Simulations for Reflected-Shock Waves in Combustible Gas in a Shock Tube.

The present paper treats numerical simulations for detonation initiations behind reflected-shock waves in a shock tube. The two-dimensional thin-layer Navier-Stokes equations with chemical effects are numerically solved by the use of a combined method consisting of the Richitmyer-FCT scheme, the Crank-Nicolson scheme and a chemical calculation step. Effects of chemical reactions occurring in shock-heated hydrogen, oxygen and argon mixture are estimated in the simulations by using a simplified reaction model. Simulations are carried out referring to experiments by several authors. Results of simulations reveal a mechanism of triple-shock generation in reaction shock waves. Computed flow fields for strong ignition in hydrogen and oxygen are in good qualitative agreement with visualized ones in experiments. A simulation referring to mild ignition predicts a feature that the ignition starts from distinct kernels. It is also predicted that ignition occurs immediately behind a normal reflected-shock wave but does not occur behind a bifurcated oblique shock wave.