Control of Laminar-to-Turbulent Transition in Hypersonic Boundary Layer with Porous Surface

This study investigates control of laminar-to-turbulent transition in a hypersonic boundary layer using a porous surface. An optimal porous surface is designed to maximize the damping of the Mack 2nd mode based on a reflection coefficient model that accounts for fabrication constraints of an electrochemical-etching process. The stabilization performance is evaluated using linear stability theory (LST), and the delay of transition is demonstrated through direct-numerical simulation (DNS). In the current DNS, the two-dimensional Mack 2nd mode and a pair of oblique modes are introduced into the DNS inlet to simulate a fundamental-breakdown transition. The absorptive characteristics of the porous surface are modeled using a time-domain impedance boundary condition. LST shows that the designed porous surface effectively suppresses the Mack 2nd mode over a wide range of frequencies. Consequently, the porous surface prevents transition within the DNS domain, resulting in a substantial reduction in surface heat flux.