The interaction of 2D vortices in a developing pulsed plasma jet

Two-dimensional vortex pairs were continuously generated by dielectric-barrier-discharge (DBD) pulsed plasma actuators, whose transformation to a free jet in the near field was investigated using a time-resolved particle image velocimetry (PIV) technique. At low modulation frequences, the plasma-induced vortex pairs developed into a free jet with little or no interactions. As the modulation frequency was increased, however, strong vortex interactions started taking place to initiate the leapfrogging, which continued every two plasma pulses. This helped sustain significant plasma-induced thrust further downstream. With a further increase in the modulation frequency, initial vortex pairs merged with a loss of jet thrust. In this study, these vortex interaction behaviours were carefully investigated using the wavelet spectral analysis as well as measured mean velocity and turbulent intensity profiles. Finally, the dynamics of leapfrogging vortex pairs and the mechanism of vortex merger initiation were investigated to depict the uniqueness in the 2D vortex interactions in a developing pulsed plasma jet.