Computational modeling of pollutant transport, dispersion and deposition is described. Particular attention is given to transport and deposition of contaminant particles in atmospheric flows around buildings, in street canyons and near bridges. The Eulerian-Eulerian and Eulerian-Lagrangian models are outlined. Particular attention was given to the use of advanced anisotropic turbulence models and a Lagrangian particle trajectory analysis. The procedure for simulating the instantaneous turbulence fluctuating velocity vector with the aid of random field model sis described. Examples of dispersion and deposition of pollutants near buildings, in street canyons and near bridges are discussed. It is shown that the computer simulation can predict the features of the experimentally observed pollutant concentration data.

1. Faculty of Environment
Integrated GIS-based
GIS-
Experimental-
Experimental-Computational
Methods for Urban Air Pollution
Modeling
Amir M. Yadghar
PhD Candidate
University of Western Ontario
24 Dec. 2008
Air Pollution Air Pollution Definition
‫آﻟﻮدﮔﻲ ﻫﻮا ﻋﺒﺎرت اﺳﺖ از وﺟﻮد ﻫﺮ ﻧﻮع آﻻﻳﻨﺪه اﻋﻢ از‬
‫ﺟﺎﻣﺪ، ﻣﺎﻳﻊ و ﮔﺎز در ﻫﻮا ﺑﺑﻪ ﻣﻘﺪار و در ﻣﺪت زﻣﺎﻧﻲ ﻛﻪ ﻛﻴﻔﻴﺖ‬
‫ﻴﻴ‬ ‫ز‬ ‫رر‬ ‫ﻳﻊ ز ر ﻮ‬ ‫ﺟ‬
‫زﻧﺪﮔﻲ را ﺑﺮاي اﻧﺴﺎن و دﻳﮕﺮ ﺟﺎﻧﺪاران ﺑﻪ ﺧﻄﺮ اﻧﺪازد و ﻳﺎ ﺑﻪ‬
.‫آﺛﺎر ﺑﺎﺳﺘﺎﻧﻲ و اﻣﻮال، ﺧﺴﺎرت وارد آورد‬
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2. ‫ﻣﺪﻟﺴﺎزي آﻟﻮدﮔﻲ ﻫﻮا – ﭼﺮا؟‬
‫ﻣﺪل آﻟﻮدﮔﻲ ﻫﻮا‬
‫1( ﺑﺮآورد اﻧﺘﺸﺎر آﻻﻳﻨﺪه ﻫﺎ‬
‫ﻣﺪﻟﺴﺎزي آﻟﻮدﮔﻲ ﻫﻮا – ﭼﺮا؟‬ ‫ﻣﺪﻟﺴﺎزي آﻟﻮدﮔﻲ ﻫﻮا – ﭼﺮا؟‬
‫3( ارزﻳﺎﺑﻲ اﺳﺘﺮاﺗﮋي ﻫﺎي ﻛﻨﺘﺮﻟﻲ ﺟﺎﻳﮕﺰﻳﻦ‬ ‫2( ﺷﻨﺎﺳﺎﻳﻲ ﺻﺤﻴﺢ ﻣﻨﺎﺑﻊ‬ ‫5( ﺗﺨﻤﻴﻦ اﺛﺮات ﻣﻀﺮ ﺑﺮ ﺳﻼﻣﺘﻲ‬ ‫4( ﻧﻈﺎرت ﻣﺆﺛﺮ‬
‫٢‬

3. ‫ﻣﺪﻟﺴﺎزي ﻛﻴﻔﻴﺖ ﻫﻮا – ﭼﮕﻮﻧﻪ؟‬ ‫ﻣﺪﻟﺴﺎزي‬
1. Empirical Equations (US EPA, ASHRAE)
2. Physical models (water flume, wind tunnel, etc.)
‫ﻣﺤﺪوده ﻫﺎي ﻻزم ﺑﺮاي ﻣﺪل ﺳﺎزي‬
3. Computational Fluid Dynamics (CFD)
Numerical (computer) models:
1. Gaussian models (ISC3, AERMOD, SCREEN3)
‫ﻓﺎﻛﺘﻮرﻫﺎي ﻣﺸﺘﺮك در ﻣﺪل ﻫﺎ‬
2. Puff models (CALPUFF)
‫ﻣﺪل ﻫﺎي ﻛﻴﻔﻴﺖ ﻫﻮا‬ Experimental Methods
Dispersion Modeling - These models are typically used in the permitting
Different kinds
process to estimate the concentration of pollutants at specified ground-level
receptors surrounding an emissions source.
Different fields
Photochemical Modeling - These models are typically used in regulatory or
policy assessments to simulate the impacts from all sources by estimating
pollutant concentrations and deposition of both inert and chemically reactive
Why?
pollutants over large spatial scales.
Receptor Modeling - These models are observational techniques which use
the chemical and physical characteristics of gases and particles measured at
source and receptor to both identify the presence of and to quantify source
contributions to receptor concentrations.
٣

4. ‫ﻣﺪﻟﺴﺎزي ﻓﻴﺰﻳﻜﻲ‬ ‫ﺗﻮﻧﻞ ﺑﺎد‬
A wind tunnel is a research tool developed to assist
with studying the effects of air moving over or
around solid objects.
‫ﺗﻮﻧﻞ ﺑﺎد – ﻻﻳﻪ ﻣﺮزي‬ ‫ﺗﻮﻧﻞ ﺑﺎد – ﻛﺎرﺑﺮد‬
Atmospheric Boundary Layer (ABL)
Pedestrian-level Wind Environment
Wind Climate studies
Snow and Ice studies
Indoor Air Quality studies
Simulation of Downburst
Atmospheric dispersion of gaseous pollutants in complex terrain
٤

5. GPS Dropwindsonde ‫دﺳﺘﮕﺎه‬ CFD
Computational Fluid Dynamics (CFD) is one of the
branches of fluid mechanics that uses numerical methods
and algorithms to solve and analyze problems that involve
fluid flows Computers are used to perform the millions of
flows.
calculations required to simulate the interaction of fluids and
gases with the complex surfaces used in engineering. Even
with simplified equations and high-speed supercomputers,
only approximate solutions can be achieved in many cases.
Ongoing research, however, may yield software that improves
the accuracy and speed of complex simulation scenarios such
as transonic or turbulent flows.
CFD CFD Methods Consideration
• Topography and complex geometry: choose of the co-ordinate
The tests and modelings demonstrate the possibilities of CFD
system and computer grid;
techniques in solving a broad range of air pollution problems. The • Turbulence closure for air pollution modelling: modified k-ε model
g
for stable stratified ABL;
CFD techniques are rather complex, but capable of handling
• Boundary conditions for vertical profiles of velocity for stable-
situations where due to complex geometry, thermal effects or flow
stratified atmosphere;
conditions other simpler methods fail. • Effects of the radiation and thermal budget of inclined surfaces to
dispersion of pollutants;
• Artificial sources of air dynamics and circulation
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6. CFD Modeling
Navier-Stokes :‫ﻣﻌﺎدﻟﻪ ﺣﺎﻛﻢ‬
FLUENT
CFD ‫ﻧﻤﻮﻧﻪ اي از ﻣﺪﻟﺴﺎزي ﺑﺎ‬ Wind Tunnel Tests
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7. Wind Tunnel Tests Wind Tunnel Tests
Wind Tunnel Tests Eulerian Advection/Diffusion Models
Wind speeds and concentrations are specified in a
stationary co-ordinate system (i.e. as “fields”)
y y ( )
Wind speed field is found using computational fluid
dynamics (CFD)
Advection diffusion equation solved for concentration
field.
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8. ‫‪Geographical Information System‬‬ ‫‪GIS STRUCTURE FOR AIR POLLUTION MODELLING‬‬
‫‪Traffic Demand‬‬ ‫‪Driving cycles‬‬ ‫‪Meteorological‬‬
‫&‬ ‫&‬ ‫&‬
‫ﺳﻴﺴﺘﻢ اﻃﻼﻋﺎت ﺟﻐﺮاﻓﻴﺎﻳﻲ، ﻣﺠﻤﻮﻋﻪي ﺳﺎزﻣﺎن ﻳﺎﻓﺘﻪاي از ﺳﺨﺖ اﻓﺰار، ﻧﺮم‬ ‫‪Road Network‬‬ ‫‪Fleet composition‬‬ ‫‪Climatic Data‬‬
‫اﻓﺰار، اﻃﻼﻋﺎت ﺟﻐﺮاﻓﻴﺎﻳﻲ، روش و ﻧﻴﺮوي اﻧﺴﺎﻧﻲ ﻣﺘﺨﺼﺺ اﺳﺖ ﻛﻪ ﺟﻬﺖ‬
‫ﻛﺴﺐ، ورود، ﺳﺎزﻣﺎﻧﺪﻫﻲ، ذﺧﻴﺮه، ﺑﻪ ﻫﻨﮕﺎم ﺳﺎزي، ﭘﺮدازش، ﺗﺤﻠﻴﻞ و ﺗﻠﻔﻴﻖ‬
‫‪GEOGRAPHIC INFORMATION SYSTEM‬‬
‫اﻃﻼﻋﺎت اﻳﺠﺎد ﻣﻲﺷﻮد. ﺑﻨﺎﺑﺮ اﻳﻦ ﺳﻴﺴﺘﻢ اﻃﻼﻋﺎت ﺟﻐﺮاﻓﻴﺎﻳﻲ ﻋﻼوه ﺑﺮ ذﺧﻴﺮه و‬
‫‪Traffic‬‬ ‫‪Emission‬‬ ‫‪Dispersion‬‬
‫ﺳﺎزﻣﺎﻧﺪﻫﻲ اﻃﻼﻋﺎت ﺟﻐﺮاﻓﻴﺎﻳﻲ ﺑﻪ ﺷﻜﻞ رﻗﻮﻣﻲ و اﻣﻜﺎﻧﺎت ﺑﺎزﻳﺎﺑﻲ ﺳﺮﻳﻊ و ﺑﻪ‬ ‫‪Model‬‬ ‫‪Model‬‬ ‫‪Model‬‬
‫ﻫﻨﮕﺎم ﺳﺎزي اﻃﻼﻋﺎت، اﺑﺰار و ﻗﺎﺑﻠﻴﺘﻬﺎي ﻻزم را ﺑﺮاي اﻧﻮاع ﭘﺮدازشﻫﺎ،‬
‫ﺗﺤﻠﻴﻞﻫﺎي ﻓﻀﺎﻳﻲ، ﺗﻠﻔﻴﻖ و ﻣﺪلﺳﺎزي اﻃﻼﻋﺎت ﺟﻐﺮاﻓﻴﺎﻳﻲ ﻓﺮاﻫﻢ ﻣﻲﺳﺎزد.‬
‫‪GIS‬‬ ‫‪Traffic Flows‬‬ ‫‪Concentrations‬‬
‫‪Emissions‬‬
‫‪Mapping‬‬ ‫‪Mapping‬‬
‫‪Mapping‬‬
‫‪Traffic Routes Data Layer‬‬
‫‪Topography‬‬
‫٨‬

9. Urban Blocks Land Use GIS Model 1 – Example 2
CO – Cell Modeling CO (LDV) – Buffer Modeling
٩

10. ‫ﻧﺘﺎﻳﺞ‬
CO – Ordinary Kriging Model
Analysing
Ali ‫ﺗﺤﻠﻴﻞ‬
‫ﺗ ﻠﻞ‬
Verifying ‫ﺑﺮرﺳﻲ‬
‫از ﺗﻮﺟﻪ ﺷﻤﺎ ﻣﺘﺸﻜﺮم‬
‫ﭘﻴﺸﻨﻬﺎدﻫﺎﻳﻲ ﺑﺮاي آﻳﻨﺪه‬
Integration between computational methods,
experiments and numerical methods in
environmental modeling especially air pollution
modeling, is an area in its infancy.
١٠