Indiana GIS Conference,
Remote sensing Workshop
March 12, 2007
EXTREME WIND AND AIR QUALITY SIMULATIONS
FOR INDIANAPOLIS
Dr. Erdal Yilmaz, CFD Laboratory, Mechanical Engineering Department , IUPUI
Email: eyilmaz@iupui.edu Web: http://engr.iupui.edu/cfdlab

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CFD (Computational Fluid Dynamics): numerical solution of the gas/liquid flow equations
Solving flow equations for urban atmospheric conditions
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Low speed (incompressible) compared to aerospace and most mechanical engineering problems
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Turbulent flow by nature
Comparatively big geographic area (> 1mile x 1mile)
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Need bigger grid size (>>1 millions elements)
NOT a tornado simulation study
Can be coupled to atmospheric prediction models

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Air quality simulation
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Dispersion of NOX emission from vehicles
Gaseous pollutant (SO2, CO, CO2, NOX etc.) release from plants
Security
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Hazardous plume simulation, Homeland Security concerns
On demand support for emergency response teams
City planning
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Wind pattern analysis for existing building clusters
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Simulations for city expansion
Exterior architectural and structural design
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(HVAC systems installations etc… )
Assist dispute resolution for wind damage
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Insurance: CFD tools to identify effect of building topology

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More than 20 years of experience
Several simulation software, Fluent, STAR-CD etc and in-house tools
Parallel computing with more than 2048 processors (IU BIG Red parallel cluster)
Projects from Rolls-Royce, Cummins, Carrier, Eli-Lilly, NASA,
Indiana State and more.

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Architectural resources: All buildings have external geometry in the form of a CAD file
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LIDAR data: Point clouds but needs to be converted to surface.
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Pictometry and others
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Surface/volume CAD model is needed.
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Sufficient grid density and boundary layer grids are needed.
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Surfaces are triangulated, volume is defined by tetrahedral or cubic elements
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Flow boundary conditions are defined
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Grid size may vary 1 to 100 millions elements

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Flow solution
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Boundary conditions are defined: wind inflow, outflow, wall (ground/buildings) condition, gas (pollutant) flow are and mass fractions, surface temperatures, surface roughness etc.
Flow model feature: steady/unsteady, turbulence model, flow solver parameters
Solution may take 10-100 CPU hours.
Post-Processing
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Usually most fun part of whole process!!!
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Data is huge needs powerful computer (memory, speed, graphics)
Solution layers/planes at different altitude or sections, extraction of flow properties, and 3D virtual reality display.
Data extraction can be generated by batch runs
Can be integrated into GIS mapping services

LiDAR point clouds CAD geometry
AutoCad drawing (reduction is needed)
CFD grid, (GAMBIT) CFD flow solution (FLUENT)

Weather data from the National Oceanic and
Atmospheric Administration (NOAA) shows that, on
April 15, 2006, Indianapolis had winds as high as
85mph which created damage to Regions Bank building in the downtown.

Straight wind velocity at the top of the west face of the Regions
Bank tower reaches to
100 mph,
+15 miles more than actual wind speed, due to partial blockage of the other buildings.

What does 800 pascal mean?
~10 people standing on a glass panel
Note that at the NW corner loads are at the same strength from both sides

Motivations
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Building canyons or clusters affect dispersion of the gaseous pollutants in urban areas.
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There are medical studies causing child asthma hospitalization at low concentrations of SO2 (100-250 ppb, Ref. 1,2)
References:
[1] Toxicological Profile For Sulfur Dioxide, US Department of Health and Human Services, Public Health Service, Agency for Toxic
Substances and Disease Registry, ATSDR, December 1998
[2] “Effect of short-term exposure to gaseous pollution on asthma hospitalization in children: a bi-directional case-crossover analysis,”
M Lin, Y Chen, R T Burnett, P J Villeneuve and D Krewski ,J. Epidemiol. Community Health 2003;57;50-55

NO2 CO
SO2
Based on EPA (Environmental Protection Agency) records for 1999.

The Clean Air Act, 1990, requires Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards for pollutants considered harmful to public health and environment.
Pollutant
Carbon Monoxide
Nitrogen Dioxide
Sulfur Dioxide
Standards
9 ppm , 10mg/m3
35 ppm, 40mg/m3
0.053 ppm, 0.1mg/m3
0.03 ppm,
0.14 ppm
0.50 ppm, 1.3mg/m3 (2 nd )
Averaging Times
8-hour
1-hour
Annual
Annual
24-hour
3-hour
Quantities are not to be exceeded once a year, except annual averaging times.

A local emission source iso-surfaces at EPA standard values iso-surface of the concentration > 0.5 ppm
Wind speed= 19 mph
Wind Direction: SW (225deg) iso-surface of the concentration > 0.14 ppm
Note:
All dispersion simulations have been done with low resolution CFD grid due to memory limitation of the computer. Current grid size is 1.2 million cells. However, parallel simulation is planned with finer grid scale, hence better solution quality.

Upwind
Downwind around building surfaces causes pollutants diffuse into street level.
Downwind
Colored contours are in ppm

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CFD can provide city level fine details of the wind flow patterns and dispersions of the gaseous pollutant
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CFD solution database can provide instant access combined with GIS mapping services.
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Firefighters, homeland security response teams, city planners, architects, and environmental study/monitoring groups can benefit from CFD integration

Extreme wind CFD solution is imported into ARCGIS software (velocity vectors)

Extreme wind CFD solution is imported into ARCGIS software (velocity contours)

Dispersion of SO2 mapped on Aerial Image iso-surface of the concentration > 0.5 ppm iso-surface of the concentration > 0.14 ppm

Following database is proposed from CFD results:
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Wind direction: 5 degrees interval, total of 72 individual cases,
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Wind speed: 5-85 mph, total of 20 individual cases,
CFD solution time: 24 hours/case/processor for sufficient mesh density
Total # of CFD case runs = 72x20 = 1440 cases
Total CPU hours = 1440x20 = 34560 hours/proc., or
= 45 days on 32 CPU parallel cluster.
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2D Images from the solution: 20 slices along z-direction
3D images from the solution: 4 different angles
Properties to display: 5 (pressure, velocity vectors, temperature etc… )
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Number of image extraction for each case = (20+4)* 5 = 120
Total # of images =1440x120 = 172,800 images
User input parameters to request the data:
1) wind direction,
2) wind speed, and
3) 3D section parameters.

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Building topology changes the wind patterns hence causing more complicated wind flow structure in the downtown area.
Regions Bank tower was exposed to higher wind speed due to upstream building blockage hence causing stronger wind forces on the window panels. It was also exposed to highly recirculating unsteady wind structure.
Integration of the CFD solutions into GIS mapping services can provide street level wind patterns, pressures, temperatures, etc. for a wide range of GIS users.
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Building topology affects street level dispersion of the pollutants. Some buildings have upwind on the front face while some have downwind.
Comparison with actual ambient monitoring will be necessary to validate the model with finer grid resolutions. In addition, other source of SO2 in the area should be included into the model for more accurate representation of the results.
This is an ongoing research. Therefore, no conclusion regarding air pollution from any emission sources has been drawn yet.

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MURI (Multidisciplinary Undergraduate Research Institute) in
IUPUI for supporting this research,
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IMAGIS (Indianapolis Mapping and Geographic
Infrastructure System) for providing LiDAR data and Autocad
Model of the Downtown Indianapolis,
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Environmental Affairs, CTE Perry K. Steam Plant, for providing flue gases data.