(Solved) Turbulence model and Y+ value

Junta_20361

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.

 

Thank in advance!
Best regard!

 

 

Altair Forum User

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.

 

Junta_20361

Altair Forum User 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.

acupro

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.

Junta_20361

thanks Acupro,

very detail answer.
best regards!