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-   -   What exactly is y+ /yplus and how to calculate it? (http://www.cfd-online.com/Forums/fluent/123147-what-exactly-y-yplus-how-calculate.html)

 Marabelle September 5, 2013 07:49

What exactly is y+ /yplus and how to calculate it?

Hello!
I am modeling a transient Heat-transerfer model with the k-kl-w method in FLUENT. I am quite a beginner and still try to understand the whole process. I heard/read lots of people talking about y+ and as I understood in my case I need an y+ around 1 to reach convergence. Did I understand it right that it has something to do with the near-wall grid resolution and the velocity at that place? But I have no idea how to calculate it or how to access it in ANSYS. And then, also how to change this value? Could anyone please help me?
Mara

 flotus1 September 5, 2013 09:41

The wiki has an article about Yplus:

http://www.cfd-online.com/Wiki/Dimen...e_%28y_plus%29

As you will notice, this dimensionless wall distance depends on the distance from the wall. In simulations of turbulent flows, the Yplus-values are obtained from the width of the first cell near the wall.
Accordingly, if you want to change Yplus for a simulation, you have to change your mesh.

 Marabelle September 5, 2013 17:14

Thanks for your very quick anwer! The post already cleared it a bit! But still I have to learn a lot more to understand fully, what I am doing when Simulating... respectively what to do to get good convergence...

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