Three Dimensional Structure Of Boundary Layers In Transition To Turbulence

A unified theory of secondary instability in wall-bound shear flows has been developed. This theory rests on Floquet systems of stability equations and permits classification and quantitative analysis of different modes of secondary instability in the three-dimensional stage of laminar-turbulent transition. The catalogue of solutions is consistent with observations and predicts other phenomena that have not been identified in experiments. The theoretical results have been used to reproduce patterns in flow visualizations by computer animation. Analysis of the energy balance has shown a feedback loop between mean flow, two-dimensional, and three-dimensional disturbances that is considered key to the process of self-sustained transition. Various techniques have been developed to investigate details of the nonlinear three-dimensional processes involved in this feedback loop. Keywords: Boundary layer, Stability, Transition.