[badar]

Hi, I am New user of CFD..I am doing work on open channel flows...flow in river with air at the top....I know VOF model will be used but i am encountring boundary conditions implementation (water and air flows separately)...plz help me out

[DarioMD]

What's your problem exactly?
I have implemented models of open channels with three boundary conditions.
A velocity inlet, pressure outlet and wall conditions.
This dependent of what you are modeling. If is a river with current water in or the river bed without water, etc. It is not generally.
In the "boundary condition" menu you can change the phase's percent in the boundary condition, like the velocity inlet.

[badar]

Originally Posted by DarioMD

What's your problem exactly?
I have implemented models of open channels with three boundary conditions.
A velocity inlet, pressure outlet and wall conditions.
This dependent of what you are modeling. If is a river with current water in or the river bed without water, etc. It is not generally.
In the "boundary condition" menu you can change the phase's percent in the boundary condition, like the velocity inlet.

i am using pressure inlet/pressure outlet boundary conditions....At the inlet i want to give volume fraction of each phase (air/water) separately...but it is not giving me exact option of defining volume fraction of each phase in fluent...what boundary condition should be given to open surface (at top).?What is the importance of region adaption in this problem? i am also encountering patching problem of water phase....it should be given value of 1 0r between 0 and 1?

[landerfwc]

To change volume fraction of phases at the inlet, you have to choose a secondary phase under Boundary conditions/Phases. The default value is mixture, you are not able to change it there.

Regarding patching, after the initialization you should patch the area/volume designated for water by volume fraction of water equal to 1.