Non-parallel stability of boundary layer flows

Abstract : The spatial stability of two-dimensional incompressible boundary-layer flows is analyzed by using the method of multiple scales. The analysis takes into account the streamwise variations of the mean flow, the disturbance amplitude, and the wavenumber. The theory is applied to the Blasius and the Falkner-Skan flows. For the Blasius flow, the non-parallel analytical results are in good agreement with the experimental data. The results show that the non-parallel effects increase as the pressure gradient decreases.