True-VOF vs. False-VOF

edi ghirardi

Hi to everybody,

I carried out a liquid sloshing CFD study with Fluent 6.2 VOF model, and I have a few questions about the model implemented in the solver.

Well, I know that the VOF model in Fluent is actually a variable-density approximation of the "real" VOF model by Hirt and Nichols and I also know that Flow Science (Hirt is one of the founders, if I'm not wrong) claims Flow 3D to be one of the few codes (the only one?) with all the three essential features needed to properly model free surfaces (-a scheme to describe the shape and location of a surface, -an algorithm is required to evolve the shape and location with time, -free surface boundary conditions at the surface).

I'm actually going into details of the problem these days and trying to understand whenever and however this approximation will affect the results of the simulations. So my questions are:

1) Has anyone ever faced such a situation? I would really appreciate if someone would share his own experience and deal it with mine...

2) I think that Fluent's VOF model lacking feature is the ability to apply a boundary condition at the interface between the phases (velocity gradients, etc...), I'm right?

3) A fine mesh can improve the model and make the lack neglectable?

4) When body forces' effects decrease and surface tensions, wall adhesion become pre-eminent is the variable-density model even worse?

5) What codes (both commercial and freeware) have the best multiphase models implemented (VOF or even other techniques)?

Thank you in advance for any contribution,

Edi.