Quasi-detonation reflection over cylindrical wedges

Quasi-detonation reflections over concave and convex wedges were experimentally investigated in a narrow channel. Experiments were conducted in a 110 × 15 mm2 cross-sectional channel filled with stoichiometric hydrogen–oxygen diluted with 40% argon. A porous nickel plate was used as the “velocity deficit promotor” to generate quasi-detonations. Soot foils were applied to record the evolution of the reflection behaviors, while pressure sensors monitored wave velocity. The common feature of the reflective structures is that the height of the Mach stem decreases with increased αi (αi is the overdrive degree of the incident wave). For concave wedges, the Mach Reflection (MR) terminates earlier with higher αi, with the triple-point trajectory lying between the inert Chester–Chisnell–Whitham (CCW) theory and the reactive CCW theory. Meanwhile, the critical wall angle is found to be decreased with αi, particularly at a larger effective radius (R). In the case of convex wedges, the MR appears earlier with higher αi, resulting in an increased critical wall angle. Finally, for detonation waves exhibiting velocity deficits on both cylindrical wedges, the dispersion of the critical wall angle is significantly reduced at high αi. The critical wall angle on the concave wedge asymptotically converges toward the predictions of reactive CCW theory as the αi increases, while that on the convex wedge gradually converges to the prediction of two-shock theory.