Quantitative Investigation of Ballistics Flow Fields by Background Oriented Schlieren Technique

The ballistics field is known by the presence of several complex phenomena such as muzzles and flying projectiles flow fields. Consequently, numerical simulations are commonly used to model these complicated flows. However, the validation process of these codes has proven to be problematic due to the lack of experimental quantitative data. In this context, the present paper describes the application of the Background Oriented Schlieren technique (BOS) as a quantitative investigation tool in the ballistics field. We illustrate that BOS can accurately capture the main characteristics of the studied configurations: Firstly, we discuss the visualization and the density field reconstruction around a Bullet Simulated Projectile BSP flying at supersonic velocities and a sniper projectile flying at supersonic and transonic velocities. We demonstrate that these fields are in satisfactory agreement with the results of Taylor and Maccoll's equation and numerical simulation. Then, the findings of the BOS visualization of the precursors and the propellant flow fields are presented. To this end, the salient features accurately captured by the BOS technique such as vortex rings, shock bottles, Mach, and blast wave are described both qualitatively and in terms of density profiles. Two improved approaches that are essential to the aforementioned analysis are proposed: the first is related to density field reconstruction based on Abel inversion and the second approach is a phase separation procedure.