摘要：

We numerically solve the governing partial differential equations to study nonlinear evolution of crossflow disturbances in incompressible as well as compressible boundary layers. When the amplitude of these disturbances become sufficiendy large, the flow field becomes highly inflectional and unstable to high-frequency oscillations (secondary instability) which lead to breakdown to turbulence in three-dimensional boundary layers. Using the 2D eigenvalue approach, we consider secondary instability of crossflow vortices in swept-wing flows, discuss their structure and the associated production mechanism. The results for a swept-cylinder show the existence of secondary oscillations of about 17 kHz yielding good agreement with the experiments of Poll (1985). Calculations for a supersonic boundary layer show secondary oscillations approaching frequencies of 1 MHz.

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