An investigation on the quantitative correlation between urban morphology parameters and outdoor ventilation efficiency indices

Syracuse, NY

Urban outdoor ventilation and pollutant dispersion have important implications for the urban planning and design of urban morphology. In this paper, two urban morphology parameters including Floor area ratio (FAR) and Building site coverage (BSC) are attempted to investigate the quantitative correlation with urban ventilation indices. Firstly, we present an idealized model including nine basic units. The FAR of model is constant 5.0, and the BSC increases from 11% to 77%, which in consequence generates 101 non-repetitive asymmetric forms. Next, the Computational Fluid Dynamics (CFD) is employed to evaluate the ventilation efficiency of pedestrian level within each model’s central area. Six indicators including air flow rate (Q), mean age of air (τp), net escape velocity (NEV), purging flow rate (PFR), visitation frequency (VF) and resident time (TP) are used to assess the local ventilation performance. Results clearly show that when the FAR of the plot is specified, the local ventilation performance does not present an obvious linear relationship. 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 forms with high BSC have better ventilation performance. This shows that for an urban, it not always exists poor local ventilation under the high-density conditions. The local ventilation performance can be effectively improved by rationally arranging the architectural arrangement within the plot. These findings suggest a preliminary way to build up the correlation between urban morphology parameters and ventilation efficiency. Even though the application of these results to the real cities require further research, but for this paper, it presents a feasible framework to the urban designers.

https://surface.syr.edu/ibpc/2018/GB3/1