Aerodynamic analysis of an AK-47 bullet moving at mach 2.0 in close proximity to the ground

Abstract

The bullet is shot near the wall or the ground during urban warfare. This nearness leads to a pressure distribution on the bullet's entire body, which is asymmetric. For every case of difference in the height of the ground/wall proximity, the shock reflection angle changes, and a particular shock wave's effect on the bullet varies. In the present study, the flowfield around a 7.82-mm bullet of an AK-47 Rifle moving at a supersonic speed of Mach 2 near the ground is studied using Computational Fluid Dynamics. Computational simulations have been carried out for the bullet moving at different heights from the nearby wall. The level of impact on the projectile is illustrated from the region of nearest influence to a ground distance which is five times the bullet's diameter. Ground effects from height to diameter ratios (h/D) of 0.25 to 5 are showcased, describing the influence on overall flowfield, pressure coefficient distributions, lift drag, and moment coefficients. The wake region flow field is also analyzed. It has been observed that a detached bow shock wave is generated at the tip of the bullet, which increases the drag coefficient experienced by the bullet. Generation of lift is the maximum for certain h/D cases like 1.0, 1.5, and 2.0 as the shock reflections from the ground hit the bullet. Further increasing the altitude from the near-wall reduces the lift and drag forces acting on the bullet due to the lesser ground effect. From the present investigation, the heights above the h/D ratio of 2.0 are suitable for firing the shot.

Keywords

• external ballistics
• ground effect
• urban warfare
• near wall proximity
• bullet's computational aerodynamics