Numerical simulation of the effects of canopy properties on airflow and pollutant dispersion in street canyons

Abstract

The air flow and pollutant concentration fields in a street canyon affected by trees could affect the comfort and health of residents. At present, the description of the non-uniform/discontinuous distribution of leaves is difficult. In this study, the leaf distribution in the canopy was characterized by establishing non-continuous (uniform/random) algorithm based on a numerical simulation method, and the effects of canopy properties including, height, porosity and uniform/random leaf distribution, on the airflow and pollutant concentration fields in urban street canyons were investigated. The position of the tree canopy was found to directly affect the airflow field form and the air velocity distribution in the street canyon at low inflows. The average air velocity in the street canyon could be reduced significantly when the top of the tree canopy is near the top of the street canyon. The air velocity and pollutant concentration in the street canyon would vary only slightly due to the canopy porosity. Due to the increasing canopy porosity, the air velocity would increase, and the pollutant concentration would be reduced. The leaves are non-continuous and uniformly distributed at constant porosity, which does not significantly change the velocity distribution and pollutant concentration in the street canyon.

Effect of Viscosity Action and Capillarity on Pore-Scale Oil–Water Flowing Behaviors in a Low-Permeability Sandstone Waterflood

“…The arbitrary polyhedral finite volume method in OpenFOAM [26,27] is used to discretize the pore-scale dynamic equations. The following procedure is used to solve the pore-scale models:…”

Spatial distribution of PM2.5 concentration around high-rise residential buildings during peak traffic hours in autumn and winter seasons

“…14 On the other hand, controlling the diffusion of pollutants can be achieved such as by urban spatial layout 15,16 and road greening configuration. 17,18 For the influence of urban morphology, urban morphology indicators (building density, building height, plot ratio, etc.) have an important role in the diffusion of pollutants.…”

Numerical Simulation of Pollutant Spread in a Double-Deck Viaduct

“…The flow of air currents and the dispersal of contaminants in the canyon have been studied extensively over the past few decades. The methods commonly used in the research are field measurement [7], wind tunnel experiment [8][9][10], and numerical simulation of computational fluid dynamics (CFD) [11][12][13][14][15][16][17]. Previous studies have focused on the following aspects: the aspect ratio of the street canyon; aspect ratio is a critical parameter, and the structure of the flow field in the canyon with different aspect ratios is not precisely the same; the researchers found that when the aspect ratio is small, there is only one clockwise vortex in the street canyon, and when the aspect ratio becomes larger, there are multiple vortices in the canyon and the direction will be changed [18][19][20].…”