Post on 20-Dec-2015
Source Terms
• Constant Concentration
• Injection Well
• Recharge
May be introduced at the boundary or inthe interior of the model
Q
Constant Concentration(Z&B, p. 283)
cs
at boundary
e.g., NAPL source area
Injection Well
Qcs
well
Recharge
R, cs
Mass Flux = R (x y) cs
Problem Set #3Source Terms and Chemical Reactions
• Constant Concentration
• Injection Well
• Recharge
• retardation• 1st order decay
Problem Set #3Two Layers
This screen shows aconstant concentrationsource. Contours ofhead are also shown.
Confined layers
Note the water table
Flow field for anunconfined upper layerwith areal recharge anda recharge source cell.
Problem Set #3
0.0
10.0
20.0
30.0
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50.0
60.0
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Time
Co
nce
ntr
atio
n
Parts 1 and 2: Producebreakthrough curves underdifferent assumptions aboutthe source term and chemicalreactions.
Problem Set #3 – Part 3 - Remediation
TVD Solution
Numerical error causedby high Peclet number
0.0
10.0
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Time
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nce
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atio
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0.0
12.0
24.0
36.0
48.0
60.0
0.0 0.6 1.2 1.8 2.4 3.0
Time
Layer 2
Concentration vs. Time at pumping well
Central Finite Difference Solution
Problem Set #3 – Part 3 - Remediation
TVD Solution
Numerical error causedby high Peclet number
0.0
10.0
20.0
30.0
40.0
50.0
60.0
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Time
Co
nce
ntr
atio
n
Courant Numberx
tvCr
Cr < 1
Peclet Numberx
D
xvPe
Pe < 4
Pumping well isrepresented by 4 nodes
50 m grid
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5.0
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45.0
50.0
55.0
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Time (years)
Co
nce
ntr
atio
n
100 m grid spacingPeclet number = 5
50 m grid spacingupper left node in the pumping complexPeclet number = 2.5
TVD solution
100 m grid 50 m grid – near centerof pumping compex
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0.0 0.6 1.2 1.8 2.4 3.0
Time
Concentration vs. Time at pumping well
0
10
20
30
40
50
0.0 0.6 1.2 1.8 2.4 3.0
Time
Concentration vs. Time at pumping well
TVD Solution