Numerical analysis of the effect of roof types and porch on particle dispersion and deposition around a low-rise building

Abstract

Outdoor air quality demonstrates one of the major challenges for preserving human health and the environment and also involves the indoor environment of buildings. Accordingly, besides urban morphology, building form should be considered as a passive strategy to reduce regional particle deposition and dispersion. In this framework, this study numerically pursues the influence of building shape on improving outdoor air quality around buildings. For this pursuit, eight cases of low-rise buildings with different roof types and a porch at different heights are compared with a simple building form with a flat roof to examine their impact on airflow and particle dispersion and deposition around low-rise buildings. The RNGk−ε turbulence model, in line with the discrete particle model (DPM) is implemented to model particulate flow and investigate particle dispersion and deposition. The discrete random walk (DRW) model is used to simulate the turbulent particle concentration. The results confirm that the combination of shed roof and porch can reduce the amount of particle deposition on the downstream wall of the building by about 20% less than the building with a flat roof. Moreover, using a porch at different heights integrated with a flat roof accumulates more particles on the downstream wall. Evidently, the vortex size influences particle concentration around buildings depending on the building shape. These findings will be helpful for designers regarding the impact of porch and roof types to improve outdoor air quality around buildings. Additionally, these promotions can be employed for decreasing particle deposition on buildings’ walls.