A quantitative method to detect the ventilation paths in a mountainous urban city for urban planning: A case study in Guizhou, China

In this paper, a new frontal area index (FAI) mapping method is presented to describe the surface roughness of Renhuai, as an example of typical medium high mountain gorge type Karst city. Comparing with the traditional calculating method of FAI, a local topography (hills) factor is added to the calculation of the FAI in each 100 m x 100 m grid cell. The results show that the modified FAI is more strongly related to the mountainous land-use type than traditional, and local topography regions with large podium structure had higher values than other urban land-use types in mountainous city. With the frontal area index mapping procedure and a self-compiled least cost path analysis method, the potential airflow corridors traversing through the study area can be located, and the total computation time is shorter and less than 1s. Air volume, a significant measurement index of urban ventilation capacity, is then simulated in computational fluid dynamics model (CFD-PHOENICS) to confirm the significance and efficiency of these specific ventilation corridors. Based on our findings, the government and urban planners may use the descendent maps to understand the urban ventilation paths within a mountainous city for urban local renovation decisions.