Analysis of three-dimensional structures in boundary layers

A perturbation scheme, based on the simultaneous expansion of primary and secondary modes, is used to study the prebreakdown flow field. Results of the analysis are in good agreement with experiments for amplitudes in excess of 5 percent. For peak-valley splitting, the analysis captures the development of the high shear layer associated with breakdown. Subharmonic modes evolve differently, with the region of high shear concentrated near the wall.