Abstract
The turbulent flow characteristics in the symmetry planes of unforced and excited elevated transverse jets were studied experimentally in a wind tunnel. Jet pulsations were generated by means of acoustic excitation. The jet Reynolds number and the jet-to-crossflow momentum-flux ratio were 1000 and 1.2, respectively. A high-speed particle image velocimeter was employed to measure the velocity field. Exciting the transverse jet at Strouhal numbers less than about 0.53 caused the synchronized flapping-jet mode. Exciting the transverse jet at Strouhal numbers larger than about 0.77 induced the synchronized shear-layer-vortices mode. As the transverse jet was excited in the synchronized flapping-jet mode, the jet shot to high altitude and was drastically less deflected than the unforced transverse jet. The jet-wake vortex ring disappeared and the bifurcation lines moved upstream. The fluctuation intensities, vorticities, and turbulent shear stress of the excited transverse jet exhibited drastically higher values than those of the unforced transverse jet. The Lagrangian integral time and length scales of the transverse jet excited at the resonance Strouhal number were drastically smaller than those of the unforced one.
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