Numerical simulation on ignition with shock tube - Effect of reflected shock wave - boundary layer at adiabatic wall interaction on ignition

A reflected shock wave in two-dimensional shock tube is studied numerically using Navier-Stokes equations with the detailed oxy-hydrogen reaction mechanism. The results reproduced mild and strong ignition behind the reflected shock wave, in particular, the detailed mild ignition process, which was not shown well in past research. Owing to the interaction between the viscous boundary layer and the reflected shock wave, the latter has a lambda shock configuration. The flow behind the lambda shock wave becomes a complex vortical structure; thus, the reactive gas mixture flowing along the detached vortices reaches high temperature and pressure because of compression at the tube side walls. The chemical reaction starts at the location that reaches the auto-ignition temperature to create flame kernels. The above history is appropriate for the process in which a flame kernel appears at the location between the triple point of the lambda shock wave and the tube wall, but is insufficient for the process in which a flame kernel appears near the tube center, which is above the triple point of the lambda shock wave.