Unsteady detonation with thermodynamic nonequilibrium effect based on the kinetic theory

In this paper, unsteady detonation is simulated and investigated from the viewpoint of kinetic theory. The deviations of the velocity distribution function from the equilibrium state are studied in the evolution of detonation. It has been discovered that the characteristics of the deviation around the detonation wave are significantly different from those in the post-wave region. Besides, the kinetic moments of the reaction term have been simulated, verified and analyzed in detail. In addition, the reaction manifestation is defined to describe the global effects of kinetic moments due to chemical reactions. It is interesting to find that there are three types of periodic oscillations of the reaction manifestation during the evolution of the unsteady detonation. Via the fast Fourier transform, it can be seen that the reaction manifestation is mainly composed of several signal frequencies. Moreover, the impact of rate constants of the two-step reaction scheme on the reaction manifestation is studied, and the influence of chemical heat is investigated as well.