Why urban wind design?
The UrbalTerre company was in charge of designing the new urban area which will be built on the Citadel of Bonifacio (Corsica Island), city which is also known as the “Daughter of the Wind”, one of the windiest city in Europe. The volumes and locations of the buildings were designed in order to take into account the pedestrian comfort which is a major issue considering the strength and frequencies of the wind blowing all along the year. To do so, the urbanism specialists combined both experiments in the Atmospheric Wind Tunnel of CSTB and numerical simulations carried out with the UrbaWind software developed by Meteodyn.
Study based on measurements and numerical simulations
First the weather data, recorded by a weather data station located 3km south-east of Bonifacio has been “extrapolated” to the location of Bonifacio to take into account the topography. CFD simulations were performed in order to compare the wind speed and direction seen by the weather station with the wind speed at the location of the project. This weather data was the input of both the measurements and numerical simulations.
A first version of the project was tested in the wind tunnel. Particle Image Velocimetry measurements were carried out on a 1/100th scale model of the project. PIV fields parallels the ground were performed at a height of 1.5m full scale (1.5cm model scale) in order to assess the wind velocity close to the ground. The results were then translated, combining measurements and weather data, into a probability of exceeding a comfort threshold velocity.
From the results of the wind tunnel measurements, UrbalTerre’s team was able to iterate many versions of the project in order to optimize the pedestrian comfort thanks the numerical simulations with UrbaWind. The optimized version of the project was then tested another time in the wind tunnel. Remaining issues were solved inside the wind tunnel using iterative PIV measurements.
This study is then combining both numerical simulations as well as experimental measurements, at different scales, in order to build a quantitative assessment of the pedestrian comfort using the advantages of both approaches.