CFD prediction of urban outdoor ventilation around a building group: impact of high-rise building’s height and distance variation

Outdoor ventilation is very complex because various parameters such as air velocity, airflow conditions, large domain, and different building geometries are involved in urban ventilation. Earlier studies mainly investigated the flow structure around a group of low-rise buildings under the influence of a high-rise building located in the center of building blocks. However, the impact of an isolated tall building upstream of a group of low-rise buildings has been less examined. Therefore, this paper evaluates the height and distance variation effects of an isolated high-rise building on the air pattern and velocity ratio of a group of low-rise blocks. The standard k-ε model was used to run 3D steady RANS simulations. ANSYS FLUENT was used to validate CFD simulations with wind-tunnel measurements. From the results, the existence of a tall building can significantly affect the flow pattern within downstream blocks and street canyons. Enlarging the height of a tall building can increase the airspeed by 23% in front of the central low-rise buildings, while the lowest distance between the tall building and the building group has the highest velocity ratio (the ratio of the pedestrian wind speed to the measured wind speed at 2.25 m above ground level in the reduced-scale model). The results can be helpful for architects and urban decision-makers in neighborhood construction or renovation projects. © 2023, The Author(s), under exclusive licence to Springer Nature Switzerland AG.