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  3. Surface roughness and y+

Surface roughness and y+

    • November 16, 2023 at 1:24 pm
      Lisa Svensson
      Subscriber

      Hi!

      I have added surface roughness into my k-omega SST model, and I'm unsure about how to interpret the y+ value. For a smooth pipe, it should be around 1, and with the added roughness I can't get it below 20. I've tried searching online, but I can only find information about wall functions, not specifically for being in the viscous layer.

      I would greatly appreciate some insight into this or if anyone knows where I can find information about this! 

      Thanks!

    • November 17, 2023 at 2:29 pm
      Federico
      Ansys Employee

      y+ is shifted when surface wall roughness is introduced, making it difficult to reach values near y+~1.

      You can read on this here: 7.4.15.3.1 Standard Law-of-the-Wall Modified for Roughness (ansys.com)

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