CFD Online Discussion Forums - Implementation of the Low-Reynolds-number Chien model

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:

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     /\  y

      |

      |

      |

      ------------>  x



____________________________________________

->                                                                    ->

->                                                                    ->

->                                                     *             ->

->_________            _ ,    °   .________,*________->

                  |         |  |         |                

                  |____ _|  |___ __|





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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