Y plus for a fuel rod bundle.

Forums code_saturne usage
1

Hi again everyone,
I would just like some clarification on something. I am working on a fuel bundle, and I am unsure if I calculated my y plus value correctly. I used an online Y plus calculator that my peers advised me to use.
http://www.pointwise.com/yplus/

https://www.nuclear-power.net/nuclear-engineering/fluid-dynamics/internal-flow/hydraulic-diameter-2/

In regards to the reference length, when looking through code saturne documents it talked about the hydraulic diameter.

https://www.code-saturne.org/cms/sites/default/files/file_attach/BPG/BPG-3-Cell-Size-At-The-Wall.pdf

https://www.nuclear-power.net/nuclear-engineering/fluid-dynamics/internal-flow/hydraulic-diameter-2/

I used this value as the reference length for calculating my y plus. Is this correct?

2

Hello.
This reference length is an approximate boundary layer length (I believe, in streamwise direction). It’ doesn’t affect required first cell height much so it’s not critical. Just check the Y+ after the calculation and ensure that it doesn’t exceed 2…3 in the area of interest and that it’s not too low (like 0.1 or lower).