Coupled effects of argon dilution and lateral expansion on the structure and stability of hydrogen–oxygen detonations in semi-confined channels

A numerical study on detonation propagation in a semi-confined channel under various argon dilution conditions was performed using the open-source field operation and manipulation-based density compressible reactive solver, coupled with a detailed chemical reaction mechanism for hydrogen–oxygen mixtures, with the computational model validated through comparison with experimental data reported in the literature. It focuses on the structural evolution of the detonation wave at the corner and investigates the coupling mechanism between lateral expansion and inert gas dilution. The results show that, in the absence of lateral dilution, the leading shock induced by sudden geometric expansion undergoes transient decoupling from the reaction front. The detonation wave can recouple with the reaction front and restore its structure through intensified compression generated by triple point collisions. Under lateral argon dilution, increasing argon concentration weakens the reaction zone's response to shock compression. The decoupling behavior evolves from a local transient phenomenon to sustained decoupling, accompanied by a reduction in the lateral expansion range of the detonation wave. The flow field structure transitions from stable propagation to instability and ultimately to complete failure as the dilution concentration increases. When the argon concentration reaches 70% or higher, the detonation wave largely loses its self-sustained propagation capability and cannot maintain a complete cellular structure within the lateral expansion region. The nonlinear coupling effect induced by lateral expansion and inert dilution aggravates the decoupling between the leading shock and the detonation reaction front, thereby governing the transition of the detonation wave from stable propagation to failure.