Processing of Groups

In order to restrict the isocut and/or the surface calculation to certain areas of the model, the user might specify the groups of elements that should be used.

The groups can be read from the result database (specified by the parameter DATABASE) or the onf group file (specified by the parameter GROUP_FILE, deprecated). Then, the available group names and in addition the group ALL_ELEMENTS containing all elements, can be used as values of the following parameters:

  • GROUP_EXCLUDE: the elements of the group are ignored for all operations;
  • GROUP_INCLUDE: the elements of the group are marked as normal and are used for the (iso)surface calculation;
  • GROUP_SURFACE: the surface of the elements will be calculated even if they would be deleted or cut otherwise.

Any number of these commands can be specified. If an element belongs to several groups mentioned in the commands, the last command applies. For example, in order to restrict the isocut to a single group MY_GROUP, the following parameters should be specified, in the following order: 

  GROUP_EXCLUDE = ALL_ELEMENTS
  GROUP_INCLUDE = MY_GROUP

Group names are case insensitive.

Important:

If used, the ONF group file must be compatible with the model file. In case of adaptive calculations, the ONF group file should be updated using fem2onf applied to the FEM file for the required iteration.

Support of group operations in Tosca Structure.gui is limited. It is only possible to restrict the results to a single target group. All further group operations must be input manually.

Example

The example shown in the figure below contains two design regions DESIGN_ELEM1 and DESIGN_ELEM2, the first being the lower part of the model and the other one the upper part. Using group commands, various results can be obtained, as shown in the figure.



No group operations, the result contains the complete model.


GROUP_EXCLUDE = ALL_ELEMENTS

GROUP_INCLUDE = DESIGN_ELEM2

The result only contains the upper part of the model.


GROUP_EXCLUDE = ALL_ELEMENTS

GROUP_INCLUDE = DESIGN_ELEM1

GROUP_SURFACE = DESIGN_ELEM2

The result contains the smoothed lower part and the original surface of the upper part.

Groups are also used at another place: Restricting the output to certain nodes. 

      ND_GROUP = node_group

This command removes elements from the smooth output that contain nodes not present in the specified node group. This is especially handy for shape optimizations if you would like to get the output only for the design area or the mesh smooth area.