Granular temperature at Pressure Outlet BC


I have selected Pressure Outlet BC and have set the outlet pressure to atmospheric. However, I also find an entry in the .mfx file for the granular temperature boundary condition for the outlet (please see screenshot below).

Is the granular temperature at the outlet not calculated by the code based on the solids concentration and other process conditions at the outlet? Perhaps it is only an initial guess?

Please clarify.

Thank you.

c7.mfx (11.8 KB)

@pbalas Thanks for the report.

Something is not quite right here! For pressure outlet, the granular temperature controls are not shown in the GUI, so you can’t (easily) set bc_theta_m.

If I edit the file (carefully) outside of MFiX and remove that setting, it gets re-added at startup when the MFiX GUI checks the data file to make sure all required keys are present.

There was an issue where leaving bc_theta_m unset for Inlet BCs caused a crash, so we added this default value setting. It looks to me that it’s being inappropriately applied to outlets as well as inlets. I think this is incorrect.

However, it’s not clear that this value is used at all when the solver runs. I’ll try to find out more and get back to you about this.

Thanks for your input,

– Charles

I think this value is used in case of backflow only. Should be safe to leave in the file.

Hi Charles, Jeff,

Thank you.


I just commented out the bc_theta_m in the .mfx file and tried it in the CLI. It runs well.

As you say, it would appear to be a superfluous setting that is not used by the solver.

Thank you again.