Learning Forum

[BehrouzMohammadian]

Hi Ansys Community! I am modeling air injection into a tank with moving water inside it. I use mixture model with interfacial area concentration. I was wondering what is the effect of slip velocity in phase interaction section on my solutions. When I turn it on I can't get a converged solution. What is the difference with the VOF model if I use none in Slip velocity? Thank you so much!

[Prashanth]

Hello,

You can find the slip model theory here: 14.4.6. Relative (Slip) Velocity and the Drift Velocity.

When you have it on, the secondary phase slips relatively to the primary phase and the algebraic relative velocity formulation is considered. It is applicable for low relaxation times.

[Rob]

To add, the VOF model tracks the free surface whereas the Mixture model assumes a more diffuse second phase. So, the former will track the air injection and it's break up to bubbles only in the mesh is sufficiently resolved (5+ cells across the bubble) whereas the latter will show a volume fraction somewhere between zero and one as the bubbles disperse or coalesce.