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Unphysical temperature with mixing plane

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Old   October 28, 2018, 06:19
Lightbulb Unphysical temperature with mixing plane
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Enrico De Filippi
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Hi, I'm simulating a stage of an axial turbine. I'm making a comparison between CFX and OpenFoam and the velocity, pressure and density fieds are the same, while the temperature field is unuual in the rotor, thus affecting the Mach calculation. As it's an wxpansion, the temperature should decrease and so it does in the stator, but at the mixing plane it has an unusual increase and then it decrease again but obviously it is not the correct field. Maybe it's due to a energy non conservation across the mixing plane or the MRF zone introduce some error. I've had the same results with steadyCompressibleMRFFoam and steadyUniversalMRFFoam. I'm simulating a compressible real gas, but also the same case with ideal gas shows the same behaviour, even with different mesh. Did anyone already face this kind of problem or do you have an idea about this mistake and how to solve it?
Thanks in advance.
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Old   October 29, 2018, 15:05
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mauricio
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Hi.
Just guessing here..

Are the boundary conditions properly set for the T file/variable in the 0 directory?
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Old   October 29, 2018, 16:14
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Yes, they are the same as in the tutorial https://github.com/Unofficial-Extend...ineMixingPlane , so I guess they are correct.
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Old   October 30, 2018, 06:33
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Hi.
That was my first guess. Second guess would be for you to check the other boundary conditions of every other variable. Check the reference pressure, the transport and thermophysical properties. Also, check for wrong boundary condition assignments. You have many patches, one may be wrong across the input files.. idk.. But, IF every other result matches the CFX one, this is really weird. You might wanna check the type of solver both codes are running and coupling physics among the momentum-pressure-density.
Also, always check every tutorial you run. They are written by experts, but they are still humans, sometimes it's a matter of an uploaded file with an older version and everything just fails.


It's hard to pin point these issues in these case w/o carefully inspecting it.

Keep digging and you'll surely find the nasty bug!
gl!
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Old   October 30, 2018, 12:53
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Thank you very much for your suggestions. All the boundary conditions seem fine for me. Probably the error is inside the thermophysical properties since I'm simulating a real gas and real gas library is still under development in the extended version, so maybe ther's somethng tricky inside. I hope I can find a solution as soon as possible, even if I'm investigating it for a while.
Thanks for the encouragment!
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