Ansys Employee

If you have a look into the theory in Fluent we look for particles in the same cell: not a perfect solution, but this does avoid the looping problem you're seeing. I'd read the Theory Guide to our collision model, and then look at the references: tracking those backwards (and forwards to where they're referenced) should give you some pointers.

When/if you do come up with a good solution let us know: our Developers may be interested!