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Sixth International Symposium on Turbulence and Shear Flow Phenomena
June, 22-24, 2009 , Seoul National University, Seoul, Korea

DOI: 10.1615/TSFP6

MECHANISM OF VORTEX GENERATION AND ITS CONTRIBUTION TO MIXING ENHANCEMENT IN A CONTROLLED COAXIAL JET

pages 823-828
DOI: 10.1615/TSFP6.1320
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RESUMO

The mechanism of vortex generation and its contribution to mixing enhancement in a coaxial jet controlled by miniature ap actuators are investigated experimentally and numerically. First, flow visualization and PIV measurement are carried out in order to study the velocity field induced by the apping motion of actuators and the resultant vortex ring generation in the initial inner and outer jet shear layers. Then, we numerically simulate such near-field evolution and associated mixing process by assuming the periodic velocity profile of difierent frequencies at the outer nozzle exit. In addition, the three-dimensional vortical structures and mixing property are studied under two difierent control conditions, i.e., axisymmetric and helical apping modes. As a result, it is found that the helical forcing mode generates more streamwise vortices in the shear layers than the axisymmetric mode. This enhancement is due to the increased production of rib vortex structures through tilting and subsequent stretching of vortices generated by apping.

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