Learning Forum

[Lisa Svensson]

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!

[Federico]

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)