You may select from the transport boundary conditions listed below.

**No energy flux.** The energy mass flux across the boundary is zero.
This boundary condition is available only for boundary segments that
are assigned a "no flow" boundary condition.

**Specified temperature at boundary.** The temperature
at the boundary is set at the specified value. In the model, this is
implemented by setting the temperature at boundary cells to the specified
value.

**Specified temperature of inflow.** The temperature of flow
across the boundary into the domain is set at the specified value.
This boundary condition effectively sets the energy flux across the
boundary into the domain. This energy flux is equal to the inflow temperature
times the heat capacity of the fluid times the fluid flux.

**Specified conductive flux at boundary.** The flux of energy
by conduction across the boundary into the domain (in units of [Q/LT], or [J/ms]
for SI units) is set at the specified value.
This boundary condition is available only for boundary segments that
are assigned a "no flow" boundary condition.

**Default outflow.** This boundary condition must be specified
along boundaries of possible seepage faces, evaporation/transpiration,
and where flux or volumetric flow rate is specified in the
direction out of the domain. For all the above cases except evaporation,
the energy flux out of the domain is computed by multiplying the
temperature at boundary cell by the fluid heat capacity and the outflow flux (dispersive flux
out of the domain is not allowed). For evaporation,
the evaporating water is assumed remove no energy from the domain.

**Transport Boundary Condition Options**

For any boundary segment, the available options for transport boundary conditions depend on the flow boundary condition specified for that segment.

For boundary segments that are assigned "no flow" boundary condition, the options for transport boundary conditions are:

- No energy flux
- Specified temperature at boundary
- Specified conductive flux at boundary

For boundary segments that are assigned flow boundary conditions of "specified pressure head", "specified total head", "specified flux into domain", or "specified volumetric flow into domain", the options for transport boundary conditions are:

- Specified temperature of inflow
- Specified temperature at boundary

For boundary segments that are assigned flow boundary conditions of "specified flux out of domain", "specified volumetric flow out of domain", "evaporation/transpiration", or "possible seepage face", the sole option for transport boundary condition is:

- Default outflow

See also:

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