Boundary condition of free surface model

Tony

Dear all,

I use Fluent to model the water ejecting from a small pipe. I tried to use VOF model and define the free surface area as pressure_inlet, but it did not converge. My model has one velocity_inlet, one pressure_inlet and one pressure_outlet. Can anyone recommend the way to help the simulation converged ? I tried to follow all instructions in the manual, but it still not converged.

By the way, I search how to model the free surface and I got three ways to do it as follow :

1. Define the surface as a wall and then put the Shear stresses to 0 for x and y.

2. Define the surface with symmetry boundary condition.

3. Use VOF model and set the surface as a pressure inlet.

Can anyone explain the differences between these boundary conditions ? or recommend which way is good for the water jet ?

Thank you for your kind attention.

Tony