Behavior of the series of laminar vortex rings with circumferential flow, so-called swirl, were investigated using flow visualization, to evaluate the transport efficiency of the ejected fluid as vortex rings. In this study, the interval time of the vortex ring ejection, the formation number of vortex ring LO/DO (the normalized length of the ejected slug of fluid), and the angular velocity of the ejected fluid ω are changed, while the mean ejection velocity is fixed. When vortex rings were generated at a short time interval, independent of LO/DO and ω, they were broken, and most of the fluid included in them was diffused near the orifice. When the vortex rings with little mutual interference were generated at an appropriate interval time, the breakdown of vortex ring structure is suppressed with moderate swirling flow. In those cases, each vortex ring moves separately for a long distance and the distribution area becomes wider as LO/DO increases.
2014 by The Japan Society of Mechanical Engineers