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IBC August 3, 2021 15:00

Y-plus value for turbulent models
 
Hello,

What is the recommended y-plus value for the standard k-epsilon model?

rupak504 August 4, 2021 21:51

Y+ is a non-dimensional distance from the wall to first node of your mesh, which is required by your turbulence model to clearly define the boundary layer region. Having said that, the correct value of Y+ depends on many factors, such as flow behavior, Reynolds number etc...., If you are not sure about the Y+ value, you can start with a safe value i.e. 1, keep in mind that, this affects your computational expense and time, and then if its overkill, you can increase it in your future simulations.

EleGiova August 7, 2021 15:01

Hi, what I understood and studied if you are using k-epsilon models you can either use a Low Reynolds or a High Reynolds approach.


If you are using a Low Reynolds approach that means you are supposed to have a yplus = 1 more or less, so you have to use a two layers treatment of the wall such as Enhanced wall treatment (you find it in the drop down list).

If you are using a High Reynolds approach you must have a 30 < yplus < 500 and can use the wall function as standard, scalable etc.


You can have a look here for this kind of theory: https://www.afs.enea.it/project/nept.../th/node98.htm .

Anyway what I suggest you to do is that of calculate an esteem of the yplus based on your case dimensions (https://www.pointwise.com/yplus/index.html), start from this and do some stationary calculations (like 50 iterations something like this) and plot the yplus (xyplot - turbulence - wall yplus) and see if you are on the range you expected.

Hope this will help,
E.G

EleGiova August 7, 2021 15:02

Ps. I don't recommend to use standard k-epsilon model, much better RNG or realizable.


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