I am trying to solve pneumatic conveying system with dense solid flow regime (void fraction varies from 1 to 0.35), using CFDEM two-way coupled solver. The versions are OpenFoam 5.0 and LIGGGHTS-Public 3.8.0.
The simulation diverges with very high (1e+16) Courant number. The pressure and velocity numbers become unrealistic at timestep when Courant number increases unrealistically.
The simulation runs longer when CFD timestep and coupling interval are higher.
I keep DEM timestep fixed to 1e-5 seconds and change the CFD timestep as per CouplingInterval. T
(1) when CouplingInterval is 100 and CFD timestep=1e-3, it diverges after 18.9 seconds of simulation
(2) when CouplingInterval is 20 and CFD timestep=2e-4, it diverges after 3.8 seconds
(3) when CouplingInterval is 10 and CFD timestep=1e-4, it diverges after 2 seconds
The model settings in couplingProperties are attached in text file here.
Can you please suggest what could be the reason?
There is similar observation reported in link
Thanks and regards