Study of Vortical Structures in a Cross-Shaped Jet

Vortical structures in a cross-shaped jet have been investigated, using a flow visualization technique by laser-fluorescent dye while controlling vortex evolutions under excitation. The corner regions of vortical structures close to the orifice undergo severe deformation due to the self-induced velocity; the outward corners become flat and the inward corners generate outward ejection. The excitation at low frequencies produces the large-scale vortical structures, the strong self-induced velocity switching over the normal and diagonal axes of the cross-shaped vortices. The deformed vortical structures are stretched under the effect of the mean flow, discharging small vortices from the tips of corners through the cut-and-connect mechanism.