Yplus and wall functions for an airfoil
 

Hi guys!
That's my first time here, and I'm pretty new on CFD, thus I'll probably ask you something really basic.
I'm actually dealing with RANS simulation of a flow over an airfoil, with a Reynolds number of 300'000. I need to analyze the behaviour of lift and drag coefficients at changings of the angle of attack, from 0° till about 13°.

Now my problem is about the Yplus, the heigth of 1st cell and the wall functions. I know that i have to choose a certain value of Yplus to obtain the 1st cell spacing. People told me to choose Y+ = 1 but, with my data, the spacing ends up to be really small (about 0.03 mm), creating a too dense mesh. I've red that using wall funtions could avoid this problem, allowing you to use a higher value of Y+ (i guess i understood that these functions assume true the logaritmic law of the near-wall velocity)

Now my questions are:
-Which is the wall function i should use for this problem?
-therefore, what Y+ do i have to take?
-if i can use higher y+, will i miss information about the pressure coefficients?

Hope you can help !!:D

You don't really have much of a selection to choose any wall functions.

Only thing I'll say is that if you're using kwSST or k-omega models then your y+ had better be close to 1. For k-epsilon based models, enhanced wall treatment is wayy better than standard wall functions and is probably a good place to start. Most if not all of the wall functions used in Fluent are blended wall functions so you don't have to worry about getting a large enough y+ to make sure the log law is being used. Just make the mesh as fine as you can afford and let it crank.

Thanks for the answer !

Do you think k-epsilon is a good model to predict the pressure coefficients on an airfoil with a mesh C-type?
I have to calculate them till the stall, and i don't know if k-epsilon works good when the boundary separation happens.

Moreover is it possible to see the flow ricirculation with the k-epsilon? cause I've done some tries with high angles of attack and it doesn't seem to appear on the graphic animations (With an y+<10 on the mesh).

Thanks !