The potential of the height-to-width ratio as an indicator to characterize the ventilation performance of a canyon in the urban context

Abstract The height-to-width ratio (H/W) of canyons has been proven to be a significant indicator related to ventilation performance (airflow status and ventilation efficiency), which can help designers assess urban ventilation performance and guide the design quickly. However, previous research focused on the canyons in ideal geometric settings rather than in the urban context. This study explores whether the relationships between H/W, airflow status, and ventilation efficiency of ideal form studies apply to canyons in the urban context. Firstly, the relationship between the three in ideal geometric settings is sorted out by literature reviews. Then, the validity of the findings of ideal form studies in in the urban context is verified, using a typical residential area, Nanjing, China, as a case. This study found that H/W can affect the ventilation performance to a certain extent in in the urban context. However, most canyons’ airflows are affected by complex environmental factors, turning into different flow types (Deviation Type, Crossing Type, and Multivortex Type), which reduces the correlation between H/W, airflow status, and ventilation efficiency of canyons in the urban context.