Alan H Huber

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A FRAMEWORK FOR FINE-SCALE COMPUTATIONAL FLUID
DYNAMICSAIR QUALITY MODELING AND ANALYSIS

• Alan H Huber
• Physical Scientist PhD, QEP
• NOAA, ASMD, in partnership with the US EPA,
• National Exposure Research Laboratory, RTP, NC,
  USA
• THE 5TH ANNUAL CMAS CONFERENCE, Chapel Hill, NC
• October 18, 2006

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What is Computational Fluid Dynamics (CFD)?

• Computational (having to do with mathematics
  computation)
• Fluid Dynamics (the dynamics of things that
  flow)
• CFD is built upon fundamental physics equations
  equations of motion and conservation. CFD
  applications range from numerical weather
  prediction to vehicular aerodynamics design.
• CFD applications are linked with advances in
  computing software and hardware. CFD software is
  characterized by the physical models in the
  software.
• Fine-scale CFD applications closely match the
  true geometry of the physical objects and
  processes being modeled.

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Brief Background before electronic computers

• Philosophical Interests in Fluid Flow
• Newtons Physical Equations (1686)
• Navier-Stokes Equations (1823)
• V. Bjerknes Notions of Numerical Weather
  Prediction (1904)
• L.F. Richardson First Numerical Weather
  Prediction (1922)

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Brief Background with electronic computers
Progression to Air Quality Modeling

• First Electronic Computers (1940s)
• J. Charney First Computer Numerical Weather
  Prediction (April 1950)
• Numerical Modeling of Air Quality Promoted by US
  EPA in 1970s and 1980s
• CMAQ Evolves in the 1990s to Present
• CMAQ Continues to Evolve with Advancing
  Computation Hardware and Software

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Challenge to Relate to Human Exposure
Assessment Four Questions Modeling Should Help
Answer

• How many people are exposed ?
• What is the level of each persons exposure?
• What are the causes of exposure?
• How can exposures be altered efficiently?

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Total Exposure Concentrations Local Sources
Regional Background
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Urban Exposures Beyond the Lamp Post
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Roadway Exposures Within the Roadway or
Neighborhood Microenvironments
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Human Exposure

• A human is only exposed to what can possibly
  contact his body.
• Air quality concentrations need to be linked to
  temporal and spatial scales associated with
  profiles of human exposure relevant to supporting
  health risk assessments

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Making Fine-Scale CFD Application Routine

• Computational resources. Today, industrial
  complexes can be practically modeled by most
  workstations, while complex urban areas can only
  be modeled by the cluster systems.
• Develop best-practice methods.
• CFD codes have many options.
• Develop user-friendly interfaces for general
  application. Air quality modelers should be able
  to run routine applications.
• Interface CFD software with other models.

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Support/Collaborators

• Wei Tang National Research Council Post Doc
  with EPA, 2003-2005 (2.5 years)
• Matt Freeman, Richard Spencer EPA Scientific
  Visualization Center under EPA contract with
  Lockheed-Martin
• Karl Kuehlert, Brian Bell, Walter Schwarz EPA
  Cooperative Research and Development Agreement
  with Fluent, Inc
• Michael Lazaro EPA Memorandum of Cooperation
  withArgonne National Laboratory
• Department of Homeland Security New York City
  Urban Dispersion Program
• Army Research Laboratory MSRC Visualization
• and Supercomputing Facility

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Application of Fine-scale CFD Models

• Develop databases to complement the dearth of
  exposure measurements.
• Support the development of Human Exposure
  Factors.
• Support the development of subgrid
  parameterization for CMAQ.
• Interface with CMAQ

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Present CMAQ

• Multi-scale Multi-pollutant
• Various Chemical and Physical Processes
• Common Linkage of Meteorology, Emissions, and Air
  Quality
• Regional Applications gt 10 km grid
• Urban Applications gt 1 km grid

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Potential for Interfacing CMAQ CFD with
Fine-scale CFD Models

• Increasing computational capacities make it
  possible to extend CMAQ to spatially fine-scales.
  Finer temporal scale may be more difficult.
• Interface CMAQ when needed with a separate
  fine-scale (subgrid) model.
• Pass information between separate CMAQ and
• fine-scale model.

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Example Fine-scale CFDThink Inside the Box

• A few example solutions follow
• While the example cases do not involve thermal
  heating, methods have been developed for adding
  heat fluxes to any grid face or volume.
• Motion of objects can be added.
• Particle physics can be added.
• Chemistry can be added.

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Fine-scale CFD Modeling of Urban Neighborhoods
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Example Wind FieldWhat is the direction of the
freestream winds?
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Example Winds from Southwest
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Surface Winds and with Plume Concentration within
Building Arrays
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Plume Initiated from Different Point Locations
- but within an Identical Wind Field.
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Horizontal Planes - Vertical Velocity
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Area-averaged Winds Urban Canopy
Parameterization
Wind speed
Wind direction
Upstream Inlet Blue
Upstream Inlet Blue
Area-averaged over same horizontal slice-plane
shown in the previous slide.
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Automobile Microenvironments
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Modeling Urban Roadways - Including the Vehicle
Effects
TKE
Grid Resolution
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Modeling Urban Roadways - Including the Vehicle
Effects
Concentration
Wind Velocity
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SUMMARY STATEMENT

• CMAQ-like air quality modeling systems may evolve
  to support the critical needs for modeling human
  exposures to air pollutants.
• Continued advances in computing hardware and
  software make it possible and increasingly more
  practical to consider extending present CMAQ air
  quality models to increasingly finer scales.
• Fine-scale CFD should be interfaced with CMAQ
• Fine-scale CFD should support CMAQ
  parameterizations
• Fine-scale CFD models can also be applied
  independent of larger scale grid models to
  support the development of human exposure factors
  and the human exposure profiles that are
  dominated by local source emissions.

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Disclaimer

• The research presented here was performed under
  the Memorandum of Understanding between the U.S.
  Environmental Protection Agency (EPA) and the
  U.S. Department of Commerce's National Oceanic
  and Atmospheric Administration (NOAA) and under
  agreement number DW13921548. This work
  constitutes a contribution to the NOAA Air
  Quality Program. Although it has been reviewed by
  EPA and NOAA and approved for publication, it
  does not necessarily reflect their policies or
  views