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-   -   Any idea on how to obtain Yplus value for interior cells? (http://www.cfd-online.com/Forums/fluent-udf/99758-any-idea-how-obtain-yplus-value-interior-cells.html)

g0800276 April 11, 2012 02:00

Any idea on how to obtain Yplus value for interior cells?
 
Although C_Wall_Dist can calculate the distance between a cell and the nearest wall, we could not identify this wall and thus can not get the wall shear stress, which is required for the calculation of Yplus.

I have searched, through the entire google, for this problem without a solution. Do you have any idea to share with us?

Regards,
Joshua Zhu

Ati_CFD August 18, 2013 09:18

calculation of y+ for interior points?
 
Quote:

Originally Posted by g0800276 (Post 354108)
Although C_Wall_Dist can calculate the distance between a cell and the nearest wall, we could not identify this wall and thus can not get the wall shear stress, which is required for the calculation of Yplus.

I have searched, through the entire google, for this problem without a solution. Do you have any idea to share with us?

Regards,
Joshua Zhu

Quote:

Originally Posted by om3ro (Post 251529)
I'm trying to implement the Chien model with OpenFoam, but I have some general doubts on the description of y+.

The Chien model uses y+ for the definition of the damping factors.

Suppose to describe a 2D duct flow in with the following configuration:

HTML Code:

<pre>

    /\  y
      |
      |
      |
      ------------>  x

____________________________________________
->                                                                    ->
->                                                                    ->
->                                                    *            ->
->_________            _ ,      .________,*________->
                  |        |  |        |               
                  |____ _|  |___ __|


</pre>

y+ is defined as: y+ = (U_t * y) / nu

and U_t(x) = sqrt(tau_w(x) / rho)

y+, U_t, tau_w are functions of x!!!

It is necessary to define for each point (x,y) of the numerical domain the x coordinate in which define y+, U_t and tau_w.

An example:

In both points identified with " * ", tau_w must be evaluated in " , ".
But in the point " ", shall tau_w be associated with " , " or with " . " ?

Does anybody have experience on this aspect? What is the principle to adopt in this task?

Marco


Hi,
The Chien model uses y+ for the definition of the damping functions.
Does anybody have knowledge about calculation of y+ for interior points?

Best Regards,
AtiCFD


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