On the influence of viaduct and ground heating on pollutant dispersion in 2D street canyons and toward single-sided ventilated buildings

This paper employs Computational Fluid Dynamic (CFD) simulations to investigate the influence of ground heating intensities and viaduct configurations on gaseous and particle dispersion within twodimensional idealized street canyons (typical aspect ratio H/W = 1) and their transport from outdoor to leeward and windward rooms of naturally-ventilated buildings. Without viaduct, the ground heating exists at the street ground above which the pollutant source is located, while in the presence of viaduct the ground heating only occurs at the viaduct ground surface and pollutant source is slightly above the viaduct. Results show that viaduct significantly reduces overall spatial mean indoor concentrations of gaseous pollutant (< K >) and indoor particle number (PN) in all rooms being the elevated pollutant source above the viaduct compared to those without the viaduct. Road barriers on the viaduct slow down the flow above it and slightly increase indoor < K >, but they reduce indoor PN due to the enhanced particle deposition onto viaduct surfaces. The uniform heating of street ground or viaduct ground surface strengthens recirculation flows in street canyon, reducing < K > and PN of fine particle (diameter d = 1 mm), but for larger particles indoor PN distribution is complicated by the interaction of gravity, buoyancy and wind-induced recirculation. Although further investigations are still required to propose a practical framework on viaduct design, this paper is one of the first attempts to study the effect of viaduct on street pollutant dispersion.