[Tingyun YIN]

Hi, everyone,

I have several questions about the near wall treatment for SST in CFX. As known, automatic near wall treatment uses the blending function between wall function and Low-Re to modify w equation. Here are some questions:

1. When I check the value of solver Y plus, it is different from Y plus. However, in the definition of solver Y plus, as shown in 01.png, it uses the same wall distance of the first wall point. Why it is different when I check the post?

2. Regarding the blend between the analytical expression for w in the logarithmic region, as shown in 02.png, what is the definition of u*?

3. In my case, the geometry is very complicated. Y plus varies from 0 to 50. So, How the automatic near wall treatment works? At higher Y plus areas, wall function dominants. At lower Y plus areas, Low-Re dominants. As shown in 03.png, square root is used with two expressions. I mean the blending function works smoothly. We can't claim only Low-Re works but dominants at low Y plus areas. For example, we cannot claim that when we keep Y plus under 11.06, only the Re-low will work. We can say that Re-low dominants, because the value of w(log) is smaller than w(vis). The more smaller the Y plus, the more effect the Re-low will make.

4. If I understand the Help Document correctly, the wall function used in the blending is the Standard Wall Function?

Any comments are appreciated.

[Tingyun YIN]

After checking the previous posts in this forum and ANSYS help document, I still don't get any satisfied answers. Any comments?