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UDS for gas-phase in cavitation models bug

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Old   December 31, 2015, 00:38
Default UDS for gas-phase in cavitation models bug
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shaham
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Hi everyone,

I want to implement a new cavitation model using DEFINE_CAVITATION_RATE and I need to define a UDS for non-condensable gases mass fraction in the gas phase. I came up with a problem, which I don't know the reason for that. The problem is:
when I enable the cavitation model, and define a UDS for gas phase, and set the boundary condition of the UDS at inlet as a constant value, the UDS value comes to zero right after the inlet. I found out that this occurs when the gas_volume_fraction*gas_density is less than a certain value. The values I set are 0.0001 for vol. fraction and 1 for gas density. The inlet value for UDS doesn't affect the results. I used the UDF to set the *m_dot for cavitation to 0 to make sure there is no mass transfer. therefore, I can see the gas volume fraction spreading in the geometry, but not the UDS value.

So I wonder if anyone can tell me what the reason is, whether it is a bug or it is fixable? I hope I can find a solution, because using the mass transfer UDF is a pain!

P.S. If you want to test it yourself, define two phase, mixture phases, liq and gas for any geometry. for inlet, gas volume fraction set to 0.00001 and gas density 1, liq density 1000.
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