Models based on dynamical features of the wall layer

Recent experimental and theoretical results related to the turbulence production process near a wall are reviewed. It is argued that the principal element of boundary-layer turbulence is the convected hairpin vortex and that bursting of the wall-layer flow is a viscous-inviscid interaction provoked by the adverse pressure gradient due to the vortex. The consequences of this picture for the development of models for the mean near-wall flow are discussed. Recent models for the mean . wall-layer velocity profile, in both two-and three-dimensional boundary layers, which are based on the dynamical picture presented here, are reviewed