Transverse Waves and Ignition Dynamics in Oblique Detonations of Different Shock-Detonation Transition Types

The transition from an Oblique Shock Wave (OSW) to an Oblique Detonation Wave (ODW) can occur either abruptly or smoothly, depending on flow parameters, geometry, and mixture properties. Abrupt transitions exhibit a sudden change from a non-reacting OSW to a reacting ODW at the so-called “multi-wave’’ point, whereas smooth transitions involve gradual adjustments in both the flow and reaction zones. Although prior studies have examined smooth and abrupt transitions as means for ODW initiation, the influence of viscous boundary/shear layers on the initiation structure remains insufficiently resolved, which also highlights the key distinctions between Navier–Stokes and Euler formulations. This work first investigates how viscous boundary/shear layer effects modify the initiation-zone structure and influence the OSW–ODW transition types in a stoichiometric H2–air mixture. Building on this analysis, we then evaluate how different OSW-ODW transition modes impact downstream detonation behavior, including the transverse-wave development and the progression from pseudo-cellular (non-jetting) to fully cellular (jetting) patterns. High-resolution direct numerical simulations (DNS) with detailed chemistry are performed for different flight Mach number and altitude cases to identify the physical mechanisms governing both the initiation process and its downstream evolution.