two mesh in CFD and DEM

Submitted by dan_nott on Fri, 05/18/2018 - 18:36

Hi,
when I generate the region to initialize particles, I found that we should import the geometry and mesh in the dem settings and not use the openfoam geometry/mesh automotively. May I ask if they are relative independent mesh system in the simulation? is this possible to use two different set of geometry/mesh set for the DEM maybe should be in the fluid domain defined in openfoam?

Regards,
Dan

Forums:

paul | Mon, 05/21/2018 - 09:29

Yes.

OF and LIG use independent simulation domains, i.e. particles can be outside the OF domain and not experience drag force, but still move according to the contact laws in LIG or the OF domain can be larger than the region in which the particles move.

dan_nott | Mon, 05/21/2018 - 18:30

Dear Paul,

Thanks for your reply. i have another two question further. If there are particles outside fluid domain, is the interactions between fluid and particles are switched off or we assumed that the velocity of fluid as zero. Another question is when we use two set of mesh, is the fluid-particle interactions, drag, pressure, etc. are calculated or averaged based on the fluid mesh from openfoam?

Dan

paul | Tue, 05/22/2018 - 09:00

1. Drag force calculation is entirely skipped.
2. I do not understand your problem. During every coupling step,
- CFDEMcoupling locates the particles in the OF mesh,
- interpolates/determines fluid velocity and such,
- averages particle velocities on the mesh,
- calculates drag coefficients for each particle and momentum exchange coefficients (Ksl) on the mesh.
For particles, a drag force \propto C_d,i * (U_fluid - u_p,i) is applied and for flow, a momentum exchange term \proptop Ksl*(U_fluid - U_particles,cellavg) is applied.