A direct numerical simulation (DNS) was carried out to study twin swirling jets which are issued from two parallel nozzles at a\nReynolds number of Re = 5000 and three swirl levels of S = 0.68, 1.08, and 1.42, respectively.The basic structures of vortex-vortex\ninteraction and temporal evolution are illustrated.Thecharacteristics of axial variation of turbulent fluctuation velocities, in both the\nnear and far field, in comparison to a single swirling jet, are shown to explore the effects of vortex-vortex interaction on turbulence\nmodifications.Moreover, the second order turbulent fluctuations are also shown, bywhich themodification of turbulence associated\nwith the coherent or correlated turbulent fluctuation and turbulent kinetic energy transport characteristics are clearly indicated. It is\nfound that the twin swirling flow has a fairly strong localized vortex-vortex interaction between a pair of inversely rotated vortices.\nThe location and strength of interaction depend on swirl level greatly.Themodification of vortex takes place by transforming largescale\nvortices into complex small ones, whereas the modulation of turbulent kinetic energy is continuously augmented by strong\nvortex modification.
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