In the present work the propagating modes of detonation wave in supersonic hydrogen-air mixtures are investigated in narrow rectangular channels. To clarify the effect of the detonation wave interaction with the boundary layer on the evolution and propagation of detonation phenomenon, high-speed laser schlieren experiments and adaptive Navier-Stokes (NS) simulations (pseudo-DNS) combined with a detailed reaction model are performed. The experimental results show that after successful ignition, two propagating modes are observed and can be classified as Oblique shock-induced combustion/Mach stem-induced detonation (OSIC/MSID) and pure Oblique shock-induced combustion (OSIC). For the OSIC/MSID mode, a Mach stem induced overdriven detonation is generated in the middle of the main flow. For the pure OSIC mode, no detonation wave but two oblique shock-induced combustion regions are generated throughout the whole channel with the overall structure taking a thwartwise V shape. The OSIC/MSID and pure OSIC propagation modes are further confirmed by pseudo-DNS employing a detailed reaction model and dynamic adaptive mesh refinement for the same conditions as utilized in the experiments. The numerical results show that because of subsonic combustion near the walls induced by the boundary layers, the OSIC/ MSID is not entirely symmetrical, while for the pure OSIC mode, larger fluctuations are observed along the oblique shock waves resulting from enhanced instabilities due to additional chemical heat release.
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