Formation of a shockwave from subsonic vortex ring collisions of varying geometries

Vortex rings form as a slug of air moves through an opening, such as the end of a shock tube. Shock tubes have been used extensively in explosives research and have various geometries and designs. Boundary layer forces cause the air exiting an opening to curl back upon itself creating the vortex. Previous studies have shown the interaction of vortex rings with solid walls, and in collision and reconnection with other vortex rings with circular openings. This study uses explosively formed shock waves to study the collision of vortex rings in air with different geometries visually through Schlieren videography. Upon exiting the tube, the vortex rings are traveling at subsonic velocities, but after head-on collision, produce a shock wave. Different geometry vortex rings have different velocities upon exiting the tube, but still produce a shock wave after collision. Both the circular and square vortex rings trap air between them before collision. As more air becomes trapped, the pressure increases, creating a pressure gradient. The collision of the vortex rings causes a rapid release of air creating the resulting shock wave. Comparison of the shock and vortex velocities is performed.