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Session 5, Unit 9 Modeling in the Presence of Stable Layers

Session 5, Unit 9 Modeling in the Presence of Stable Layers. Dispersion under a Stable Layer. Review of ground reflection Reflection by ground and a ceiling One reflection. Dispersion under a Stable Layer. n reflections Text p. 11-2, Eqn. (11.1) & (11.2)

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Session 5, Unit 9 Modeling in the Presence of Stable Layers

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  1. Session 5, Unit 9Modeling in the Presence of Stable Layers

  2. Dispersion under a Stable Layer • Review of ground reflection • Reflection by ground and a ceiling • One reflection

  3. Dispersion under a Stable Layer • n reflections • Text p. 11-2, Eqn. (11.1) & (11.2) • When n (completely mixed in the vertical direction), the ground level concentration becomes

  4. Dispersion under a Stable Layer • Fumigation • The above formula applies or • Lf=H+2z • yf= y(stable)+H/8

  5. Dispersion within a Stable Layer • Fanning plume • No ceiling reflection [ET=0 in eqn. (11.1)] • Use  values under stable conditions. y> z

  6. Dispersion between Two stable Layers • Plume trapping • y should be adjusted to a value greater than the one determined by the P-G curves. • Reduce number of reflections to only one. • Extreme case – if plume fully penetrate the elevated inversion, the ground level concentration is set equal to zero.

  7. Session 5, Unit 10The ISC3 Model BPIP

  8. ISCST3 Fundamentals • Basic plume equation • For a steady-state Gaussian plume, the hourly concentration at downwind distance x and crosswind distance y is: • Q – Pollutant emission rate • K – Conversion factor • D – Decay term

  9. ISCST3 Fundamentals • V – Vertical term including: • Effective stack height • Stack tip downwash • Factors that influence plume rise • Vertical dispersion, including ground and ceiling reflections • Terrain elevation and receptor height • Deposition and depletion

  10. ISCST3 Fundamentals • y, z – Dispersion coefficients • Determined generally by the methods described in previous sessions • Adjusted for • Building wake effects • Huber-Snyder downwash method • Schulman-Scire downwash method • Buoyancy induced dispersion

  11. ISCST3 Fundamentals • us – Wind speed at stack height • Adjusted using the power law

  12. ISCST3 Fundamentals • Building wake effects • Wake effect boundary • Lb = Lesser of building height and projected width • Boundary: • 2Lb upwind • 5Lb downwind • 0.5Lb on each side

  13. ISCST3 Fundamentals • Building wake effects • Huber-Snyder Procedures • Calculate plume rise due to momentum alone at a distance of 2hb • For unstable conditions: • For stable conditions:

  14. ISCST3 Fundamentals • H=hs+h (no stack tip downwash correction) • Determine applicability of Huber-Snyder procedures • Not applicable if: • H>2.5hb, or • H>hb+1.5hw • Otherwise applicable • Huber-Snyder method – Modify y and z • If H<1.2hb, modify both y and z • If 1.2hb<H<2.5hb, modify z only • Detailed calculations for modifying y and z are on Text p.14-14 thru 14-16 • The method cannot address cavity issues (cavity is assumed to be in existence within 3hw for tall buildings or 3hb for squat buildings)

  15. ISCST3 Fundamentals • Schulman-Scire Procedures • Applicable when hs<hb+0.5LB • The method adjusts z’ by decay factor A: z’’ =A z’ • Calculation of A: • A=1, if hehb • A=(hb-he)/2LB+1.0, if hb<he hb+2LB • A=0.0, if he> hb+2LB

  16. ISC3 General Features • Multiple sources in any of four categories (point, volume, area, and open pit) • Sources can be grouped in a single run • Variable emission rates • Cartesian or polar grids and multiple grids in a single run • Rural or urban options • Plume rise • Building downwash; but no cavity • Stack tip downwash

  17. ISC3 General Features • Depositions (dry and wet) and depletions • Buoyancy-induced dispersion • Wind speed adjustment • Various averaging time • All terrain • Calm-wind • One command regulatory default options • Pollutant decay • ISCST3, ISCLT3, and ISCEV

  18. Using ISCST3 • Two common input files: • Run stream files • Met data input files • Run stream files 5 Sections • Model options – CO Pathway • Source inputs – SO Pathway • Receptor network – RE Pathway • Met data input – ME Pathway • Output options – OU Pathway

  19. Using ISCST3 • Run stream files – CO example CO STARTING TITLEONE A Simple Example Problem for the ISCST Model MODELOPT DFAULT RURAL CONC AVERTIME 3 24 PERIOD POLLUTID SO2 RUNORNOT RUN EVENTFIL EVENTEXP.INP ERRORFIL ERRORS.OUT CO FINISHED

  20. Using ISCST3 • Run stream files – SO example SO STARTING LOCATION STACK1 POINT 0.0 0.0 0.0 ** Point Source QS HS TS VS DS ** Parameters: ---- ---- ---- ---- --- SRCPARAM STACK1 1.00 35.0 432. 11.7 2.4 BUILDHGT STACK1 36*34. BUILDWID STACK1 35.43 36.45 36.37 35.18 32.92 29.66 25.50 20.56 STACK1 15.00 20.56 25.50 29.66 32.92 35.18 36.37 36.45 STACK1 35.43 33.33 35.43 36.45 0.00 35.18 32.92 29.66 STACK1 25.50 20.56 15.00 20.56 25.50 29.66 32.92 35.18 STACK1 36.37 36.45 35.43 33.33 SRCGROUP ALL SO FINISHED

  21. Using ISCST3 • Run stream files – RE example RE STARTING GRIDPOLR POL1 STA POL1 ORIG 0.0 0.0 POL1 DIST 100. 200. 300. 500. 1000. POL1 GDIR 36 10. 10. POL1 END RE FINISHED

  22. Using ISCST3 • Run stream files – ME example ME STARTING INPUTFIL PREPIT.ASC ANEMHGHT 20 FEET SURFDATA 94823 1964 PITTSBURGH UAIRDATA 94823 1964 PITTSBURGH DAYRANGE 1-10 ME FINISHED

  23. Using ISCST3 • Run stream files – OU example OU STARTING RECTABLE ALLAVE FIRST-SECOND MAXTABLE ALLAVE 50 MAXIFILE 3 ALL 30.0 MAXIALL.FIL 25 MAXIFILE 24 ALL 10.0 MAXIALL.FIL 25 ** The following card was changed to use the PLOT format instead of UNFORM. POSTFILE 24 ALL PLOT PSTALL.FIL 21 POSTFILE PERIOD ALL PLOT PSTANALL.FIL 22 ** Note that the following two input cards generate PLOTFILEs with the file ** unit dynamically allocated by the ISCST program. When porting the model ** to another computer system, the user may need to specify the file units ** as is done on the previous four input cards. PLOTFILE 3 ALL 2ND PLT03ALL.FIL PLOTFILE 24 ALL 2ND PLT24ALL.FIL OU FINISHED

  24. Using ISCST3 • Met files – Example (ASCII format) 94823 64 94823 64 64 1 1 1 251.0000 3.0866 268.1 5 517.2 455.0 64 1 1 2 268.0000 5.1444 268.7 4 505.9 505.9 64 1 1 3 274.0000 5.1444 269.3 4 494.6 494.6 … 64 1 121 90.0000 10.2888 273.7 4 438.8 438.8 64 1 122 92.0000 6.1733 272.0 4 456.0 456.0 64 1 123 80.0000 8.2310 272.0 4 473.1 473.1 64 1 124 80.0000 7.2022 272.0 4 490.2 490.2 64 1 2 1 66.0000 7.2022 270.4 4 507.2 507.2 64 1 2 2 62.0000 6.6877 269.8 4 524.3 524.3 …

  25. Using ISCST3 • Running ISCST3 • Prepare input files • Run stream file – Use WordPad, Notepad, or other text editor to create and edit file • Select modeling parameters for each sections (CO, SO, RE, ME, and OU) • For each source • Digitize stack locations (x,y,z) • Provide stack parameters (emission rate, stack height, stack temperature, exit velocity, and stack diameter) • Digitize buildings, perform building downwash analysis using BPIP (discussed later), and cut the results from BPIP output and paste them into the SO section

  26. Using ISCST3 • Digitize receptors • Receptor grids – range and spacing (coarse grid, medium grid, fine grid, tight grid, property line receptors, discrete receptors) • Place a receptor at each node of grids • For each receptor, digitize x, y, and z • Consider digital terrain data • Met data file • From agencies • Unprocessed data vs. model ready data • ASCII vs. binary files

  27. Using ISCST3 • Executable: ISCST3.EXE • Run from DOS C:\>ISCST3 input.dat output.lst • Review results in the output list file • Post processing • Commercial software packages • Breeze - Trinity Consultants • Beeline • Lakes

  28. BPIP • BPIP – Building Profile Input Program • Used to generate building profile data to be included into ISC3 for building downwash analysis • For each stack, BPIP determines influencing nearby buildings and calculate GEP • For each stack, BPIP calculates building heights and projected widths of influencing buildings based on 36 wind directions. The output is used in ISC3 for downwash analysis.

  29. BPIP • BPIP input - Example 'BPIP users guide test case #1 - input file with 1 bldg and 4 stacks.' 'ST' 'METERS' 1.00 'UTMN', 210. 1 'L-Shape' 1 13.00 6 26 -10. -20. -10. 80. 40. 80. 40. 30. 90. 30. 90. -20. 2 'Stk100' 11.00 25.00 -10.00 -20.00 'Stk101' 12.00 25.00 164.00 159.00

  30. BPIP • BPIP primary output – Example … SO BUILDHGT Stk100 26.00 26.00 26.00 26.00 26.00 26.00 SO BUILDHGT Stk100 26.00 26.00 26.00 26.00 26.00 26.00 SO BUILDHGT Stk100 26.00 26.00 26.00 26.00 26.00 26.00 SO BUILDHGT Stk100 26.00 26.00 26.00 26.00 26.00 26.00 SO BUILDHGT Stk100 26.00 26.00 26.00 26.00 26.00 26.00 SO BUILDHGT Stk100 26.00 26.00 26.00 26.00 26.00 26.00 SO BUILDWID Stk100 111.07 107.16 100.00 115.85 128.17 136.60 SO BUILDWID Stk100 140.88 140.88 136.60 128.17 115.85 100.00 SO BUILDWID Stk100 107.16 111.07 111.60 108.74 108.74 111.60 SO BUILDWID Stk100 111.07 107.16 100.00 115.85 128.17 136.60 SO BUILDWID Stk100 140.88 140.88 136.60 128.17 115.85 100.00 SO BUILDWID Stk100 107.16 111.07 111.60 108.74 108.74 111.60 …

  31. BPIP • BPIP summary output • GEP results • Running BPIP • Running on DOS C:\>BPIP input.dat output.dat sum.lst

  32. Midterm Review Questions

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