Y+ range suitable for a 650000Reflow of an airfoil

Johari Gregorio

I'm working on a 2d airfoil profile (s809). I have to obtain the curve of Cd and Cl for different flow directions (from 0 to 90°)...

I realized that a single-mesh approach doesn't give good results so I decided to make meshes for 3 different range of angle of attack. Following the advices I found in this forum, I've tried to obtain a Y+ in the range of 100 - 300. I'm using a K-E model realizable with a non uniform wall function approach. I've set the convergence criteria as 10-6 for X and Y velocity and 10-3 for continuity, K and E.

The problems I faced concern the range between 55° and 90°, in which the fluent does not reach the convergence. I reduced the defoult relaxation factors but it didn't change the situation: the residual are always fluctuating!

Same question:

1)Is it right the Y+ range of 100-300 for a 650000Re flow?

2)does the no-convergence depends on the mesh?

3)what should I do to have the convergence beetween 55° and 90°

To achive an optimization of the result in fluent, when I get the convergence I use the option Adapt>>Y+ fixing the range 100-300. After the adaptation, the mesh is refined where required and I use to iterate again and get again the results of Cl and Cd..what do you think about this approach?is it a good one?

really thanks for all whom can help me

Johari (getting 3years-degree in mechanical engineer)