transport.chem.dat file 3 waters –background, o 2 (solution 1) –sewage effluent, nh 4 + and cl...

Transport.chem.dat FileTransport.chem.dat File

3 waters3 waters– Background, OBackground, O22 (solution 1) (solution 1)

– Sewage effluent, NHSewage effluent, NH44++ and Cl and Cl-- (solution 2) (solution 2)

– Rain ORain O22 (solution 3) (solution 3)

NHNH44++ oxidation oxidation

– SOLUTION 1 and 2 contain dissolved oxygenSOLUTION 1 and 2 contain dissolved oxygen

– SOLUTION 2 only NHSOLUTION 2 only NH44+ +

– NONO33- - produced where NHproduced where NH44

++ and O and O22 mix mix

NN2(aq)2(aq) and NO and NO22-- are disabled in .chem.dat are disabled in .chem.dat

Data to be written for Model ViewerData to be written for Model Viewer11

Transport.chem.datTransport.chem.dat

22

Changes for Solute TransportChanges for Solute Transport

1.1. Save As…Save As…2.2. Set solute transport and transient flowSet solute transport and transient flow3.3. Check dispersivitiesCheck dispersivities4.4. Check distribution of chemical conditionsCheck distribution of chemical conditions5.5. Initial head distributionInitial head distribution6.6. Check associated solutions of BCCheck associated solutions of BC7.7. Specify flux of sewage effluentSpecify flux of sewage effluent8.8. Set time step and simulation lengthSet time step and simulation length

33

Save AsSave As Save model—File|Save As… Save model—File|Save As…

transport.p4wtransport.p4w

44

Enable Solute TransportEnable Solute Transport

55

Enable Transient FlowEnable Transient Flow

66

Transport Calculations Require Transport Calculations Require Dispersivity ParametersDispersivity Parameters

MEDIAMEDIA

Retain default of 1 m longitudinal Retain default of 1 m longitudinal and transverse dispersivityand transverse dispersivity

77

Numerical Dispersion: Numerical Dispersion: Upstream-in-space, backward-in-timeUpstream-in-space, backward-in-time

2502

x

space

502

tv

time

Grid spacing is 500 mGrid spacing is 500 m

Velocity is 100 m/yr, 1 yr time stepVelocity is 100 m/yr, 1 yr time step

88

IC: Set Chemical Initial ConditionsIC: Set Chemical Initial Conditions

Default CHEMISTRY_IC should have SOLUTION Default CHEMISTRY_IC should have SOLUTION

11

99

IC: Use Steady-State Head Condition: IC: Use Steady-State Head Condition: flow.head.dat or ex5.head.200.datflow.head.dat or ex5.head.200.dat

1010

Flux: Solution 3 for PrecipitationFlux: Solution 3 for Precipitation

1111

Flux: Sewage BedsFlux: Sewage Beds Draw an Draw an

arbitrary boxarbitrary box Flux Flux

boundaryboundary Flux scheduleFlux schedule

(next page)(next page) Solution 2 Solution 2 Z faceZ face

1212

Denis LeBlanc’s Flux Estimates (m/d)Denis LeBlanc’s Flux Estimates (m/d)

Beds 1-4 Beds 5-8 Beds 9-12 Beds 13-16 Beds 19-25

0 0 0 0 0 0

1936 -0.037 0 0 0 0

1941 -0.114 -0.114 -0.114 -0.114 -0.114

1946 -0.023 -0.023 -0.023 -0.023 -0.023

1956 -0.126 -0.126 -0.126 0 0

1971 -0.05 -0.05 -0.05 0 0

1978 -0.114 0 0 0 0

1984 0 -0.038 -0.038 0 0

1996 0 0 0 0 0

1313

Flux: Copy Zone for 4 More Sewage BedsFlux: Copy Zone for 4 More Sewage Beds

X 279725 to 279825X 279725 to 279825 Y 821500 to 821600Y 821500 to 821600 Z 0 to 20Z 0 to 20

Flux: Modify Box Zone for Sewage Beds 1-4Flux: Modify Box Zone for Sewage Beds 1-4

Click on zone in BC treeClick on zone in BC tree Ctrl-c, Ctrl-vCtrl-c, Ctrl-v Choose “specified flux”Choose “specified flux”

1414

Flux: Locations for Sewage BedsFlux: Locations for Sewage Beds

X min X max Y min Y max Z min Z max

Beds 1-4 279725 279825 821500 821600 0 20

Beds 5-8 279625 279725 821425 821525 0 20

Beds 9-12 279525 279625 821475 821575 0 20

Beds 13-16 279400 279500 821575 821675 0 20

Beds 19-25 279500 279600 821700 821800 0 20

1515

Flux: Sewage BedsFlux: Sewage Beds

1616

Set Print Frequencies for HDF FileSet Print Frequencies for HDF File

Double Click PRINT_FREQUENCYDouble Click PRINT_FREQUENCY

– Select years for HDF Select years for HDF chemistrychemistry

– Print every 2 yearsPrint every 2 years– Data to be written Data to be written

are selected in are selected in SELECTED_OUTPUT SELECTED_OUTPUT section of section of transport.chem.dattransport.chem.dat

1717

TIME: Set Time Step and Simulation LengthTIME: Set Time Step and Simulation Length

End time 1946End time 1946

Time step 1 yrTime step 1 yr

Start time 1936Start time 1936

Double Click TIME_CONTROLDouble Click TIME_CONTROL

1818

Running the ModelRunning the Model

SaveSave

Run the model Run the model

1919

View NHView NH44++, NO, NO33

--, and O, and O22

– Set to 1946Set to 1946 Toolbox|CropToolbox|Crop

– X min 0.45 X min 0.45 Ctrl-d changes Ctrl-d changes

viewview

Toolbox->Data N(5)Toolbox->Data N(5) Toolbox->AnimationToolbox->Animation

N(5) = NON(5) = NO33- - speciesspecies

2121

NHNH44++, NO, NO33

--, O, O22

NHNH44++ from effluent from effluent

NONO33-- from oxidation from oxidation

– Note faster flow at Note faster flow at toptop

OO22 consumed consumed

2222

To Decrease Numerical DispersionTo Decrease Numerical Dispersion

Refine resolution Refine resolution – Horizontal 250 mHorizontal 250 m– Vertical 2.5 m -20 to 20 mVertical 2.5 m -20 to 20 m– Time step 0.5 yrTime step 0.5 yr

2323

Refined GridRefined Grid Refined resolution Refined resolution

– Horizontal 250 mHorizontal 250 m– Vertical 2.5 m -20 Vertical 2.5 m -20

to 20 mto 20 m– 0.5 yr time step0.5 yr time step

Original resolution Original resolution – Horizontal 500 mHorizontal 500 m– Vertical 2.5 m -20 Vertical 2.5 m -20

to 20 mto 20 m– 1 yr time step1 yr time step

2424

NHNH44++

NONO33--

OO22

2525

SummarySummary Introduction PHAST for WindowsIntroduction PHAST for Windows Must always test numerical accuracyMust always test numerical accuracy

– Numerical dispersion for B-I-T, U-I-SNumerical dispersion for B-I-T, U-I-S– Oscillations for C-I-T, C-I-SOscillations for C-I-T, C-I-S

Cape CodCape Cod– Heads look goodHeads look good– Plume direction problematicPlume direction problematic– Tiny dispersivity is a killer, working on implicit Tiny dispersivity is a killer, working on implicit

TVD methodTVD method

2626

My Model Doesn’t Work: What to My Model Doesn’t Work: What to do when things go wrongdo when things go wrong

Start simple!Start simple! Add complexity sequentiallyAdd complexity sequentially

Check problem definition for completeness and correctnessCheck problem definition for completeness and correctness

– Properly posed problem that is physically realisticProperly posed problem that is physically realistic– Shape of regionShape of region– Spatial property distributions (Model Viewer, Spatial property distributions (Model Viewer, prefixprefix.O.probdef).O.probdef)

– Boundary condition distributions (Model Viewer, Boundary condition distributions (Model Viewer, prefixprefix.O.probdef).O.probdef)

– Initial conditions (Model Viewer, Initial conditions (Model Viewer, prefixprefix.O.head and .O.head and prefixprefix.O.comps).O.comps)

2727


Grid may be too coarse (GRID)Grid may be too coarse (GRID)– Numerical oscillation Numerical oscillation – Excessive numerical dispersionExcessive numerical dispersion

Time step may be too long (TIME_CONTROL)Time step may be too long (TIME_CONTROL)– Numerical oscillation Numerical oscillation – Excessive numerical dispersionExcessive numerical dispersion– Excessive operator splitting errorExcessive operator splitting error

2828


Check tolerance and controls on iterative Check tolerance and controls on iterative solver (SOLUTION_METHOD)solver (SOLUTION_METHOD)

Check controls on automatic time-step Check controls on automatic time-step algorithm for steady-state flow algorithm for steady-state flow (STEADY_FLOW)(STEADY_FLOW)

Review the simulation history Review the simulation history – Time steps (Time steps (prefixprefix.log).log)– Maximum changes in head (Maximum changes in head (prefixprefix.log).log)– Solver iterations (Solver iterations (prefixprefix.log).log)– Global balance tables (Global balance tables (prefixprefix.O.bal).O.bal)

2929


Use most robust numerics Use most robust numerics – Set backwards-in-time and upstream-in-Set backwards-in-time and upstream-in-

space differencing space differencing – Set equal dispersivities in all directionsSet equal dispersivities in all directions– No cross dispersionNo cross dispersion

Simplify the problemSimplify the problem– Flow onlyFlow only– Conservative transportConservative transport– Simplify the region and boundary conditionsSimplify the region and boundary conditions

3030


Look for errors in chemistryLook for errors in chemistry– Run batch chemistry in PHREEQCRun batch chemistry in PHREEQC– Run 1D transport in PHREEQCRun 1D transport in PHREEQC

Most problems with convergence in Most problems with convergence in chemistrychemistry– RedoxRedox– Small total concentration of element (~1e-14)Small total concentration of element (~1e-14)

Lack of chemical convergence may be the Lack of chemical convergence may be the result of a poor transport solution result of a poor transport solution (oscillations)(oscillations)

3131


Contact me Contact me [email protected]

3232

The purpose of computing is insight, The purpose of computing is insight, not numbers.not numbers.

--R.W. Hamming (1962)--R.W. Hamming (1962)

The purpose of computing is insight, The purpose of computing is insight, not pictures.not pictures.

--L.N. Trefethen (1998)--L.N. Trefethen (1998)

3333

transport.chem.dat file 3 waters –background, o 2 (solution 1) –sewage effluent, nh 4 + and cl...

Documents