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CHT , multiphase, rotating domain. Can't get a solution

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Old   December 9, 2014, 22:42
Default CHT , multiphase, rotating domain. Can't get a solution
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Ghazlani M. Ali
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Hi all,
I've been trying to successfully simulate a conjuguate heat transfert simulation where I "inject" oil in a rotating fluid domain. The setup is shown in the picture below:



It's a rotating fluid domain, with solid wall heated at 500K. There is a fix domain, where oils flows in a steady-state fashion. both domains are connected using frozen rotor interface. I would like to see the oil's path when the rotating domain pass through the oil. Some first result were obtained and shown in the picture below (It's a coarse mesh):



This is the isothermal model and it runs well, problems come when I activate Total energy. The simulation starts running until I try to do a backup. I still don't get how am I supposed to do some troubleshooting if cfx does not give me some results (even if they are bad). I get fatal error bounds in air.density@rotating.
I don't get the error if I switch to air gaz 25C. So, Ideal gas causes CFX to crash. What I tried next, is to set the air density as:


Again, this is the Ideal gas equation for density, so CFX crashes. But if I replace the pressure by my reference pressure. It keeps running, but converges to an unrealistic results.

Sorry for the long post. How to deal with the error "Fatal bounds error detected." I've seen some post where it indicates negative value. But I monitered my densities, and their range is not critical.
Forgot to mention, The RPM is very High here, around 25000. The thermal model can runat low RPM (600) but crashes at 15000 and above.

May be the whole setup is not right, I have tought of another way to inject oil, If you guys really think that this one is bad, I will show you the other one, may it is more suitable.
Thanks a lot in advance for your help and ideas.
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Old   December 10, 2014, 00:25
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That is the coolest image posted on the forum, in a crayon sort of a way.

At first glance I would be suspecting that you are getting negative densities because this device has small regions of cavitation in reality. You might need to use a cavitation model to keep these regions under control.
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Old   December 10, 2014, 09:58
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Thank you Glenn for your response. I am curious tough, cavitation was off in the isothermal model, and it was running well. When I monitor my densities, I don't get negative values... Refining the mesh did not work. I am suspecting the setup.
Is there a way to know where I get negative densities ?
update: cavitation model did not help...
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Last edited by diamondx; December 10, 2014 at 12:11. Reason: update
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Old   December 10, 2014, 12:12
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Update 2: I'm setting the heat transfer as fluid dependent, set the air as isothermal, and the oil as total energy. it does not crash for the first iteration, I'll see where this is going...
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