# 2D Airfoil modeling using Spalart Allmaras Model

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 April 15, 2010, 05:54 2D Airfoil modeling using Spalart Allmaras Model #1 New Member   Mahbub Islam Join Date: Mar 2010 Location: Bangladesh Posts: 24 Rep Power: 14 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.

 April 15, 2010, 11:42 #2 Senior Member   Join Date: Nov 2009 Posts: 411 Rep Power: 18 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. Do

 April 15, 2010, 12:49 #3 New Member   Mahbub Islam Join Date: Mar 2010 Location: Bangladesh Posts: 24 Rep Power: 14 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.

 April 15, 2010, 14:51 #4 Senior Member   Join Date: Nov 2009 Posts: 411 Rep Power: 18 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. Do

 April 16, 2010, 00:08 #5 New Member   Mahbub Islam Join Date: Mar 2010 Location: Bangladesh Posts: 24 Rep Power: 14 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.

 April 16, 2010, 00:14 #6 New Member   Mahbub Islam Join Date: Mar 2010 Location: Bangladesh Posts: 24 Rep Power: 14 Hello DoHander , my mail id : mahbub.me.buet@gmail.com

 Tags naca2412, spalart allmaras, turbulence, turbulence model