Hello everyone,
I just started learning MFIX and ran into one error while trying the tutorial 3.5. I am using MFiX version 19.3.0.
I get a warning saying “WARNING: velocity higher than the maximum allowed velocity: 25.000” and the solution diverges after a few iterations when running with the specified conditions in the tutorial.
I speculated that the reason for this could be the coarse grid or large time step size. So, I tried running the simulations using a finer mesh and a smaller time step size. But the warning still appears leading to divergence after a few iterations.
I observed that the option of Flip STL normals is to be selected in the mesher tab for pre-processing. However, I do not any such option while setting the case. Other than this, all the settings have been specified as shown in the MFiX documentation of tutorial case 3.5.
Please help me identify where am I going wrong.
Please post your .mfix file and others might be able to test it.
fludizedbed.mfx (11.6 KB)
Attached is the .mfx file of the case.
The warning I receive while running the case is:
WARNING: velocity higher than maximum allowed velocity: 25.000 (to change this adjust the scale factor MAX_INLET_VEL_FAC)
After some iterations, the solution diverges giving the following error.
ERROR time_step.f:193
DT < DT_MIN. Recovery not possible!
I was running the same tutorial and I got exactly the same error. Compared to the tutorial instructions, I noticed that in my version (19.3.1) I can’t check “Flip STL normals” and that when I create the wall region I can’t check “Slice facets” (as the tutorial shows here). Thanks!
Edit: To temporarily avoid this problem, I uninstalled version 19.3.1 and installed 19.2.2 and the simulations runs fine on it.
I tested the file you posted above in MFIX-19.3.0. You actually simulated the flow outside of the STL (first figure), that is why your simulation diverged.
You can add a keyword out_stl_value=-1 in the .mfix file in the GUI.
Advanced—>search STL—> select out_stl_value–> set it to -1. (second figure)
Third figure shows that the simulaiton can run without any error.
It works perfectly.
Thanks Xi Gao!!