MarAlder
commented
3 years ago Please excuse the late answer to this question!
From CPACS 2 to 3 there has been a significant change in the definition of coordinates in the component segments. I assume that you are aware of it, but just for comparison the old and the new definition.
With regard to the wingRibsPositioningType, in CPACS 3.2 the documentation has been updated. There it is said that the reference line is used for the rib spacing (see here):
The ribReference is the reference line for the computation of the rib set spacing. It can either be a sparUID or "trailingEdge" or "leadingEdge"
and etaStart/etaEnd:
EtaStart defines the innerBorder location of the beginning of the rib set on the ribReference line. Please note, the eta is relative to wing eta coordinate!
From this I would say that CPACS 3 now fits to your original interpretation and that the documentation is complete. Is this sufficient for your tasks or do you depend on CPACS 2 for your current activities?
Unfortunately I lack some practice with CPACS 2 (before my time as CPACS coordinator) and how TiGL interpreted it back then, so I try to reconstruct from comparision between CPACS 2 and 3. I will try to get further feedback from CPACS 2 users and come back to you.
The CPACS 2.3.1 documentation explicitly states that the eta_start and eta_end coordinates of the wingRibsPositioningType are relative to the wing eta coordinate. However, when I generate the ribs this way and compare them with the geometry generated by TIGL, I get different results. When I use an eta coordinate relative to the ribReference line, I do seem to get the same results as TIGL.
So I was wondering: is this a mistake in the CPACS 2.3.1 documentation, does TIGLviewer interpret this incorrectly or am I misunderstanding the eta coordinate?
I have attached the relevant CPACS file. AGILE_DC2.zip