You can still use the PBE approach and settling will be due to interfacial momentum and buyoancy. If you want to incoporate a physic/kernel which I never "used" before and that kernel can be interpreted as breakage kernel then you can use the PBE Macros to do that or just use generaic DEFINE_SOURCE Macros to achieve that: I am not sure what is better as you are here the expert and you know the theorical background behind this "deposition".
You are navigating away from the AIS Discovery experience