DEM particle interactions with lagrangian phase
 

Hello, I am doing sand tracking.
DEM and lagrangian model are been used.
But each time when I defined DEM - Particle Interations -PhasePair 1: sand - sand, and PhasePair 2: sand - Wall, then I try to run, the two phase pair will automatically gone!
An error shows as attached picture show "DEM particle interactions not defined", but I have already defined as I mention as Phasepair 1 and 2, it just gone by itself when run!:confused:
I am so confusing.
Looking for solution, thanks for help!

I figure out I have to select the interact phase instead of just change the name as sand: water, or sand: sand.
Thanks.