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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?
I would really appreciate your answers,
thanks in adveance!
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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