Assessment of pedestrian wind environment in urban planning design

Pedestrian wind environment is one of the urban physical environments that have a significant impact on the overall wellbeing of a city and its dwellers. It is important to be able to assess pedestrian wind environment in the urban planning design stage. Such assessment is intrinsically an in-design assessment and should be based on spatial analysis. The methodology developed considers the probabilistic nature of the assessment by determining an 80-percentile ambient wind speed as the boundary condition for wind environment simulation. The assessing criteria include mechanical comfort, safety, and amplification factor. Their threshold values are based on comparisons of existing criteria. In addition, the concept of tolerance factor, which takes into account the psychological effects of different urban spaces on people, is integrated into the assessment system. The assessment methodology can be used by urban planners in parallel with the process of designing urban physical spaces. A case study of the downtown area of an urban planning project near Lake Tai in China is conducted to demonstrate the application of the assessment methodology. Two limitations of the methodology need to be noted. First, it relies on CFD techniques to obtain the wind environment and therefore, the simulation must be conducted with considerable care and circumspection. Secondly, the methodology does not include the thermal and ventilation effects of pedestrian wind.