Projectile Aerodynamics Overtaking a Shock Wave

Abstract

A projectile that passes through a moving shock wave experiences drastic changes in the aerodynamic forces as it moves from a high-pressure region to a low-pressure region. These sudden changes in the forces are attributed to the wave structures produced by the projectile–shock-wave interaction and are responsible for destabilizing the trajectory of the projectile, consequently leading to a loss of projectile stability and control efficiency. A computational study was performed here using a moving-grid method to analyze the effects of the projectile overtaking amoving shock wave on the projectile aerodynamic characteristics. A one-dimensional analysis was also carried out to identify the projectile overtaking criteria. The analytical results show that the projectile overtaking flowfields canbe in a subsonic or supersonicflowregime, based on the relative projectileMachnumber.However, it is found that the actual flowfields in the present computations cannot be distinguishedwith the relative projectileMach number only, because theblast-wave strength is diminishingwith time and space. The aerodynamic characteristics of the projectile are hardly affected by the overtaking process for smaller blast-waveMach numbers, as the blast wave will become weak by the time it is overtaken by the projectile. The projectile drag coefficient is more greatly affected by the unsteady flow structures through which the projectile travels in the near field than by the overtaking process.