Regions of existence of discrete spectral modes in a Blasius boundary layer

The discrete spectrum of two-dimensional perturbations of the flow in a Blasius boundary layer is investigated. It is shown that, on the front section of the surface in the flow, there are flow regions where there are no modes of the discrete spectrum. On travelling downstream a Tollmin–Schlichting mode initially arises and then, successively, other modes that emerge from under the cut of the complex plane corresponding to a continuous spectrum of vortex waves. The regions of existence of modes in the plane of the parameters of the problem are determined.