Browsing by Author "Tu, JY"

Now showing 1 - 11 of 11
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    A bubble mechanistic model for subcooled boiling flow predictions
    (Taylor & Francis, 2010-08-17) Yeoh, GH; Tu, JY
    Population balance equations combined with a three-dimensional two-fluid model are employed to predict subcooled boiling flow at low pressure in a vertical annular channel. The MUSIG (Multiple-Size-Group) model implemented in CFX4.4 is extended to account for the wall nucleation and condensation in the subcooled boiling regime. Comparison of model predictions against local measurements is made for the void fraction, bubble Sauter diameter, interfacial area concentration, bubble population density, and gas and liquid velocities covering a range of different mass and heat fluxes and inlet subcooling temperatures. Good agreement is achieved with the local radial void fraction, bubble Sauter diameter, interfacial area concentration, bubble population density, and liquid velocity profiles against measurements. However, further improvement is needed for the accurate prediction of the vapor velocity using the present bubble mechanistic model. A proposal to include an algebraic slip model to account for bubble separation in the MUSIG boiling model is presented. © 2022 Informa UK Limited
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    Computational fluid dynamics: a practical approach
    (Elsevier, 2018-01-26) Tu, JY; Yeoh, GH; Liu, GQ
    Computational Fluid Dynamics: A Practical Approach, Third Edition, is an introduction to CFD fundamentals and commercial CFD software to solve engineering problems. The book is designed for a wide variety of engineering students new to CFD, and for practicing engineers learning CFD for the first time. Combining an appropriate level of mathematical background, worked examples, computer screen shots, and step-by-step processes, this book walks the reader through modeling and computing, as well as interpreting CFD results. This new edition has been updated throughout, with new content and improved figures, examples and problems. © 2018 Elsevier
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    Computational fluid dynamics: a practical approach
    (Elsevier, 2007-10-26) Tu, JY; Yeoh, GH; Liu, CQ
    Computational Fluid Dynamics (CFD), once the domain of academics, postdoctoral researchers or trained specialists, is now progressively becoming more accessible to graduate engineers for research and development as well as design-oriented tasks in industry. Mastery of CFD in handing complex flow and heat industrial problems is becoming ever more important. Competency in such a skill certainly brings about a steep learning curve for practicing engineers, who constantly face extreme challenges to come up with solutions to fluid flow and heat transfer problems without a priori knowledge of the basic concepts and fundamental understanding of fluid mechanics and heat transfer. © 2008 Elsevier
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    Computational fluid dynamics: a practical approach
    (Elsevier, 2012-09-27) Tu, JY; Yeoh, GH; Liu, CQ
    Computational Fluid Dynamics, Second Edition, provides an introduction to CFD fundamentals that focuses on the use of commercial CFD software to solve engineering problems. This new edition provides expanded coverage of CFD techniques including discretisation via finite element and spectral element as well as finite difference and finite volume methods and multigrid method. There is additional coverage of high-pressure fluid dynamics and meshless approach to provide a broader overview of the application areas where CFD can be used. The book combines an appropriate level of mathematical background, worked examples, computer screen shots, and step-by-step processes, walking students through modeling and computing as well as interpretation of CFD results. © 2012 Elsevier .
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    Computational fluid dynamics: a practical approach
    (2023-05-09) Tu, JY; Yeoh, GH; Liu CQ; Tao, Y
    Computational Fluid Dynamics: A Practical Approach, Fourth Edition is an introduction to computational fluid dynamics (CFD) fundamentals and commercial CFD software to solve engineering problems. The book is designed for a wide variety of engineering students new to CFD, but is also ideal for practicing engineers learning CFD for the first time. Combining an appropriate level of mathematical background, worked examples, computer screen shots, and step-by-step processes, this book walks the reader through modeling and computing, as well as interpreting CFD results. This new edition has been updated throughout, with new content and improved figures, examples and problems. © 2023 Elsevier
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    Computational techniques for multiphase flows
    (Elsevier, 2009-10-01) Yeoh, GH; Tu, JY
    Mixed or multiphase flows of solid/liquid or solid/gas are commonly found in many industrial fields, and their behavior is complex and difficult to predict in many cases. The use of computational fluid dynamics (CFD) has emerged as a powerful tool for the understanding of fluid mechanics in multiphase reactors, which are widely used in the chemical, petroleum, mining, food, beverage and pharmaceutical industries. This book enables scientists and engineers to the undertand the basis and application of CFD in muliphase flow, explains how to use the technique, when to use it and how to interpret the results and apply them to improving applications in process engineering and other multiphase application areas including the pumping, automotive and energy sectors. © 2009, Elsevier Ltd.
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    Experimental and numerical study on the hemodynamics of stenosed carotid bifurcation.
    (Springer, 2010-12-01) Cheung, SCP; Wong, KKL; Yeoh, GH; Yang, W; Tu, JY; Beare, R; Thanh, P
    Numerical simulation is performed to demonstrate that hemodynamic factors are significant determinants for the development of a vascular pathology. Experimental measurements by particle image velocimetry are carried out to validate the credibility of the computational approach. We present a study for determining complex flow structures using the case of an anatomically realistic carotid bifurcation model that is reconstructed from medical imaging. A transparent silicone replica of the artery is developed for invitro flow measurement. The dynamic behaviours of blood through the vascular structure based on the numerical and experimental approaches show good agreement. © 2010, Springer.
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    Gas-liquid flows in medium and large vertical pipes.
    (Elsevier, 2011-03-01) Duan, XY; Cheung, SCP; Yeoh, GH; Tu, JY; Krepper, E; Lucas, D
    Gas-liquid bubbly flows with wide range of bubble sizes are commonly encountered in many industrial gas–liquid flow systems. To assess the performances of two population balance approaches – Average Bubble Number Density (ABND) and Inhomogeneous MUlti-SIze-Group (MUSIG) models – in tracking the changes of gas volume fraction and bubble size distribution under complex flow conditions, numerical studies have been performed to validate predictions from both models against experimental data of Lucas et al. (2005) and Prasser et al. (2007) measured in the Forschungszentrum Dresden-Rossendorf FZD facility. These experiments have been strategically chosen because of flow conditions yielding opposite trend of bubble size evolution, which provided the means of carrying out a thorough examination of existing bubble coalescence and break-up kernels. In general, predictions of both models were in good agreement with experimental data. The encouraging results demonstrated the capability of both models in capturing the dynamical changes of bubbles size due to bubble interactions and the transition from “wall peak” to “core peak” gas volume fraction profiles caused by the presence of small and large bubbles. Predictions of the inhomogeneous MUSIG model appeared marginally superior to those of ABND model. Nevertheless, through the comparison of axial gas volume fraction and Sauter mean bubble diameter profiles, ABND model may be considered an alternative approach for industrial applications of gas–liquid flow systems. © 2011, Elsevier Ltd.
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    Local prediction of subcooled boiling flow in an annular channel with the influence of bubble coalescence and break-up mechanisms
    (International Group On Research Reactors, 2003-03-24) Yeoh, GH; Tu, JY; Li, YZ
    Population balance equations combined with a three-dimensional two-fluid model are employed to predict subcooled boiling flow at low pressure in a vertical annular channel. The MUSIG (MUltiple-SIze- Group) model implemented in CFX4.4 is extended to account for the wall nucleation and condensation in the subcooled boiling regime. Comparison of model predictions against local measurements is made for the void fraction, bubble Sauter diameter and gas and liquid velocities covering a range of different mass and heat fluxes and inlet subcoolings. Good agreement is achieved with the local radial void fraction, bubble Sauter diameter and liquid velocity profiles against measurements. However, significant weakness of the model is evidenced in the prediction of the vapour velocity. Work is in progress to overcome the deficiency of the extended MUSIG model by the consideration of an algebraic slip model to account for bubble separation.
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    Modelling horizontal gas-liquid flow using averaged bubble number density approach
    (SAGE Publications Ltd, 2010-06-01) Li, C; Yeoh, GH; Cheung, SCP; Tu, JY
    In this study, the internal phase distributions of gas-liquid bubbly flow in a horizontal pipe have been predicted using the population balance model based on Average Bubble Number Density approach. Four flow conditions with average gas volume fraction ranging from 4.4% to 20% have been investigated. Predicted local radial distributions of void fraction, interfacial area concentration and gas velocity have been validated against the experimental data. In general, satisfactory agreements between predicted results and measured values have been achieved. For high superficial gas velocity, it has been ascertained that peak local void fraction of 0.7 with interfacial area concentration of 800 m-1 can be encountered near the top wall of the pipe. Some discrepancies have nonetheless been found between the numerical and experimental results at certain locations of the pipe. The insufficient resolution of the turbulent model in fully accommodating the strong turbulence in the current pipe orientation and the inclusion of additional interfacial force such as the prevalent bouncing force among bubbles remain some of the outstanding challenging issues need to be addressed in order to improve the prediction of horizontal gas-liquid bubbly flow. © 2020 by SAGE Publications Ltd
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    Review of population balance modelling for isothermal bubbly flows
    (Multi Science Publishing, 2009-06-01) Cheung, SCP; Yeoh, GH; Tu, JY
    In this article, we present a review of the state-of-the-art population balance modelling techniques that have been adopted to describe the phenomenological nature of isothermal bubbly flows. The main focus of the review can be broadly classified into three categories: (i) Numerical approaches or solution algorithms of the PBE; (ii) Applications of the PBE in practical gas-liquid multiphase problems and (iii) Possible aspects of the future development in population balance modelling. For the first category, details of solution algorithms based on both method of moment (MOM) and discrete class method (CM) that have been proposed in the literature are provided. Advantages and drawbacks of both approaches are also discussed from the theoretical and practical viewpoints. For the second category, applications of existing population balance models in practical multiphase problems that have been proposed in the literature are summarized. Selected existing mathematical closures for modelling the "birth" and "death" rate of bubbles in gas-liquid bubbly flows are introduced. Particular attention is devoted to assess the capability of some selected models in predicting bubbly flow conditions through detail validation studies against experimental data. These studies demonstrate that good agreement can be achieved by the present model by comparing the predicted results against measured data with regards to the radial distribution of void fraction and sauter mean bubble diameter. Finally, weaknesses and limitations of the existing models are revealed are suggestions for further development are discussed. Emerging topics for future population balance studies are provided as to complete the aspect of population balance modelling. © 2009, Multi Science Publishing