Impact of aspect ratio on unstart flow characteristics in hypersonic inlet

This study employs numerical simulation methods to investigate the flow characteristics of hypersonic inlets with different aspect ratio configurations under unstart conditions. Through comprehensive analysis of shock wave structure evolution, wall pressure distribution characteristics, and key performance parameters including mass flow ratio and total pressure recovery coefficient, the influence mechanism of aspect ratio on inlet unstart modes is revealed. The results demonstrate three distinct unstart modes: small separation on body (SSB), large separation on body (LSB), and dual-separation on both body and lip (DSBL). Furthermore, as the aspect ratio increases, the broadwise spillage effect weakens, and when exceeding a critical value, the DSBL transitions to LSB flow mode. Increasing the aspect ratio reduces the self-start performance of inlet while simultaneously improving key performance indicators such as pressure ratio, mass flow ratio and total pressure recovery coefficient, which provides important theoretical support for the design and optimization of hypersonic inlets.