Hi,
I’m currently running a very simple collapsing bed in a vacuum simulation in MFiX with DEM. However, I am running into some unexpected behavior at start-up. My particles initially start evenly dispersed at rest throughout the system at a particle volume fraction of 0.02 (roughly 36,000 particles in the system):
However, immediately after this, many of the particles in the system skyrocket to relatively high velocities in all directions, seemingly at random:
As you can see, in just 0.01 s of sim time, the particles have jumped from rest to many being well above 0.5 m/s in vel magnitude. Obviously, this is not realistic given that gravity should be the only meaningful force acting on the particles by this point.
My best guess right now is this is due to some adverse interaction between how my particles are being initialized and the linear spring dashpot collision model. Essentially, I think my “springs” are being initialized as partially compressed when the simulation starts and that stored energy is being released upon start-up.
If someone could let me know if I’m on the right train of thought here and what I could do to fix it, it would be much appreciated. If any more information is needed, feel free to ask. Thanks!