Effects of Porous Walls on Hypersonic Boundary Layers over a Sharp Cone

A theoretical linear-stability analysis is used to consider the effect of a passive porous wall on the first Mack mode of a hypersonic boundary layer on a sharp slender cone. The effects of curvature and of the attached shock are included for axisymmetric and nonaxisymmetric disturbances. The flow in the hypersonic boundary layer is coupled to the flow in the porous layer. The theoretical models of the porous walls developed in previous studies are used for regular microstructures and random microstructures. The physical parameters chosen correspond to those of their studies. The resulting transcendental equations are solved numerically. Neutral solutions are presented, indicating a destabilizing effect of the porous wall. The spatial growth rates determined demonstrate that the porous wall leads to a significant increase in growth rates for nonaxisymmetric modes. The effects of varying the porous-wall parameters are investigated.