URBAN CFD EXTREME WIND AND AIR QUALITY SIMULATIONS FOR INDIANAPOLIS Dr. Erdal Yilmaz, CFD...
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Transcript of URBAN CFD EXTREME WIND AND AIR QUALITY SIMULATIONS FOR INDIANAPOLIS Dr. Erdal Yilmaz, CFD...
URBAN CFDURBAN CFDEXTREME WIND AND AIR QUALITY EXTREME WIND AND AIR QUALITY SIMULATIONS SIMULATIONS FOR INDIANAPOLISFOR INDIANAPOLIS
Dr. Erdal Yilmaz, CFD Laboratory, Mechanical Engineering Department , IUPUI
Email: [email protected] Web: http://engr.iupui.edu/cfdlab
Indiana GIS Conference, Remote sensing WorkshopMarch 12, 2007
Urban CFD
CFD (Computational Fluid Dynamics): numerical solution of the gas/liquid flow equations
Solving flow equations for urban atmospheric conditions Low speed (incompressible) compared to
aerospace and most mechanical engineering problems
Turbulent flow by nature Comparatively big geographic area (> 1mile x
1mile) Need bigger grid size (>>1 millions elements)
NOT a tornado simulation study Can be coupled to atmospheric prediction
models
Where to use Urban CFD
Air quality simulation Dispersion of NOX emission from vehicles Gaseous pollutant (SO2, CO, CO2, NOX etc.) release from
plants Security
Hazardous plume simulation, Homeland Security concerns On demand support for emergency response teams
City planning Wind pattern analysis for existing building clusters Simulations for city expansion
Exterior architectural and structural design (HVAC systems installations etc… )
Assist dispute resolution for wind damage Insurance: CFD tools to identify effect of building topology
CFD in IUPUI
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 BIGRed parallel cluster) Projects from Rolls-Royce, Cummins, Carrier, Eli-
Lilly, NASA, Indiana State and more.
CFD Steps
Generate CAD model Architectural resources: All buildings have external geometry
in the form of a CAD file LIDAR data: Point clouds but needs to be converted to
surface. Pictometry and others
Generate CFD Grid/Mesh Surface/volume CAD model is needed. Sufficient grid density and boundary layer grids are needed. Surfaces are triangulated, volume is defined by tetrahedral
or cubic elements Flow boundary conditions are defined Grid size may vary 1 to 100 millions elements
CFD Steps (cont)
Flow solution 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 Usually most fun part of whole process!!! 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
CAD and CFD models
AutoCad drawing (reduction is needed)
LiDAR point clouds CAD geometry
CFD grid, (GAMBIT) CFD flow solution (FLUENT)
Extreme Wind Condition
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.
Extreme Wind Solutions
Extreme Wind Solutions (cont)
Regions Bank Tower: CFD Solutions
Regions Bank Tower: CFD Solutions (cont)
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.
Wind Force and Pressure
What does 800 pascal mean?~10 people standing on a glass panel ~10 people standing on a glass panel
Note that at the NW corner loads are at the same strength from both sidesNote that at the NW corner loads are at the same strength from both sides
Air Quality Simulations
Motivations
Building canyons or clusters affect dispersion of the gaseous pollutants in urban areas.
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
Pollutant Sources: Geographic Locations
NO2 CO SO2
Based on EPA (Environmental Protection Agency) records for 1999.
Ambient Air Quality Standard
Pollutant Standards Averaging Times
Carbon Monoxide 9 ppm , 10mg/m335 ppm, 40mg/m3
8-hour1-hour
Nitrogen Dioxide 0.053 ppm, 0.1mg/m3 Annual
Sulfur Dioxide 0.03 ppm, 0.14 ppm 0.50 ppm, 1.3mg/m3 (2nd)
Annual24-hour3-hour
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.
Quantities are not to be exceeded once a year, except annual averaging times.
Dispersion of SO2
A local emission sourceiso-surfaces at EPA standard values
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.
iso-surface of the concentration > 0.5 ppm
iso-surface of the concentration > 0.14 ppm
Wind speed= 19 mphWind Direction: SW (225deg)
Effect of Building Topology
Upwind
Downwind
Downwind around
building surfaces
causes pollutants
diffuse into street level.
Colored contours
are in ppm
CFD Solutions for GIS Mapping Services
CFD can provide city level fine details of the wind flow patterns and dispersions of the gaseous pollutant
CFD solution database can provide instant access combined with GIS mapping services.
Firefighters, homeland security response teams, city planners, architects, and environmental study/monitoring groups can benefit from CFD integration
Geo-referenced CFD
Extreme wind CFD solution is imported into ARCGIS software (velocity vectors)
Geo-referenced CFD (cont)
Extreme wind CFD solution is imported into ARCGIS software (velocity contours)
Geo-referenced CFD (cont)
iso-surface of the concentration > 0.5 ppm iso-surface of the concentration > 0.14 ppm
Dispersion of SO2 mapped on Aerial Image
CFD Database for GIS Map Services
Following database is proposed from CFD results: Wind direction: 5 degrees interval, total of 72 individual cases, 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. 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… ) 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.
Conclusions
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.
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.
Future Work
Comprehensive CFD modeling with fine grid scale
CFD solutions as a GIS layer in GIS mapping services
Acknowledgments
MURI (Multidisciplinary Undergraduate Research Institute) in IUPUI for supporting this research,
IMAGIS (Indianapolis Mapping and Geographic Infrastructure System) for providing LiDAR data and Autocad Model of the Downtown Indianapolis,
Environmental Affairs, CTE Perry K. Steam Plant, for providing flue gases data.