I thought it may be useful to write down a few examples of the sort of things that confuse new users...
Recently Im going through the SIF file, trying to understand it line by line, but I really dont get far before I have very basic questions I can't answer, but ought to be able to answer from the reference material. (Of course maybe I have just missed it in the documentation, and I will be told RTFM!)
For example I have a SIF file with:
Code: Select all
Body 1
Target Bodies(1) = 1
But then later, I find other examples which DONT include Target Bodies under Body. So now all sorts of questions arise, like:
* Is it just because there is one body that we dont need to specify since its not ambiguous?
* or does the number after 'Body' now refer to a external entity, and not just a reference internal to the SIF file?
* or is Target Bodies only required when you want to include multiple bodies under one Elmer body?
Edit: I think I can answer this now. P12 of the solver manual states: "Note that the integer in the body section name is an identifier for the body itself." So presumably:
* Body section numbers are external references to physical groups in the mesh file, if there is one body
* Target Bodies(1) = n will override this behaviour either (i) if you want a more consistent approach of cleanly separating internal references from external references, OR (ii) if you need to specify more than one external body.
Note that the sentence I quoted above is not in a reference manual under "Body...", but just a sentence among many others in the solver manual, whose full meaning may not be obvious to a beginner at the first reading, particularly as it does not stress that its an *external* reference to a mesh physical group, unlike other section identifiers in the sif file which are (AFAIK) all internal. The words 'the body itself' are ambiguous.
End Edit
Similarly I find under 'Solver' section:
Code: Select all
Solver 1
Equation = Elastic Plates
Or again something like:
Code: Select all
Solver 1
Procedure = "Smitc" "SmitcSolver"
(Edit: I think Ive found the answer to this one. "Smitc" is the module and "SmitcSolver" is the subroutine. Both are required. But I needed to find this detail in the models manual so I could understand the syntax, rather than have the syntax defined first in a reference manual.) End Edit
So my point is that a complete and unambiguous reference manual is required for keywords in the sif file, at least the basic ones. I understand that Elmer is a research tool first and foremost, and people are adding keywords all the time. But if Ive faced these sorts of problems with the simplest keywords I guess others have too. Probably when they were first added, each keyword had an intuitively obvious role, but they may not remain so as additions and changes are made. Many people probably just cut and paste and accept that "it seems to work like this, that's just what you do", because one feels stupid asking such basic questions on the forum.