1993 Volume 36 Issue 2 Pages 300-306
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 use of a method combining the Richitmyer-FCT scheme, the Crank-Nicolson scheme and a chemical calculation step. Effects of chemical reactions are estimated in the simulations by using a simplified reaction model in which rate coefficients are determined so that the induction times and the characteristic times of the exothermic reactions are fitted to data of a H2/O2/Ar mixture. 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 flowfields for strong ignition in hydrogen and oxygen are in good qualitative agreement with visualized ones in the experiments. A simulation referring to mild ignition predicts such a feature that the ignition starts from distinct kernels. It is also predicted that an ignition occurs immediately behind a normal reflected-shock wave, but does not behind a bifurcated oblique shock wave.