Computational modelling of airflow in urban street canyon and comparison with measurements

The main goal of this study was to predict the airflow in a street canyon surrounded by an urban area using CFD modelling. In the street geometry described in the main part, the actual airflow directly influences air infiltration into buildings. Different models of turbulence were tested as well as specific wind boundary conditions. A correct assignment of boundary conditions (i.e., mainly wind conditions) is a very important step to obtain results that are comparable with measurements. Results of 3D airflow in the street canyon were obtained for different velocities and directions of an undisturbed wind above the roof level. Wind conditions were prescribed in two different ways, as a velocity profile on the incoming side of the solution domain, in the other as a fixed velocity in the layer where the wind velocity was measured. Results of calculations are compared with measurements done in the studied street canyon. Individual models of turbulence were tested to obtain the best agreement between predictions and measurements.