Vortical structures of a round jet formed bifurcating flows using synthetic jets

Bifurcating flows are formed in a jet and are called side jets. It has been known that velocity fluctuation is periodic and high and vortex rings significantly deforms at the potential core in a round jet. Although the effect of helical modes appears in the natural transition, it is not essential for the formation of side jets. To reveal vortical structures in a round jet with side jets, bifurcating flows were formed in a round air jet using synthetic jets. By three synthetic jets generated at the outlet of a nozzle, three bifurcating flows form at the end of potential core and their starting positions are fixed. It was found a bifurcating flow are formed at the mountain part of a wavy deformed vortex ring and between a pair of streamwise vortices, and the bifurcating flow is induced flows by rotations of three vortices. In this research, since the growth process of streamwise vortices was unknown in the experiments, a numerical simulation of the controlled jet was performed. The bifurcating flows are induced by developed streamwise vortex pairs in the braid region at the upper side of a vortex ring. The vortex pairs grow from the inside of the vortex ring in the downstream to the outside of the successive vortex ring in the upstream. The vortex pairs go upstream in the jet.