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[NickFL]

I posted the following below in the Fluids forum, so sorry if anyone has already read it.

I am working with a really terrible STL file and I am trying to mesh it using the meshing in Fluent (Fault Tolerant). I have worked through some simplified versions of my model and had no problems. But when working through the actual model, it is exhibiting a peculiar behavior.

What is wrong, please see in the image below, is that when a surface mesh is created it does not go all the way to the tunnel walls. (I have created the bounding box to be 0 slack in the x and z directions). It seems like I am missing a step of imprinting the edges of the STL on the tunnel walls. The mesh on the tunnel walls is refined due to the proximity of the surface. But without the surface going all the way to the tunnel walls, the resulting volume mesh allows a shortcut for the flow to avoid contacting the surface. Of course this means a lot of fluid will take this path with less resistance.

I am currently using 23R1 but have experienced the same problem in an earlier version. That is why I feel I am missing a step that was not necessary in my simplified models.

 

When I shrink the tunnel walls to be only 90% (using -0.05 for the External Flow Boundary Box Parameters), the mesh goes to the walls, but sometimes these "flowers" form as extensions past the bounding box. One is shown in the image below on the left side. The xmin boundary is shown and there is a protrusion beyond it. Again I think this is a consequence of missing the imprint step.

Another attempt was made trying to do the imprint in SpaceClaim just locks the computer up.

 

Thank you for your time and any insight you can provide.

[Keyur Kanade]

From second image it looks like there is some leak. Please check the leakage. 

Please go through help manual for more details 

Regards,

Keyur

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[NickFL]

Keyur, thanks for the advise. Both images were generated with the same mesh controls, except with a reduced tunnel size. With that knowledge, and the knowledge that the mesher gives the following warning: 

---- Warning--- Inner wrap for void material point fluid-region-1 is not created. There is no leakage at global min size.

I feel confindent the only way there could be leakage is when it squeezes through the tunnel wall because there is no "imprint".

What I have found that helps is using the Extract Edge Features. It is located under Advanced under Describe Geometry and Flow. Here I can set the edge-group to be "collective" between my surface and the tunnel walls. Then one can use the Preview to view the extracted edges in the viewer in Pink. This seems to help, but I am having trouble with a couple other things at the moment, so I am trying to work through those first and will update later.

[Keyur Kanade]

Yes, extracted edges are very important in fault tolerant workflow for imprints.