Topics relate to Fluent, CFX, Turbogrid and more

LES variable clarification

    • Alek Nino

      I would like to know the equations that relate mean and RMS velocity components. I have found some other posts that relate the variables but are pretty old and wanted to confirm ANSYS's relation specifically. If someone could share the relations or a link to ANSYS documentation that would be great. 

      The specific names of the variables in CFD Post in question are:

      Mean X Velocity, Mean Y Velocity, Mean Z Velocity

      RMS X Velocity, RMS Y Velocity, RMS Z Velocity

      Velocity u, Velocity v, Velocity w

      My goal is to use these variables to calculate the turbulent kinetic energy and turbulent intensity and I also want to confirm that I am using the right variables to display my velocity contours. 

      Thanks in advance!

    • Federico Alzamora Previtali

      Hello Alek, 

      Velocity [u,v,w] is the instantaneous resolved velocity -> Ui;

      Mean Velocity [u,v,w] is the time averaged resolved velocity -> {Ui}^bar

      RSME Velocity [u,v,w] is the fluctuating velocity -> Ui'


      Ui = {Ui}^bar + Ui'


    • Alek Nino

      Thank you for your response, but is the RMS velocity the same as RMSE or do I need an additional expression to obtain RMSE. A previous post that answered this question wasn't very clear to me so some clarification would be great. From what I understand, if they are different, then is Ui' = SQRT(U_RMS^2), where Ui' is the RMSE velocity.

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