[Tobi]

Hey everybody,

at the moment I am checking out the ANSYS Fluent overset capabilities and for that purpose, I created a simple domain in which I want to close a channel. The User-Tutorials-Guide was already checked and the tutorial was performed - however, here everything is already set-up correctly in terms of the mesh.

My steps:

• Created the background domain and meshed it
• Created the door and meshed it
• Starting fluent -> import the background mesh
• Add the door mesh
• Change the interface boundaries from the door mesh to the type "overset"
• creating an interface between background-mesh and component-mesh (door)
• via the cell zone I added a mesh motion to move the door
• starting the analysis

The problem is, that for any reason the calculation of U, k, omega is almost at level 0 - so nothing happens here. Only the cell-zone of the door moves up. I attached the simple case for testing purposes.

Any support is warmly welcomed and I guess I made a bad mistake somewhere. In FOAM I know that you are not allowed to push the overset mesh over the background mesh. However, in the tutorial (bomb falling down), the overset-mesh exceeds the background mesh too.

Case File: https://Holzmann-cfd.com/forum/Fluent-Overset.zip

[munjalpu]

Hello Tobias,

I have never used sliding mesh with overset so this is an unexplored area for me as well. I frequently use it with UDF. After looking at your setup, I have a few recommendations.

- Your overset setup looks correct. I would separate the overset and sliding mesh to debug this.

First:
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- Have overset mesh imported first. Shift it by some distance from the wall it's attached to right now and try moving it using a simple UDF and see if it works.
- That will validate our overset setup that it works.

Second:
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- Remove the sliding mesh and only have overset mesh with no motion and initialize the flow.
- That would identify issues with the overlapping walls. (I checked your case, and that seems to be the issue, but still double check)


You can also try looking into the how to have Fluent recognize the overlapping walls. Look at the command-line options given in the ''Overset Topologies'' and ''Overset Domain Connectivity'' of User guide. ''Debug cut hole'' or ''cut control'' may be the key here!

Additional tips for overset debugging in Fluent:
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- After initialization. Go to Display ->turn on overset from side menu of display -> display plane you drew earlier. You should see no overlapping cells inside door.
- For debugging use Hybrid initialization and see how residuals are behaving. In your case, you will see residuals to be 0+00000 i.e. there are issues with your setup.
- Fluent gives the option to visualize the cells for overset technique. This is the best way to debug overset cell issues. I would go to command-line options for overset and visualize cell type "solve" and "orphan". [ define/overset-interfaces/mark-cells (choose cell types) ] You can display these registers to see which cells or region is causing the issue.

Hope this helps!