Fluids

Fluids

Y+ for K omega SST in a micro channel with surface roughess not coming out.

    • jonheb
      Subscriber

      Hi there I was wondering if you could help me out with a similar problem.


      I am modelling a micro channel with k omega SST turbulence and there is a constant heat flux also added at the wall of my micro channel. 


      I have modelled the micro channel as a smooth flow initially and have been getting a Y+ of 1 for Reynolds of 40k approx., but when I add a roughness ks of 9.84e-5 the Y+ is now 200+. I don't understand what I need to do in order to get it back to Y+=1 again, I have played with the bias of the mesh and tried increasing the number of cells but very little happens.


      I am trying to see the sublaminar layer in so that I can see the effects of heat transfer.

    • Raef.Kobeissi
      Subscriber

      hI,


      Adding wall roughness does affect the Y+ Value. To understand the relationship I advise you to read the documentation.


      Regards


       


       

    • mdfaizan444
      Subscriber

      hey, i am working in a wavy channel in which i want to calculate y+ value... i tried to calculate from your website but it requires boundary layer length that i not know.. so plz help me regarding this.  And also how to calculate the Nussult number in 2D flow, like as 3D flow will it be calculated from area weighted average?

    • DrAmine
      Ansys Employee

      For channel there is some other correlations to get the friction factor. Check the blog of our partner: https://www.computationalfluiddynamics.com.au/tips-tricks-cfd-estimate-first-cell-height/


       


      For your other questions please create a new thread.

    • LorenzoMazzei
      Subscriber

      hI,


      Adding wall roughness does affect the Y+ Value. To understand the relationship I advise you to read the documentation.


      Regards



       Actually, the virtual wall shift approach should change the y+ value given the ks+ value. At that point the shear should be calculated depending on the new y+ value, using wall integration or wall function. Am I right?

    • DrAmine
      Ansys Employee
      Yes.
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