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NESC9739 2DFLOW.

2DFLOW, 2-D Drainage Winds and Diffusion Simulation

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1. NAME OR DESIGNATION OF PROGRAM:  2DFLOW.
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2. COMPUTERS
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Program name Package id Status Status date
2DFLOW NESC9739/01 Tested 13-FEB-1987

Machines used:

Package ID Orig. computer Test computer
NESC9739/01 DEC VAX 11/780 DEC VAX 11/780
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3. DESCRIPTION OF PROGRAM OR FUNCTION

2DFLOW is a vertically integrated dynamical drainage flow model developed from conservation equations for momentum and mass in a terrain following coordinate system. Wind fields from the dynamical model drive a Monte Carlo transport and diffusion model. The model needs only topographic data, an Eulerian or Lagrangian time scale, and a surface drag coefficient for input data; it can be started with a motionless atmosphere.
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4. METHOD OF SOLUTION

The system of dynamical equations is solved numerically with a second-order finite difference scheme. Advection  of mass and momentum is calculated by the second upwind differencing or "donor cell" method.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM:
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6. TYPICAL RUNNING TIME:
NESC9739/01
NEA-DB executed the test case included in this package  on a VAX-11/780 computer in 8 minutes, 17 seconds of CPU time.
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7. UNUSUAL FEATURES OF THE PROGRAM

2DFLOW has the following features  which make it attractive as a practical tool for estimating the concentrations of pollutants released into nocturnal drainage winds: 1) No wind or temperature data are needed. A surface drag coefficient and Eulerian or Lagrangian time scale are required, but  the model is not sensitive to their exact value. High resolution topographic data are required. 2) The model has been successfully tested at sites with rugged mountainous terrain and at a site with gently rolling terrain. 3) The model is two-dimensional (vertically  integrated) so its computational requirements are moderate. 4) Maximum pollutant concentrations are predicted to within factors of  2 to 10 at specific points, based on observed and simulated concentration time series.
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8. RELATED AND AUXILIARY PROGRAMS:
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9. STATUS
Package ID Status date Status
NESC9739/01 13-FEB-1987 Tested at NEADB
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10. REFERENCES:
NESC9739/01, included references:
- A.J. Garrett and F.G. Smith:
  Two-Dimensional Simulations of Drainage Winds and Diffusion
  Compared to Observations.
  Reprinted from "Journal of Climate and Applied Meteorology",
  Vol. 23, No. 4, pp. 597-610  (April 1984)
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11. MACHINE REQUIREMENTS:  500K bytes.
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12. PROGRAMMING LANGUAGE(S) USED
Package ID Computer language
NESC9739/01 FORTRAN-77
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13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:
NESC9739/01
VMS V4.3 (VAX-11/780).
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14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:
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15. NAME AND ESTABLISHMENT OF AUTHORS

         A.J. Garrett
         Savannah River Laboratory
         Aiken, South Carolina 29808
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16. MATERIAL AVAILABLE
NESC9739/01
File name File description Records
NESC9739_01.001 Information file 79
NESC9739_01.002 2DFLOW Source Program 776
NESC9739_01.003 2DFLOW test case input data 20
NESC9739_01.004 2DFLOW topographical data library 59
NESC9739_01.005 2DFLOW sample output (concentrations data) 159
NESC9739_01.006 2DFLOW sample output (winds data) 289
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17. CATEGORIES
  • R. Environmental and Earth Sciences

Keywords: Monte Carlo method, air pollution, diffusion, flow models, surface air, topography, turbulence, weather.