Interior Ballistic Simulation for 9 mm Gun for Bullet and Blank Shot Applying Spalart-Allmars Turbulence Model

Abstract

Internal ballistic for a bullet shot and a blank shot in a 9 mm gun was simulated. The length and the thickness of the barrel of the gun were 125 mm and 3 mm, respectively. In this simulation viscous Spalart-Allmars turbulence model was applied and the movement of the bullet was modeled with six degrees of freedom. Four different initial conditions for the bullet were considered that involved the initial position of the bullet in the barrel, pressure of gas behind the bullet, and speed of the bullet in that position. The simulated muzzle speed for each initial condition was compared to experimental data and the error (in %) for each initial condition was calculated. Also, Mach number, gas pressure, flow field, and sound pressure level were simulated in the area outside of the gun barrel. Sound level reduced in both axial and radial directions but the reduction of sound in the radial direction was more than axial direction. In the case of the blank shot, also, it was observed that the reduction of sound in the radial direction was more than the axial direction. The sound pressure level for the bullet shot at the muzzle was 239.7 dB and for the blank shot, it was 220.5 dB at the muzzle. In both bullet and blank shots, it is observed from simulations that at the muzzle of the gun pressure of gas dropped and speed increased significantly. Mach number outside of the barrel was more than 1, which means the flow of gas was supersonic, and in some regions, Mach number reached 6. The shock wave produced from the supersonic flow of gas is detectable in the simulations.