Experimental Visualization of Hypersonic Boundary Layer Transition

초록

Hypersonic aircraft design faces a significant challenge in the form of aerodynamic heating, exemplified by aircraft like X-51, HGB, and HTV2. Surface temperatures during hypersonic flight can reach extreme levels, up to 2200K, causing severe damage. Aerodynamic heating impacts the aircraft surface and varies with the boundary layer's state. Laminar boundary layers exhibit low heat transfer rates, resulting in minimal damage. However, turbulence drastically increases heat transfer rates, leading to thermal damage. The transition region from laminar to turbulent flow experiences the highest heat transfer rates. To mitigate this, techniques are employed, such as heat shields, surface cooling jets, and porous surfaces, to maintain a laminar boundary layer. The Mack Second Mode instability is a primary trigger for laminar-to-turbulent transition. Delaying this instability through porous surfaces reduces turbulence-related damage. However, applying porous materials across the entire surface increases weight, making selective application crucial. This study aims to visualize the Mack Second Mode and measure surface heat transfer rates to diagnose boundary layer transition. © 2025, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.