cfd application in mechanical engineering

8/10/2019 CFD application in mechanical engineering

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What is Compu tat ional Flu id Dynam ics

(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 fromnumerical 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 geometryof the physical objects and processes being modeled.


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Br ief Backg round

before electronic compu ters

Philosophical Interests in Fluid Flow

Newtons Physical Equations (1686)

Navier-Stokes Equations (1823)

V. BjerknesNotions of Numerical

Weather Prediction (1904)

L.F. RichardsonFirst Numerical

Weather Prediction (1922)


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Br ief Backg round

w i th elect ron ic compu ters

:Prog ress ion to A ir Quali ty Modeling

First Electronic Computers (1940s)

J. CharneyFirst 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

Fou r Quest ions Model ing

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 Concentrat ions =

Local Sources + Regional Backg round


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Roadway Exposu res:

With in the Roadway or Neighborhood

Microenvi ronments


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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 routineapplications.

Interface CFD software with other models.


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Support /Col laborators

Wei Tang: National Research Council Post Docwith EPA, 2003-2005 (2.5 years)

Matt Freeman, Richard Spencer: EPA Scientific Visualization Centerunder EPA contract with Lockheed-Martin

Karl Kuehlert, Brian Bell, Walter Schwarz: EPA Cooperative Researchand Development Agreement with Fluent, Inc

Michael Lazaro: EPA Memorandum of Cooperation withArgonne National Laboratory

Department of Homeland Security: New York City Urban DispersionProgram

Army Research Laboratory MSRC Visualizationand Supercomputing Facility


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App l icat ion of

Fine-scale CFD Models

Develop databases to complement the

dearth of exposure measurements.

Support the development of HumanExposure Factors.

Support the development of subgrid

parameterization for CMAQ.

Interface with CMAQ


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Presen t CMAQ

Multi-scale Multi-pollutant

Various Chemical and Physical

Processes

Common Linkage of Meteorology,

Emissions, and Air Quality

Regional Applications > 10 km grid

Urban Applications > 1 km grid


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Example Fine-scale CFD

Think 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 gridface or volume.

Motion of objects can be added.

Particle physics can be added. Chemistry can be added.


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Fine-scale CFD Model ing o f

Urban Neighborhoods


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Example Wind Field

What is the direct ion o f the freestream w inds?


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Example: Winds from Southwest


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Surface Winds and w ith Plume

Concentrat ion wi th in Bui ld ing A rrays


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Plume Ini t iated from

Different Poin t Locat ion s

- bu t w ithin an Ident ic al Wind Field.


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Hor izon tal Planes

- Vert ical Veloc ity


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Area-averaged * Winds

Urban Canopy Parameterization

Wind speed Wind direction

*Area-averaged over same horizontal slice-plane shown in the previous slide.

Upstream Inlet: Blue

Upstream Inlet: Blue


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Automobi le

Microenvi ronments


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Model ing Urban Roadways

- Includ ing the Vehic le Effects

TKEGrid Resolution


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Modeling Urban Roadways

- Inc lud ing the Veh icle Effects

ConcentrationWind Velocity


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Disclaimer

The research presented here was performedunder the Memorandum of Understandingbetween the U.S. Environmental Protection

Agency (EPA) and the U.S. Department ofCommerce's National Oceanic andAtmospheric Administration (NOAA) andunder agreement number DW13921548. Thiswork constitutes a contribution to the NOAA

Air Quality Program. Although it has beenreviewed by EPA and NOAA and approvedfor publication, it does not necessarily reflecttheir policies or views

cfd application in mechanical engineering

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