The impact of high-density urban spatial form on urban vertical ventilation and thermal comfort in extreme cold region

The influence of the spatial form and roughness of an actual urban area on the distribution of the comfort zone of the wind and thermal environment is crucial for the liveable and sustainable development of urban spaces. Four cases in Harbin, a high-density city in an extremely cold region, were selected as the analysis objects, with six spatial shape parameters and two aerodynamic roughness parameters. The overall urban status was simulated by computational fluid dynamics and the thermal environment. The results showed that in spaces containing buildings, the urban spatial form significantly affected the aerodynamic roughness of the city. The comfortable wind speed decreases by 16.30–23.96 percentage points in the main rough surface and by 6.29 to 7.52 percentage points in a non-thermal stress environment. The prediction and interpretation degree of the influence of the morphological parameters of the comfortable wind and thermal environment was high. The numerical limit of the spatial morphological parameters was also clarified to ensure that the wind comfort was higher than 66.36 %, and the thermal comfort was higher than 22.83 %. Priority was given to controlling the spatial building height and distribution density. These findings provide valuable spatial impact results for the initial layout stage of urban space planning and a set of simulation frameworks for large-scale urban spaces, making it possible to simulate and analyse the wind and thermal environments of high-density urban spaces in extremely cold regions.