Data identifier: 3DRA [-] (only in 3D model files, *.3d)

By specifying a closed boundary (i.e. the first node number corresponds to the last node number), the entire area or one or more sub-areas of a 2D horizontal model can be extended into the 3rd dimension. This is done using the menu Mesh 3D 3D boundary Add/Generate. The node numbers of the boundary nodes are automatically saved separately for each boundary in an anti-clockwise order.

In order to be able to calculate several separate 3D areas without a surrounding 2D horizontal model, these areas must have the same number of ZKOR layers, must not have any geometric overlaps and must be connected by at least one node to the GLEI attribute.

If there is a 2D model with one or more 3D sub-areas, the boundary condition at the 3D boundary nodes can be influenced by the sign of the node numbers in the 3DRA boundary definition numbers (see see 2D/3D model structure):

• If the node numbers are entered as positive, an equal potential head (= horizontal flow only) is applied as a boundary condition over the depth when generating the 3D mesh.

• If this is not desired for some or all nodes, the corresponding node numbers must be entered with a negative sign. Which will not apply the above boundary condition.

Applying equal potential heads over the depth as described above is only possible if the 3D area does not extend over the entire modelled area. For a complete 3D model, the boundary conditions (fixed potential heads, mass flow rates) must be specified explicitly, as the potential heads are not equal over the depth.