Structure of turbulent boundary layers perturbed over short length scales

Research on the structure of turbulent boundary layers over undulating surfaces and large applied pressure gradients turbulence gives rise to some clarification of concepts (validity of logarithmic wall functions, and when equilibrium or memory effects are more important), approximate turbulence models, and better understanding of the accuracy of existing turbulence models (mixing-length, k-epsilon, and second-order). The aim of this paper is to describe a few of these developments and highlight recent developments.