Unrealistic Courant Number. Simulation diverges with lower CouplingInterval

Submitted by tuks123 on Thu, 10/31/2019 - 09:03

Hello Users,

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

https://www.cfdem.com/forums/optimal-coupling-interval-time

Thanks and regards
Tuks

AttachmentSize
Plain text icon couplingproperties.txt3.7 KB