SEMINAR: ANZIAM Meeting/Seminar

Passive porous walls have been investigated as a means for delaying transition to turbulence in hypersonic flow. Here a theoretical linear stability analysis will be presented to consider the effect of a porous wall on the first (viscous) instability mode of a hypersonic boundary-layer flow over a sharp slender cone. The effect of curvature and of the attached shock is included for axisymmetric and non-axisymmetric disturbances. The flow in the hypersonic boundary layer is coupled to the flow in the porous layer. Asymptotic methods are used for large Reynolds number and large Mach number. The linear results for neutral stability and spatial instability will be presented for physical parameters and porous wall models, chosen to correspond to relevant experiments. The effects of varying the porous wall parameters will be shown. A weakly nonlinear stability analysis has been carried out allowing an equation for the amplitude of disturbances to be derived. The coefficients of the terms in the amplitude equation determine the effects of nonlinearity. The stabilising or destabilising effect of nonlinearity is found to depend on the cone radius. The presence of porous walls significantly influences the effect of nonlinearity.