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[vitus]

transient no convergence.png

[Keyur Kanade]

As ANSYS Staff, we can not download attachments. Please upload images using upload image functionality.
Before proceeding, please check orthogonal quality of the mesh.
The min orthogonal quality should be above 0.1 to proceed to solver. If it is less than 0.1 then please improve the mesh.
First check the locations of the bad elements. Please see following video for the same.

https://www.youtube.com/watch?v=ZDADSSN8hOs

Once you have locations, please check if you can improve mesh using different mesh sizing. Please see following video.

https://www.youtube.com/watch?v=w4q6q8nKF3U

If this does not help, you may need to check if you can use pinch control or virtual topology.

https://www.youtube.com/watch?v=wdKMqfJV1Ys
https://www.youtube.com/watch?v=RELLrEJ9chg

If this does not help, please go to geometry and modify or simplify geometry at those locations in SpaceClaim.

Also make sure you have sufficient refined mesh to get convergence. Please cross check turbulence model you are using and then check the mesh requirement for the same. Please search forum for the same.
Regards Keyur
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[vitus]

Thanks for your quick answer to visualize my problem I'll add the images:
So u see the boundary layers look strange at the corners of inlets and outlets (first pic 7 layers, second pic 3 layers)

I did this heat exchanger similar to a tutorial, where the mesh looked like this:

The things I changed are : -scaling it down from radial cross section of diameter 50 mm to rectangular cross section 18 mmx12mm
-making cell sizes of tpms smaller
Which turbulence model might fit for this case?
Regards
Vitus

[Keyur Kanade]

You can remove prism from inlet and outlet. Create prisms only on walls.
Please mention quality of the mesh.
As you change geometry dimentions, you will need to change mesh sizes accordingly.
Regards Keyur
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[vitus]

Hello keyur Im currently using flunt mesh (fault tolerant)... so the values I can adjust are only target Surface mesh skewness (default on 0.8) and target volume mesh skewness (default on 0.96).
My current orthogonal mesh quality is 3.4e-2... looks like I have to improve this.
The geometry Im using is based on a STL mesh (exportet from another programm and then imported into spaceclaim). So maybe the STL file should be refined first...?
Where would u start?
Thanks in advance :)

[Keyur Kanade]

Yes, if your STL is very coarse, please refine it first and then import it in SpaceClaim.
Also please check manual on giving face sizing.
Regards Keyur
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