The time-averaged velocity profile near a wall collapses to a universal form in wall units:
Where u⁺ = u/u*, y⁺ = y·u*/ν, κ ≈ 0.41 (von Kármán), and B ≈ 5.0 (smooth wall).
The log layer spans the "overlap region" between viscous and outer scales — it is one of the most robust results in turbulence. Velocity fluctuations in this region scale as u'rms ∝ u*.