Title: Air exchange in urban canyons with variable building width: a numerical LES approach

Authors: Michela Garau; Maria Grazia Badas; Simone Ferrari; Alessandro Seoni; Giorgio Querzoli

Addresses: Dipartimento di Ingegneria Civile, Ambientale e Architettura, Università degli Studi di Cagliari, via Marengo 2, 09123, Cagliari, Italy ' Dipartimento di Ingegneria Civile, Ambientale e Architettura, Università degli Studi di Cagliari, via Marengo 2, 09123, Cagliari, Italy ' Dipartimento di Ingegneria Civile, Ambientale e Architettura, Università degli Studi di Cagliari, via Marengo 2, 09123, Cagliari, Italy ' Dipartimento di Ingegneria Civile, Ambientale e Architettura, Università degli Studi di Cagliari, via Marengo 2, 09123, Cagliari, Italy ' Dipartimento di Ingegneria Civile, Ambientale e Architettura, Università degli Studi di Cagliari, via Marengo 2, 09123, Cagliari, Italy

Abstract: The aim of this work is to gain further insight into the role played by the building aspect ratio (ARB, i.e., the ratio of the building width, WB, to the building height, H) and its influence on street canyon flow. We carried out a series of large eddy simulations with arrays of obstacles with different widths, ranging from 0.5 to 2.0, and two canyon aspect ratios (ARC, i.e., the ratio of the canyon width, W, to H) ARC = 0.5 and ARC = 1.0. Experimental data was obtained in a water channel for the corresponding configuration and used to validate numerical simulations. Results were found strongly dependent on the building aspect ratios, with two distinct behaviours identified with respect to the canyon aspect ratio. The residence time decreases with decreasing ARB, irrespective of the canyon aspect ratio, suggesting that ARB and ARC can be optimised to guarantee optimal street canyon ventilation in urban planning.

Keywords: urban street canyon; large eddy simulation; flow exchange rate; building aspect ratio.

DOI: 10.1504/IJEP.2019.101836

International Journal of Environment and Pollution, 2019 Vol.65 No.1/2/3, pp.103 - 124

Received: 22 Jan 2018
Accepted: 07 Jan 2019

Published online: 22 Aug 2019 *

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