scalable wall function, 3<y+<11
 

I obtain a wide range of y+ values (5-200) with a coarse mesh, realizable k-e and scalable wall function. And there is lots of y+ values (40 %) in the buffer layer, which is supposed to be pretty bad.

Is it a good idea to use scalable wall function and refine only the first layer of near-wall mesh in order to obtain 100 % of y+<11? Heat transfer will be included in the model eventually. I can't afford a fine mesh with y+<1 and 10-20 layers on the walls. Geometry is too complex and conditions are changing significantly in time, so adjusting the mesh locally is not an option either.

Thanks ahead for your suggestions

Hi,

I know it is a quite an old post but I find myself in exactly the same situation. What approach did you follow?

Cheers
Andrea

In the end I used enhanced wall treatment because it blends linear and logarithmic laws. From theory guide 15.0 section 4.14.5.2: This formula also guarantees the correct asymptotic behavior for large and small values of y+ and reasonable representation of velocity profiles in the cases where y+ falls inside the wall buffer region (3 < y+ < 10).

I was thinking to do the same. What do you reckon is the minimum number of prism layers to be used with this approach? I am aware that if you want to integrate NS equations up to the wall (i.e. EWT with first cell y+ at about 1) you need at least 10 cells within the boundary layer.

However this not the approach I am going to follow, since most of my cells are in the log layer (y+ of about 60) and I only have three prism layers. Is that enough with EWT? and with scalable wall functions?

Andrea

Hi all,

since (if I got it right) near wall analysis it's not a goal for you, maybe you could just coarsen the mesh in order to have y+>30 everywhere and then use the standard wf.