A study on the unsteady aerodynamics of projectiles in overtaking blast flow fields

Abstract

Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.

A projectile that passes through a shock wave experiences drastic changes in the aerodynamic forces. These sudden changes in the forces are attributed to the wave structures produced by the projectile-shock wave interaction. This sort of unsteady interaction normally takes place in the near filed of ballistic ranges, SILO injections, retro-rocket firings, etc. A computational study using a moving grid method is performed to analyze the effect of the projectile-shock wave interaction. Cylindrical and conical projectiles have been employed to study such interactions. It is found that the projectile configurations hardly affect its total aerodynamic characteristics when it overtakes a blast wave. However, it is noticed that the projectile configurations do affect the unsteady flow structures and hence the drag coefficient for the conical projectile shows considerable variation from that of the cylindrical projectile. The projectile aerodynamic characteristics, when it interacts with the secondary shock wave are analyzed. It is also observed that the change in the characteristics of the secondary shock wave during the interaction is different for different projectile configurations. Viscous simulations were also carried out to investigate the effect of viscosity in the flow field. It is observed that the viscosity hardly affects the projectile aerodynamic characteristics but it alters the shock structures of the unsteady flow fields.