Numerical simulation on formation process of high-enthalpy flow fields in hydrogen-driven shock tunnels

To comprehensively investigate the formation of high-enthalpy flow fields in hydrogen-driven shock tunnels, this study conducted an in-depth numerical simulation using an implicit algorithm with second-order spatial accuracy and dual-time stepping. The simulation covered the entire evolution from tunnel initiation to the establishment of a stable flow field at the nozzle exit. Results demonstrate that under initial conditions of 50 MPa hydrogen in the high-pressure section and 100 kPa air in the low-pressure section (both at 300 K), the double diaphragms ruptured at 8.54 ms. By 10.20 ms, the flow pressure at the nozzle inlet reached 29.8 MPa with a temperature of 3500 K, and remained stable for 6.80 ms. The shock wave evolution in the throat region exhibited a characteristic sequence: incident shock; oblique shock; shock train; bow shock; lambda shock. In the downstream nozzle section, a primary shock wave formed fint, followed by a secondary shock. These two shocks propagated cooperatively downstream, ultimately establishing a stable flow field at 13.00 ms, which persisted for 2.00 ms. The stabilized flow field exhibited a core region with a Mach number of about 9.1, static pressure of about 900 kPa, and static temperature of about 260 K, while a uniform flow zone with a diameter of approximately 840 mm was achieved at the nozzle exit. This research enhances the fundamental understanding of high-enthalpy flow dynamics in shock tunnels and provides critical insights for optimizing ground-based hypersonic testing facilities to meet the demands of advanced aerospace vehicle development.