[hamidciv]

hi dear all I'm working on a project with one of my friends i do making geometry and the mesh, but I did have problems in the ansys cfx settings , i attach picture of my model in pdf file.I have modeling a flip bucket spillway for compared numerical and experimentaldata, According to the experimental data My goal here is to for Q=600 verified my model, but according Q=VA, basing experimental data in inlet section with depth and velocity with value( D=1.01, b=33.88, v=27.68) my Q is equal to Q=947, because inlet section input after aeration , I think the inconsistency Q due to the high amount of mixing water and air in model.
My problem is the definition of the volume fractions of water and air , note that I read free surface flow over a bump but in this model inlet and outlet At a high level were not,How do I define VOLUME FRACTION UP AND DOWN ( WATER AND AIR)?
whether to achieve the flow rate(Q=600) at the inlet based on experimental data?
I'm so confused and do not mind learning theory, Friends if you have any advice please tell me
Thanking you in anticipation.
regards

[ghorrocks]

Are you sure your inlet condition is appropriate? You have not included the losses associated with the entrance to the spillway.

[hamidciv]

hi glenn horrocks , thank you for taking time for me
I considered inlet section in L point , that drawn in attached image, i have completed data for L point( i.e velocity, pressure, depth) ,that i selected velocity and depth in inlet section, but discharge(Q) according experimental data for Q=600 with experimental data for L point Is inconsistent, note that my experimental data is valid, I asked my question of teacher, he says because of the mixing of water and air in the model. with information data in inlet L point my discharge obtain Q= 947, Now the situation , how define volume fraction in model?

Thank you for your attention

[hamidciv]

excuse me, i forgot attach my image in previous post

[ghorrocks]

I am no expert in spillway design but most the spillways I have seen are very aerated when they discharge. This means a homogenous free surface model is not going to work. You are probably going to need an inhomogenous model, but probably still with a free surface model. Then you can model the free surface, water and aeration of the water.

This approach makes it easy to define a volume fraction for the incoming flow. You just put the aerated bit in the aeration volume fraction.

[hamidciv]

You just put the aerated bit in the aeration volume fraction????
If it is possible for you, You mean to express more clearly. If you can explain a little more about the definition of the volume fractions, how define aeration volume fraction??
Unfortunately, none of the guys did not help me
thanks a lot for the time that I put.

[ghorrocks]

First of all - Do you expect the flow in the spillway to be highly aerated? I need to know if I am on the right track.

[hamidciv]

hi dear glenn horrocks, thank you for spending time for me.
as respects, i considered my geometry after aeration ramp, Unconscious a lot
of air entered in my flow, so my fluid volume increases that i think inconsistency Q is Resulting from aeration. So I think the impact of aeration must be considered.
thanks a lot

[ghorrocks]

In that case a homogeneous free surface model will not work. You will need an inhomogeneous free surface model like I describe in post #5.

So make sure you are famniliar with homogeneous free surface models (for instane the free surface flow over a bump tutorial) and inhomogeneous multiphase models (like the multiphase flow in a mixing vessel tutorial). I do not know of any inhomogeneous free surface model tutorials so you are going to have to work out how to combine them yourself.