I am working on a cold flow model of a disengager meant to replace a cyclone in a chemical looping system. I’m using the TFM solver. I’m relatively inexperienced with CFD software in general, but most recently I’ve been running into an issue related to the void fraction of my particles specified in the Inlet boundary condition. I want it to be 0.0012, but the DT drops below the threshold within 1.5 s of simulation time. Adjusting it to 0.005 allowed the simulation to solve to completion, but going up to 0.05 had the DT drop below the threshold at ~173 s of simulation time. I’m guessing this involves some other issues with my setup, but I’m at a loss so I’ve uploaded it below. Any suggestions are appreciated!
The time step drops? It is fine if the time step drops. MFiX tries to adjust this time step on the fly to make sure the simulation is converging and minimize the time to solution.
It runs better with the attached. I reduce the size of the inlet and outlet so they only cover the relevant areas (there could be a conflict with the stl wall since the mesh is so coarse). I also changed the fluid and solids normalization. There is also room for improvement in the mesh. I haven’t tried to change it since I am not sure if you can afford a finer mesh.