how can one simulate free surface with fluent to rersearch dip velocity phenomena?

hi, in fluent, only VOF is able to simulate free surface flows..

what do you mean with "dip velocity"?

dip velocity means that due to secendary current in open channel ,max velocity doesn't occure at free surface. in outer region in open channel , turbulance dissipation is larger than its production so assuming zero gradiant for epsilon isn't sutable at there .

If you are interesting in the variation of the free surface then the VOF model is the only that can simulate the free surface. But i think that in this case you can only have two flow phases "Air" and "water". I dont think that you can apply a secondary phase that flows within the water.

If the secondary flow that you want to examine is say well underneath the free surface and posible variations in the free surface does not affect the velocity field of the secondary subaqueous flow, then you should define the free surface boundary with a "Symmetry" boundary condition or as a wall with zero shear and use the mixture or the eulerian multiphase model using two phases. Water being the primary phase and the secondary fluid being the secondary dispearsed phase.

secendry current in open channel result of damping and generation of turbulence fluctuation ,not a new phase enters the water phase. my question is that is it possible to modify the symmetry b.c?