Information about file EPgErr.log and INFO set_bc0.f:575

MFiX
#1

Hi, Mfix community

I’ve been simulating some cases based on tutorial 3.2 TFM and I find in the EPgErr file the text:

One or more cells have reported a negative gas volume fraction (EP_g).

I am not getting any message of error during the simulation. What does this message mean about the simulation? Does it mean the solution is diverging?

However, I get the following message in the beginning:

INFO C:\tools\miniconda3\conda-bld\mfix-solver_1556302768954\work\model\set_bc0.f:575

Outflow PC defined: IJK_P_g remaining undefined

which I also do not understand, since the bc_p_g(BC) is defined. I am attaching herewith the .mfx file. The mesh in the file is coarse and I am willing to run several simulations to understand when the solution becomes independent of the mesh configuration. Thank you!

cvm1.mfx (13.5 KB)

#2

It is not uncommon to have a time step fail to converge or even diverge. This is sometimes caught by field variables reporting unphysical values (negative volume fraction, negative pressure, negative density, etc.) In the even that this happens, the adaptive time stepping algorithm in MFIX will decrease the time step size (dt) and restart the time step. Usually the code can recover from these events.

The Outflow BC defined: IJK_P_g remaining undefined is a normal message. It means that the MFIX has detected a pressure outflow and will not impose any constraints on the pressure field. If no outflow is given, MFIX will fix the pressure in a single cell to improve convergence and prevent the pressure field from wondering.

#3

Understood. Thank you!