Fluids
Also, do a search on this site for:
"Interparticle collisions"
The 2 results you get will be threads that I replied to others about this same type of thing
It contains a reference to an outside tutorial on a case study/tutorial regarding your globe container geometry and the dynamics of interparticle collisions.
However, it should suffice for your needs
Good luck!
Israel "Izzy" Long
Motion and Title Design for Broadcast-Film-DS
izzylong.com