Y+

[EngAP]

I am having trouble understanding the use of Y+ when creating the boundary layer. I understand that it is important to ensure the boudary layer is detailed enough to capture the physics but also to use the minimum number of cells.

Could someone help me in my understanding of the use of Y+ to estimate the thickness of the first layer.

Thanks.

 

[cpinz]

The wall unit, Y+, has different values depending on which part of the boundary layer (b.l.) you are considering when investigating the wall region:
1) the laminar sub-layer (Y+ less than 5)
2) the blending region ( 5 < y+ < 30 )
3) the log-law region (30 <Y+ < 1000 ).

It's also related to the turbulence model chosen in a cfd analysis: for a turbulence model chosen , a preferable range of Y+ must be obtained , to consider valid the analysis. And what drives this range will be the size of the first cell adiacent to the wall.

Have a look the manual of the code that you use..it's always the first thing to do.

Cpinz