[prasantasarkar]

Hello,

I am trying to predict the lift and drag coefficient of a NACA 23012 airfoil with gurney flaps. I am having problems at higher angle of attack and the solution keeps oscillating. I believe the problem is due to stall and flow separations. My y+ value is within the range of 1. Kindly suggest what kind of turbulence model can attain convergent solution.

[gfoam]

At HAOA no one turbulence model can give you a converged solution, if you have a large areas of separated flow. Is there some formulation that can give a converged solution such as PseudoTransien formulations and others, But the fenomena of flow separation at HAOA may be an unsteady one, so you must use the transient solver.
Regarding to the turbulence model, I recomend you to use the SSTkw or RNGke, but I don't think you can get a acceptable value of Cd, only within a 30% error not less. Also you have to use high orcer schemes of discretization of second or third order. Regards.
Gonzalo

[prasantasarkar]

Dear Gonzalo

Thank you for the reply. I am using second order discretization schemes for the solution. I had tried out using transient solver but not getting proper convergence or solution. Would try out some other methods. kindly let me know if you have any other suggestions.
Pras

[gfoam]

Mmm, also there is the problem with the mesh and its resolution. Try using diferents meshes with different number of points on the surface and see what results you get. Always try to keep the y+)1 and the growth rate of the boundary layer mesh less than 1.15. Also, make sure you are resolving the entire boundary layer within the BL mesh. And, well its a matter of experience and trial and error until you became confident with your results and methods. Regards. Gonzalo