Abstract-A vortex ring launched into quiescent water is used to generate and transport solid particle clusters. A vortex ring launcher, comprising a cylinder and piston, is mounted at the bottom of a water tank. One-hundred spherical, polyacetal particles (mean diameter: 1.52 mm, density: 1417 kg/m 3 ) are placed on a mesh stretched near the cylinder outlet. The piston is used to discharge water in the cylinder vertically upward into the tank; this launches a particle-laden vortex ring. This solid-liquid two-phase flow is investigated at the Reynolds number Re, defined by the piston velocity and the cylinder diameter, of 6500, 7500, and 13000. When Re=6500, the particles are not entrained in the vortex ring, and therefore a cluster is not produced. Particles are entrained just after the launch of vortex rings at Re=7500 and 13000. These particle clusters are transported by the convection of the vortex ring. The velocity of water in the central vertical cross-section of the vortex ring decreases because of the particles, resulting in decreased circulation of the vortex ring. This reduction is more severe for lower Re.Index Terms-Solid-liquid, two-phase flow, vortex ring, particle entrainment, Piv.

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