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Duc_Hoang

(Solved) Turbulence model and Y+ value

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Hello expert,

I am new to CFD and i have some questions about turbulence model and Y+ value.

  1.  There is a lot of turbulence model provided in AcuSolve: Spallart Allmaras, K-epsilon, K-omega,...
    - So which model should be used for some specified case?
     
  2.  The value Y+ is used to determined the "first cell height" while meshing.
    - what is the value of Y+ should i used to calculate "first cell height"?
    - Does it depend on type of flow (internal/ external) or chosen turbulence model?
     

the following picture was taken in HyperMesh > Utility browser.

image.png.fbbf55af85566a986c05d8be1ee8b7ad.png

 

Thank in advance!
Best regard!

 

 

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Hi,

The y+ value depends upon the accuracy of solution required in the near wall region for your simulation and also the turbulence model chosen. Spalart-Allmaras, the standard acusolve wall function, can handle y+ values below 300.

 

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26 minutes ago, Nimisha Srivastava said:

Hi,

The y+ value depends upon the accuracy of solution required in the near wall region for your simulation and also the turbulence model chosen. Spalart-Allmaras, the standard acusolve wall function, can handle y+ values below 300.

 


hi Nimisha,

Thanks for your detail answer.

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You'll achieve better accuracy with lower Y+ values - at the cost of more mesh and longer simulation runtime.  For example, you'll typically get a more accurate solution with Y+ = 20 than you would with Y+ = 100.  However, maybe the level of accuracy at Y+ = 100 is enough for your purposes.  That's where it becomes 'engineering' instead of just running a simulation.  You can run a mesh sensitivity study to see how the solution of interest changes as you modify the meshing parameters.

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