Learning Forum

[prabu]

Hello,

How should one select Y+ value in meshing for a open channel problem.

1. A video by Raef https://www.youtube.com/watch?v=kecgPw-VmPU   Shows that y+ values kept well below 1 for a flat plate problem.

however, in a literature "A three-dimensional flow model for different cross-section high-velocity channels" by abdulla, it is mentioned a range of 30

Is there any rule of thumb for selecting a  Y+ values. 

Thanks

PRABU

[DrAmine]

If you want to resolve the viscous sublayer then you need to sick to yplus < 5 (Low-Re). If you do not want that you have to yplus>30 (High-Re). In that range the log-law of wall will be deployed to provide suitable  b.c' s at the wall. The linear profile in the vissoucs sublayer and  logarithm profile in the inner turbulent layer are not good in the buffer layer: The linear law would have 20% deviance from results there (buffer layer 5

Actually Fluent provide for Epsilon and Omega based approaches an automatic wall treatment which would blend between both approach (low-Re and High-Re approach) based on cell wall distance or turbulent Reynolds Number.

 

[raul.raghav]

If you want more information regarding the y+ values and different near wall treatments, please refer to:

/forum/forums/topic/neat-wall-tratment/

[prabu]

Hello,

Many thanks Amine and Rahul. 

Thanks

[DrAmine]

You are welcome. If you think this issue is resolved please do not forget to mark it as such

[José Mantovani]

 You can also use a y+ calculator in web, to calculate the y heigth of the cells adjacent to wall. In the link below, have a y+ calculator that make the calculations with the condition of you are using FLUENT.

https://www.computationalfluiddynamics.com.au/tips-tricks-cfd-estimate-first-cell-height/

Hugs,

Mantovani.