Over the past few months, I have been experimenting with the fictitious domain solver 'cfdemSolverIB' and have discovered a few bugs / limitations (CFDEMcoupling v. 2.7.1). I realize the solver is experimental, but I thought I'd share what I've found to raise awareness for new users and to identify areas for future development.
From my experience, as implemented, the fictitious domain solver cfdemSolverIB does not appropriately handle force calculations when the immersed particle occupies cells with differing cell volumes.
For example, here is a test case with a falling particle in a small vessel. In the first case, the mesh is uniform (i.e., constant cell volume). In the second case, there is a mesh refinement region in the bottom half of the container:
It appears that when the particle moves into the refinement region that the calculation of the forces along the particle boundary is not performed properly (i.e., the forces originating from the cells in the refinement region are larger than they should be). I need to investigate this further to understand what's happening, but I thought I would raise awareness for now.
Edit: I can confirm that the bug persists in version CFDEMcoupling v. 2.9.0