Hypersonic Boundary-Layer Stability Over a Cone with Combined Local Cooling and Local Metasurface Treatment

View Video Presentation: https://doi.org/10.2514/6.2023-3419.vid The field of modern aviation has been intrigued by the potential of sustained hypersonic flight. However, several aerodynamic challenges impede the efficient operation of hypersonic vehicles, including the laminar to turbulent boundary layer transition. This transition results in an increase in heat transfer and aerodynamic drag, which are significant drawbacks of hypersonic boundary-layer flow. While active cooling or thermal protection systems can alleviate these adverse effects, they add additional cost, weight, and complexity to the system. To address these challenges, we have conducted research to investigate several methods for stabilizing the instabilities in hypersonic boundary-layer flow. Our study has found that a combination of local wall cooling and a porous surface placed on the solid wall can be effective in stabilizing Mack's first and second modes, which in turn can delay the boundary-layer transition. We have employed a high-order accurate flow solver to calculate the steady flow for a free-stream Mach number of 6.0 and a unit Reynolds number of 25.59 \times 10^6/m, and the unsteady flow results have been obtained with a modeled admittance for the porous surface. Our study focuses on the stabilization effect of the local cooling strip with a porous surface over a 5-degree half-angle cone with a 0.0254mm nose bluntness. Our results indicate that end effects associated with junctures between solid and porous surfaces may be important for axisymmetric geometries as they introduce oscillations to the flow, unlike two-dimensional wedge flows. These oscillations are only observed if the metasurface length is long enough. However, despite the oscillations, the amplitude of the disturbance was significantly damped out by the local cooling-local metasurface treatment.