Numerical Study of Diffraction in the Gaseous Detonation with Regular Cell Structure

Two dimensional numerical simulation of detonation diffraction is done in the mixture with the activation energy of 15 which has regular cellular structure, from a small cannel to a larger one with aspect ratio of two. Modeling is based on reactive Euler equations and One-step Arrhenius rate law. The width of the small cannel size is considered enough that at least 5 cells are in the width. The results obtained from detonation cell structure are shown that during the detonation transition from small cannel to larger one, firstly cell structures disappear in up and down of the front. With more detonation front going forward in the large cannel, all of the five cells are deleted and maximum local march of detonation is on the center line of the cannel. Study of detonation front during diffraction also showed that the local separation of the reaction zone from precursor shock waves occurs at upper and lower part of the detonation front. These results -that are in agreement with experiment- are due to the gas dynamic effect and effect of cooling of detonation front by expansion waves. Interaction between weakening of detonation by expansion waves and amplification of it by perturbation, triple points and corresponding transverse waves, has led to unstable behavior of detonation. The present results have shown that amplification of triple points and corresponding transverse waves, after the collision with the wall, are essential role in the reinitiating of detonation.