Influence of trailing jet instability on the dynamics of starting jets

The starting jet produced by the discharge of a submerged fluid stream through a circular orifice is investigated both numerically and experimentally for moderately large values of the jet Reynolds number, Re. Low-amplitude sinusoidal perturbations were superimposed to the jet exit velocity to reproduce the effect of flow perturbations on the trailing jet and leading vortex ring dynamics. While the trailing jet is strongly modified by flow perturbations, the evolution of the total circulation, as well as the leading vortex dynamics, remain relatively unaffected, and thus can be considered as more robust indicators of the dynamics of starting jets.