An Investigation of the Quantitative Correlation between Urban Morphology Parameters and Outdoor Ventilation Efficiency Indices

Abstract

Urban outdoor ventilation and pollutant dispersion have important implications for urban design and planning. In this paper, two urban morphology parameters, i.e. the floor area ratio (FAR) and the building site coverage (BSC), are considered to investigate their quantitative correlation with urban ventilation indices. An idealized model, including nine basic units with FAR equal to 5, is considered and the BSC is increased from 11% to 77%, generating 101 non-repetitive asymmetric configurations, with attention to the influence of plan density, volume ratio, and building layout on ventilation performance within urban plot areas. Computational Fluid Dynamics (CFD) simulations are used to assess the ventilation efficiency at pedestrian level (2m above the ground) within each model central area. Six indices, including the air flow rate (Q), the mean age of air (τ P ), the net escape velocity (NEV), the purging flow rate (PFR), the visitation frequency (VF), and the resident time (TP) are used to assess the local ventilation performance. Results clearly show that, fixing the FAR, the local ventilation performance is not linearly related to BSC, but it also depends on buildings arrangement. Specifically, as the BSC increases, the ventilation in the central area does not keep reducing. On the contrary, some forms with low BSC have poor ventilation and some particular configurations with high BSC have better ventilation, which indicates that not all high-density configurations experience poor ventilation. The local ventilation performance can be effectively improved by rationally arranging the buildings. Even though the application of these results to real cities requires further research, the present findings suggest a preliminary way to build up a correlation between urban morphology parameters and ventilation efficiency tailored to develop a feasible framework for urban designers.

A Wind Tunnel Study on the Correlation between Urban Space Quantification and Pedestrian–Level Ventilation

“…Atmosphere 2019, 10, 564 3 of 19 measurement points from the perspective of urban spatial characteristics. Meanwhile, in the research on the correlation between urban spaces and wind environments, wind environment analysis is usually conducted in designated spaces [27][28][29]. When the research area is a large real urban area, with a complex and disordered space, it is necessary to 'define' the space first before conducting the correlation study.…”

“…Therefore, for correlation research, it is necessary to locate measurement points from the perspective of urban spatial characteristics. Meanwhile, in the research on the correlation between urban spaces and wind environments, wind environment analysis is usually conducted in designated spaces [27][28][29].…”

An analysis of wind conditions at pedestrian level in the selected types of multi-family housing developments

“…Several factors play a vital role for ventilation. They include: geometric proportions of streets [1,8,11,34,36], variations in building height [9,26], building intensity expressed in Floor Aspect Ratio and Building Coverage Ratio [25,29]. Moreover, geometric features, though not sufficiently tested yet, may exert an impact on the efficiency of urban ventilation [19].…”

A Quantitative Study of Geometric Characteristics of Urban Space Based on the Correlation with Microclimate

“…On the basis of urban-like geometry, some scholars have abstracted the model into a more representative real city and added more morphological parameters to investigate the relationship between morphology and microclimate. Through fixing the floor area ratio in urban planning and changing the building coverage, Peng conducted over 100 2 of 13 ideal urban plot configurations to investigate the relationship between the coverage changes and the local ventilation efficiency [10]. You studied the relationship between the length of the building, the distance between the buildings within residential community and the ventilation performance of the local space [11].…”