Launch Dynamics of Supersonic Projectiles

The aerodynamics of projectiles launched from barrels of various devices is quite complicated due to their interactions with the unsteady flowfield around them. A computational study using a moving grid method is performed here to analyze various fluid dynamic phenomena in the near field of a gun, such as the projectile–shock wave interactions and interactions between the flow structures and the aerodynamic characteristics of the projectile when it passes through various flow interfaces. Cylindrical and conical projectiles have been employed to study such interactions and the fluid dynamics of the flowfields. The aerodynamic characteristics of the projectile are hardly affected by the projectile configuration during the process of the projectile overtaking the primary blast wave for small Mach numbers. However, it is noticed that the projectile configurations do affect the unsteady flow structures before overtaking and hence, the unsteady drag coefficient for the conical projectile shows considerable variation from that of the cylindrical projectile. The projectile aerodynamic characteristics during the interaction with the secondary shock wave are also analyzed in detail. It is observed that the change in the characteristics of the secondary shock wave during the interaction is fundamentally different for different projectile configurations. Both inviscid and viscous simulations were carried out to study the projectile aerodynamics and the fluid dynamics. Although the effect of the viscosity on the projectile aerodynamic characteristics is not significant, the viscosity greatly affects the unsteady flow structures around the projectile.