Fluids

Fluids

Velocity Profile

    • Ann
      Subscriber

      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
      Subscriber
      What is the velocity profile input that are you providing to Fluent?
    • Ann
      Subscriber
      Thanks for your reply. I've attached the first few readings


    • Karthik R
      Administrator
      Hello:
      Can you create a xy plot in Fluent and check what you see after you read your profile file?
      Karthik
    • DrAmine
      Ansys Employee
      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
      Subscriber
      Hey, that's what I am getting for the velocity at the inlet


    • DrAmine
      Ansys Employee
      Can you please add the screenshot of the inlet BC?
    • Ann
      Subscriber

    • Ann
      Subscriber


    • Ann
      Subscriber
      H


    • Ann
      Subscriber
      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
      Ansys Employee
      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
      Subscriber
      Sorry can you illustrate more on how to set the direction to be normal?
    • DrAmine
      Ansys Employee
      You change the velocity specification method to "Normal to Boundary".
    • Ann
      Subscriber
      Yes, I have tried that before but unfortunately still getting the same results.

    • Ann
      Subscriber
      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
      Ansys Employee
      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
      Ansys Employee
      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
      Subscriber
      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
      Ansys Employee
      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
      Subscriber
      Now I got the velocity plot, however, the contouring and velocity vectors got missed up with changing the Y.




    • DrAmine
      Ansys Employee
      In the xy plot select Y for Y Axis.
    • Ann
      Subscriber
      Does that what you mean?


    • DrAmine
      Ansys Employee
      No.
    • DrAmine
      Ansys Employee
      Y axis select mesh then Y coordinate
    • Ann
      Subscriber

    • Ann
      Subscriber
      Here is what I got




    • Rob
      Ansys Employee
      Please show the velocity contour on the inlet, local range and node values off.
    • Ann
      Subscriber
      Hey Rob I have attached a pic



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



    • DrAmine
      Ansys Employee
      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
      Subscriber
      Thank you so much . I finally managed to get the results right. I appreciate your help!
    • DrAmine
      Ansys Employee
      Great
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