Effect of the Instabilities in the Overlying Atmospheric Boundary Layer on the Street Canyon Ventilation

Human health and air quality in urban areas are important problems that are linked to the pollution dispersion and ventilation capacity of urban streets. The ventilation mechanism and transfer process within urban streets is in strong connection with the instabilities in the overlying atmospheric boundary layer. In this study, we aim to use computational modelling to investigate the coupling between the flow within three-dimensional urban canyons and the turbulent structures in the above canyon flow. The state of the atmospheric boundary layer over an idealized urban area is controlled by the condition of the upstream topography. The transport phenomena in urban canyons is examined under different upstream conditions to reveal the ventilation mechanism in urban areas.