BC in Simple Channel Flow Problem
 

Hi,

I am using the converge simple channel flow tutorial and changing the inlet pressure boundary condition to impose more and more pressure gradient on the flow. However at some point, the simulation crashes when the pressure difference between inlet and outlet is more than 20 Pa.

Error that comes up is this

JOB ABORT invoked by rank 0:
ERROR: Something is wrong in function get_temp_from_table_massfrac: upper_energy_value must be greater than lower_energy_value!
upper_energy_value is -nan, and lower_energy_value is -nan.

I use the same boundary and initial condition as in the tutorial except modifying the inlet and initial pressure to 100020 Pa.

Is there something that I am doing is not correct?

Thanks

Hello,

From the error message we can see that NaN was detected. This indicates that one or more of the equations did not converge and blew up.
You can look in the log file to see which equation is causing the issue. Detailed information in the log file is printed when the screen_print_level is set to 2.

What is the version number and release date of CONVERGE that you are using?

Thank you,

Hi Anshul,

Thanks for your reply. I am currently using v2.3 (Jan 29, 2016).

Yes the screen_print_level is already set to 2.

Which log file should I refer to? result.out?

And what causes only small pressure difference (20Pa) for the simulation to blow up? Should I change the type of solver as well?

Thanks

Hello,

When you run CONVERGE from a terminal, lot of information is printed on the screen. Many times we direct the screen output to a file and this file is commonly referred to as log file.
It is possible that result.out might contain that information.
You can check Figures 22.9-22.11 in CONVERGE Manual to see how a log file looks.

Thank you,

Hello Anshul,

I have the same problem as Hmzha. Error that comes up is:

ERROR: Something is wrong in function get_temp_from_table_massfrac: upper_energy_value must be greater than lower_energy_value!
upper_energy_value is nan, and lower_energy_value is nan.

I have a .log where, as you told, I could see which equation blew up.

Where can I detect this error?

Thanks in advance

Hi, I am working on a pressure-based steady problem and am encountering this same error. Did you sort it? Or if anyone else has any suggestions.

Thanks

Hi,

In my case, the error was that the mesh was too coarse or too thin so the turbulence didn't work well.

If you have generated a .log, you could know what equation blew up.

I hope this explanation would help you!!

Hi,

JOB ABORT invoked by rank 0:
ERROR: Something is wrong in function get_temp_from_table_massfrac: upper_energy_value must be greater than lower_energy_value!
upper_energy_value is -nan, and lower_energy_value is -nan.

The above error generally occurs when energy goes out of bounds, i.e. there is no temperature corresponding to the internal energy that we are solving for. Please make sure that you are using the recommended settings for solving all the conservation equations, also have a look at the geometry and make sure you have appropriate number of cells for narrow regions of the geometry.

If you are still encountering this error, please send your case setup to support@convergecfd.com for further support.

Thanks,
It seems I was able to get rid of the energy_value error by either removing a permanent fixed embedding cylinder or decreasing the base grid, but then was encountering segmentation fault. I am using default values for the conservation equations. An interesting note is that I can run the same grid/mesh settings with a transient solver. Let me know if I should start a new thread or send my .cvg to the support email.

Hey everyone,
could anyone figure out what problem is whenever this error appears?
ERROR: Something is wrong in function get_temp_from_table_massfrac: upper_energy_value must be greater than lower_energy_value!
upper_energy_value is nan, and lower_energy_value is nan.

Any idea what does it mean?!

New thread created for the above.

Hey everyone,
I recently encountered the same issue by only increasing the inlet gas temperature, has anyone figure out what problem is?
WARNING: temperature extrapolation error found
FATAL ERROR: Something is wrong in function get_temp_from_table_massfrac: upper_energy_value must be greater than lower_energy_value!
upper_energy_value is nan, and lower_energy_value is nan.