Bow-shock stability analysis of high-enthalpy hypersonic vehicles

High-velocity vehicles require advanced thermal protection systems due to the extreme temperatures they encounter. Although rare in Earth's atmosphere, the bow shock in front of these vehicles can cause instabilities under certain conditions, leading to an early transition to turbulence. This transition significantly intensifies heat transfer, making thermal design increasingly challenging. Understanding the conditions that trigger this transition is therefore critical for vehicle design. In this work, we investigate transition mechanisms driven by large density gradients induced by strong bow shock waves. To this end, we conduct global and transient growth stability analyses of representative geometries found in hypersonic vehicles. Our analysis employs a shock-fitting computational framework that accounts for chemical equilibrium as well as translational, rotational, vibrational, and electronic energy modes. We explore the influence of geometric configurations in combination with key flow parameters, including Mach number, Reynolds number, and gas mixture composition. The results identify the flow regimes most susceptible to instability and reveal the underlying physical mechanisms responsible for perturbation amplification.