Study of multiple solution phenomenon for hypersonic air inlet

From current study the flow states of hypersonic inlet are classified into two types: start and unstart. Between start and unstart exists the double solution region, which forms the classical double solution theory of air inlet. However, because the shock in hypersonic inlet strongly interferes and interconnects with the boundary layer, it is very hard for the classical double solution theory to explain all flow phenomena. Profound study was done to improve understanding of hypersonic inlet and 4 distinct types of flow mode which disrelated with overrating were discovered from experiments, supplemented with CFD calculations. They are flow mode of start, large separation on body (LSB), small separation on body (SSB), and dual-separation on both body and lip (DSBL). The study also found that there is hysteresis phenomenon between the four types of flow mode and that their pairwise combinations produce six types of double solution region. Furthermore, according to the historical status and different entry paths, the study found out three types of triple solution region: “start + LSB + DSBL”, “LSB + SSB + DSBL”, and “start + SSB + DSBL”. The study results not only greatly enrich the theory of hypersonic inlet, but also have great significance in guiding engineering practice of air inlet.