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Two separated volumes in one simulation

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Old   May 19, 2022, 13:10
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Hello,

I'm trying to simulate a flow of air from one inlet A to a mystery box to an outlet B. The box can't be modelled directly as it is too complicated so it's just a solid part. I thus have 4 boundary conditions + walls (cf screenshot): inlet A (not visible), inlet of the box (green) which is defined as an outlet of the fluid domain, outlet of the box (red) which is defined as an inlet of the fluid domain, outlet B (orange).

I am using part-based meshing so I end up having a unique mesh and one volume for the 2 distinct topological volumes I have. Convergence of residuals is very hardly observed, and the drop of pressure does not give me the result I had when I tried with only one topological part of the domain (red to orange).

I am thus wondering if Starccm is able to manage 2 virtually independant volumes like this. I am suspecting this is the issue. Does anybody have any idea about that?

I am also wondering if it is possible to apply conditional boundary condition: I know some properties of the mystery box and I would like, for instance, for the air exiting the box to be 10K above the air entering the box. I am suspecting I have to use interfaces for this but I have no clue how to do it; I have no experience with interface.

Hopefully everything is clear enough. Thank you for you help!
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Old   May 19, 2022, 18:54
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I and many others have mapped variables from entirely different sources onto simulations, so it's definitely doable in Star to map from one location to another within the same simulation.

Use custom functions and define it as Temperature + 10K and use this as the inlet temperature boundary condition for the other domain.
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Old   May 20, 2022, 06:27
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Thanks for your reply,

For the issue of mapping one location to another:
I have generated a surface average report "TempBoxInlet" of the temperature at the box inlet. Using custom field function, I reference this report and add 10. But I get the error "invalid field function type for box outlet". getReportValue($TempBoxInlet, ".*") is not helping either.

For the global issue:
So having multiple topologically different fluid volumes defined as a unique region is not supposed to cause any issue in starccm?
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Old   May 20, 2022, 08:42
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I have found a solution for the issue of mapping one location to another. I just need to generate the report from the fluid volume part and not from the region, and it magically works. Hope this can help anyone struggling with the same problem.

Still unsure starccm is able to properly manage multiple separated volumes, but I guess there is no reason for it not to?
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