Problems with connectivities and surface repair

rmurray · February 17, 2015, 02:58

Hi all,

I am currently working on a big CAD design of a turbine blade in its environment and I need to create a mesh of the solid metal and the fluid cavities (in and out). I got the CAD in STP and CatPart formats. To give a scale, the STP file is 120Mo big.

To prepare the domains I needed to do some operations (few subtract and imprint for the connectivities) which were done in the CAD modeler. When I transfer the body to tesselated parts, it works and I can split my surfaces to prepare the boundaries. However, when I transfer all my domains for meshing, I get "Warning - failed to merge PatchContacts for parts=Body1 and Body2"
What does it mean ?

The second thing is that it appears, when going into surface repair that for the same 2 parts, I have "free edges" and "non manifold edges". The CAD was supposedly clean, but it seems not... How can I fix that ?

Many thanks for your help

rmurray · February 19, 2015, 07:39

To go on on this thread,

I have a model with large scale differences. The biggest surfaces are 0.1m size and the smallest ones about 1E-5 m in size. would this yield any problem with boolean operations ?

fluid23 · March 10, 2015, 11:20

Avoid STP. That is not a good option for import in my experience. Go back to your CAD model if you can and do your subtract there. Bring bodies for your fluids surrounding your structure and any soilids that you want thermal data in to star-ccm+. Before bringing it in, make sure that you only have solid bodies you want and no extra surfaces or anything like that. Then use a parasolid file to import your geometry. That is usually the most robust option.

If your CAD model is of reasonable quality then you shouldn't have to deal with failed parts contacts. However, if you do.... Delete the contact under Geometry then go into surface repair and select Merge/Imprint and imprint those two bodies again. When you remesh your surface mesh it should give you a new contact here that conforms to the imprint. At least that has worked for me in the past with similar issues.

fluid23 · March 10, 2015, 11:21

Sorry... I was thinking STL, not STEP. Step files aren't too bad but can cause probelms with surfaces occasinally. I would still recommend a parasolid file.

rmurray · March 10, 2015, 11:30

Hi,

Thank you for your support,

I managed to find out that star-ccm+ somehow messed with my CAD when I did an imprint in the CAD modeler (faces were off shape). It is fixed and no more problem !

fluid23 · March 10, 2015, 12:35

Ah, yes. I had the same issue, today even.

February 17, 2015, 02:58	Problems with connectivities and surface repair	#1
rmurray New Member Join Date: Feb 2015 Posts: 3 Rep Power: 11	Hi all, I am currently working on a big CAD design of a turbine blade in its environment and I need to create a mesh of the solid metal and the fluid cavities (in and out). I got the CAD in STP and CatPart formats. To give a scale, the STP file is 120Mo big. To prepare the domains I needed to do some operations (few subtract and imprint for the connectivities) which were done in the CAD modeler. When I transfer the body to tesselated parts, it works and I can split my surfaces to prepare the boundaries. However, when I transfer all my domains for meshing, I get "Warning - failed to merge PatchContacts for parts=Body1 and Body2" What does it mean ? The second thing is that it appears, when going into surface repair that for the same 2 parts, I have "free edges" and "non manifold edges". The CAD was supposedly clean, but it seems not... How can I fix that ? Many thanks for your help

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February 19, 2015, 07:39		#2
rmurray New Member Join Date: Feb 2015 Posts: 3 Rep Power: 11	To go on on this thread, I have a model with large scale differences. The biggest surfaces are 0.1m size and the smallest ones about 1E-5 m in size. would this yield any problem with boolean operations ?

March 10, 2015, 11:20		#3
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 17	Avoid STP. That is not a good option for import in my experience. Go back to your CAD model if you can and do your subtract there. Bring bodies for your fluids surrounding your structure and any soilids that you want thermal data in to star-ccm+. Before bringing it in, make sure that you only have solid bodies you want and no extra surfaces or anything like that. Then use a parasolid file to import your geometry. That is usually the most robust option. If your CAD model is of reasonable quality then you shouldn't have to deal with failed parts contacts. However, if you do.... Delete the contact under Geometry then go into surface repair and select Merge/Imprint and imprint those two bodies again. When you remesh your surface mesh it should give you a new contact here that conforms to the imprint. At least that has worked for me in the past with similar issues.

March 10, 2015, 11:21		#4
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 17	Sorry... I was thinking STL, not STEP. Step files aren't too bad but can cause probelms with surfaces occasinally. I would still recommend a parasolid file.

March 10, 2015, 11:30		#5
rmurray New Member Join Date: Feb 2015 Posts: 3 Rep Power: 11	Hi, Thank you for your support, I managed to find out that star-ccm+ somehow messed with my CAD when I did an imprint in the CAD modeler (faces were off shape). It is fixed and no more problem !

March 10, 2015, 12:35		#6
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 17	Ah, yes. I had the same issue, today even.