Study on the spatial control of turbulent mixing enhancement using synthetic jets

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The high intensity of turbulence and the strong turbulent mixing in a circular synthetic jet are studied by ensemble averaged velocities, smoke visualization and LES numerical simulation. The strong mixing is observed at some distance from the orifice, and it can be attributed to the mixing caused by the organized motion of deformed vortex rings and the longitudinal vortices in the process of vortex ring collapse. It is found that the vortex rings collapse without direct interference by neighbouring vortex rings, and the location of vortex collapse moves to downstream as the stroke of the alternating flow is increased.A short coaxial pipe was placed behind the orifice in the cavity and effect on the location of vortex collapse was studied. And the synthetic jet from a contraction nozzle instead of an orifice was studied to examine the effect on the vortex collapse. The results indicate these are possible methods of spatial control of turbulent mixing enhancement by synthetic jets.