HydroGeoSphere/Solute Mass Balance

Sample solute mass balance output

By default, solute mass balance information for each species is computed at each time step and written to the prefixo.lst file. Figure 5.18 shows some sample output as it appears in the .lst file:

**********************************************************************************
MASS BALANCE SPECIES  1 - Uranium
**********************************************************************************
 (Time =   1999.00999999978       Time-step =  9.999999776482582E-003 )
RATE OF MASS EXCHANGE                 IN                  OUT
TOTAL
   Fixed head nodes             100.0000006818      0.0000000000
   Fixed concentration nodes    150.0985515732      0.0000000000
   NET1 EXCHANGE RATE (IN-OUT)                                    250.0985522550

MASS ACCUMULATION                  COMPONENT         SUBTOTAL
   In storage:
      Porous medium               2.5001748233
      Porous medium (sorbed)  35749.9997988755
   ACCUMULATED                                  35752.4999736989
   Lost by decay:
      Porous medium               0.0000000708
      Porous medium (sorbed)      0.0010116896
   DECAYED                                          0.0010117604
   EXCHANGED (via chemical reactions)               0.0000000000
   INITIAL (stored at start of timestep)        35750.0000000000
   NET2 RATE OF ACCUMULATION                                      250.0985515100
      i.e. (ACCUMULATED -DECAYED +(-)EXCHANGED -INITIAL)/delta

   NET (since start of simulation)                250.0985515100

MASS BALANCE ERROR
   Absolute: (NET1-NET2)                                            0.0000007450
   Relative: (NET1-NET2)/(abs(NET1)+abs(NET2))/2.0                  0.0000000015
**********************************************************************************

Figure 5.18: Sample Mass Balance Information for Example PM CD

No solute mass balance

This instruction prevents solute mass balance information from being written to the listing file.

• • •

This detailed mass balance information is also written to a TECPLOT formatted ascii output file called, for example, prefixo.mass_balance_species_001 so that it can be easily visualized.

Summary mass balance information

Summary mass balance information is written to a TECPLOT formatted ascii output file called, for example, prefixo.mass_balance_summary so that it can be easily visualized. For each timestep in the transport solution, one line per species is written to the file. Each line has columns labelled as follows:

1. time Simulation time.
2. Tmass Total mass in the system.
3. dBoundary Change in mass due to sources and sinks.
4. dStored Change in mass stored.
5. dBoundary - dStored Error.
6. (dBoundary - dStored)/Tmass*100) Normalized error.
7. Species Species number.

Besides being plotted with TECPLOT, such output can be imported into an editor (e.g. Microsoft Excel) and sorted to facilitate, for example, the creation of a plot of mass balance error versus time for a given species.

Cumulative mass balance information

Cumulative mass balance information is written to a TECPLOT formatted ascii output file called, for example, prefixo.mass_balance_cumulative so that it can be easily visualized. For each timestep in the transport solution, one line per species is written to the file. Each line has columns labelled as follows:

1. time Simulation time.
2. In (cumulative) Mass in since start of simulation.
3. Out (cumulative) Mass out since start of simulation.
4. Stored Change in mass stored since start of simulation.
5. In+Out-Stored Error.
6. Species Species number.

Besides being plotted with TECPLOT, such output can be imported into an editor (e.g. Microsoft Excel) and sorted to facilitate, for example, the creation of a plot of mass balance error versus time for a given species.