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-   -   Enhanced wall treatment and Enhanced wall functions (http://www.cfd-online.com/Forums/fluent/95766-enhanced-wall-treatment-enhanced-wall-functions.html)

Alina January 1, 2012 23:38

Enhanced wall treatment and Enhanced wall functions
 
Hello,

I'm reading the help of FLUENT_6.3.26 and now in the enhanced wall treatment section.

Here it says the enhanced wall treatment is available with k-epsilon and RSM while the enhaced wall functions are available with SA, k-omega, and LES, which means the enhanced wall functions are not available with k-epsilon. (right?)
But at the first part of the this section, it says the enhanced wall functions are used with coarse meshes and FLUENT can combine the two-layer model with enhanced wall functions.
So if I use k-epsilon model and choose the enhanced wall treatment, what will FLUENT choose when the meshes are not fine enough for the two-layer model which is employed in the enhanced wall treatment?

duri January 2, 2012 06:41

Enhanced wall functions/treatments are not for coarser mesh. Its for mesh size inbetween standard wall function Y+ and viscous sublayer y+. If there is a variation of y+ in this regime enhanced wall function can handle this.

BigBen January 3, 2012 19:48

Enhanced Wall Treatment: EWT is used to solve mesh with Y+ between 1 and 5
EWT is available with k-epsilon.
However, if your mesh is too coarse for this Y+ and your Y+ value is between 30 and 300 (please avoid between 5 and 30 for Y+) then EWT s like a simple wall treatment and start like the first point is outside of the exponential part of the Boundary Layer.

In 2 words, EWT is not taken into account if Y+ is over 30 even if the option is quoted. The solution will be less accurate but you 'll get a solution.


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