Viscous sublayer
= Viscous sublayer
{title2=$\delta\sim\nu/u_*$}
{wiki}
The near-wall region where molecular momentum diffusion dominates turbulent transport. Using the <shear velocity> $u_*=\sqrt{\tau_d/\rho}$ gives the viscous wall length $\nu/u_*$. The precise extent depends on the chosen crossover criterion and wall condition. In this region constant stress and no slip give $U\simeq u_*^2z/\nu$; the logarithmic <law of the wall> applies outside it.