Passive urban ventilation by combined buoyancy-driven slope flow and wall flow: Parametric CFD studies on idealized city models

► Parametric CFD is used to study the effect of slope flow on city ventilation. ► The katabatic flow is conducive to mitigate the urban heat island. ► In our simulation, when the building is lower than 60 m, the slope wind dominates. ► When the building is as high as 100 m, the urban wall flow is important. ► The pedestrian air change rate can be as high as 300 ACH.