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Open AccessArticle

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

Institute for Atmospheric and Earth System Research/Physics, Faculty of Science, 00014 University of Helsinki, Finland
Finnish Meteorological Institute, 00101 Helsinki, Finland
Institute of Meteorology and Climatology, Leibniz Universität Hannover, 30419 Hannover, Germany
Institute for Atmospheric and Earth System Research/Forest Sciences, Faculty of Agriculture and Forestry, 00014 University of Helsinki, Finland
Author to whom correspondence should be addressed.
Atmosphere 2018, 9(2), 65;
Received: 2 January 2018 / Revised: 9 February 2018 / Accepted: 11 February 2018 / Published: 13 February 2018
(This article belongs to the Special Issue Recent Advances in Urban Ventilation Assessment and Flow Modelling)
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 km 2 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. View Full-Text
Keywords: LES; ventilation; urban planning; dispersion; air quality LES; ventilation; urban planning; dispersion; air quality
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MDPI and ACS Style

Kurppa, M.; Hellsten, A.; Auvinen, M.; Raasch, S.; Vesala, T.; Järvi, L. Ventilation and Air Quality in City Blocks Using Large-Eddy Simulation—Urban Planning Perspective. Atmosphere 2018, 9, 65.

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