Browsing by Author "Cheung, SCP"

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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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    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