CFD-DEM with cyclic boundary conditions running extremely slow

MFiX How to
#1

Hi advanced users,

I found that in MFIX-CFD-DEM simulations, changing wall boundary conditions from no-slip to cyclic can slow down the simulations by a factor of 20 or more. Is it a bug? Is there any way to address this problem? I am using the MFiX-22.2.2. Actually, I also found the same problem using versions before MFiX-22.2.2.

#2

For the cyclic BC, are you applying a mass flux or pressure drop? Please attach both input files.

#3

test.zip (23.3 MB)
Hi Jeff,
Thanks for your reply. I used a mass flux. Attached are my case files. The number of particles is large. I used 24 processors in parallel.

#4

I am not seeing that much of a difference. The cyclic case runs about twice as slowly as the no-slip-wall case. I used a 4x10x1 parallel decomposition with MFiX 22.4. I think the cyclic case runs slower due to the extra communication along the cyclic boundaries but it is not 20 times slower for me.

#5

Hi Jeff,

Thanks for validating this. Maybe it is because the number of processors I am using for parallel running is not good for the cyclic boundary condition. I will try to use the same parallel settings as yours.