A Front-capturing Method for the Numerical Simulation of Dispersed Two-phase Flow PDF Download
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Author: Emil Rustam Ardeshir Coyagee
Publisher:
ISBN: 9789090221601
Category :
Languages : en
Pages : 133
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Book Description
Author: Emil Rustam Ardeshir Coyagee
Publisher:
ISBN: 9789090221601
Category :
Languages : en
Pages : 133
Get Book Here
Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 5
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Book Description
Because of the complexity of two-phase flow phenomena, two-phase flow codes rely heavily on empirical correlations. This approach has a number of serious shortcomings. Advances in parallel computing and continuing improvements in computer speed and memory have stimulated the development of numerical simulation tools that rely less on empirical correlations and more on fundamental physics. The objective of this work is to take advantage of developments in massively parallel computing, single-phase computational fluid dynamics of complex systems, and numerical methods for front capturing in two-phase flows to develop a computer code for direct numerical simulation of two-phase flow. This includes bubble/droplet transport, interface deformation and topology change, bubble/droplet interactions, interface mass, momentum and energy transfer.
Author: Cl Kleinstreuer
Publisher: Routledge
ISBN: 1351406485
Category : Science
Languages : en
Pages : 472
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Book Description
This graduate text provides a unified treatment of the fundamental principles of two-phase flow and shows how to apply the principles to a variety of homogeneous mixture as well as separated liquid-liquid, gas-solid, liquid-solid, and gas-liquid flow problems, which may be steady or transient, laminar or turbulent.Each chapter contains several sample problems, which illustrate the outlined theory and provide approaches to find simplified analytic descriptions of complex two-phase flow phenomena.This well-balanced introductory text will be suitable for advanced seniors and graduate students in mechanical, chemical, biomedical, nuclear, environmental and aerospace engineering, as well as in applied mathematics and the physical sciences. It will be a valuable reference for practicing engineers and scientists. A solutions manual is available to qualified instructors.
Author: Grétar Tryggvason
Publisher: Cambridge University Press
ISBN: 1139496700
Category : Computers
Languages : en
Pages : 337
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Book Description
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 interface terms are included as singularity distributions. Several applications are discussed, showing how direct numerical simulations have helped researchers advance both our understanding and our ability to make predictions. The final chapter gives an overview of recent studies of flows with relatively complex physics, such as mass transfer and chemical reactions, solidification and boiling, and includes extensive references to current work.
Author: Dokyun Kim
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
An accurate and robust numerical method has been developed to simulate turbulent two-phase flows. The phase interface is tracked by the level-set method to capture frequent topological changes due to breaking or merging. Because of the broad-band characteristics of length scales in two-phase flow, a Lagrangian drop breakup model has been developed, which is coupled to the level-set method. In this approach, small subgrid droplets produced from resolved ligaments are then transferred from the level-set representation to the Lagrangian particles. The further secondary atomization is handled by a stochastic breakup model. When pinching-off of ligaments is not resolved on the level-set grid, a capillary breakup model is used to predict the drop size distribution from the pinching off and inserted as Lagrangian drops. This method improves the mass conservation as well as reducing the computational cost. For a high-fidelity simulation of two-phase flow, a new numerical algorithm has been developed to improve the robustness of the numerical method. The conservative formulation of Navier-Stokes equations is solved with a density correction term in the present method. The density flux terms are calculated from the level-set field for accuracy. In addition, a constant coefficient Poisson system is solved for pressure to satisfy the continuity equation in the fractional-step method. In order to show the capability of the method as an efficient tool in the breakup process, the atomization of a round liquid jet surrounded by a coaxial gas is considered. The numerical results are consistent with the observed breakup mechanisms in the experiment and the stability analysis. The drop size distribution of the resulting spray after breakup is also compared with the experimental data. The subgrid drops are also predicted by the Lagrangian drop breakup model, which shows the applicability of our method for numerical simulation of the atomization process. Both theoretical and numerical approaches are employed to investigate the stability mechanisms of the air layer drag reduction (ALDR) phenomenon. A linear viscous stability analysis is performed by solving the Orr-Sommerfeld equations in a two-dimensional two-phase Couette-Poiseuille flow configuration that mimics the far-downstream region from an air injector. Air-layer stability is reduced as the free-stream velocity, Froude number, and velocity gradients at the air-liquid interface are increased, whereas the air-layer stability is enhanced as the gas flow rate and surface tension force are increased. Nonlinear stability characteristics are also studied using numerical simulations with the same Couette flow configuration as indicated in the linear stability analysis. The study shows that the Weber number has a significant effect on the breakup of the phase interface. As the Weber number increases, the liquid ligaments become thinner, requiring higher grid resolution. Therefore, for simulations of high Weber number flows, the use of a Lagrangian spray breakup model is essential to predict the dynamics of subgrid-scale liquid structures. Direct Numerical Simulation (DNS) of two-phase flow is also performed to investigate the air layer drag reduction (ALDR) phenomenon in turbulent water flow over a backward-facing step. The Reynolds and Weber numbers based on the water properties and step height are 22,800 and 560, respectively. The total number of grid points is about 271 million for DNS. Two different air-flow injection rates are examined to investigate the mechanism and stability of the air layer. For high air-flow rate, the stable air layer is formed on the plate and more than 90% drag reduction is obtained, whereas, in the case of low air-flow rate, the air layer breaks up and ALDR is not achieved. The initial Kelvin-Helmholtz instability causes the streamwise wave structure, while turbulence interaction forms the spawise waves and causes ligament breakups. However, overall rupture of the air layer is mainly determined by the stability of the streamwise wave. The stability of the streamwise wave can be predicted from the stability analysis in the far-downstream region.
Author: Andrea Prosperetti
Publisher: Cambridge University Press
ISBN: 1139459902
Category : Mathematics
Languages : en
Pages : 392
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Book Description
Thanks to high-speed computers and advanced algorithms, the important field of modelling multiphase flows is an area of rapid growth. This one-stop account – now in paperback, with corrections from the first printing – is the ideal way to get to grips with this topic, which has significant applications in industry and nature. Each chapter is written by an acknowledged expert and includes extensive references to current research. All of the chapters are essentially independent and so the book can be used for a range of advanced courses and the self-study of specific topics. No other book covers so many topics related to multiphase flow, and it will therefore be warmly welcomed by researchers and graduate students of the subject across engineering, physics, and applied mathematics.
Author: Lan Zhang
Publisher:
ISBN:
Category : Mathematics
Languages : en
Pages :
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Book Description
In this dissertation, we present numerical schemes in simulating immiscible two-phase flow problems. The goal of this work is to find unified solutions for numerical modeling of any kind of immiscible two-phase flow with moving interface. Fluid flows are modeled using Navier Stokes equations with discontinuous coefficients. We introduce the Volume Fraction method to evaluate discontinuous integrals arise from the variational formulation in the Finite Element method. The use of Volume Fraction method avoids the approximation of the Dirac Delta function, and therefore no regularization procedures are needed. Several operator splitting variants are studied in detail in linearized and non-linearized fashion, when we want to evaluate the discontinuous coefficients. Interface is captured using the Level Set approach, where a transport equation is solved numerically with fourth order scheme without any stabilization terms. The surface tension effect is implemented in a semi-implicit way, thus larger time steps can be used compared with the explicit method. A recent, well-developed re-initialization technique is included as a way to preserve the signed distance property of the Level Set function. All mentioned numerical methods are used to build two-dimensional solvers. Solvers have been tested both with single-phase flow and two-phase flow benchmark problems. In particular, the bubble dynamics are presented to validate stated numerical schemes.
Author: Volfango Bertola
Publisher: Springer
ISBN: 3709125383
Category : Technology & Engineering
Languages : en
Pages : 433
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Book Description
This is an up-to-date review of recent advances in the study of two-phase flows, with focus on gas-liquid flows, liquid-liquid flows, and particle transport in turbulent flows. The book is divided into several chapters, which after introducing basic concepts lead the reader through a more complex treatment of the subjects. The reader will find an extensive review of both the older and the more recent literature, with abundance of formulas, correlations, graphs and tables. A comprehensive (though non exhaustive) list of bibliographic references is provided at the end of each chapter. The volume is especially indicated for researchers who would like to carry out experimental, theoretical or computational work on two-phase flows, as well as for professionals who wish to learn more about this topic.
Author: Matthew James Buoni
Publisher:
ISBN:
Category :
Languages : en
Pages : 134
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Book Description
Author: China Rama Lakshman Anumolu
Publisher:
ISBN:
Category :
Languages : en
Pages : 422
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Book Description
Numerical method to simulate phase-change phenomena is developed using gradient augmented level set strategy (GALS) for advection and reinitialization. Sharp capturing of jump in velocity and pressure is achieved using Ghost Fluid Method. A single phase approach is followed to obtain solution for the energy equation where the governing equation is solved in each fluid phase by explicitly identifying the interface. Explicit identification of the interface is used to properly chose stencil locations in approximating convection and diffusion terms of the energy equation so that a single phase treatment is enforced in the solution procedure. Two approaches to locate the interface are studied in this work; (i) a cubic Hermite interpolating polynomial which is inherent to GALS approach and yields spatially fourth order accurate interface location, (ii) a level set weighted approach which has been used in the level set literature that locates the interface using adjacent level set values as weights along a given axis on a cell edge. The added advantage of cubic Hermite interpolating polynomial over traditional level set weighted approach in approximating the differential terms near the interface is demonstrated. Numerical simulation of phase-change phenomena using level set approach has been the topic of research in the past, however comparison of different numerical strategies with in the category of level set methods have not been presented. Using the level set transport step as the key difference we present a comparative study in this work. Test cases include 1D Stefan problem, 1D absorption problem, 2D bubble growth under a prescribed mass transfer rate, 2D Frank sphere type problem, and a 3D growing bubble subjected to buoyant forces. Both GALS and SLS approaches yielded similar results for 1D test cases due to the choice of the function which is linear and is continuously reinitialized maintaining the signed distance property, resulting in the interface location upto same level of accuracy. Gradient augmented level set based numerical approach resulted in slightly better results for test cases in higher dimensions and with high fluid density ratios.
