Motion of Vortex Rings in Water

Abstract

Experimental studies were made on the motion of vortex rings ejected from a circular or a lenticular orifice into water. The vortex rings were made visible by fine grains of tin made by electrolysis, and photographs were taken. The diameters and the traveling velocities of the vortex rings were determined from these photographs. There is a favorable range of impulse to produce the stable vortex ring. The traveling velocity of the vortex ring is composed of the velocity of the jet flow and the self-induced velocity of the vortex; the former decays rather rapidly and the latter decreases slowly in time as \sqrtνt, where t is the time and ν is the kinematic viscosity of water. The vortex ring ejected from a lenticular orifice changes its shape intermittently, and the period of deformation is prolonged continually, while the traveling distance during one period is nearly constant.