CFD Online Discussion Forums

CFD Online Discussion Forums (
-   FLUENT (
-   -   Mesh size for turbulence modeling (

villager July 16, 2012 15:17

Mesh size for turbulence modeling
Good day everyone!
I try to simulate fully developed turbulent flow (k-e RNG model, enhanced wall function because of 1<y+<5 in FLUENT y+ contours). But I have only two-three finite-volume cells at boundary layer, instead of 10-12. Is the last requirement strict and I've got wrong simulation results?

flotus1 July 16, 2012 16:19

With y+ around 1, it is highly recommended to have a sufficient number of prism layers to resolve the boundary layer.
If you only have 3 prism layers and y+ is around 1, then the prism cells only cover the viscous sublayer of the bondary layer.
The rest of the boundary layer will be poorly resolved and the results will suffer from the increased numerical diffusion in an unstructured mesh (assuming your mesh is not of the stuctured hexahedral type)

2-3 Cells might be ok when using scalable wall functions with y+ around 60, but not in this case.

All times are GMT -4. The time now is 05:51.