Effects of Passive Porous Walls on the First Mode of Hypersonic Boundary Layers Over a Sharp Cone

Abstract

Abstract : A theoretical linear stability analysis is used to consider the effect of a porous wall on the first 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 linear results for neutral stability and spatial stability are presented for physical parameters and porous wall models, chosen to correspond to relevant experiments. The effects of varying the porous wall parameters are investigated. A weakly nonlinear stability analysis is carried out allowing an equation for the amplitude of disturbances to be derived. The coefficients of the terms in the amplitude equation are evaluated for axisymmetric and non-axisymmetric disturbances. The stabilizing or destabilizing effect of nonlinearity is found to depend on the cone radius. The presence of porous walls significantly influences the effect of nonlinearity.