Trying to use VOF model, but solution is diverging

[rahul_kv]

I am trying to use VOF model in a pipe flow in a tank, with air and water, Pressure inlet at pipe inlet and whole tank with all its walls as pressure outlet is my boundary conditions. But my solution is getting diverge after 100 or 200 iterations. What could be the reason for this or how to avoid the situation?

[SRP]

Hi,

Can you please share more details related to the setting you used for VOF? In addition, how is your mesh quality?

[rahul_kv]

This is my mesh quality:

Minimum Orthogonal Quality = 7.48746e-02 

Maximum Aspect Ratio = 3.21902e+02 

In VOF, I selected implicit and in phase interaction surface tension coefficient is constant 0.072N/m, surface tension force modelling is enabled.Viscous as SST K omega.

In solution methods, scheme is PISO and also tried with coupled and simple. and first or second-order upwind both and pressure as PRESTO! all other settings were kept deafault.

[SRP]

Hi,

Thank you for sharing details.

I suggest you to try explicit scheme with compressive interface capturing scheme for stability. In addition also try to adjust time step to maintain stability.

[rahul_kv]

If I am using an explicit scheme, it will convert into a transient state, but I want to use a steady state.

[SRP]

Hi,

You need to use explicit scheme for volume fraction parameters-Formulation. It will not convert solution to transient.

You can check fomulation of implicit and explicit here: 14.3.4. Volume Fraction Equation