Effect of triangular roof angle on dispersion of gaseous pollutants and particulate matter
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RESEARCH ARTICLE
Effect of triangular roof angle on dispersion of gaseous pollutants and particulate matter Xiaoxiao Zhang 1 & Chunmei Wang 1 & Xiaoping Liu 2 & Taotao Zhou 1
&
Changfa Tao 1,3 & Qin Shi 1
Received: 30 July 2020 / Accepted: 2 November 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The Euler–Lagrangian method is adopted to simulate the dispersion of gaseous pollutants and particulate matter (PM) in isolated street canyons, and the influences of the roof angle on the flow structures and distributions of gaseous pollutants and PM are analyzed in detail. Numerical simulation results indicate that gaseous pollutants and PM in the canyons present three typical single main clockwise vortex, transition vortex, and double vortex structures, which are identified at increasing roof slopes. Gaseous pollutants and PM demonstrate the lowest concentration of pollutants when a single vortex structure exists. The concentration of gaseous pollutants and PM reaches the highest value in pedestrian-level areas when the flow field is in a transitional vortex structure. Unlike gaseous pollutants, the concentration of PM does not always decrease with increasing altitude, and higher PM concentrations sometimes occur in the mid-level areas of the canyon. A small roof incline angle is generally recommended for discharging gaseous pollutants and PM. Keywords Street canyons . Numerical simulation . Euler–Lagrangian method . Roof angle . Flow field . Pollutant diffusion
Nomenclature Cα Pollutant concentration (kg/m3) Dα Pollutant molecular diffusion rate (kg/s) dp Particle diameter (m) ! F Additional force (N) H Building height (mm) K Dimensionless concentration mp Particle mass (kg) P Dynamic pressure (pa) Q Pollutant release rate (kg/s) Re Reynolds number
Responsible Editor: Marcus Schulz * Taotao Zhou [email protected] * Changfa Tao [email protected] 1
School of Automotive and Transportation Engineering, Hefei University of Technology, Hefei 230009, Anhui, China
2
School of Civil Engineering, Hefei University of Technology, No. 193, Tunxi Road, Hefei 230009, Anhui, China
3
Intelligent Vehicle Labs of Anhui Province, Hefei University of Technology, No. 193, Tunxi Road, Hefei 230009, Anhui, China
Si Sct uH ui 0 ui 0 0 ui u j up W Wb
The source term of the momentum equation caused by particle matter Turbulent Schmidt number Inlet velocity (m/s) Time-averaged velocity components, (m/s) Pulsation velocities (m/s) Reynolds stresses (N) Particle velocity (m/s) Street canyon width (mm) Pollution source width (mm)
Greek symbols β Triangular roof angle (°) α Wind profile index ρ Fluid density (kg/m3) ν Air kinematic viscosity (m2/s) ∇ Definition operator δij Kronecker delta symbol νT Kinematic eddy (turbulent) viscosity (m2/s) κ The turbulent kinetic energy (J) ε Turbulence kinetic energy dissipation rate ρp Particle density (kg/m3) τr Particle relaxation time (s) μ Molecular viscosity of the continuous phase
Environ Sci Pollut Res
Introduction With the development of modern society, au
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