The Conditions Scheme of Near–wall Perturbations Development in a Hypersonic Boundary Layer

The conditions scheme of near–wall perturbations development in a hypersonic boundary layer under the non–stationary self–induced pressure is constructed. It is shown that the major factors forming the disturbed flow are: (1) the surface enthalpy value, (2) the viscous–inviscid interaction level and (3) the subsonic or supersonic kind of the boundary layer main part. It is obtained in the linear approximation that the increasing of the viscous–inviscid interaction level or the boundary layer supersonic main part influence leads to the upstream disturbances propagation weakening and to its downstream amplification. The decreasing of the viscous– inviscid interaction level or the increasing of the boundary layer subsonic main part influence have the inverse action. The surface cooling intensifies the influence of the boundary layer main part and the surface heating intensifies the influence of the boundary layer near–wall part. It is shown that the near–wall perturbations can travel upstream. 1