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TRANSPORT_CONDITION

In setting up transport conditions, first create a list of self-consistent solute concentration constraints, and then associate them with various time points.

Required Cards:

TRANSPORT_CONDITION <name>

Specifies the name of the transport condition and opens the block.

TYPE <string>

Specifies the type of the transport boundary condition (options for <string> include: DIRICHLET, DIRICHLET_ZERO_GRADIENT, NEUMANN, ZERO_GRADIENT, EQUILIBRIUM):

DIRICHLET : Specified concentration

DIRICHLET_ZERO_GRADIENT : Dirichlet (specified concentration) for inflow and zero diffusive gradient for outflow (i.e. only advective transport is considered on outflow).

MEMBRANE_FILTER : Works like a membrane filter. Water can pass through and solutes cannot (e.g., useful for mimicking evaporation at the land surface when modeling single-phase variably saturated flow). The assignment of a CONSTRAINT is required, but the concentrations are ignored.

NEUMANN : Specified solute flux (not currently implemented)

ZERO_GRADIENT : Prescribes a third-type or Robin boundary conditon for inflow and zero diffusive gradient for outflow.

EQUILIBRIUM : Only applicable to the SOURCE_SINK card. Attempts to set the concentrations at cells within the associated region in equilibrium with the constraint concentrations through a rather large, hardwired rate constant. The user should be careful to check that equilibrium is being reached before trusting the code.

CONSTRAINT

A CONSTRAINT block may be embedded within a TRANSPORT_CONDITION, but the CONSTRAINT may not change over time. This is the same as using CONSTRAINT_LIST with a single CONSTRAINT starting at time zero.

CONSTRAINT_LIST

Opens a block for specifying a list of constraints over time. Interpolation is not allowed as nonlinear chemistry cannot be accurately calculated with linear interpolation.

Optional Cards:

TIME_UNITS <string>

Specifies the units for the times in the constraint list. If not specified, SI (seconds) is assumed.

Examples

TRANSPORT_CONDITION Initial
  TYPE DIRICHLET_ZERO_GRADIENT
  CONSTRAINT_LIST
    0.d0 initial
  /
END

TRANSPORT_CONDITION U_source
  TYPE DIRICHLET
  TIME_UNITS s
  CONSTRAINT_LIST
    0.d0 U_source
    336000.d0 Initial
  /
END

TRANSPORT_CONDITION 3rd_type_bc
  TYPE ZERO_GRADIENT
  CONSTRAINT_LIST
    0.d0 river_water
  /
END

TRANSPORT_CONDITION evaporation
  TYPE MEMBRANE_FILTER
  CONSTRAINT_LIST
    0.d0 any_constraint_name
  /
END

Example of embedding CONSTRAINT “initial” within TRANSPORT_CONDITION “Initial”

TRANSPORT_CONDITION Initial
  TYPE DIRICHLET_ZERO_GRADIENT
  CONSTRAINT initial
    CONCENTRATIONS
      H+       7.3              M Calcite
      Ca++     1.20644e-3       T
      Cu++     1.e-8            T
      Mg++     5.09772e-4       M Dolomite
      UO2++    2.4830E-11       T
      K+       1.54789e-4       T
      Na+      1.03498e-3       Z
      HCO3-    -3.5             G  CO2(g)
      Cl-      6.97741e-4       T
      F-       2.09491e-5       T
      HPO4--   1.e-8            M Fluorapatite
      NO3-     4.69979e-4       T
      SO4--    6.37961e-4       T
      Tracer   1.e-7            F
      Tracer2  1.e-7            F
    /
    MINERALS
      Calcite         0.1         1.
      Metatorbernite  0.          1.
    /
  /
END