Simulation of chemical reactions in a fluidized bed indicates Dt < Dt_min

MFiX
,
1

I am using MFIX version 25.1.2 to simulate a chemical reaction in a pseudo-two-dimensional fluidized bed using DMP on Linux. At 0.02 seconds into the simulation, it suddenly fails to converge and displays the error message “DT<DT_MIN.” But when I uncheck “Enable energy equations,” the simulation runs normally. How can I resolve this issue? Thank you.

mto4_1_2026-04-08T223231.946010.zip (8.4 MB)

2

Try running with explicit coupling enabled (Solids>DEM, check “Enable explicit coupling of interphase quantities”). I have your case running up to 0.3s without issue. This was on version 25.3

Separately, I was able to run without error by using a dt_max of 1e-5s, though this is obviously slower. An overnight run reached 5.5s without error.

1 Like
3

you also unchecked the Stiff chemistry once you uncheck the energy equation?

4

Thank you! I check “enable explicit coupling of interphase quantities“. There were no issues with convergence

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5

Yes, but the error still occurs.