Learning Forum

[Anadi_Mondal]

Hello,

In the first model, I am using uniform velocity as input to get a parabolic velocity at the outlet. Then use this velocity profile in UDF as input for the second model. Actually, I need this velocity profile(PARABOLIC PROFILE) to write the mass source term in UDF for the second model.

Could anyone give me an idea of how can I implement this in ANSYS?

While I was searching online about it, I got a source where they wrote velocity profile as follows:

F_CENTROID(pos,f, tf);

vap_vel = 0.6543*pos[2]*pos[2]*pos[2]-7.706*pos[2]*pos[2]+ 32.44*pos[2]-28.95;

[here I just write 2 lines because I understand other lines but am only confused with vapor profile]

Here F is the outer surface (face) of a tube in 3D, and the flow is in the Z direction(Axial axis is Z). Could anyone tell me how the velocity profile equation can be a function of pos[2] while the flow is in the Z direction?

Regards,

Anadi

[Amine Ben Hadj Ali]

You can write profile from first run and use it at your inlet in the second run.
You can discard the first run and just crate a parabolic velocity profile in the second run using Fluent Expressions or DEFINE_PROFILE UDF. I do not understand the part with the source terms.

[Anadi_Mondal]

I don't know the velocity profile(equation) yet. Is it possible to get/derive the equation of parabolic velocity profile from the first model using uniform velocity at inlet?
Actually, I need to use the above velocity to write a UDF (Ex. mass source).
I got an example online where they wrote the velocity profile in the second model as,F_CENTROID(pos,f, tf), vap_vel = 0.6543*pos[2]*pos[2]*pos[2]-7.706*pos[2]*pos[2]+ 32.44*pos[2]-28.95;
I am not sure how they wrote velocity profile as a function of Z coordinate(pos[2]) when the flow is in Z direction. Here F (face) is the tube outer face in 3D. Is it possible to express velocity profile as a function of pos[2] ?
Regards Anadi

[Amine Ben Hadj Ali]

Parabolic Velocity Profile does not require a lot: just the mid-line / poitn where the velocity is the max and the mean velocity.
I do not know the source of your example and I cannot comment on it. You can express your profile as you want to express. Fluent User's Guide has an example how to define a velocity profile. Similar can be done via UDF.

[Anadi_Mondal]

The profile you gave is for laminar flow. Actually, I will easily get a velocity profile for laminar and turbulent flow from any fluid mechanics book. I have no problem here.
Will you check the flowing UDF that I got online? Will you give me an idea of how can we write the velocity profile this way? Usually, velocity is changed along the radial axis, but here pos[2] is the axial coordinate.
Here, the loop is over the outer surface(face) of a 3D tube and the flow is in the axial Z direction.

Regards Anadi

[Amine Ben Hadj Ali]

Perhaps the one who wrote the UDF his Pos[2] is in his radial direction. Just adjust to your need.