Flow features of shock-induced combustion around cylindrical projectiles

Shock-induced combustion around a cylindrical projectile is numerically studied using a simplified twostep chemical reaction model consisting of the induction and the exothermic reactions. In a series of simulations by changing the exothermic progress parameter and projectile diameter, the presence of unsteady modes such as regular regime and large-disturbance regime are revealed as well as the combustions around a spherical projectile. The oscillation periods for each unsteady mode agree well with previous experimental and numerical observations around the spherical projectile. Around the cylindrical projectile, instability is much stronger than that around the spherical projectile, and cellular structure with transverse waves easily occurs in front of the projectile. This type of unsteady behavior does not have periodicity and is newly classified as unsteady state. Although the exothermic progress parameter, E₂/R, in the chemical reaction model is dominant to the appearance of the unsteady behavior around the spherical projectile, the E₂/R has no influence on the unsteady mode around the cylindrical projectile. The diameter is the key factor in determining the unsteady mode, because the unique unsteady mode appears with a certain diameter without dependence on the exothermic progress parameter. Thus, the prediction method developed for the spherical projectile is not applicable to the classification of unsteady combustion around the cylindrical projectile.