Gaseous And Particulate Gaseous And Particulate Dispersion In Street Dispersion In Street

CanyonsCanyons

Kambiz NazridoustKambiz NazridoustDepartment of Mechanical and Aeronautical Engineering

Clarkson University, Potsdam, NY 13699-5725

1. 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

2. Examine the Accuracy of Major Turbulence Models with Experimental Data for Street Canyon Modeling

3. Examine Gaseous Air Pollution from Vehicular Exhaust and Industries inside the Street Canyons

4. Examine Particulate Transport and Deposition in Street Canyons for Different Particle Sizees and Flow Conditions

Objectives

Model Schematic

b (m) h (m) w (m) L (m) H (m)

2D, Exact (Wind Tunnel Model)

0.06 0.06 0.9 0.98 0.4

2D, Symmetric 20 20 1 980 200

2D, Asymmetric 20 10, 15, 20 1 980 200

2D,Variable Street Width20, 40, 60 10, 15, 20 1 980 200

Computational Grid

Boundary ConditionsPlane of Symmetry

Outflow1/7th power inlet velocity

Vehicular Emission Line SourceQ=4 lit/h

All walls: -No slip velocity boundary condition-Zero Diffusive Flux-Stick upon impact

Le

ew

ard

Win

dw

ard

0j

xj

U

jx

j'u

i'u

ix

P1

jx

iU

jU

ti

U

jil

lkikl

ljkjl

lik

s

)2(ji

)2(ijijji1

ijk

ikj

k

jkiji

kk

'u'ux

'u'u'u'ux

'u'u'u'ux

'u'uk

xc

k3

2'u'u

kc

3

2

x

U'u'u

x

U'u'u'u'u

xU

t

Governing Equations

Continuity:

Momentum:

Reynolds Stress Transport Model:

CO2 Concentration –Asymmetric Canyon Configuration

Flow Field Results

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

Flow Field Results

Velocity Vector Field 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

Flow Field Results

Wind Tunnel Experiment

Computational Grid of the Exact Dimensions of the Wind Tunnel Experiment

Measurement Points of Wind Tunnel Experiment by Meroney et al. (1996)

(a) Leeward (b) Windward

Comparison with Wind Tunnel Experiment

(a) 1st Roof (b) 2nd Roof

Comparison with Wind Tunnel Experiment

Particulate Emissions

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

Le

ew

ard

Win

dw

ard

Particulate Emissions

Particle Relaxation time

Stokes-Cunningham Slip Correction Factor

Stokes Number

Capture Efficiency

Motion of Spherical Particle

Particle Capture Efficiency vs. Particle Diameter for Different Surfaces

Particulate Deposition Patterns

(a) Windward Wall; (b) Leeward Wall; (c) Roofs; (d) Road

Particle Capture Efficiency vs. Stokes Number for Different Wind Velocities

Particulate Deposition Patterns

Particulate Deposition Patterns

Particulate Deposition Patterns

Future WorkFuture Work

Computational Model

Computational Model

Flow Field Results

Flow Field Results

Flow Field Results

Flow Field Results

Flow Field Results

1. The present simulation has reasonable agreement with the experimental data from wind tunnel experiment performed by Meroney et al (1996).

2. Among the turbulence models used in this study, Reynolds Stress Transport model (RSTM) shows better agreement with experiment in most of the cases.

3. For higher wind speeds less gaseous emission will happen on the walls of the buildings.

4. Particle transport and deposition on the surfaces depend on the wind speed and size of the particles.

5. Particle deposition is controlled by Brownian motion for low velocities and Gravity for large particles.

Conclusions