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-   -   how to adapt yplus,ystar?(standard wall function) (https://www.cfd-online.com/Forums/fluent/42610-how-adapt-yplus-ystar-standard-wall-function.html)

scott October 18, 2006 16:53

how to adapt yplus,ystar?(standard wall function)
 
how to adapt yplus,ystar? please give me the procedure i have read the manuel but no success best regards

sach October 18, 2006 23:06

Re: how to adapt yplus,ystar?(standard wall functi
 
hey there is no direct solution but the trial and error. the first guess of y +; you can have from miller's aproximation but again its try and hit. In practice normaly for small hydraulic diameters you try to resolve with 0.8 to 1 mm first layer and 1.2 growth and 3 layers in y direction normaly most of the problems get solved with this aproach let me know if it works sachcool80@gmail.com

MM October 19, 2006 01:43

Re: how to adapt yplus,ystar?(standard wall functi
 
http://www.cfd-online.com/Forum/main...cgi?read=44320


Ralf Schmidt October 19, 2006 04:54

Re: how to adapt yplus,ystar?(standard wall functi
 
Hi!

the difficulty in adapting yplus is, that fluent can only modify the cell size by spliting the cells in half or by removing nodes. So the yplus will be either half or about dubble the former value.

You can check that, when you display the grid close to the wall, than perform a yplus adaption and display the same view again.

Either nothing happens (because Fluent can not achieve the changes in cell size) or the valus are about dubbled or they are the half of the former valus.

So, use the suggestions from sach and MM the design your grid BEFOR exporting it into fluent.

Ralf


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