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-   -   Y+ adaptation problem- FLUENT (http://www.cfd-online.com/Forums/fluent/90799-y-adaptation-problem-fluent.html)

aggie July 21, 2011 01:07

Y+ adaptation problem- FLUENT
 
I want to keep y+ below 10 in a k-epsilon turbulence model flow analysis. The flow domain is the gap between the rotating shaft and the outer casing. I did meshing using hex/cooper and my initial mesh number is 385k nodes. The problem is when I want to do the y+ adaptation, I end up with a total mesh number of more than 5 million and the y+ is still far higher than 10. It seems that if I want to make it below 10, I will need around 10 million nodes which will make it almost impossible for me to continue performing simulations.

Any idea about how to keep y+ below 10 without having millions of nodes?

sail August 1, 2011 04:29

Quote:

Originally Posted by aggie (Post 316862)
I want to keep y+ below 10 in a k-epsilon turbulence model flow analysis. The flow domain is the gap between the rotating shaft and the outer casing. I did meshing using hex/cooper and my initial mesh number is 385k nodes. The problem is when I want to do the y+ adaptation, I end up with a total mesh number of more than 5 million and the y+ is still far higher than 10. It seems that if I want to make it below 10, I will need around 10 million nodes which will make it almost impossible for me to continue performing simulations.

Any idea about how to keep y+ below 10 without having millions of nodes?

the y+ adaptation is really expensive in fluent because it will divide each cell in 4 (8 in 3d). your best chance is to start again with a mesh that has a first cell height more closer to the value you want and refine only where the flow accelerate for some reason.

Elio September 11, 2013 18:59

Dear Vieiri,

I am modeling a 3D case of a vertical axis wind turbine. As you said I calculated the first layer however i got a y+ value of 708 after 1 complete rotation of the turbine!!! It's a complete mess. I need a y+ value of 1. I already have 11 million elements. Do you think the solution has not converged completely yet? Or is there any other way? Please advise


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