Experiments are conducted in a smooth 10 $\times$ 10 mm square cross-section, 1-m long channel, closed at the ignition end and open at the other end. Simultaneous two-direction schlieren visualization is used to investigate the three-dimensional dynamics of transition to detonation for a stoichiometric H₂–O₂ mixture. Results show the existence of two distinct structures before detonation onset: (i) asymmetric, composed of an oblique shock trailed by a flame, that runs preferentially along the wall, and seems to get ignited inside the boundary layer developed by the precursor shock; (ii) symmetric, referred to as strange wave in literature, propagating roughly at the speed of sound in combustion products. The combined effect of shock induced preheating and viscous heating near walls seem to be responsible for the formation of the complex flame-shock interactions observed. A simple thermodynamic analysis applied to the strange wave using the experimentally measured wave speed yield a pressure ratio of $~$ 15 during its steady propagation; furthermore, an estimate of the total energy losses required to thermodynamically realize such propagation regime revealed that approximately half of the energy released by combustion should be dissipated (i.e. momentum and heat losses). Finally, simultaneous two-direction optical access allows to map the exact location of detonation onset, showing that 78 $\text{\%}$ of cases exploded in corners, highlighting the role of corner flows and boundary layers in transition to detonation at this scale.

实验在流畅的10进行 $\times$横截面为10毫米见方，通道长为1米，在点火端关闭，另一端打开。同时使用双向Schlieren可视化技术研究化学计量H ₂ -O ₂混合物向爆轰转变的三维动力学。结果表明，在爆炸开始之前，存在两个不同的结构：（i）不对称，由火焰拖曳的倾斜冲击构成，其优先沿壁延伸，并且似乎在由前体冲击形成的边界层内部被点燃；（ii）对称，称为奇异波在文献中，以燃烧产物的声音速度大致传播。冲击诱导的预热和壁附近的粘性加热的共同作用似乎是所观察到的复杂火焰-冲击相互作用的形成的原因。使用实验测量的波速对奇异波进行简单的热力学分析，得出压力比为$〜$15在稳定传播期间；此外，对通过热力学实现这种传播方式所需的总能量损失的估计表明，应释放燃烧释放的大约一半能量（即动量和热损失）。最终，同时进行双向光学访问可以绘制爆炸起爆的确切位置，表明78$\text{％}$ 爆炸中的爆炸案例突出显示了在这种规模的爆炸过程中，拐角流动和边界层的作用。