摘要：

A technique for the analysis of the evolution of wave disturbances in plane-parallel flows of the boundary-layer type is proposed. This method is equally suitable in regions of linear, weakly nonlinear, and highly nonlinear flow evolution. Using this method, the relative efficiency of parametric excitation of background subharmonic pulsations by a primary wave with linear and nonlinear critical layers is studied. A decrease in the rate of parametric growth of subharmonics in the field of a strong wave is found. Threshold amplitudes for the formation of various types of transition in the boundary layer are measured. It is shown that the S- and K-transitions are related to regimes of weakly nonlinear evolution and nonlinear critical layer of the primary wave.

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