2.5D overset case

Ron.CC · January 24, 2022, 06:17

Hello guys,
@louisgag
I'm trying to run a 2.5D case using overset mesh of OF2012. As you can see in the pictures, I'm focusing on the aerodynamic characteristic of a thin panel. The background mesh is generated by blockMesh and the overset mesh is made by Fluent Meshing for fine boundary layers. The two sets of meshes are of the same distance in z direction.The solver is overPimpleDyMFoam.

For the overset settings, I use overset BC for the 4 overset patches go through the whole z direction. And slip for the 2 overset patches on the front and back.But the solver identify all the cells as HOLE. I also tried overset BC for all the 6 overset patches but it gets the same problem.

Would you please give me some advice? Thank you in advance.

louisgag · January 25, 2022, 10:51

Hi,
I'm not sure I can help debug your case but two quick notes on the top of my head:
1. wouldn't it be better to have overset patches where you have slip, unless you are actually going through the whole third dimension...
2. I would take a similar overset tutorial case and one step at a time transform in into your case, that should work.

Ron.CC · January 25, 2022, 11:19

Quote:

Originally Posted by louisgag

Hi,
I'm not sure I can help debug your case but two quick notes on the top of my head:
1. wouldn't it be better to have overset patches where you have slip, unless you are actually going through the whole third dimension...
2. I would take a similar overset tutorial case and one step at a time transform in into your case, that should work.

Thank you Louis.
1.I have also tried overset patches for all the 6 surfaces but the result is the same, all the cells are identified as hole.
2.Actually the overset mesh (including the thin panel) is going through the whole third direction. I thought this is the definition of 2.5D case. Am I wrong about this?
3.I'm curious about the 2.5D case you mentioned in the bug tracker before. Are there any similarities between your and my case?

sati · January 25, 2022, 12:38

Hello,

considering your case is 3D, you should always keep a few cells between every overset patches and the outer boundary conditions of your case.

Which means that with the current implementation of overset in OpenFOAM, you cannot model a 2.5D case.

nsf · January 25, 2022, 18:33

Hi,

Actually with minor modifications the overset patch can go outside the background mesh. I did some work on this a while back. Sadly I had to move on to other tasks.

I did file a bug report:
https://develop.openfoam.com/Develop.../-/issues/1683

However you have wall-to-wall contact which is more challenging. If you are willing to dig in to the problem I could elaborate. You would have to modify the inverseDistanceCellStenicl.

best regards

louisgag · January 29, 2022, 05:47

Hi Ron,

2. you are right, in the wrost case you would get instability for a suddent change of BC
3. yes, quite similar. You may have an issue with the searchBox (either its size/location or the number of divisions). You can check this by running with cellVol overset which does not require any search box and will give you a hint whether the problem lies there...

hbulus · February 10, 2022, 04:20

You have to creating zones with topoSet dict in system file. Then define overset zones with setField dict. In that way, OF understand where the overset region at.

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January 25, 2022, 10:51		#2
louisgag Senior Member Louis Gagnon Join Date: Mar 2009 Location: Stuttgart, Germany Posts: 338 Rep Power: 18	Hi, I'm not sure I can help debug your case but two quick notes on the top of my head: 1. wouldn't it be better to have overset patches where you have slip, unless you are actually going through the whole third dimension... 2. I would take a similar overset tutorial case and one step at a time transform in into your case, that should work.

January 25, 2022, 12:38		#4
sati New Member Join Date: Mar 2015 Posts: 16 Rep Power: 11	Hello, considering your case is 3D, you should always keep a few cells between every overset patches and the outer boundary conditions of your case. Which means that with the current implementation of overset in OpenFOAM, you cannot model a 2.5D case.

January 25, 2022, 18:33		#5
nsf Senior Member Nicolas Edh Join Date: Mar 2010 Location: Uppsala, Sweden Posts: 123 Rep Power: 18	Hi, Actually with minor modifications the overset patch can go outside the background mesh. I did some work on this a while back. Sadly I had to move on to other tasks. I did file a bug report: https://develop.openfoam.com/Develop.../-/issues/1683 However you have wall-to-wall contact which is more challenging. If you are willing to dig in to the problem I could elaborate. You would have to modify the inverseDistanceCellStenicl. best regards

January 29, 2022, 05:47		#6
louisgag Senior Member Louis Gagnon Join Date: Mar 2009 Location: Stuttgart, Germany Posts: 338 Rep Power: 18	Hi Ron, 2. you are right, in the wrost case you would get instability for a suddent change of BC 3. yes, quite similar. You may have an issue with the searchBox (either its size/location or the number of divisions). You can check this by running with cellVol overset which does not require any search box and will give you a hint whether the problem lies there...

February 10, 2022, 04:20		#7
hbulus Member Join Date: Dec 2018 Posts: 75 Rep Power: 7	You have to creating zones with topoSet dict in system file. Then define overset zones with setField dict. In that way, OF understand where the overset region at.