Hypersonic Boundary Layer Stabilization via Fully Resolved Local Metasurface Structures

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 increases heat transfer and aerodynamic drag, which are significant drawbacks of sustained 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. Several recent studies suggested using a combination of local cooling-local metasurface (LCLM) structures to address these challenges. A local wall cooling combined with a metasurface 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. In LCLM studies in the literature, the metasurface structures are modeled with a boundary condition to solve the viscous eigenvalue problem. In this study, we investigate the hypersonic boundary layer flow with local metasurface by fully resolving the metasurface structures. We have employed a high-order accurate flow solver, OK-DNS, to calculate the steady flow for a free-stream Mach number of 6.0 and a unit Reynolds number of 25.59 × 10⁶/m. In order to resolve the metasurface structures, we utilized a simplified immersed boundary method. The results show the spatial evolution of disturbances that interact with the local metasurface cells, emphasizing the coating effect on the outflow fields.