Unsolvable convergence problems (TFM, 2D spouted bed)

MFiX
#1

Hi everyone!
I’m sorry for taking up your precious time.
I created a 2D conical spouted bed under the TFM model.When I simulate particle flow, the mfix prompt does not converge.I found the sentence “Run diverged/stalled :frowning: Recovered: Dt= 0.28243E-03 :-)” in the log.I checked the mfix guide and mfix forum and found some solutions.I have tried the following measures:
(1) Modify the time step; (2) Increase the number of iteration steps; (3) Change the discrete method; (4) used a line preconditionner; (5) turned off the stall detection；(6)Reduce underrelaxation factors；(7)Removing small cut-cells.
However these measures did not solve my problem.
This problem bothered me for a long time.I can’t find a working solution.I attached the case.
test3.mfx (17.3 KB)
How can I fix this non-convergence problem? I sincerely look forward to your reply！

#2

First, double check the packed bed void fraction. The value you used of 0.98 is unusual. You may also start with a fluffed bed instead of a packed bed.

For the numerical settings, use the default tolerance (tol_resid) of 1E-4 instead of lowering it to 1E-5. Then increase the number of gas pressure equations to 200 (Numerics>Linear solver).

You may also consider using ideal gas law for the gas density instead of incompressible fluid.

#3

Thank you very much for your reply.I successfully solved the divergence problem as you suggested.This case is working normally.
I found the value of the bed void ratio from the article. I may have misunderstood this value.
Thanks again for your reply！

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