abt k-ep and viscous sublayer

AMV

I first apologize for asking a very preliminary question in this forum of high intellect people. The Q is: In k-epsilon model , obtaining formular for G , epsilon ( source and sink terms of k equation ) at the "wall adjacent cell" is easy if ypplus > 11.63. If ypplus < 11.63 , then we can calculate tau_wall from linear profile and then calculate G = tau_wall * up/yp where up = vel parallet to wall and yp is normal distance of first point from wall. But how to calculate epsilon ? which goes as the sink term of the K equation and also which is needed for giving wall b.c. for epsilon equation. Actually to get the asymptotic variation of epsilon at wall , I used epsilon = 2*nu*tke/y^2 but it fails. Can somebody help ? THANKING you !