Coupled CFD-DEM simulation - losing particles

Asked by Kahlil Fredrick Cui on 2018-03-03

Hello!

I am doing a very simple simulation exercise with coupled CFD-DEM, with Esys particle for the DEM part. Its very similar to the slope_friction.py simulations, only now the particles are underwater. Somehow, after several iterations, the number of particles decrease (as if they disappear) which causes the simulation to crash. I made sure that the time steps are small enough to minimize computational errors.

I know this problem is not solely attributable to ESyS and it might be to coupling code parameters. I am just hoping someone here might have some idea as to why this happens. Any input helps!

Question information

Language:
English Edit question
Status:
Solved
For:
ESyS-Particle Edit question
Assignee:
No assignee Edit question
Solved by:
Dion Weatherley
Solved:
2018-03-05
Last query:
2018-03-05
Last reply:
2018-03-05
Best Dion Weatherley (d-weatherley) said : #1

Hi Kahlil,

The usual way particles "disappear" from ESyS-P simulations is by moving outside the simulation spatial domain boundaries. I would first check that the simulation domain is large enough to prevent this from occurring.

If that is not the source of your problem and the time-step increment is small enough, I'd be looking at the coupling code. Specifically, ensure that coupling forces applied to DEM particles are not excessively large. This might cause particles to "flee" the simulation domain.

I hope this helps.

Cheers,

Dion

Hello Dion!

We have found out that the cause of this is due to the ratio of the fluid mesh size and the particle size. The particles were almost as large as fluid cells and I guess for larger velocities the cell would fail to take the particle into account.

Thank you very much for taking the time to answer! I will consider this as part of the possible scenarios whenever this happens again.

Kahlil Cui