Relation between coherent vortices and entrainment was experimentally investigated in a natural or an acoustically excited plane jets through a flow visualization and hotwire measurement. For the natural jet, the entrainment increased when shift from the symmetric to the antisymmetric vortex arrangement occurred in the nonlinear interaction region. When antisymmetrically excited, the entrainment was greatly enhanced and jet width was enlarged. For the symmetric excitation, vortex tubes had wavy configuration in the nonlinear interaction region. As the intensity of excitation increased, the wavy configuration maintained until more downstream but its scale became smaller. At u(sub f)/U(sub 0) = +/-8 percent, the vortex pairing occurred and sub-harmonic components appeared in the energy spectra.
Visualization of vortex behavior and its effects on the characteristics of a plane jet
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