Visualization of muzzle flow and projectile in flight flow using the background oriented schlieren technique

The present paper focuses on the development of a non-intrusive measurement techniqueand the implementation of a quantitative flow visualization method based on BackgroundOriented Schlieren (BOS). The gun muzzle flow, the aerodynamics, and the ambient airprojectile interaction are visualized. In BOS, the experimental set-up of conventionalSchlieren (mirrors, lenses, and knife-edge) is replaced by a background pattern and a singledigital camera. The proposed measurement technique and the implemented algorithm arefirst validated through the temperature measurement of a flame-induced distorted flow field.An acceptable accuracy is recorded, the measurement error being less than 3-5% of the fullscale. Second, the muzzle flow and the flow field around a 5.56 mm projectile in free flightwas captured and analyzed. The captured structures such as vortex, barrel shock, Mach disk,and blast wave show a good agreement with those issued from the conventional Schlierenset-up.