Transcript Defining Solutions

Transport Calculations
Advection
1
2
3
4
5
6
n
Dispersion
1
2
3
4
5
6
n
Reaction
1
2
3
4
5
6
n
ADVECTION
• Cells are numbered from 1 to N.
• Index numbers (of SOLUTION,
EQUILIBRIUM_PHASES, etc) are used to
define the solution and reactants in each cell
• SOLUTION 0 (or N+1) enters the column
• Water is “shifted” from one cell to the next
ADVECTION
• TRANSPORT adds dispersion, stagnant
zones, and heat transport
ADVECTION
• Number of cells
• Number of shifts
• If kinetics—time
step
ADVECTION
• Output file
– Cells to print
– Shifts to print
• Selected-output file
– Cells to print
– Shifts to print
T.1.Exercise
1.
Run the Oklahoma simulation in a 10-cell column.
a. Change the log K to –15 for the following two surface
complexation reactions:
Hfo_wOH + Mg+2 = Hfo_wOMg+ + H+
Hfo_wOH + Ca+2 = Hfo_wOCa+ + H+
b. Initial conditions: equilibrate the following brine with calcite
and dolomite.
SOLUTION_SPREAD
-units mol/kgw
Description Number
brine
Temp
1
25
pH
pe
O2(g) -0.7
5.713
4
Ca
0.4655
Mg
0.1609
Na
Cl
C
S
As
charge
uMol/kgw
5.402
6.642 0.00396 0.004725
0.05
T.1.Exercise (continued)
c. Initial conditions: Equilibrate 1 mol of exchanger with the
reacted brine and place in each cell of the column.
d. Initial conditions: Equilibrate 0.07 mol of surface complexation
sites with the reacted brine. Assume 600 m^2/g specific surface
area and 30 grams of sorbing material. Place the surface in each
cell of the column.
e. Define evaporated rainwater with the following composition:
SOLUTION_SPREAD
-units mol/kgw
Description Number
20xRainwater
Temp
0
pH
25
pe
O2(g) -0.7
4.6
4
Ca
Mg
0.192
0.036
Na
0.123
Cl
0.134
C
S
charge
0.011
0.235
T.1.Exercise (continued)
f. Assume the rainwater reacts with calcite
and dolomite in the soil zone and the soil
zone pCO2 = 10^-1.5. This water flows into
the column.
g. Replace half the pore volume of the column
with the infilling water.
h. Plot pH, Cl (mol/kgw) and total dissolved As
(ug/kgw) versus cell number.
T.2.Questions
1. Describe the Cl- profile in the column at
the end of the simulation.
2. Describe the pH profile in the column at
the end of the simulation.
3. What is the pH at which arsenic appears
to become a problem?
TRANSPORT
• Cell lengths
Velocity=length/time step!
• Dispersivities
TRANSPORT
• Boundary
conditions
• Flow direction
• Diffusion coefficient
• Heat
TRANSPORT
• Stagnant cells/dual
porosity
-One stagnant cell
-Multiple stagnant cells
PHAST
• 3D Flow model
• PHREEQC chemistry
• Capabilities
–
–
–
–
Specified, leaky, flux boundary conditions
Water table/confined
Wells
Rivers
• Sequential iteration
– Transport all elements conservatively
– Run reactions in each cell
– Repeat
PHAST
• All the data for flow model—porosity,
hydraulic conductivity
• All the data for solute transport model—
dispersivity, boundary conditions
• All the data for chemistry
– Apply initial conditions by index numbers of
PHREEQC
– Associate solutions by index numbers for
boundary conditions
PHAST
• Flow and transport file
– Keyword driven input
– Same input style as PHREEQC
• Chemistry data file
– Exactly a PHREEQC input file
FLOW ANDTRANSPORT DATA FILE
GRID
-uniform x
-uniform y
-uniform z
MEDIA
-zone
0. 0. 0. 90000.
-porosity
-long_dispersivity
-trans_dispersivity
-Kx
-Ky
-Kz
-storage
0
0
0
48000. 400.
0.22
4000.
50.
1.373e-5
1.373e-5
1.373e-7
0
90000 16
48000 9
400 5
FLOW-AND-TRANSPORT DATA FILE
FLUX_BC
-zone
30000. 3000. 400. 90000. 45000. 400.
-flux
-10e-5
-associated_solution
1
SPECIFIED_VALUE_BC
# Lake Stanley Draper
-zone
30000. 14000 300. 32000. 20000. 400.
-head
348.
-associated_solution
1
LEAKY_BC
-zone
0. 48000. 0. 29000. 48000. 400.
-hydraulic
1.618e-5
-thickness
30000.
-head
305.0
-associated
1
CHEMISTRY_IC
-zone
0. 0. 0. 90000. 48000. 400.
-solution
2
-equilibrium_phases
2
-exchange
2
-surface
2
MODELVIEWER
•Solid/None
•Model features
•Grid lines
•Color bar
• Show—select items to be present in the visualization
MODELVIEWER
•Data
•Color bar
•Geometry
•Model features
•Crop
•Animation
• Tools—select menus by which you can change
the look of the features selected by Show.
Buttons
• Left mouse—3D rotate
• Shift Left mouse—2D rotate in plane of
screen
• Middle mouse—Drag
• Right mouse—Grow and shrink
MODELVIEWER
T.2.Exercise
1. Run phast from a command prompt in the
directory Friday\phast.ok
phast ok
2. Start ModelViewer
3. File->Open Friday\phast.ok\ok.mv
4. Use ModelViewer to make an animation of
the evolution of arsenic in ground-water
chemistry in Central Oklahoma