Microclimate and urban planning

CAD of the project and example of wind computation map with pressure coefficient


Optimization of numerical parameters in CFD tools to improve natural ventilation assessment in complex urban area

This paper presents a validation of a CFD numerical approach with optimized numerical parameters. Data from wind tunnel experiment is compared with numerical results on mean pressure coefficient. Numerical optimization investigates influence of inlet profile, mesh size and turbulence parameters. Suitable chosen numerical parameters can decrease discrepancies on pressure coefficient by 20%.

Wind condition creates high and low pressures on building’s external faces. This gradient of pressure will drive wind inside building. Pressure distribution is first order of investigation when natural ventilation matters. Database of pressure coefficient is widely used inside dynamic thermal simulation software. Those tables are convenient when geometry is simple and there is no interaction with neighbour buildings. Nevertheless, reality of an urban project is far from such ideal cases. More complex tools are required to assess mean pressure on building walls: wind tunnel or numerical simulation using computational fluid dynamic (CFD) can handle such task. 

By using commercial code "UrbaWind”, velocity field in a complex area was compared with wind tunnel experiment with an average of 5% error on mean velocity. 

Pressure coefficient on buildings with neighbour interaction is here performed using optimization of numerical parameters according to the correlation with the experimental results. 

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