HydroGeoSphere/Drain Flux

NOTE: not tested or fully implemented, but will be something like this.

Assigns a drain flux boundary condition, as described in Section 3.7.1 to nodes in the specified set. These nodes are normally located on the surface of the domain. The fundamental difference between river and drain flux nodes is that drain nodes only allow water to flow out of the system, depending on the difference in head between the drain node and the specified drain head value.

The following instructions can be used as input to the Type instruction inside the Boundary condition...End instruction group to assign a drain flux boundary condition:

Simple drain

Sets the input type to be a drain flux drainage boundary condition.

• • •

For example:

boundary condition
    type
    simple drain

    node set
    my_drain
    
    time value table
    0.0      1.e-5     25.
    end

end

This example shows the use of a time value table instruction to define the drain conductance (1.e-5) and drain head (25.) values. This would not be very useful in most cases, since conductance and head would vary from drain node to drain node. In such cases, the inputs would be defined by a time file table, with unique values given for each node:

boundary condition
    type
    simple drain

    node set
    my_drain

    time file table
       0.0    my_drain.lst
    1000.     none
    end

end

Here, the drain flux boundary condition would become inactive after time 1000 and the nodes would become unconstrained. In this case, the file my_drain.lst would contain two values per line, the drain conductance and head value, and one line for each node in the set.