Abstract
The flowfield produced by a vortex ring approaching a sphere was investigated mainly by means of smoke visualization technique. The main result obtained was that a vortex ring could pass over a sphere, although a vortex pair, i. e. the two-dimensional case corresponding to a vortex ring, could not pass over a cylinder, and the generation of the secondary vortex ring due to separation and the subsequent interaction with the main ring could be observed. Some characteristics of the ring before and after the pass-over were measured and the decays of circulation and kinetic energy were estimated by using the results.
Some numerical calculations based on both Lewis' solution and Wang's solution were carried out in order to obtain some information about the viscous effects in the actual flowfield. The difference between calculated and measured results was remarkable after the pass-over, because the separation was not taken into account in both theories.
