The structure turbulence near walls

Resumen

The study of turbulence near walls has experienced a renaissance in the last decade, largely because of the availability of high-quality numerical simulations. The resulting emerging models for the viscous and buffer layers over smooth walls are briefly reviewed. It is shown that these near-wall layers are essentially independent of the outer flow, and that there is a family of numerically-exact nonlinear structures which account for about half of the energy production and dissipation in the layer. The other half can be modelled in terms of the unsteady bursting of those structures. Many of the best-known characteristics of the wall layer, such as the dimensions of the dominant structures, are well predicted by these models. It is also noted that as much as two thirds of the friction coefficient in wall-bounded flows at moderate Reynolds numbers depends on processes below y+ = 50, and that this fraction decays only logarithmically when the Reynolds number increases