HydroGeoSphere/Seepage

A seepage boundary condition can be applied to any node, but they are usually restricted to those on the surface of the domain. If the hydraulic head at a seepage node rises above its elevation, it becomes a specified head node, and the pressure head is set to zero and water is allowed to flow out. If, subsequently, the hydraulic head drops below the node elevation, then it reverts to an unconstrained state.

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

Seepage
Sets the input type to be a seepage boundary condition.
 * &bull; &bull; &bull;

For example:

This example shows that a time-value table is not mandatory, since a pressure head of zero is applied if the nodal head is above the nodal elevation. However, if you wish to turn the seepage boundary condition on or off, then this can be accomplished by including a time value table instruction:

The value 1.0 at time zero is ignored, but the NODATA value -99999 at time 10.0 causes the boundary condition to be turned off and the nodes become unconstrained.