Learning Forum

[Ann]

I have been supplied with an inlet velocity profile. The profile is supposed to be fully developed at the inlet, however, when I enter the velocity profile in my simulation it doesn't consider it as fully developed. Am I supposed to write a UDF for the velocity profile to be fully developed? Thanks in advance.

The first plot is what I get at the inlet

[aitor.amatriain]

What is the velocity profile input that are you providing to Fluent?

[Ann]

Thanks for your reply. I've attached the first few readings

[Karthik Remella]

Hello:
Can you create a xy plot in Fluent and check what you see after you read your profile file?
Karthik

[DrAmine]

Magnitude is not really you are looking for: verify in Fluent either as mentioned or by plotting the values at the Inlet using Profile Values. Something is definitely wrong.

[Ann]

Hey, that's what I am getting for the velocity at the inlet

[DrAmine]

Can you please add the screenshot of the inlet BC?

[Ann]

[Ann]

[Ann]

H

[Ann]

My inlet is velocity inlet
Outlet: pressure
The yellow side is symmetry
the other walls are set to be walls.
And I am trying to study the airflow around the cube

[DrAmine]

Are the x,y,z really the direction vector of the velocity? I think that is wrong. You should set the direction to be normal.

[Ann]

Sorry can you illustrate more on how to set the direction to be normal?

[DrAmine]

You change the velocity specification method to "Normal to Boundary".

[Ann]

Yes, I have tried that before but unfortunately still getting the same results.

[Ann]

The thing that I don't understand is that for the inlet velocity profile, Fluent considers only one velocity (Lowest magnitude velocity). Basically, it treats the profile velocity as a constant velocity. I am not sure does that means I have to write an expression for the inlet velocity profile, or it is something wrong with the inlet BC

[DrAmine]

Check your scales? The dimensions? I still think this is not Fluent error but user's error.
Sure one can create an Expression to have a parabolic or 1/n rule for velocity profile.

[DrAmine]

Also please check the format of Profiles in User's Guide. Try to stick to the format it requires: Comma Separated Values Files (Comma)

[Ann]

Sorry to confuse you. So when I enter a velocity inlet profile with a fully developed flow (as shown in the first pic plotted using excel), I am supposed to achieve it at the inlet without writing any expression?
Also the model that I took from the data in excel, should it be with the same dimensions as the model I am entering the data in?
Yes, I have made sure that it is csv. I have been trying to achieve the correct results for one month now, but I am not achieving the right results.

[DrAmine]

Your height coordinate is which direction? It seems to be in Y-direction. Your Excel-Sheet used negative Y values: now check the Y-values at your inlet.
One month on this issue is long time.

[Ann]

Now I got the velocity plot, however, the contouring and velocity vectors got missed up with changing the Y.

[DrAmine]

In the xy plot select Y for Y Axis.

[Ann]

Does that what you mean?

[DrAmine]

No.

[DrAmine]

Y axis select mesh then Y coordinate

[Ann]

[Ann]

Here is what I got

[Rob]

Please show the velocity contour on the inlet, local range and node values off.

[Ann]

Hey Rob I have attached a pic

[Rob]

You are going to see an acceleration over the blockage, and it's quite close to the inlet given the blockage factor. If you plot the last image of the previous page in the same way how does it look?
The profile looks like what I'd expect in an environmental flow (atmospheric boundary layer), if so, what did you set the sky as?

[Ann]

I have tried to set the top boundary to be wall and symmetry in both cases I am not getting the right results.

[DrAmine]

I have a feeling the profile is wrong as it does match to negative y values which you do not have in your inlet. So correct your profile.

[Ann]

Thank you so much . I finally managed to get the results right. I appreciate your help!

[DrAmine]

Great