Bispectral analysis of nonlinear processes in the hypersonic boundary layer on a porous cone surface

The results of the experimental investigation of the nonlinear stage of laminar-turbulent transition in the hypersonic boundary layer on porous and impermeable cone surfaces are presented. The bispectral analysis is applied to show that the porous surface suppresses the subharmonic resonance due to second mode disturbances. It is established that on the porous surface nonlinear processes develop more slowly than on the impermeable surface. This behavior indicates that the subharmonic resonance plays the role of a catalyzer in transferring energy from the mean flow to low-frequency disturbances in transition process, in much the same way as it occurs in a subsonic boundary layer.