[manxu]

Hi,

I used VOF multiphase to check the engulfing of a water droplet falling on an oil bath.
It should ideally engulf the water droplet because the spreading coefficient of oil over water is positive based on surface tension coefficients (ie: Swa - Soa - Sow > 0).
I have tried using both CSS and CSF model for surface tension available in Fluent 14.5. But the water droplet seems to just spread over the oil bath which is not physical (correct me if am wrong)(attached picture -noengulf.png) . This raises a couple of questions :

1. Is Fluent VOF capable of capturing the surface tension forces properly in a multiphase model (involving liquid-liquid-gas) ?

2. From the result that I have got, it does look like the contact line dynamics for a three phase (L-L-Gas) is not effectively captured by Fluent(correct me if I am wrong). But isn't this supposed to be the foundation for many multiphase simulations using VOF ? So are all the simulations involving surface tension forces in a multiphase VOF model not accurate ?

[manxu]

Do anybody have atleast faced similar issues ? Please do share if you have come across anything vaguely related to this issue.

[Zaktatir]

Fluent VOF is capable of capturing the surface tension forces almost properly (Grid dependency/OhneSorge Number )in a multiphase model. The Problem of spurious velocities is not FLUENT problem but deals with the the approximation of the (unknown) interface and the approximation of the curvature in capillary forces.