Hello
I know from previous posts that the local numeration of element faces for a 4-noded tetrahedron are as follows:
1-2-3 2-4-3 3-4-1 4-2-1
I would like to ask what is the local numeration for a quadratic (10-noded) tetrahedron? I have been looking throught the documentation for this but cannot find it.
PS: My goal is to write a script that gets the element face based on 11 inputs which are as follows:
proc face_elements {ElementNum FaceNode1 FaceNode2 FaceNode3 FaceNode4 FaceNode5 FaceNode6 FaceNode7 FaceNode 8 FaceNode9 FaceNode10}
I just found them by making 1 quadratic element in GiD and then assigning various face_element conditions to it to determine the local element enumeration. For quadratic elements the faces are numbered as follows:
Face 1 → nodes 1 2 3 5 6 7
Face 2 → nodes 2 3 4 6 9 10
Face 3 → nodes 1 3 4 7 8 10
Face 4 → nodes 1 2 4 5 8 9
It would be nice if this kind of information was either 1) provided in the GiD documentation or 2) accessible via some sort of tcl command
The faces of linear elements are described with a picture at the ‘GiD customization manual’, Appendix B (Classic problemtype)
(find the words GlobalNodes or LocalNodes)
https://www.gidhome.com/documents/customizationmanual/APPENDIX%20B%20(classic%20problemtype%20system)/PROBLEMTYPE%20’CLASSIC’/Template%20files/Commands%20used%20in%20the%20.bas%20file/Multiple%20values%20return%20commands
About the quadratic case: you can consider it to identify faces exactly like the linear case, consider only the ‘n fist corner nodes’
e.g. for the quadratic tetrahedra consider only its first 4 nodes, (the local numeration of GiD is hierarchical, first appear the corner nodes, and after the quadratic ones (and for its faces consider only the first 3 nodes, ignore the last 3 quadratic nodes)
the order of local face nodes provided by GiD .bas or Tcl related commands is this for a tetrahedron (see pictures of manual)
face 1: 1-2-3
face 2: 2-4-3
face 3: 3-4-1
face 4: 4-2-1
traversing a face in this order the normal vector (counter-clock wise rule) will point inside the element
Do you want: knowing the list of local nodes of a face obtain the local face index? (e.g a face index from 1 4 for a tetrahedron)
If nodes are provided ordered (with GiD order) then is a little easier,
for example if the face nodes are
2-4-3
then checking only that the first node is ==2 do you know that is the face 2 (the only face starting by this node)
if nodes are provided unordered (without GiD order) then it could be the face 1, 2 or 4, because only the face 3 doesn’t has the node 2