Research Projects Supported by HKU's High Performance Computing Facilities
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Researcher:
Dr Chun-ho Liu, Department of Mechanical Engineering
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Project Title:
Turbulent Flow, Pollutant Transport, and Chemical Processes in the Atmospheric Boundary Layer
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Project Description:
Turbulent flow and transport are non-linear and chaotic sciences consist of broad range of spatio-temporal scales. Conventional Reynolds-averaged approaches hardly account for the detailed motions exhibited in turbulent flow and transport. The turbulent transport phenomena are further complicated in stratified flow existing in the atmospheric boundary layer. Numerical approaches help control all the parameters and record all the detailed turbulence properties in the spatial as well as temporal domains. Hence, direct numerical simulation (DNS) and large-eddy simulation (LES), which calculate explicitly the most significant energy-carrying scales, are used to investigate the transport behaviors in fluid turbulence as well as in the atmospheric boundary layer. As most of the air pollutants are not inert nor well-mixed, chemical mechanisms for air pollutants are incorporated into the fluid turbulence model to investigate the correlation between the physical and chemical processes of air pollutants in fluid turbulence and the atmospheric boundary layer.
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Project Duration:
One year
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Project Significance:
• To develop a cross-disciplinary numerical model that calculates the atmospheric flow, turbulent transport, and pollutant chemistry.
• The numerical model can be elaborated to account for the air pollution problems encountered in Hong Kong. Better understanding of the scientific processes underneath helps predict and ease the problems.
• The numerical model can be used to perform environmental impact assessment for city planning and development.
• The results from the numerical model construct a comprehensive database that helps develop design guidelines and engineering references.
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Results Achieved:
Referred Journal Papers
• Liu, C.-H., Leung, D. Y. C., and Woo, C.-M. (2003), ¡§Development of a scalable finite element solution to the Navier-Stokes equations¡¨, Computational Mechanics 32, 185-195.
• Liu, C.-H. and Leung, D. Y. C. (2001), ¡§Study of Turbulence and Pollutant Dispersion Under Neutrally and Unstably Stratified Atmospheric Using a Second-Order Closure Boundary Layer Model¡¨, International Journal of Environment and Pollution 16, 16-27.
• Liu, C.-H. and Leung, D. Y. C. (1998), ¡§Evaluation of an Atmospheric Boundary Layer Model Used for Air Pollution Studies¡¨, Journal of Applied Meteorology 37, 1561-1576.

Conference Proceedings
• Liu, C.-H. and Leung, D. Y. C. (2004), ¡§Turbulent Transport of Passive Scalar Emitted from Line Sources in an Open Channel Flow¡¨, Third International Conference on Computational Fluid Dynamics, July 12 to 16, 2004, Toronto, Canada.
• Liu, C.-H., Woo, C.-M., and Leung, D. Y. C. (2004}, ¡§On the Performance Analysis of a Parallel Finite Element Solution to the Direct Numerical Simulation of Fluid Turbulence on Linux Clusters¡¨, Symposium on Scientific Computing, January 12, 2004, Hong Kong.

Works in Progress
• Liu, C.-H., Woo, C.-M., and Leung, D. Y. C. (2003), ¡§Performance Analysis of a Linux PC Cluster Using a Direct Numerical Simulation of Fluid Turbulence Code¡¨, manuscript submitted to International Journal of High Performance Computing Applications.
• Liu, C. H. and Leung, D. Y. C. (2004), ¡§Turbulent Transport of Passive Scalar Emitted from Line Sources in an Open Channel in Stable, Neutral, and Unstable Stratification¡¨, in preparation.
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Figure 1. Instantaneous turbulent plume behavior behind passive and inert line sources placed at different emission heights zs on the vertical plane of an open channel with neutral stratification (Liu and Leung 2004).
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Remarks on the Use of High Performance Computing Cluster:
The HPC Cluster provides a high speed and large memory platform that significantly shortens the computation time. Moreover, it helps increase the scale of calculations so that more detailed studies can be undertaken.
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Email Address
liuchunho@graduate.hku.hk
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