FORMATION OF SOLITONS IN TRANSITIONAL BOUNDARY-LAYERS - THEORY AND EXPERIMENT

This work brings together experimental and theoretical studies of nonl inear stages aimed at the K-regime in boundary-layer transition, and s ome combined theoretical and experimental results are discussed. It is shown that the initial stages in the formation of so-called spikes, o bserved in many experiments, may be described very well by the asympto tic theory. These flashes-spikes are shown to be (in certain regimes) possible solitons of the boundary layer and governed by the integral-d ifferential Benjamin-Ono equation. Properties of the spike-solitons, o btained both theoretically and experimentally in the quasi-planar stag es of their development, are presented. Features of the disturbance be haviour connected with the subsequent development of three-dimensional ity are also discussed, as are the effects of viscosity and shorter le ngthscales. The main conclusion of the work concerns the hypothesis of the possible soliton nature of the flashes-spikes (within limits), wh ich seems reliably corroborated by the good agreement found between th e theory and the experimental data.