Instability of projectile-induced combustion

A series of works on the instability of projectile-induced combustion flying into the detonable gas mixture are presented in the paper. There are two kinds of instabilities around the spherical and cylindrical projectile, and the both are periodically generated in front of the projectile. One is called the regular regime and the other is the large-disturbance regime. The characteristics in the flowfields are explained using the experimental photographs, and the mechanism of the periodic behavior for each case is proposed based on the wave interaction on the stagnation streamline in the simulation results. Furthermore, an effective non-dimensional parameter has been proposed to quantitatively classify the unsteady flow regime of shock-induced combustion around a hypervelocity spherical projectile into a detonable gas mixture. The parameter consists of the ratio of the fluid characteristic time scale to the chemical characteristic time scale. The proposed non-dimensional parameter can predict the unsteady flow regime of shock-induced combustion based on the small analytical computations estimating the chemical and fluid characteristics without the ballistic range apparatus or the simulations on the high performance computer.