Book Description

A nonlinear theory of turbulent coherent structures near walls has been developed based on the assumption that the eddies are flat, with large horizontal dimensions compared to their thickness. Turbulence in the outer part of the boundary-layer may be modelled as a linearly driven system with nonlinearities confined to the near wall region. A new model for near wall turbulence based on the concept of an instantaneous mixing length gives a mean velocity profile valid from the wall to the beginning of the log region. The effect of Large Eddy Break-up devices on the boundary layer was modelled as a wake deficit. The wake acts as a barrier to structures crossing the wake. Measurements of the skin friction behind LEBU's using a variant of the Stanton tube are in agreement with other techniques. Keywords: Turbulent boundary layer; Boundary layer control; LEBU(Large Eddy Break Up); Eddies(Fluid Mechanics), Structural properties; Boundary layer transition; Active walls; Flexible structures; Shear stresses; Drag reduction.