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kati March 17, 2006 13:16

There was a discussion about t
There was a discussion about this earlier, but there didn't seem to be a final conclusion (at least I didn't find one).

I'm trying to model a mixer in a pipe and to reduce the cell count I thought I could use "nonconformal boundaries" (okay that's Fluent-language), one before and one after the mixer. So there is two pairs of patches that I should stitch together.

I can do the stitching for one pair at time, without getting major error messages, but if I try to do it to a mesh with one couple already stitched, it complains about mixed unused nodes and exits.

Does someone know should it work for two pairs, and if yes, give some hints how to do that? For example I don't know what to do with all the zone files it creates, I just renamed them so stitchMesh wouldn't find them. When trying it I moved polyMesh from 1 back to constant, don't know if it should work that way. The version I'm using is 1.2.

kati March 17, 2006 14:08

Sorry about the double posting
Sorry about the double posting... Is there a way to cancel the own messages?

I got an idea of combining the two pairs into one pair (one patch included then two separate areas, the other patch the same areas but different mesh structure), but that gave the same error message as after stitching one pair: mixed used and unused points at the end of point list.


fra76 May 22, 2006 11:55

I have a quite similar problem
I have a quite similar problem: I'd like to use "nonconformal boundaries" around a boundary layer, as shown in the picture:

Well, when I use the stitchMesh command this way:
stitchMesh . prova_stitch prism-side-8 prism-side-8-retri-31
I get the following error:
Adding point and face zones
Reading all current volfields

--> FOAM FATAL ERROR : Duplicate point found in cut face. Error in the face cutting algorithm for global face 3(1062 4710 4774) local face 3(12 240 244)
Slave size: 488 Master size: 600 index: 0.
Face: 5(1062 10124 10244 29022 29142)
Cut face:

While, when I try to swap master and slave patches I get:

stitchMesh . prova_stitch prism-side-8-retri-31 prism-side-8

Adding point and face zones
Reading all current volfields

--> FOAM FATAL ERROR : Face 100815 reduced to less than 3 points. Topological/cutting error B.
Old face: 2(4006 13989) new face: 2(4006 13989)

From function void slidingInterface::coupleInterface(polyTopoChange& ref) const
in file slidingInterface/coupleSlidingInterface.C at line 1664.

FOAM aborting

You said that you could stich the first pair of faces.
Any suggestion?


kati May 22, 2006 14:11

Hi Francesco, Sorry, I don'
Hi Francesco,

Sorry, I don't have an answer to your question. I gave up with my case. What I did find out, was that one pair with more than one continuous region worked with simple meshes. So it seemed to have something to do with the quality of the meshes. Because the mesh in my case was complicated and not really good quality, I didn't work on it any further.


fra76 May 24, 2006 02:04

Thanks for the answer, even if
Thanks for the answer, even if it leaves me almost hopeless.
You mean that you cannot deal with "nonconformal boundaries", isn't it?
We're planning a fluent/foam comparison on an aerodynamics study of a sport motorbike, using the same mesh, of course.
The problem is how to treat the side of the prismatic boundary layer, and I hoped the stitchMesh could help me.

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