Computational Fluid Dynamics Simulations of Phase Distribution in Adiabatic Upward Bubbly Flows Using Interfacial Area Transport Equation PDF Download
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Author: Xia Wang
Publisher:
ISBN:
Category : Fluid dynamics
Languages : en
Pages : 176
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Book Description
Abstract: In analyzing gas-liquid two-phase flows, it is imperative to take into account the bubble-bubble and bubble-eddy interactions, which may result in bubble coalescence and/or disintegration. The bubble coalescence and disintegration will further affect the interfacial structure, which could, to a first-order approximation, be characterized by the interfacial area concentration and void fraction. In this thesis, a one-group interfacial area transport equation (IATE) that was developed in the literature to describe the evolution of the interfacial area concentration in bubbly flows was implemented into a computational fluid dynamics (CFD) code, namely, FLUENT. Previous studies demonstrated that the following three bubble interaction mechanisms were essential in bubby flows of interest: coalescence of bubbles due to bubble random collisions driven by turbulence, coalescence of bubbles due to wake entrainment, and disintegration of bubbles caused by turbulent eddy impact. These three mechanisms have been taken into account in the one-group IATE. The current study focuses on examining the capability of FLUENT with the one-group IATE in predicting the phase distribution in adiabatic bubbly flows. Eulerian multiphase model in FLUENT 6.2.16 is applied, in which two sets of conservation equations are applied to each phase separately but coupled through interfacial transfer terms. The constitutive relations of the interfacial transfers are provided using the interfacial area concentration described through the IATE. CFD simulations of adiabatic upward bubbly flows in a circular pipe have been carried out in this study. In the simulation, the interfacial area concentration is first introduced into FLUENT as a user- defined scalar and then the corresponding IATE is solved for the interfacial area concentration. In addition, the associated modifications to the interfacial drag force model and turbulence model are made to reflect the evolution of the bubble size by replacing the constant bubble diameter in those models with the Sauter mean diameter, which is a function of the void fraction and interfacial area concentration. With comparisons between the simulation results and available experimental data, satisfactory agreement has been achieved, which demonstrates that FLUENT code with the one-group IATE provide valuable simulation tool for bubbly two-phase flows.
Author: Xia Wang
Publisher:
ISBN:
Category : Fluid dynamics
Languages : en
Pages : 176
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Book Description
Abstract: In analyzing gas-liquid two-phase flows, it is imperative to take into account the bubble-bubble and bubble-eddy interactions, which may result in bubble coalescence and/or disintegration. The bubble coalescence and disintegration will further affect the interfacial structure, which could, to a first-order approximation, be characterized by the interfacial area concentration and void fraction. In this thesis, a one-group interfacial area transport equation (IATE) that was developed in the literature to describe the evolution of the interfacial area concentration in bubbly flows was implemented into a computational fluid dynamics (CFD) code, namely, FLUENT. Previous studies demonstrated that the following three bubble interaction mechanisms were essential in bubby flows of interest: coalescence of bubbles due to bubble random collisions driven by turbulence, coalescence of bubbles due to wake entrainment, and disintegration of bubbles caused by turbulent eddy impact. These three mechanisms have been taken into account in the one-group IATE. The current study focuses on examining the capability of FLUENT with the one-group IATE in predicting the phase distribution in adiabatic bubbly flows. Eulerian multiphase model in FLUENT 6.2.16 is applied, in which two sets of conservation equations are applied to each phase separately but coupled through interfacial transfer terms. The constitutive relations of the interfacial transfers are provided using the interfacial area concentration described through the IATE. CFD simulations of adiabatic upward bubbly flows in a circular pipe have been carried out in this study. In the simulation, the interfacial area concentration is first introduced into FLUENT as a user- defined scalar and then the corresponding IATE is solved for the interfacial area concentration. In addition, the associated modifications to the interfacial drag force model and turbulence model are made to reflect the evolution of the bubble size by replacing the constant bubble diameter in those models with the Sauter mean diameter, which is a function of the void fraction and interfacial area concentration. With comparisons between the simulation results and available experimental data, satisfactory agreement has been achieved, which demonstrates that FLUENT code with the one-group IATE provide valuable simulation tool for bubbly two-phase flows.
Author: Xia Wang
Publisher:
ISBN:
Category :
Languages : en
Pages : 196
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Book Description
Abstract: The current study focuses on providing a reliable computational fluid dynamics (CFD) tool for two-phase flow simulations, which is capable of capturing dynamic changes of interfacial structures and achieving accurate predictions of flow behaviors. A set of interfacial area transport equations (IATEs), which dynamically evaluates the interfacial area concentration, was successfully implemented into a CFD software package, namely, Fluent. The interfacial area concentration is a key parameter in modeling the interfacial transfer terms in the two-fluid model due to mechanical and thermal non-equilibrium between the two phases. Given the various flow regimes in two-phase flows, one-group IATE and two-group IATE developed in the literature were separately incorporated into the two-fluid model and subsequently validated under different flow conditions: liquid-liquid two-component bubbly; air-water bubbly, cap-bubbly, and churn-turbulent flows. Numerical results obtained from the two-fluid model incorporated with the IATE models were generally in good agreement with the experimental data. A set of adjustable model coefficients was also established for three-dimensional simulations when the influence of the lateral phase distribution in a circular flow channel on the one-group IATE model was considered. In addition, contributions of the bubble interaction mechanisms and interfacial forces to the phase distributions of two-phase flow were numerically investigated. It was observed that the lift force was significant for the phase distributions in gas-liquid two-phase flows; however it might cause convergence issues when large bubbles exist in the flow field of interest. Furthermore, a mathematical property, i.e., the well-posedness of the proposed one-dimensional three-field model with the two-group IATE model, was studied. The necessary condition to ensure well-posedness was obtained using characteristic analysis. The momentum flux parameters were introduced to help stabilize the proposed model.
Author: Hyoung Woo Oh
Publisher: BoD – Books on Demand
ISBN: 9537619591
Category : Computers
Languages : en
Pages : 430
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Book Description
This book is intended to serve as a reference text for advanced scientists and research engineers to solve a variety of fluid flow problems using computational fluid dynamics (CFD). Each chapter arises from a collection of research papers and discussions contributed by the practiced experts in the field of fluid mechanics. This material has encompassed a wide range of CFD applications concerning computational scheme, turbulence modeling and its simulation, multiphase flow modeling, unsteady-flow computation, and industrial applications of CFD.
Author: Nikolay Ivanov Kolev
Publisher: Springer Science & Business Media
ISBN: 3642207499
Category : Technology & Engineering
Languages : en
Pages : 337
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Book Description
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 force, the lubrication force in the wall boundary layer, and the dispersion force. A pragmatic generalization of the k-eps models for continuous velocity field is proposed containing flows in large volumes and flows in porous structures. A Methods of how to derive source and sinks terms for multiphase k-eps models is presented. A set of 13 single- and two phase benchmarks for verification of k-eps models in system computer codes are provided and reproduced with the IVA computer code as an example of the application of the theory. This methodology is intended to help other engineers and scientists to introduce this technology step-by-step in their own engineering practice. In many practical application gases are solved in liquids under given conditions, released under other conditions and therefore affecting technical processes for good of for bad. Useful information on the solubility of oxygen, nitrogen, hydrogen and carbon dioxide in water under large interval of pressures and temperatures is collected, and appropriate mathematical approximation functions are provided. In addition methods for the computation of the diffusion coefficients are described. With this information solution and dissolution dynamics in multiphase fluid flows can be analyzed. For this purpose the non-equilibrium absorption and release on bubble, droplet and film surfaces under different conditions is mathematically described. A systematic set of internally consistent state equations for diesel fuel gas and liquid valid in broad range of changing pressure and temperature is provided. This new second edition includes various updates, extensions, improvements and corrections. In many practical application gases are solved in liquids under given conditions, released under other conditions and therefore affecting technical processes for good of for bad. Useful information on the solubility of oxygen, nitrogen, hydrogen and carbon dioxide in water under large interval of pressures and temperatures is collected, and appropriate mathematical approximation functions are provided. In addition methods for the computation of the diffusion coefficients are described. With this information solution and dissolution dynamics in multiphase fluid flows can be analyzed. For this purpose the non-equilibrium absorption and release on bubble, droplet and film surfaces under different conditions is mathematically described. A systematic set of internally consistent state equations for diesel fuel gas and liquid valid in broad range of changing pressure and temperature is provided. This new second edition includes various updates, extensions, improvements and corrections.
Author: Martin Sommerfeld
Publisher: Springer Science & Business Media
ISBN: 3642185401
Category : Science
Languages : en
Pages : 354
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Book Description
The book summarises the outcom of a priority research programme: 'Analysis, Modelling and Computation of Multiphase Flows'. The results of 24 individual research projects are presented. The main objective of the research programme was to provide a better understanding of the physical basis for multiphase gas-liquid flows as they are found in numerous chemical and biochemical reactors. The research comprises steady and unsteady multiphase flows in three frequently found reactor configurations, namely bubble columns without interiors, airlift loop reactors, and aerated stirred vessels. For this purpose new and improved measurement techniques were developed. From the resulting knowledge and data, new and refined models for describing the underlying physical processes were developed, which were used for the establishment and improvement of analytic as well as numerical methods for predicting multiphase reactors. Thereby, the development, lay-out and scale-up of such processes should be possible on a more reliable basis.
Author: Christophe Morel
Publisher: Springer
ISBN: 3319201042
Category : Technology & Engineering
Languages : en
Pages : 365
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Book Description
This book develops the theoretical foundations of disperse two-phase flows, which are characterized by the existence of bubbles, droplets or solid particles finely dispersed in a carrier fluid, which can be a liquid or a gas. Chapters clarify many difficult subjects, including modeling of the interfacial area concentration. Basic knowledge of the subjects treated in this book is essential to practitioners of Computational Fluid Dynamics for two-phase flows in a variety of industrial and environmental settings. The author provides a complete derivation of the basic equations, followed by more advanced subjects like turbulence equations for the two phases (continuous and disperse) and multi-size particulate flow modeling. As well as theoretical material, readers will discover chapters concerned with closure relations and numerical issues. Many physical models are presented, covering key subjects including heat and mass transfers between phases, interfacial forces and fluid particles coalescence and breakup, amongst others. This book is highly suitable for students in the subject area, but may also be a useful reference text for more advanced scientists and engineers.
Author: Mamoru Ishii
Publisher: Springer Science & Business Media
ISBN: 0387291873
Category : Technology & Engineering
Languages : en
Pages : 462
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Book Description
This book has been written for graduate students, scientists and engineers who need in-depth theoretical foundations to solve two-phase problems in various technological systems. Based on extensive research experiences focused on the fundamental physics of two-phase flow, the authors present the detailed theoretical foundation of multi-phase flow thermo-fluid dynamics as they apply to a variety of scenarios, including nuclear reactor transient and accident analysis, energy systems, power generation systems and even space propulsion.
Author: Efstathios Michaelides
Publisher: World Scientific
ISBN: 9812566473
Category : Science
Languages : en
Pages : 425
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Book Description
The field of multiphase flows has grown by leaps and bounds in the last thirty years and is now regarded as a major discipline. Engineering applications, products and processes with particles, bubbles and drops have consistently grown in number and importance. An increasing number of conferences, scientific fora and archived journals are dedicated to the dissemination of information on flow, heat and mass transfer of fluids with particles, bubbles and drops. Numerical computations and "thought experiments" have supplemented most physical experiments and a great deal of the product design and testing processes. The literature on computational fluid dynamics with particles, bubbles and drops has grown at an exponential rate, giving rise to new results, theories and better understanding of the transport processes with particles, bubbles and drops. This book captures and summarizes all these advances in a unified, succinct and pedagogical way. Contents: Fundamental Equations and Characteristics of Particles, Bubbles and Drops; Low Reynolds Number Flows; High Reynolds Number Flows; Non-Spherical Particles, Bubbles and Drops; Effects of Rotation, Shear and Boundaries; Effects of Turbulence; Electro-Kinetic, Thermo-Kinetic and Porosity Effects; Effects of Higher Concentration and Collisions; Molecular and Statistical Modeling; Numerical Methods-CFD. Key Features Summarizes the recent important results in the theory of transport processes of fluids with particles, bubbles and drops Presents the results in a unified and succinct way Contains more than 600 references where an interested reader may find details of the results Makes connections from all theories and results to physical and engineering applications Readership: Researchers, practicing engineers and physicists that deal with any aspects of Multiphase Flows. It will also be of interest to academics and researchers in the general fields of mechanical and chemical engineering.
Author: Guan Heng Yeoh
Publisher: Butterworth-Heinemann
ISBN: 0080982336
Category : Science
Languages : en
Pages : 385
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Book Description
Written by leading multiphase flow and CFD experts, this book enables engineers and researchers to understand the use of PBM and CFD frameworks. Population balance approaches can now be used in conjunction with CFD, effectively driving more efficient and effective multiphase flow processes. Engineers familiar with standard CFD software, including ANSYS-CFX and ANSYS–Fluent, will be able to use the tools and approaches presented in this book in the effective research, modeling and control of multiphase flow problems. - Builds a complete understanding of the theory behind the application of population balance models and an appreciation of the scale-up of computational fluid dynamics (CFD) and population balance modeling (PBM) to a variety of engineering and industry applications in chemical, pharmaceutical, energy and petrochemical sectors - The tools in this book provide the opportunity to incorporate more accurate models in the design of chemical and particulate based multiphase processes - Enables readers to translate theory to practical use with CFD software
Author: Andrea Alberto Mammoli
Publisher: WIT Press
ISBN: 1845641884
Category : Science
Languages : en
Pages : 545
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Book Description
Together with turbulence, multiphase flow remains one of the most challenging areas of computational mechanics and experimental methods and numerous problems remain unsolved to date. Multiphase flows are found in all areas of technology, at all length scales and flow regimes. The fluids involved can be compressible or incompressible, linear or nonlinear. Because of the complexity of the problems, it is often essential to utilize advanced computational and experimental methods to solve the complex equations that describe them. Challenges in these simulations include modelling and tracking interfaces, dealing with multiple length scales, modelling nonlinear fluids, treating drop breakup and coalescence, characterizing phase structures, and many others. Experimental techniques, although expensive and difficult to perform, are essential to validate models. This book contains papers presented at the Fifth International Conference on Computational Methods in Multiphase Flow, which are grouped into the following topics: Multiphase Flow Simulation; Interaction of Gas, Liquids and Solids; Turbulent Flow; Environmental Multiphase Flow; Bubble and Drop Dynamics; Flow in Porous Media; Heat Transfer; Image Processing; Interfacial Behaviour.
