Vacuum flow - Janaf error
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. |
The dense grid improves the situation
but I still can't get beyond 10^-4 sec for an outlet pressure of 10kPa. Any suggestions? |
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). |
Hi,
I have same problem. Could find any solution? Best, Ghazal |
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