Effect of Artificial Perturbation on Unsteady Wake Vortices in Jets in Cross-Flow

The current experimental study investigated unsteady wake vortices of jets in cross-flow in order to explore the possibility of periodic perturbation of these vortices with the method of oscillating tabs. Two triangular tabs were placed at the 90° and 270° edges of the jet orifice relative to the direction of the cross-flow. An isolated circular jet passed through a nozzle and entered the cross-flow normal to the wall. Free stream velocities up to 4.1 m/s and jet-to-cross-flow velocity ratio range between 3 and 12 were covered. Strouhal number (f_pD/U_cf) for excitation cases was about 0.19. The oscillation frequency was somewhat higher than the ‘preferred’ frequency of the wake vortices. The smoke flow visualizations did not indicate an organization of wake vortices. Artificial excitation simply tilted the jet cross section from side to side in sync with the tab oscillation.