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Wind Tunnel   |   Motion Simulator   |   Full Scale Measurement   |   Computational Fluid Dynamics
Computational Fluid Dynamics (CFD) is becoming an increasingly important analysis tool for investigating wind effects on structures and bodies and environmental wind flow. CFD is a numerical method that utilizes the solution of the equations of momentum and continuity (the Navier-Stokes equations) together with a turbulence model to simulate air flow around bluff bodies. Our CFD system is capable of running the latest turbulence models, including large eddy simulations (LES), detached eddy simulations (DES) and the more popular non-linear two equation turbulence models, such as the k-∈ model. The use of a turbulence model that is appropriate for the application allows accurate simulations of complex flows around bluff bodies that are typically found in urban environments.

Conventional CFD analysis
WWTF staff have applied CFD to a number of wind engineering projects for both consulting and research. This work has been conducted in collaboration with government and private organizations and other research institutions in Hong Kong. Typical examples of these applications include the following:

  • Air Ventilation Assessment for pedestrian comfort
  • Wind-induced pressures on structures
  • Pollution dispersion due to vehicle or industrial emissions

Advanced CFD analysis
With a dedicated and ongoing mission to conduct wind engineering research, WWTF’s CFD capabilities are used to transfer and implement the latest research and development results directly to practical wind engineering problems. This is achieved through the use of the following software.

FLUENT is a standard CFD package that has been used by many research and consulting companies for analyzing environmental fluid flows. FLUENT software allows the use of a wide range of turbulence models including large eddy simulations (LES), detached eddy simulations (DES), Reynolds averaged Navier-Stokes (RANS) and Reynolds Stress Turbulence models (RSTM).

OpenFOAM is an open source software that allows implementation of the latest research results from scientific literature. These include the latest turbulence models that may be unavailable in traditional CFD packages. An example of this saw the development of a new method to calculate pressure fluctuations based on RANS model simulations. This has the advantage of requiring lower computational resources than LES while still providing the necessary time varying information to determine the unsteady pressure fluctuations.

High Quality Results
WWTF recognizes the importance of proper verification and validation of all model studies, be it physical modeling or computational modeling, to ensure the accuracy and applicability of the study results. For CFD studies, all simulations are conducted according to the following guidelines and references:

  • AIJ guide for numerical prediction of the wind loads on buildings (2008), Tamura et al., Journal of Wind Engineering and Industrial Aerodynamics, Volume 96, page 1974-1984.

  • COST (European Cooperation in the field of Scientific and Technical Research) group: Action C14 “Impact of Wind and Storms on City Life and Built Environment” Working Group 2-CFD techniques (2004).

  • COST (European Cooperation in the field of Scientific and Technical Research) group: Action C732 “Best practice guideline for the CFD simulation of flows in the urban environment” Working Group 2-CFD techniques (2007).
The above example shows the velocity vector distribution around a single building with an opening. This was part of work done to determine the sudden pressure distribution for a building with a sudden opening of a window.
The investigation into the ventilation of a small office and distribution of carbon dioxide on indoor air quality is shown in the following diagram. This was part of a study looking into indoor air quality and thermal comfort.
Evaluation of pressure coefficients for the analysis of a noise barrier was carried out. Various configurations were investigated to determine the pressure coefficients for design purposes.

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