zone face skin command

Syntax

zone face skin <keyword ... ><range>

Primary keywords:

break-angle    internal    slot    slot-skin    use-hidden-zones

Note

• The following nomenclature / equivalence between FLAC3D and FLAC2D is used:

  • Zone faces = zone surface faces in 3D or zone edges (lines connecting gridpoints) in 2D

  • There is no 2D equivalence for 3D zone edges

Skin the model to automatically generate face groups.

“Skinning” refers to automatic face group generation, which occurs as follows: the program looks for contiguous faces and puts them into automatically named groups within the slot named skin. Two faces are not considered contiguous if: the angle between two faces exceeds the break-angle, or if the two faces belong to different groups according to the command’s slot specification. Unless internal is specified, the operation of the command is restricted to external faces.

For this command, only zone faces that have no zone on the other side, a hidden zone on the other side, or a mechanically null zone on the other side, are considered surface faces. When use-hidden-zones is used, zone faces within the specified range will be included for consideration, even if they are a part of zones that are currently hidden.

To check the skin groups, plot “Face”, select “Grouped” to “Show” grouped faces.

Group names are generated as follows:

Surface faces are assigned a name based on the face normal vector.

In FLAC3D:

If the normal vector x component is larger (in the absolute sense) than the y and z then it will be assigned the name East if it is positive or West if it is negative. If the y component is larger than the z then it will be assigned the name North if it is positive or South if it is negative. Otherwise it will be assigned the name Top if the z-component is positive or Bottom if it is negative.

In FLAC2D:

If the normal vector x component is larger (in the absolute sense) than y, then it will be assigned the name East if it is positive or West if it is negative. If the y component is larger, then it will be assigned the name Top if it is positive or Bottom if it is negative.

Internal faces (if present) are assigned the names of the group on either side that changed in order to create them, with a colon : character between. So an interface surface marking the boundary between groups Fred and George will be named Fred:George.

If more than one collection of faces is assigned the same name, then a number will be appended to the name to keep them distinct. So East1 and East2 for example.

The following keywords are currently available:

break-angle f

Specify the angle that is used to determine face contiguity for inclusion in a skin group. The default break angle is 45 degrees.

internal b

Include internal faces when creating face groups. This will assign group names to faces along internal boundaries where the zone group assignments change. The default is off.

slot s

Identify the slot that contains the groups to be used for consideration of contiguity. Use of the group logic is described in Groups. If this keyword is omitted, zone group assignments will be ignored and the internal keyword will not do anything. Use the the special any slot assignment to use all slots.

slot-skin s

Place the groups created by this command in a slot named s. If this keyword is omitted, the groups will be place in a slot named skin.

use-hidden-zones b

Include faces that are on currently hidden zones if they are within the range. By default this values is off.