Free Surface model versus VOF model
 

Hi, everyone, I want to ask a question here.
In CFX software, the Particle model is used for simulation of bubbly plume, while the Free surface model is used for tracking the interface (or free surface) flow between two continuous phases. The difference between these two models is that the interfacial area densities are dealed with the different ways in N-V equation.
In Fluent software, there also has a model, named VOF model, for tracking the interface flow. Can you tell me the differences between Free surface model and VOF model, as well as the differences between Particle model in CFX and Eulerian model in Fluent.
Thanks!