Learning Forum

[scabo]

Hi

I am trying to model 3 phase air, water, solid pipe flow in fluent. What is the best way to model that in fluent. Can i do a VoF modelling of air+water and then add DPM injections? Or are there any better approaches?

thanks

[Rob]

It depends. The various multiphase models are all "best" depending flow regime and volume fraction. 

DPM won't see the free surface in VOF, it only sees the cell fluid density & viscosity. 

[scabo]

Hi, thanks. If i make the pipe periodic in the streamwise direction for the flow, will the DPM particles follow the periodic conditions? or do i have to write UDFs to apply periodic BCs to the DPM particles?

[Rob]

Check the documentation. However, if the particles are denser than the liquid they may just finish up at the bottom of the pipe. 

[scabo]

Okay i will check the docu. even if the particles are denser than liquid it will travel some streamwise distance before settling.

[Rob]

Except it's periodic - it's already a long way downstream! 

[scabo]

Yes you are right so we have to model the DPM carefully while using periodic conditions. Cant initialise it with normal conditions. Right?

[Rob]

You can, but as you're looking at a very long pipe DPM may not do what you want. Periodic flows have their use, here you may need to model it in full.