Gaseous And Particulate Dispersion In Street Canyons Kambiz Nazridoust Department of Mechanical and Aeronautical Engineering Clarkson University, Potsdam, NY 13699-5725

Objectives Develop A Numerical Model in FLUENT™ Code Coupled with Different Turbulence Models to Simulate the Fluid Flow, Pollutant Dispersion and Particle Deposition inside the Street Canyons Examine the Accuracy of Major Turbulence Models with Experimental Data for Street Canyon Modeling Examine Gaseous Air Pollution from Vehicular Exhaust and Industries inside the Street Canyons Examine Particulate Transport and Deposition in Street Canyons for Different Particle Sizees and Flow Conditions

Model Schematic b (m) h (m) w (m) L (m) H (m) 2D, Exact (Wind Tunnel Model) 0.06 0.9 0.98 0.4 2D, Symmetric 20 1 980 200 2D, Asymmetric 10, 15, 20 2D,Variable Street Width 20, 40, 60

Computational Grid

Vehicular Emission Line Source Boundary Conditions Plane of Symmetry 1/7th power inlet velocity Outflow Vehicular Emission Line Source Q=4 lit/h All walls: -No slip velocity boundary condition -Zero Diffusive Flux -Stick upon impact Leeward Windward

Governing Equations Continuity: Momentum: Reynolds Stress Transport Model:

CO2 Concentration –Asymmetric Canyon Configuration Flow Field Results CO2 Concentration –Asymmetric Canyon Configuration

Flow Field Results Stream Functions(m2/s2) inside the Canyons for Different Wind Velocities

Velocity Vector Field inside the Canyons for Different Wind Velocities Flow Field Results Velocity Vector Field inside the Canyons for Different Wind Velocities

CO2 Concentration inside the Canyons for Different Wind Velocities Flow Field Results CO2 Concentration inside the Canyons for Different Wind Velocities

Flow Field Results Turbulence Intensity(%) inside the Canyons for Different Wind Velocities

Wind Tunnel Experiment Measurement Points of Wind Tunnel Experiment by Meroney et al. (1996) Computational Grid of the Exact Dimensions of the Wind Tunnel Experiment

(a) Leeward (b) Windward Comparison with Wind Tunnel Experiment (a) Leeward (b) Windward

Comparison with Wind Tunnel Experiment (a) 1st Roof (b) 2nd Roof

Particulate Emissions Leeward Windward Particulate Injector: -1000 Spherical Carbon Particles -0.013 m/s (for 4 lit/h volumetric flux) -3nm to 10micron All walls: -No slip velocity boundary condition -Stick upon impact

Particulate Emissions Motion of Spherical Particle Particle Relaxation time Stokes-Cunningham Slip Correction Factor Stokes Number Capture Efficiency

Particulate Deposition Patterns Particle Capture Efficiency vs. Particle Diameter for Different Surfaces (a) Windward Wall; (b) Leeward Wall; (c) Roofs; (d) Road

Particulate Deposition Patterns Particle Capture Efficiency vs. Stokes Number for Different Wind Velocities

Particulate Deposition Patterns

Particulate Deposition Patterns

Future Work

Computational Model

Computational Model

Flow Field Results

Flow Field Results

Flow Field Results

Flow Field Results

Flow Field Results

Conclusions The present simulation has reasonable agreement with the experimental data from wind tunnel experiment performed by Meroney et al (1996). Among the turbulence models used in this study, Reynolds Stress Transport model (RSTM) shows better agreement with experiment in most of the cases. For higher wind speeds less gaseous emission will happen on the walls of the buildings. Particle transport and deposition on the surfaces depend on the wind speed and size of the particles. Particle deposition is controlled by Brownian motion for low velocities and Gravity for large particles.