Abstract
The cyclic vortex rings, which are generated cyclically by a pulsating jet, appear to be an effective method for particles and fluids transport. The effect of the formation conditions of cyclic vortex rings, such as the jet pulsation conditions, conditions of an intermittent period and conditions of a nozzle length, on the behavior of vortex rings from the formation to diffusion is investigated experimentally. The results indicate that the behavior of cyclic vortex rings in the formation process are classified into three patterns, the stable type, the transition type and the unstable type, depending on the jet pulsation conditions and conditions of an intermittent period. In order to generate the stable type cyclic vortex rings which are axisymmetric vortex cores and can move to long distance, it is necessary to set an intermittent period in the pulsating waveform of a jet. The formation behavior of cyclic vortex rings without setting an intermittent period changes from the transition type to the unstable type as the Strouhal number of a pulsating jet is small. It is, then, confirmed that these types of cyclic vortex rings diffuse in an early phase. In the case of the stable type cyclic vortex rings, the volume of vortex rings becomes large as the length of a nozzle is extended.
