in Orion compression-pad and heatshield materials, resulting in a circular protuberance over a flat plate. The protuberances produce complex model flowfields, containing shock-shock and shock-boundary layer interactions, and multiple augmented heating regions on the test plate. As part of the test calibration runs, surface pressure and heat flux measurements on water-cooled calibration plates integrated with the wedge models were also obtained. Surface heating distributions on the test articles as well as arc-jet test environment parameters for each test configuration are obtained through computational fluid dynamics simulations, consistent with the facility and calibration measurements. The present analysis comprises simulations of the non-equilibrium flow field in the facility nozzle, test box, and flow field over test articles, and comparisons with the measured calibration data.
Determination of mean pressure from PIV in compressible flows using the Reynolds-averaging approach
van Gent, Paul L.; van Oudheusden, Bas W.; Schrijer, Ferry F. J.
2018-03-01
The feasibility of computing the flow pressure on the basis of PIV velocity data has been demonstrated abundantly for low-speed conditions. The added complications occurring for high-speed compressible flows have, however, so far proved to be largely inhibitive for the accurate experimental determination of instantaneous pressure. Obtaining mean pressure may remain a worthwhile and realistic goal to pursue. In a previous study, a Reynolds-averaging procedure was developed for this, under the moderate-Mach-number assumption that density fluctuations can be neglected. The present communication addresses the accuracy of this assumption, and the consistency of its implementation, by evaluating of the relevance of the different contributions resulting from the Reynolds-averaging. The methodology involves a theoretical order-of-magnitude analysis, complemented with a quantitative assessment based on a simulated and a real PIV experiment. The assessments show that it is sufficient to account for spatial variations in the mean velocity and the Reynolds-stresses and that temporal and spatial density variations (fluctuations and gradients) are of secondary importance and comparable order-of-magnitude. This result permits to simplify the calculation of mean pressure from PIV velocity data and to validate the approximation of neglecting temporal and spatial density variations without having access to reference pressure data.
A versatile embedded boundary adaptive mesh method for compressible flow in complex geometry
Almarouf, Mohamad Abdulilah Alhusain Alali
2017-02-25
We present an embedded ghost-fluid method for numerical solutions of the compressible Navier Stokes (CNS) equations in arbitrary complex domains. A PDE multidimensional extrapolation approach is used to reconstruct the solution in the ghost-fluid regions and imposing boundary conditions on the fluid-solid interface, coupled with a multi-dimensional algebraic interpolation for freshly cleared cells. The CNS equations are numerically solved by the second order multidimensional upwind method. Block-structured adaptive mesh refinement, implemented with the Chombo framework, is utilized to reduce the computational cost while keeping high resolution mesh around the embedded boundary and regions of high gradient solutions. The versatility of the method is demonstrated via several numerical examples, in both static and moving geometry, ranging from low Mach number nearly incompressible flows to supersonic flows. Our simulation results are extensively verified against other numerical results and validated against available experimental results where applicable. The significance and advantages of our implementation, which revolve around balancing between the solution accuracy and implementation difficulties, are briefly discussed as well.
Multiphasic growth curve analysis.
Koops, W.J.
1986-01-01
Application of a multiphasic growth curve is demonstrated with 4 data sets, adopted from literature. The growth curve used is a summation of n logistic growth functions. Human height growth curves of this type are known as "double logistic" (n = 2) and "triple logistic" (n = 3) growth curves (Bock
Bukhvostova, A.; Russo, E; Kuerten, Johannes G.M.; Geurts, Bernardus J.
Direct numerical simulation is used to assess the importance of compressibility in turbulent channel flow of a mixture of air and water vapor with dispersed water droplets. The dispersed phase is allowed to undergo phase transition, which leads to heat and mass transfer between the phases. We
International Nuclear Information System (INIS)
Holtz, A.; Nystroem, B.G.; Gerdin, B.
1989-01-01
The relations between degree of thoracic spinal cord compression causing myelographic block, reversible paraparesis, and extinction of the sensory evoked potential on one hand, and spinal cord blood flow on the other, were investigated. This was done in rats using the blocking weight-technique and 14 C-iodoantipyrine autoradiography. A load of 9 g caused myelographic block. Five minutes of compression with that load caused a reduction of spinal cord blood flow to about 25%, but 5 and 60 minutes after the compression spinal cord blood flow was restored to 60% of the pretrauma value. A load of 35 g for 5 minutes caused transient paraparesis. Recovery to about 30% was observed 5 and 60 minutes thereafter. During compression at a load of 55 g, which caused almost total extinction of sensory evoked potential and irreversible paraplegia, spinal cord blood flow under the load ceased. The results indicate that myelographic block occurs at a load which does not cause irreversible paraparesis and that a load which permits sensory evoked potential to be elicited results in potentially salvageable damage