Learning Forum

[SR786]

Hi,

I am looking to simulate two-phase (air-water) flow in an unbaffled STR where I want to capture the vortex depth. Later on I want to couple with three-phase flow (air-water-precipitate) using CFD-PBM.

To achieve this I will need to use Multi-Fluid VOF. I have computed an initial solution for two-phase, air-water, flow using homogeneous VOF which was very robust. I wanted to use this homogeneous VOF as initial solution for Multi-Fluid VOF with still two-phase flow. However, I notice the simulation becomes very unstable when I run Multi-Fluid VOF and seems to keep diverging. I have tried lowering URFs and time step size to no avail and I am stuck as to what to do next as there is no other way of initialising Multi-Fluid VOF (trying to start from scratch didn't work).

 

[SR786]

Hi, given that homogeneous VOF and inhomogeneous VOF have different frameworks (i.e., one uses mixture velocity and one uses velocity per phase) would it be better to first set flow field using inhomogeneous VOF where I only patch single phase (i.e., water). Once flow field is set then I introduce air phase and solve for two-phase flow? As I notice that when switching from homogeneous VOF to inhomogeneous VOF I lose the flow field even if I retain the vortex shape.