Negative Temperature chtMultiRegionSimpleFoam + thermalBaffle1D + Radiation
 

Hello everyone,

I pieced together stuff from the generous help from Tobias and Alex to create a test case. It is a very simple problem where you have 2 solids (isotropic), in air. There is a vertical wall next to the second solid, created as thermalBaffle1D.

Everything works fine until you introduce baffle. After adding baffle, the temperature in the baffle goes negative (reduces below ref value and indefinitely reduces until simulation crashes). I don't know what is exactly happening here.

While testing for radiation, I discovered that in openfoam-dev "qr" option in baffle boundary doesn't affect anything? It still has to be specified as "Qr".

@Tobi @zfaraday - you will probably have an answer to this question - this example borrows stuff from your axisymmetric meshing and circuitBoardCooling_rad tutorials respectively. Many thanks!

Updates
 

Please note that createBaffles need to be run separately. There's an error in nut patch entry for baffles -- remove compressible::

snGrad scheme
 

Note:
I suspected for a while using uncorrected scheme for sngrad in solid regions could be a reason. Changed it to corrected -- negative temperature seems to have gone away. I will confirm full resolution tomorrow.

Problem solved.

It was snGrad scheme in fact.

Thank you for your post! I don't know if this could be helpful, but I'd like to add that from OF4.1 to OF5.0, the developers changed the variable Qr (OF4) to qr (OF5).