Rob
Ansys Employee
VOF to DPM is best used when you want to track and see the dispersed phase: atomisation is a good example. In your case you have a mixed flow (we don't know how mixed and you need to define that) which then separates. Using multi-fluid VOF with a reasonable droplet or bubble size will set up the bulk flow. You can then use DPM to see what the separation efficiency is. However, you also need to understand the limitations of this approach.
Otherwise you need PBM and/or GENTOP to sort this out which will be a big compute run. and I have a lot experience in this field, and we approach these problems very carefully as the methodology used depends on a very large number of factors. The runs can also take a fair amount of time or require large amounts of compute. There's a reason a multiphase problem was used for this https://www.ansys.com/news-center/press-releases/07-18-17-ansys-saudi-aramco-kaust-shatter-supercomputing-record