[BrolY]

Here is an email exchange I had with Simon Pereira:

Questions:
I have a few questions for you regarding the blocking in ICEM CFD. Our current version of ICEM is 12.0.1.
1) Our geometry has a plane of symmetry. So, we created the blocking for the first half part of this geometry, and we want to use the symmetry option for moving our blocking to the second half part of the geometry.
But, when we associated the symmetric blocking to the 2nd geometry, it didn't work very well. The blocks or the edges are not associated with the right part or curves... Do you have a solution for this issue?

2) We created an interface to close the mesh of the first part of the geometry. When we create the whole mesh thanks to the symmetry option, the two parts have these interfaces which prevent the fluid from moving from one part to the other.
We tried to delete these interfaces, but the final mesh wasn't very good. Do you know how to handle with that?


Answers:
1) It could be that your blocking is mirrored but you still have differences due to grouping of curves. For instance, on the initial side, you associated one edge to three curves. This would automatically group those three curves (concatenate) into a single curve and then make the association. When you mirror that blocking feature, the edge tries to associate with a curve, but doesn't know to group the three curves. In these cases, the simplest sure fix is a manual one. Right click on edges (in the model tree) to select the "Show associations" option. This will create little green arrows that shows what blocking is associated to what curves. Then use "associate edge to curve" and correct any problems that you see.


2) After mirroring, your symmetry plane is in the way... First thing to check is if the nodes automatically merged. Right click on verts in the model tree and turn on the option for "numbers". Look at the symmetry vertices to check for numbers. If you see two numbers overlapping, you will need to merge them together (using merge vertex). Once they are merged, if the volume materials on either side are the same, the face edges should turn blue and the shells should no longer form. If it still gives you symmetry shells, you can go into the blocking (tab) => Edit Associations => Face to Surface and select "none". Then remove the associations from the symmetry faces (you could select individually, or from corners, or by Part).


Just one comment about your process (sorry if it seems obvious to you, but your first question made me wonder)... If your model is truly symmetrical, then it is better to simply use that symmetry boco (if your bocos are symmetrical) or perhaps mirror the mesh and delete the symmetry shell elements (if your bocos are not symmetrical). When you mirror blocking, you create a bit of a headache with the index control, so it is only worth doing if your model is somewhat similar, or mostly topologically symmetrical, but the geometry is not truly symmetrical. Then you can take advantage of the elastic nature of the blocking to fit to the actual geometry and save yourself the time of blocking it. You could also add (or remove) holes, etc. that are not symmetrical.