Ventilation and Air Quality in City Blocks Using Large-Eddy Simulation - Urban Planning Perspective

authored by: Mona Kurppa, Antti Hellsten, Mikko Auvinen, Siegfried Raasch, Timo Vesala, Leena Järvi
Abstract: Buildings and vegetation alter the wind and pollutant transport in urban environments. This comparative study investigates the role of orientation and shape of perimeter blocks on the dispersion and ventilation of traffic-related air pollutants, and the street-level concentrations along a planned city boulevard. A large-eddy simulation (LES) model PALM is employed over a highly detailed representation of the urban domain including street trees and forested areas. Air pollutants are represented by massless and passive particles (non-reactive gases), which are released with traffic-related emission rates. High-resolution simulations for four different city-block-structures are conducted over a 8.2 km² domain under two contrasting inflow conditions with neutral and stable atmospheric stratification corresponding the general and wintry meteorological conditions. Variation in building height together with multiple cross streets along the boulevard improves ventilation, resulting in 7-9% lower mean concentrations at pedestrian level. The impact of smaller scale variability in building shape was negligible. Street trees further complicate the flow and dispersion. Notwithstanding the surface roughness, atmospheric stability controls the concentration levels with higher values under stably stratified inflow. Little traffic emissions are transported to courtyards. The results provide urban planners direct information to reduce air pollution by proper structural layout of perimeter blocks.
Organisation(s): Institute of Meteorology and Climatology
External Organisation(s): University of Helsinki
Finnish Meteorological Institute
Type: Article
Journal: Atmosphere
Volume: 9
ISSN: 2073-4433
Publication date: 13.02.2018
Publication status: Published
Peer reviewed: Yes
ASJC Scopus subject areas: Environmental Science (miscellaneous)
Sustainable Development Goals: SDG 11 - Sustainable Cities and Communities
Electronic version(s): https://doi.org/10.3390/atmos9020065 (Access: Open)
https://doi.org/10.15488/3400 (Access: Open)