Changes to the vortical and turbulent structure of jet flows due to mechanical tabs

The effect of mechanical tabs on the vortical and turbulent structures in t he near fields of jet mixing flows is investigated in the present paper. In order to compare the changes of the vortical and turbulent structures of j et flows with and without mechanical tabs, flow visualization and instantan eous quantitative concentration field measurements were conducted in a wate r channel by using a laser induced fluorescence (LIF) technique. The flow v isualization confirmed the existence of a pair of counter-rotating streamwi se vortices produced by each mechanical tab in a jet flow. The generated st reamwise vortices can cause an inward indentation of ambient flow into the core jet flow and an outward ejection of core jet flow into the ambient flo w. It also showed that the process of Kelvin-Helmholtz vortex pairing was a ccelerated, the small-scale vortical structure appeared earlier and a large -scale helical coherent structure was found in the near fields of tabbed je t flows. Based on the flow visualization and instantaneous quantitative con centration field measurements, two aspects of the effect of the streamwise vortical pairs induced by mechanical tabs on the jet mixing flows were sugg ested.