THE STRUCTURE OF THE NEAR-WALL REGION OF 2-DIMENSIONAL TURBULENT SEPARATED FLOW

The time-dependent structure of the wall region of separating, separated, and reattaching flows is considerably different than that of attached turbulent boundary layers. Large-scale structures, whose frequency of passage scales on the freestream velocity and shear layer thickness, produce large Reynolds shearing stresses and most of the turbulence kinetic energy in the outer region of the shear layer and transport it into the low velocity reversed flow next to the wall. This outer flow impresses a near wall streamwise streaky structure of spanwise spacing lambda-z simultaneously across the wall over a distance of the order of several lambda-z. The near wall structures produce negligible Reynolds shear stresses and turbulence kinetic energy.