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mahbub03 April 15, 2010 04:54

2D Airfoil modeling using Spalart Allmaras Model
I am trying to find lift and drag coefficient of NACA2412 airfoil using Spalart Allmaras (S-A) Model for Reynolds number 10^6. But the solution is not converging and calculated Cd and Cl values are far from actual one. I have checked y+ value in between 1~28.

Can anyone suggest me about improving convergence criteria for S-A model? or Any reading material related to using S-A model in fluent?

Is there any special tricks on meshing? or How I can modify mesh in fluent to improve convergence?

Thank you in advance. Waiting for reply.

DoHander April 15, 2010 10:42

y+ from 1 to 28 means your grid is bad. For Spalart Allmaras you need to keep your y+ less then 1 OR larger then 100. Using a grid with y+ from 1 to 100 will give you a bad solution.


mahbub03 April 15, 2010 11:49

Thank you DoHander.

Can you suggest me any procedure by which I can reduce y+ closer to 1.
I will be highly grateful for this help.

DoHander April 15, 2010 13:51

You can estimate the height of the first row of cells at the wall imposing an y+ of say 100 and providing the Mach and Reynolds numbers for your case. You have an y+ calculator here in cfd-online from which you can estimate what is the minimum cell height at the wall.


mahbub03 April 15, 2010 23:08

Thank you DoHander. I have tried with the calculator to calculate the cell height. Not yet successful.

Probably I have to take more care about mesh formation. If you have any 2D airfoil mesh you may share with me. That will be a great help.

mahbub03 April 15, 2010 23:14


DoHander , my mail id :

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