Cannot Calculate u+ using Custom Field Functions

    • Mitchell Durbin


      I am doing a project related to turbulent flow boundary layers. I am attempting to calculate u+ so that I can make a plot of u+ vs. log(y+) along a line normal to a nozzle wall.

      I have defined u+ in the following way:

      However, a contour plot of u+ in my domain shows that u+ is zero everywhere.

      I suspected that perhaps either the velocity magnitude, wall shear stress, or density are also zero everywhere, but that is not the case:

      Interestingly, the following custom field functions also resulted in a contour of zero everywhere:

      And, the following custom field function resulted in nan everywhere.

      Clearly there is something going wrong in the custom field functions when "wall-shear" is involved. However, as mentioned above, the wall shear stress itself is NOT zero anywhere.

      How can correctly define u+ to avoid this issue?

    • Rob
      Ansys Employee

      Wall shear is technically zero on your contour as it's calculated on the wall. You're displaying on the fluid domain. 

    • SRP


      Try to create custom function for u_tau then u/u_tau.


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