Gambit & 3d open channel flow mesh problem
 

Hi,

I'm new to CFD and I couldn't find any solution with the Gambit tutorials I looked. My problem is that I have an open channel where water is flowing to a container. Here is very simple picture about it

http://img14.imageshack.us/img14/2968/channelt.png

The flow is surrounded by three walls and air where atmospheric pressure is acting. I'm having problems how to mesh the system (channel + container) 3D grid. I would appreciate any comments, thanks in advance.

what kind of problems?

I am living in thought that only closed volumes can be meshed. My channel is open to air on its one face so how can I mesh its interior? Is multiphase flow (water and air) the only solution?

you need definitively a closed volume.
Yes Multphase flow

Would this solution work:
I'll set to the boundary conditions that the three walls are stationary and on the fourth wall, there is no shear stress

you are talking about the fluent side (BC etc...) and you can open a new thread in the right subcategory (I don't have any experience with open channel) , but you need first a 3d mesh

open cahnnel flow
 

You need a "volume : brick" to assign the computational domain. You can try applying "wall" BC at 3 sides and "Pressure outlet" on the top surface and provide atmospheric pressure condition over there.

For IN, you can use "mass flow inlet/velocity inlet" & for OUT...."outflow" BC.

For open channel flow, you need to use VOF multiphase model to track air/water interface.

Hi;
The best B.C for upper side of an open channel is "symmetry".
that also helps the free surface level change automatically.