Outlet Diameter and the Vortex Generated by an Air Cannon

Abstract

Air vortex cannons generate structurally integral, coherent rings of rotating air that propagate through a surrounding medium over measurable distances. The effect of the outlet diameter of an air vortex cannon on the mass, impulse, and average velocity of air vortices produced by the cannon was investigated experimentally. Vortices generated using six outlet diameters were analysed by measuring the impulse exerted on a force plate and the impact velocity, from which the effective vortex mass was calculated. Increasing outlet diameter resulted in a monotonic power-law increase in both vortex mass and impulse, while the average velocity reached a maximum at an intermediate outlet diameter before decreasing. These results indicate that vortex performance depends on balancing the volume of air expelled with the ability to maintain vortex coherence, suggesting the existence of an optimal outlet diameter for effective vortex formation.