Background Oriented Schlieren (BOS) Technique: An Effective Flow Visualization Tool for Intermediate Ballistics

The motion of the projectile inside the gun barrel and its emergence from it causes different flow phenomena such as precursor phenomena, muzzle flash phenomena to occur, across its surrounding. The projectile is under the influence of muzzle flash shock wave till it is completely out of it. To visualize the intermediate ballistic zone of a low calibre supersonic projectile, an effective non-intrusive flow visualization tool i.e. Background Oriented Schlieren (BOS) technique is implemented here. The technique involves that the variation of density in the flow field causes change in refractive index. The BOS technique involves a background of good contrast characteristics, digital camera of good resolution. The details about the experimental set up are described in the paper. The density field is reconstructed by solving the Poisson equation in which the source term is obtained from cross-correlation between the distorted and undistorted image of the background. The muzzle flash phenomena and the density field distribution in the intermediate ballistic zone are discussed.