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

2. 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

3. 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

4. Computational Grid

5. 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

6. Governing Equations Continuity: Momentum:
Reynolds Stress Transport Model:

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

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

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

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

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

12. 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

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

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

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

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

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

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

19. Particulate Deposition Patterns

20. Particulate Deposition Patterns

21. Future Work

22. Computational Model

23. Computational Model

24. Flow Field Results

25. Flow Field Results

26. Flow Field Results

27. Flow Field Results

28. Flow Field Results

29. 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.