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November 2, 2011, 06:14 |
Vacuum flow - Janaf error
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#1 |
Disabled
Join Date: Mar 2011
Posts: 174
Rep Power: 15 |
I have been trying to simulate time dependent, pressure driven
flow through a cylindrical orifice (4.8mm diameter, 0.2mm thickness) as an intermediate step to my final geometry. The pressure upstream is 10^5 Pa and downstream 2500Pa, the temperature is 300K on every boundary surface and the gas is nitrogen. The solver I am using is rhoCentralFoam. It is reasonable to expect that the temperature drops significantly in this case (ANSYS gives a minimum temperature around 10K) and as a result I get an "out of Janaf range" error. My fvSchemes and fvSolution are the same as in the Ladenburg example. I have tried the following without success: - Changed Tlow for Janaf to 1K - Refined the mesh - Set the Max Co to 0.1 and I am currently trying an even denser mesh (200,000 elements). Any ideas? I must also note that this happens for any downstream pressure below 60000 Pa. |
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November 4, 2011, 04:07 |
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#2 |
Disabled
Join Date: Mar 2011
Posts: 174
Rep Power: 15 |
The dense grid improves the situation
but I still can't get beyond 10^-4 sec for an outlet pressure of 10kPa. Any suggestions? |
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November 14, 2011, 04:52 |
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#3 |
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Join Date: Mar 2011
Posts: 174
Rep Power: 15 |
I don't understand why is this type of error activated,
since the temperature is much higher in the moments before the divergence (minimum 280K). I am pretty sure I am doing something wrong with the boundary conditions. Any suggestions on pressure BCs for a vacuum opening of known pressure? I have already tried fixedValue, waveTransmissive and zeroGradient (which does not work because of the nature of the flow). |
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June 11, 2018, 04:14 |
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#4 |
New Member
Join Date: Jan 2017
Posts: 13
Rep Power: 9 |
Hi,
I have same problem. Could find any solution? Best, Ghazal |
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Tags |
janaf, rhocentralfoam, vacuum |
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