k-epsilon model with LBM

Sangit

Hi I am a novice in CFD. For my thesis I am implementing k-epsilon model for backward step. So for that reason I am using the the standard Launder and Spalding model with wall function. And I am assigning the boundary values at the first nodes from the wall for k and epsilon. Also I am initializing the initial value of k and epsilon at inlet.

The equation of the boundary values are at 1st nodes from wall : k=utau^^2*sqrt(c_mu) and epsilon=utau^^3/(kappa*delta)

How can i calculate the utau and y+ at the first node. I know that the initial values are valid if 20<y+<100 .And what will be the value of delta as it is the distance from the wall to the 1st node ... in my velocity mesh it is y=1 .... So i am confused .... how can I proceed .... any step by step calculation for utau , y+ and delta will be very much helpful ......