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rhoCentralFoam Negative initial temperature in simulation of gas jet into vacuum

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Old   April 18, 2018, 12:43
Default rhoCentralFoam Negative initial temperature in simulation of gas jet into vacuum
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c
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Hi all,

I am trying to simulate a gas jet going into a vacuum. I have generated a mesh using the GMSH facility, then use setField so there is a chamber at the backing pressure, and then the vacuum at a lower pressure. This is currently still very high to stop any problems occurring from large gradients.
I was having issues with floating point exceptions, but solved that problem with:
unset FOAM_SIGFPE

However, now the system goes to negative temperature and kills the simulation.

I have seen on other threads that there is an option for setting min and max temperatures, but I have not been able to do this successfully.
I have created a file called fvOptions, and tried having it in both system/ and constant/ but no change has been seen. Is this how to go about setting temperature limits with rhoCentralFoam?

I have tried changing the fvSchemes, but none of these stop the negative temperature, although some options do delay its occurrence. What are the most stable schemes to use for this type of problem?

Are there any other ways of stopping the negative temperatures? I am only interested in the density profile, so if there is a fudge fix that doesn't mess up the simulation too much I would be interested.
I seem to be able to run smaller diameter nozzles for a longer time, why is this?

I have attached the simulation (a smaller version just around the nozzle).
To set up the mesh I run the gmsh on the .geo file to create a .msh then:

gmshToFoam *.msh
transformPoints -scale ('0.001 0.001 0.001)'

Then i modify the boundary file so the front and back are empty, by changing the fab to:
fab
{
type empty;
inGroups 1(empty);

To run the simulation I do the following:
cp 0orig/* 0/.
setFields
decomposePar
mpirun -np 8 rhoCentralFoam -parallel | tee log
Attached Files
File Type: gz openfoam_gasJet.tar.gz (7.1 KB, 3 views)
File Type: zip 2D_Nozzle_150_into_Vacuum_lowRes.geo.zip (1.2 KB, 2 views)
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Old   November 19, 2020, 14:45
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Cihangir
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Location: Istanbul, Turkey
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Hey! Have you found the solution to the issue?

Now, I am trying to simulate a sonic gas jet injection to supersonic flow and conventional solution suggestions could not solve my issue. Anyone kindly can help?
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fvshemes, nozzle, nozzleflow2d, rhocentralfoam

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