LIGGGHTS Commands in CFD Simulation

Submitted by simi180 on Mon, 03/11/2019 - 11:59

Hey,

I am dealing with a problem, that i cannot solve myself. I have a CFDEM Simulation with particles in a pore. When starting the simulation, the initial flow creates a strong force on the particles, which is higher than the calculated drag force should be. So my idea is, to use the LIGGGHTS Command script in the constant folder, to unfix the "fix integr all nve/sphere" command in the LIGGGHTS script for the first, lets say 10.000 timesteps. The idea is, that in the first timesteps, LIGGGHTS does not calculate a velocity or force and the particles do not move, until there is a constant flow in the pore and the initial drag disappeared. But to my mind, it is quite difficult to find the correct way of formulating it in the LIGGGHTS Command script.
Thanks in advance

alice's picture

alice | Wed, 04/03/2019 - 16:34

Hi,

if you want to integration to start at some time, I would not add it from the beginning but with a liggghts Command at the time when you want it to begin. This will work with an execute command as you can for example find in the liggghtsCommands file of cfdemSolverPiso/ErgunTestMPI.

However, a better approach might be to generate an initial velocity field using pisoFoam and using it for time 0 in the coupling calculation (for example).

Cheers,

Alice