Effects of local cooling on hypersonic boundary-layer stability

Sustained hypersonic flight is still a significant challenge due to increased aerodynamic heating and drag force created by turbulent boundary layers. Understanding the physical mechanisms causing the second-mode (Mack-mode or acoustic-mode) dominated laminar to turbulent transition is critical for the design of next-generation hypersonic vehicles. It has been shown that cooling a vehicle’s surface stabilizes the first-mode but destabilizes the second-mode instabilities. Our primary focus is to study the control of instability modes with the use of cooling strips locally. We conducted a direct numerical simulation (DNS) study by free stream acoustic disturbances in wave packets with wide bandwidth frequencies along with localized cooling. The flow fields were varied along the 5^◦ half-angle blunt cone with 0.001 bluntness radius at Mach 6. By actively using a cooling system, or passively changing vehicles material characteristics, the cooling models can be achieved. The objective of this paper is to investigate the stabilization and excitation behaviors of local cooling strips with varying temperatures.