Boundary conditions - freestream vs fixedValue/zeroGradient
 

Hello,

I investigate airfoils and want to determine their lift and drag coefficients. Therefore I am testing different Turbulence models and solvers. So far I am using simpleFoam and pimpleFoam with kwSST and SpalartAllmaras.

After several attempts I am wondering what boundary conditions are the correct ones. So far I mixed them up a little bit. For example:

I used Freestream Boundary conditions for nut and fixedValue for nuTilda. As the result varies a lot I am wondering if always the same boundaries should be used on the patches. What I mean is for example:

nut nuTilda

Inlet freestream fixedValue
Outlet freestream zeroGradient
wall wallfunction wallfunction


Did somebody already discovered similar results? I haven't found alot on this topic in the forum nor in the userguide so any help is appreciated!!

Thanks a lot!